Rozprawy doktorskie: „Methane Reforming Catalysts”

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Shao, Huifang. "Bimetallic carbides as catalysts for dry reforming and steam reforming". Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4761.

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Thesis (Ph. D.)--West Virginia University, 2006.
Title from document title page. Document formatted into pages; contains x, 174 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 155-166).

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Ewbank, Jessica Lee. "Rational synthesis of novel reforming catalysts". Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54850.

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Biomass gasification offers the chance to produce carbon neutral, renewable fuels. One of the main problems facing the commercialization of biomass gasification technology is the presence of large quantities of methane and carbon dioxide in the biogas. Catalytic reforming of these wastes allows for effective utilization of biomass derived syngas. In most reforming studies, impregnation methods are the primary synthesis technique. Impregnation methods often lead to poor dispersion and are un-reproducible from batch to batch. In the development of a novel catalyst for reforming applications, another preparation method is implemented, controlled adsorption (CA). Ni/Al2O3 and Co/Al2O3 prepared by CA are compared against catalysts that were prepared by a more traditional method, dry impregnation (DI). It is found that controlling the metal deposition provides catalysts with higher dispersion and consequently higher activity for methane dry reforming. NiAl2O4 catalysts prepared by Pechini synthesis were also studied for catalytic conditioning of biomass derived syngas. Physicochemical characterization revealed unique structural properties, indicated a high degree of mobility of nickel in the aluminate structure, and demonstrated the regeneration properties of nickel aluminates under harsh reaction conditions, which will be important at extended reaction times when catalyst regeneration becomes necessary. Fourfold coordinated nickel species are believed to be responsible for high, stable methane dry reforming activity and metallic nickel is believed to be the active site that allows for high, stable conversion during methane dry reforming.

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Christensen, Kjersti Omdahl. "Steam Reforming of Methane on Different Nickel Catalysts". Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2167.

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The effect of crystal size on carbon formation and sintering was studied on nickel catalysts at steam reforming conditions. Different nickel supported catalysts were examined. As support three commercial hydrotalcites were used: HT30 (MgO/Al₂O₃ = 3/7), HT50 (MgO/Al₂O₃ = 5/5) and HT70 (MgO/Al₂O₃ = 7/3). These supports were compared with CaO-Al2O3 and α-Al2O3. For the sintering experiments an industrial Ni/CaAl2O4 catalyst was used for comparison. The hydrotalcite derived catalysts had different Mg/Al ratios and the lowest Mg/Al ratio gave the highest Ni dispersion. The hydrotalcite derived catalysts also had a higher dispersion than NiO/CaO-Al₂O₃, NiO/α-Al₂O₃ and Ni/CaAl₂O₄.

Carbon formation studies were performed in the tapered element oscillating microbalance (TEOM) at 823K, total pressure of 20 bar and steam to carbon (S/C) ratios of 0.08 to 2.4. The TEOM is a powerful tool for in situ catalyst characterization. All the feed gases pass through the catalysts bed and the TEOM offers a high mass resolution and a short response time. With an on-line gas chromatograph or mass spectrometer, catalyst activity and selectivity can be determined as a function of time. From the TEOM experiments it seemed that the Ni crystal size had a large effect on the carbon threshold value (S/C ratio where the carbon gasification rate equals the carbon deposition rate). Increased crystal size gave an increased carbon threshold value. It was concluded that small nickel crystals resulted in a large saturation concentration of carbon giving a low driving force for carbon diffusion and hence a lower coking rate. TOF increased with increasing Ni crystal size. This could be explained by surface inhomogeneities on the large crystals. Sintering experiments were performed at 903K and 20 bar in a fixed-bed reactor system. For all the catalysts the sintering mechanism involving particle migration seemed to be dominating. Due to a higher degree of wetting of the substrate by the nickel particle, the catalysts with smallest nickel particles showed the highest resistance towards sintering.

Hydrogenolysis of methane was used as a probe reaction for testing the catalysts activity. An increased TOF with increased Ni particle size was observed. This result coincides with results from the steam methane reforming experiments in the TEOM.

The characteristics of the hydrotalcite derived catalysts prepared by impregnation of commercial hydrotalcite supports were compared with hydrotalcite derived catalysts prepared by the co-precipitation method. An improved dispersion with decreasing Mg/Al ratio in the hydrotalcite was found. The catalysts prepared by the co-precipitation method maintained a high dispersion at increased nickel loadings. Different techniques were used to determine the Ni particle size. The results showed an excellent correlation between the Ni particle size found by chemisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM).

Paper IV is reproduced with kind permission of Elsevier, sciencedirect.com

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Brungs, A. J. A. "Transition metal carbides as catalysts for methane reforming". Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365881.

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Sitompul, J. P. "Numerical studies of methane-steam reforming within cylindrical catalysts". Thesis, Swansea University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639049.

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Hollow finite cylindrical catalysts are becoming of more interest as catalyst support not only because they produce lower pressure drops than with conventional solid pellets but also because they provide the associated extra external surface area which enhances diffusion-limited reactions. Dynamic simulation of diffusion, conduction and reactions in this type of catalyst has been studied. The numerical method, Alternating Direction Implicit Method (ADIM), has been used for solving the coupled elliptic governing equations. The simulation applied to methane-steam reforming involves multiple (parallel) reactions and multicomponent mixtures of products and reactants within the catalyst. The numerical method proposed is expected to be capable of following steep gradient of methane concentration across the cylindrical catalyst during methane-steam reforming. From a critical literature evaluation of kinetics of methane-steam reforming, it was found that the data of Bodrov et al. (1967a) and that of Kopsel and Meyer (1980) were obtained from experiments in the temperature range of industrial application. The ADIM was able to follow, successfully, the steep gradient of methane concentration during methane-steam reforming by employing kinetic expressions derived by Kopsel and Meyer (1980) within hollow, finite cylindrical catalyst. The numerical method has been used for comparative study of temperature and concentration profile across the catalyst by employing several kinetic expressions for methane-steam reforming. The kinetic expressions of Bodrov et al (1967a), modified by comprehensively reinterpreting their data, also produce diffusion-controlled profiles across the hollow finite cylindrical catalyst. The comparative study found that the kinetic expressions of De Deken et al (1982) and the more elaborate kinetics of Xu and Froment (1989) do not produce diffusion-controlled profile across the catalyst at high temperature.

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CRISTIANO, GIUSEPPE. "STEAM REFORMING AND OXIDATIVE STEAM REFORMING OF METHANE AND BIOGAS OVER STRUCTURED CATALYSTS". Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2540087.

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In 2006 the global demand for primary energy amounted to nearly 12 million tons of oil equivalent (Mtoe), to a large extent (over 80%) supplied by fossil fuels, i.e. coal, oil, and natural gas. According to the scenario suggested by the International Energy Agency (IEA), energy demand will rise in 2030 to about 17 Mtoe. Fossil fuels will remain largely dominant. Over 70% of the expected demand for the period 2008-2030 will be due to the developing countries (China, India, Middle East, Africa, Latin America). Approximately 50% of this energy demand will involve the generation of electricity, but a significant proportion (20%) will be linked to the transport sector, while the remaining 30% will be distributed between industry, services and residential use. Obviously, predictions of growth in energy demand suggested some problems: if the availability of primary sources, mainly fossil fuels, will be sufficient to meet the demand in quantity, quality and distribution; whether the progressive increase in the use of fossil sources will be compatible with environmentally sustainable development, what role other sources of energy such as nuclear and renewables can play in the future landscape and economical development?. In this scenario, the hydrogen plays a key role as an energy carrier. But the hydrogen is not available in its free form; hydrogen atoms are only available linked to other natural resources, and it must extracted somehow. Currently, most of the hydrogen on the planet is produced by steam reforming of methane, as it is the most abundant gas among the fossil fuels, at an acceptable cost and easily available through the dense network of distribution (pipelines). However, there are also other techniques of syngas production such as the partial oxidation (CPOX), the oxy steam reforming (OSR), which has the characteristic of being able to be made autothermal (ATR) and the dry reforming (DR). The dry reforming is particularly interesting because it uses as a reagent mixture methane and carbon dioxide, two gases with particular heavy greenhouse effect. In this regard the biogas (mixture of carbon dioxide and methane), produced by anaerobic digestion basically from biomass, is particularly suitable for this process since it allows avoiding the preventive separation of CO2 from methane in the production process of syngas. The main aim of this doctoral thesis is the study of the process of syngas production from methane and biogas on catalysts supported on ceramic monoliths made of cordierite, using the steam reforming (SR) process and oxy-steam reforming (OSR) process. The tests were carried out in collaboration with the Institute of Advanced Techniques for Energy "Nicola Giordano" (CNR -ITAE) in Messina (Italy). This thesis is constituted by an introductory part that covers topics related to the production and storage of hydrogen (Chapter 1, “Introduction”); a central part which describes the pilot plant used to carry on tests on steam reforming and oxy steam reforming of methane and biogas, and the preparation of the various tested structured catalysts (Chapter 2, “Experimental part”); and a final part which consists of four papers describing the various experimental works carried out (Chapters 3 to 6). Finally, conclusions on the work done are reported (Chapter 7, “Conclusions”). Chapter 3, “Methane oxy-steam reforming reaction: performances of Ru/γ-Al2O3 catalysts loaded on structured cordierite monoliths”, reports the process of production of syngas via oxy-steam reforming of methane on Ru structured catalyst supported on γ-Al2O3 as carrier. In particular, the influence of the catalyst loading, the influence of the O/C and S/C ratios, the influence of the reaction temperature and the space velocity, were specifically addressed. Chapter 4, “Syngas production by methane oxy-steam reforming: performance of Me/CeO2 (Me = Rh, Pt, Ni) catalyst lined on cordierite monoliths”, presents the process of production of syngas via oxy-steam reforming comparing the performances of three structured catalysts, based on noble and non-noble metals (Rh, Pt and Ni) supported on CeO2 as carrier, focusing on the comparison of the influence of reaction temperature and space velocity on the reactor performance. Chapter 5, “Comparative Study on Steam and Oxydative Steam Reforming of Methane with Ru and Rh Based Catalysts supported on Cordierite Monoliths”, shows the comparison between the processes of steam reforming and oxy-steam reforming of methane on two structured catalysts (Ru/γ-Al2O3 and Rh/CeO2). The two different processes on the two catalysts were studied separately, and then compared. Moreover, an energy requirement discussion on the two processes was addresses (with the support of a series of Aspen Plus® simulations), with specific reference to the energy required for the vaporization of water (the only liquid reagent), and the energy required by the reforming reaction with respect to the moles of methane fed to the process. Chapter 6, “Biogas Steam and Oxy-Steam Reforming processes over structured catalysts based on Me/CeO2 (Me = Rh, Pt, Ni) coated on cordierite monoliths”, describes the comparison between the processes of steam reforming and oxy-steam reforming of biogas on three structured catalysts, based on noble and non-noble metals (Rh, Pt and Ni) supported on CeO2 as carrier . At the time of the submission of the present doctoral thesis to the external Commission, December 2013, the first paper, presented on Chapter 3, has been submitted to the peer reviewed “International Journal of Hydrogen Energy” (manuscript nr. HE-S-13-04515-2), while the other three papers, Chapters 4 to 6, are almost ready for the submission to other international peer reviewed journals (“Applied Catalysis B: Environment”, “Applied Energy”, and “Industrial Engineering and Chemistry Research”).

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Di, Jiexun. "Development of highly active internal steam methane reforming catalysts for intermediate temperature solid oxide fuel cells". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:a36ce531-e7b2-48fb-a59b-dbca6b435643.

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Fuel processing is one of the essential parts for development of intermediate solid oxide fuel cells (IT-SOFC). Natural gas (methane) is considered as the most abundant and cost effective fuel for the production of hydrogen for IT-SOFC. The primary aim of this thesis is to use a novel precursor material—layered double hydroxide (LDH) – for developing a new type of cost effective, highly active and long lasting catalyst which can reform natural gas in IT-SOFC anode environment. Small amount of noble metals Pd, Rh and Pt are used as promoters to enhance the catalyst’s performance as while maintaining the cost relatively low. The research objectives are achieved by a series of studies including catalysts synthesis, characterisation and the catalytic activities. The thesis initially gives a comprehensive review on fuel cell and SOFC technology, steam methane reforming and reforming catalyst to provide better understanding of the research. Experimental studies include the effects of the synthetic conditions of the LDH precursors and thermal treatments on the physical, chemical behaviours and catalytic activities of the catalysts and promotional effects by noble metals. The LDH derived catalysts compositions, promoter quantities and operating conditions are optimised for the best performance in the IT-SOFC anode environment. A new method for the development of precursor sol for easy coating of the anode is developed and studied. The sol preparation is achieved by acid attack. The sol developed is found to produce better coating and has very high catalytic properties after activation. The catalysts developed were tested for their stability and self-activation ability to ensure its use in the commercial cells. The findings of the present study indicate that the catalysts developed show excellent catalytic performance and these catalysts have very high potential for further commercialisation in IT-SOFC.

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Albarazi, Abdulkader. "Development of Ni-based catalysts for methane dry reforming application". Paris 6, 2013. http://www.theses.fr/2013PA066814.

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Blaylock, Donnie Wayne. "Computational heterogeneous catalysis applied to steam methane reforming over nickel and nickel/silver catalysts". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/62730.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 182-188).
The steam methane reforming (SMR) reaction is the primary industrial means for producing hydrogen gas. As such, it is a critical support process for applications including petrochemical processing and ammonia synthesis. In addition, SMR could be an important component of future energy infrastructures as a means for producing hydrogen as an energy carrier for applications including fuel cells in automobiles and direct combustion for electricity generation. Nickel is the preferred SMR catalyst; however, the efficiency of SMR over nickel can be severely hindered by carbon formation, which leads to the deactivation or even destruction of the catalyst particles. Thus, there is significant interest in catalysts that inhibit carbon formation yet retain activity to SMR. In order to develop improved catalysts for SMR, a thorough understanding of the processes occurring on the nickel surface is needed. In this thesis, computational heterogeneous catalysis is applied to investigate steam methane reforming over nickel (Ni) and silver-alloyed nickel (Ni/Ag) catalysts. Electronic structure calculations using density functional theory (DFT) are employed to develop thermochemical landscapes describing the relative stabilities of SMR intermediates on the catalyst surfaces. In addition, DFT calculations are used to obtain kinetic parameters that describe elementary surface reactions taking place during SMR. A detailed statistical thermodynamics framework is developed to allow for the calculation of enthalpies, entropies, and free energies of the surface species at the temperatures and pressures relevant to industrial SMR. The data from the DFT calculations are used to build detailed ab inito microkinetic models of SMR over the multi-faceted nickel catalyst. The resulting microkinetic models are used to provide insight into the processes occurring on the catalyst surface through identifying the most important intermediate species and reactions occurring on the catalyst. The effects of alloying the nickel catalyst with silver are predicted through modeling the dissociative methane adsorption reaction on multiple facets of the Ni/Ag surface with varying concentrations of silver. In addition, DFT calculations are used to investigate carbon formation on the Ni and Ni/Ag catalyst surfaces, including relative stabilities of various carbon-containing intermediates and the effects of alloying the nickel surface with silver on carbon formation.
by Donnie Wayne Blaylock.
Ph.D.

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Paul, Ram Chandra. "Methane steam reforming over LaCr¦1¦-¦xNi¦xO¦3 perovskite catalysts". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0018/MQ49723.pdf.

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McFarlane, Andrew Robert. "The application of inelastic neutron scattering to investigate methane reforming catalysts". Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/4098/.

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Hydrocarbonaceous overlayers formed on a range of nickel alumina and gold-doped nickel alumina catalysts during both the H2O and CO2 reforming of methane has been examined using a number of techniques including thermal studies, XRD, TEM IR and Raman spectroscopy. These techniques have allowed both qualitative and quantitative analysis of the carbon and hydrogen components of coke to be achieved. Both amorphous carbon and filamentous carbon has been observed. Results show that changing the catalyst preparation routine effects the morphology of the carbon in both the CO2 and H2O reforming reactions. The “dry” and steam reforming reactions were also studied by inelastic neutron scattering. This technique has permitted quantitative measurements of the extent of hydrogen retention for the first time and has allowed elementary steps associated with the reaction to be explored from a new perspective. As well as determining the nature and quantity of the hydrocarbonaceous overlayers, the source of the coke has also been considered in the CO2 reforming reaction. Isotopic substitution reactions have been employed to achieve this. Temperature programmed oxidation measurements using a 13CO2 feedstream identify a clear role for the oxidant in the carbon retention process. The combination of techniques outlined above has permitted a series of elementary reactions to be proposed for both reforming reactions. Elementary surface reactions involving hydrogen are shown to be fast and efficient compared to those involving carbon. Furthermore, oxidation of carbon to CO is slower than that of carbon polymerisation. These statements are true for both CO2 and H2O reforming and suggest the CO2 reforming reaction has the potential to represent a environmentally friendly alternative to the industrially preferred steam reforming process. As well as increasing the understanding of these two highly relevant reaction systems, a range of inelastic neutron scattering reactors have been designed, built and tested under reforming conditions in order to accomplish the quantitative hydrogen measurements. An evaluation of these reactors, as well as a description of the development of the INS technique as a quantitative tool is given.

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Ramirez-Cabrera, Elvia. "Oxide catalysts for steam reforming of methane in solid oxide fuel cells". Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271143.

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Cao, Pengfei. "The development of Ni based catalysts for carbon dioxide reforming of methane". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/46876/.

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Recently, with the rapid development of human society, meeting energy demand and controlling climate change are becoming urgent issues. Carbon dioxide (dry) reforming of methane (DRM) has been considered as a promising technology as it utilizes greenhouse gas to provide high value added liquid fuel and chemicals coupling with a Fischer-Tropsch (F-T) process. In other words, this process can both improve supply of liquid fuel and eliminate global warming issues. Since deactivation of catalysts is the major obstacle for commercialization of this approach, deep understanding of this process and development of catalysts with high activity and stability are necessary to be studied. Firstly, a comprehensive thermodynamic analysis of DRM and its side reactions was performed to get a deep understanding of this process. Low CH4/CO2 ratios improve CH4 conversion and CO selectivity, but have negative influence on CO2 conversion and H2 selectivity. While, CH4 conversion, CO2 conversion (T ≥ 630°C), H2 selectivity CO selectivity and carbon formation are all enhanced at high pressures. Severe carbon formation is found at the temperature range of 546 and 703 °C, and carbon free regime is suggested under operating conditions of T ≥ 1000 °C, CH4/ CO2 mole ratio = 1 and pressure = 0.1 MPa. In addition, an index about the relationship of H2/CO mole ratio and operating conditions was established in this study. It is beneficial in both process efficiency and economics in practice as the index can be used to guide the selection of appropriate operating conditions to tune H2/CO mole ratio in syngas to satisfy different requirements of different F-T processes. As drying process has big influence on structure formation of catalysts, the effects of oven drying and vacuum freeze drying on the performance of Ni/Al2O3 in DRM were investigated. The sublimation process in vacuum freeze drying increased the BET surface area but maintain small and uniform pore structure which protect NiO particle from aggregation. Besides, since the solid ice settled nickel nitrate salt in preparation stage, the aggregation of NiO after calcination is also suppressed. Comparing to oven dried catalyst (OD-Cat), anti-deactivation of vacuum freeze dried catalyst (VFD-Cat) was enhanced, which is due to small Ni particle size and high Ni dispersion. The CO2-TPD analysis shows that the amount of basicity on catalyst VFD-Cat is more than it on catalyst OD-Cat, which helps to eliminate coke formation by enhanced the adsorption and activation of CO2. Furthermore, less carbon deposition and less graphic degree coke was detected on spent catalyst VFD-Cat. Overall, vacuum freeze drying technique is suggested to synthesis catalysts for DRM to improve its stability and resistance of coke formation. In this study, the effects of calcination method (i.e. microwave and furnace) on activity and stability of catalyst Ni/Al2O3 were also studied. Microwave calcined catalyst (MC-Cat) showed a better catalytic performance than furnace calcined catalyst (FC-Cat) because of a slow deactivation rate. Because of the advantage of homogeneous volume heating in microwave calcination process, lager total surface area of catalyst and smaller Ni particle with uniform size were observed on catalyst MC-Cat than it on catalyst FC-Cat. Moreover, the amount of basic sites on catalyst MC-Cat was increased under microwave heating, which is contribution to coke formation with less amount and lower graphic degree. Therefore, microwave calcination is suggested to improve the resistance of catalytic deactivation caused by coke deposition. Additionally, the energy saving is more than 90% for microwave calcination in this case as microwave heating is a fast and energy efficiency. To improve the stability of catalyst Ni/γ-Al2O3 in carbon dioxide reforming of methane, K2CO3 was introduced as a promoter to enhance the coke resistance of catalyst. From the results, catalyst promoted with K2CO3 (K-Ni-Al) showed a relative high activity and stability in 100 h of DRM reaction. During long term test, the activity decreased at first 20h then became stable. As K2CO3 has advantages such as high specific heat, good thermal stability, strong basicity and fast heat transfer, it can increase basicity on the surface, control Ni particle size during both reduction and reaction stages, and increase the number of active metallic Ni by weaken the metal-support interactions. Moreover, it was found that that K2CO3 could react with carbon deposition, which could build a micro-cycle to eliminate coke formation.

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Ricca, Antonio. "Innovative catalysts for process intensification of methane reforming and propane dehydrogenation reactions". Doctoral thesis, Universita degli studi di Salerno, 2014. http://hdl.handle.net/10556/1769.

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2012 - 2013
In the early decade, a rapid increase in oil consumption was recorded, that led to a widening between the predicted demand for oil and the known oil reserves. Such trend, mainly due to the growing new economies, is causing a quick increasing in oil price, that effect on European chemical industry competitiveness. In this dramatic scenario, characterized by higher cost of naphtha from crude oil, the ability to exploit novel feeds such as natural gas, coal and biomass may be the keystone for the chemical industry revival. Innovating chemical processes are thus essential for the future of the chemical industry to make use of alternative feedstock in the medium and long term future. In this direction, to open new direct routes with rarely used and less reactive raw feedstock such as short-chain alkanes and CO2 appears one of the most promising breakthrough, since in one hand it may reduce the current dependency of European chemical industry on naphtha, in the other hand may reduce the energy use and environmental footprint of industry. Despite light alkanes (C1–C4) and CO2 are stable molecules hard to activate and transform directly and selectively to added-value products, these challenges could be overcome thanks to relevant process intensifications along with the smart implementation of catalytic membrane reactors. Process intensification consists of the development of novel apparatuses and techniques, as compared to the present state-of-art, to bring dramatic improvements in manufacturing and processing, substantially decreasing equipment size/production capacity ratio, energy consumption, or waste production. The past decade has seen an increase in demonstration of novel membrane technology. Such developments are leading to a strong industrial interest in developing membrane reactors for the chemical industry. The main target of the CARENA is to address the key issues required to pave the way to marketing CMRs in the European chemical industry. The UNISA contribution in CARENA project is to study and optimize supported and unsupported catalysts in order to match to membrane reactors aimed to methane reforming and propane dehydrogenation processes. The guideline of this work was fully jointed to the UNISA involving in CARENA project. The methane reforming routes (steam- and/or auto-thermal-) are processes widely analyzed in the literature, and many studies identified Ni and Pt-group as most active catalysts, as well as the benefits of bimetallic formulation. Moreover, the crucial role of ceria and zirconia as chemical supports was demonstrated, due to their oxygen-storage capacity. In this work, great effort was spent in the reforming process intensification, in order to maximize catalyst exploit in reforming process. In order to minimize mass transfer limitations, without precluding the catalyst-membrane coupling, several foams were selected as catalytic support, and were activated with a catalytic slurry. The performances of such catalysts in the auto-thermal reforming and steam reforming of methane were investigated. Catalytic tests in methane auto-thermal reforming conditions were carried out in an adiabatic reactor, investigating the effect of feed ration and reactants mass rate. Tested catalysts showed excellent performances, reaching thermodynamic equilibrium even at very low contact time. By comparing foams catalyst performances to a commercial honeycomb catalyst, the advantages due to the foam structure was demonstrated. The complex foam structure in one hand promotes a continuous mixing of the reaction stream, in the other hand allows conductive heat transfer along the catalyst resulting in a flatter thermal profile. As a result, the reaction stream quickly reaches a composition close to the final value. Steam reforming catalytic tests were carried out on foam catalysts at relatively low temperature (550°C) and at different steam-to carbon ratios and GHSV values. The catalytic tests evidenced the relevance of heat transfer management on the catalytic performances, since the samples characterized by the highest thermal conductivity showed the best results in terms of methane conversion and hydrogen yield. The beneficial effect was more evident in the more extreme conditions (higher S/C ratios, higher reactants rates), in which the heat transfer limitations are more evident. The selective propane dehydrogenation (PDH) was one of the most attractive challenges of the CARENA project, that points to insert a membrane-assisted PDH process in a wider scheme characterized by the process stream recirculation. This approach requires to minimize inerts utilization and side-products formation. Moreover, no papers are present in literature on the concentrated-propane dehydrogenation, due to the severe thermodynamic limitations. A wide study is present in this work aimed to identify and select an optimal catalytic formulation and the appropriate operating conditions that allows the process intensification for the PDH reaction by means of a membrane reactor. In a first stage, the relevance of side-reactions in the catalytic volume and in the homogeneous gas phase was analyzed, resulting in the optimization of the reaction system. Platinum-tin catalysts were prepared, in order to study the role of each compound on the catalytic performances and lifetime. Preliminary studies have defined the optimal operating conditions, able to minimize the coke formation and then to slow down catalyst deactivation. Several studies on catalyst support highlighted the requirement to use a basic supports with a high specific surface, able to minimize cracking phenomena. Basing on such indications, CARENA partners provided two catalytic formulations optimized with respect the indicated operating conditions, that showed excellent activity ad selectivity. On these catalyst, the effect of the water dilution, the operating pressure and the presence of CO and CO2 was investigated, in order to understand the catalytic formulation behavior in the real scheme conditions. [edited by author]
XII n.s.

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Kim, Do Kyoung. "Combinatorial and conventional development of new catalysts for the CO2 reforming of methane". [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981867316.

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Darujati, Anna Rini Sekar. "Oxidation stability and activity of bulk, supported and promoted molybdenum carbide catalysts for methane reforming". Online access for everyone, 2005. http://www.dissertations.wsu.edu/Dissertations/Spring2005/A%5FDarujati%5F050405.pdf.

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Suhartanto, Thomas. "Modified nickel catalysts for carbon free carbon dioxide reforming of methane to synthesis gas". Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312296.

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Nardi, Giulia. "Synthesis, characterization and testing of catalysts for the methanation and steam reforming of methane reactions". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.

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This work of thesis is focused on the synthesis, characterization and testing of Ni-based catalysts supported on the ZrO2, Ce34Zr66O2, Ce33Zr63Pr4O2 mixed oxides to conduct the reactions of carbon dioxide methanation and steam reforming of methane at low temperature. The catalysts are prepared employing the water-in-oil synthetic technique through the incipient wetness impregnation and bulk methods to evaluate the differences resulting from their performance in a fixed-bed plant. The different supports are compared as well to investigate the effect of the Ce and Pr addition on the oxygen storage capacity of the catalysts and the consequent yields and conversions of methane. The testing of a Ni-impregnated catalyst synthetized at the ICPEES-CNRs of Strasbourg with similar conditions as the ones employed in the laboratory of Bologna constitutes a further comparison to analyze in this work. Several characterization techniques are employed to correlate the structural properties of the samples to their performance in the plant. The comparisons show the bulk-synthetized-samples to achieve higher methane yields with respect to the incipient wetness impregnated ones even though they are significantly subjected to the sintering phenomena that can cause a severe loss of activity. The methane conversion as well shows consistently higher values if the reaction is performed with the bulk-synthetized catalysts, in particular an increasing trend is individuated corresponding to a progressively enhanced oxygen storage capacity that permits to overcome the carbon formation on the catalytic sites. Eventually, the interaction between the support and the active phase is thought to represent the fundamental parameter to consider to achieve higher activities in both of the reactions together with the specific selectivity towards the products.

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Pegios, Nikolaos [Verfasser], Regina [Akademischer Betreuer] Palkovits i Matthias [Akademischer Betreuer] Wessling. "Ni-based catalysts for the dry reforming of methane / Nikolaos Pegios ; Regina Palkovits, Matthias Weßling". Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/117652805X/34.

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Jabbour, Karam. "Combined and dry reforming of methane on new Ni0/diatoms and mesoporous Ni0/alumina catalysts". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066345.

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Le reformage du méthane par CO2 et le bi-reformage (en présence de vapeur d’eau) sont deux procédés catalytiques capables de transformer du CH4 et du CO2 émis par décomposition de la biomasse. Les produits de réaction, H2 et CO sont émis avec des rapports différents, rapport de 1 dans le cas du reformage sec, de 2 dans le cas du bi-reformage. Les catalyseurs à base de nickel sont des candidats prometteurs, actifs et de faible coût en comparaison avec des métaux nobles habituels. Des désactivations par frittage et/ou par formation de dérivés carbonés (coke, nanotubes) sont attendues. La stabilisation des nanoparticules métalliques dans des parois de supports poreux structurés (i.e. Al2O3 and SiO2) est une des méthodes récemment proposée pour lutter contre ces désactivations mais les études de stabilité dans les conditions très dures du bi-reformage (haute température et présence de vapeur d’eau) ne sont pas encore décrites. L’objectif du présent travail était de synthétiser, de caractériser et de tester la stabilité de catalyseurs poreux sous les conditions imposées par le reformage du méthane: (i) d’abord en utilisant un support naturel, pas cher et très facilement accessible, des silices de diatomées macroporeuses, (ii) ensuite en préparant des silices et des alumines mésoporeuses contenant du nickel dispersé par différentes techniques. Les catalyseurs préparés par des techniques “one-pot”, mélanges de précurseurs du nickel et du support sont les catalyseurs les plus stables. Des oxydes destinés à modifier la basicité des supports (MgO, CaO) ont également été ajoutés et ont permis de minimiser la formation de coke pendant les 40h de tests catalytiques de bi-reformage
Dry and combined (steam and dry) reforming of methane are two processes for the conversion of CH4 and CO2 gases emitted from the decomposition of biomass into gaseous mixtures with controllable H2:CO (syngas) molar ratios: value of 1 in the case of dry or around 2 for combined reforming. Nickel based catalysts are found as promising candidates for these reactions displaying high intrinsic activity, lower cost and wider availability than noble metal based materials but deactivating by sintering and/or coke deposition. Stabilization and confinement (occlusion) of small metallic Ni0 nanoparticles within structured (i.e. Al2O3 and SiO2) porous oxide frameworks is one of the recent methods to overcome the deactivation in dry reforming but has not yet been considered under harsh combined reforming (high T and steam) conditions. The main objective of this work was to synthetize, characterize and test new stable catalysts for reforming reactions: (i) based on natural, cheap and widely available macroporous silica diatom oxide as support for Ni- and (ii) synthetized by various methods for control of dispersion and stability inside mesoporous alumina and silica. One-pot mesoporous alumina being the most stable catalysts in combined reforming, some modifiers (MgO or CaO) were added in order not only to get stable catalysts but also to minimize coke formation during long-term (40h) combined reforming reaction

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Pegios, Nikolaos Verfasser], Regina [Akademischer Betreuer] [Palkovits i Matthias [Akademischer Betreuer] Wessling. "Ni-based catalysts for the dry reforming of methane / Nikolaos Pegios ; Regina Palkovits, Matthias Weßling". Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/117652805X/34.

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Najfach, Aaron Jacob. "EFFECT OF MANGANESE AND ZEOLITE COMPOSITION ON ZEOLITE-SUPPORTED NICKEL CATALYSTS FOR DRY REFORMING OF METHANE". Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami1501673873019245.

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23

Daoura, Oscar. "Towards anti-coking and anti-sintering Ni@Silica based catalysts for the dry reforming of methane". Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS679.

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Le reformage à sec du méthane est un processus de conversion de CH4 et CO2 en H2 et CO ou gaz de synthèse avec un rapport molaire de 1, lequel peut servir comme matière première pour la production de carburant liquide par Fischer-Tropsch. Les catalyseurs à base de nickel sont des candidats prometteurs pour cette réaction. Ils présentent une très bonne activité, sont peu coûteux et sont plus disponibles en comparaison avec les matériaux à base de métaux nobles, mais ils se désactivent par frittage et dépôt du coke. La stabilisation de Ni par confinement et/ou par amélioration de la dispersion et de l'interaction des nanoparticules avec la silice font/fait partie des méthodes les plus efficaces et moins coûteuses pour lutter contre la désactivation lors du reformage, ce qui correspond à l’objectif principal de ce travail. Ainsi, de nouveaux catalyseurs à base de Ni, ont été synthétisés, caractérisés et testés en catalyse de reformage à sec de CH4. Trois points principaux ont été examinés: (i) Le test de l’efficacité de nouveaux supports mésoporeux (MCF) en variant la nature des précurseurs de Ni (sels ou colloïdes) incorporés par imprégnation ou synthèse directe après ajustement du pH, (ii) la préparation de monolithes mésoporeux de type SBA-15 avec une très bonne dispersion de Ni incorporé par voie « one-pot », (iii) le contrôle de la dispersion, de la taille des particules de Ni et donc de l’interaction avec de la silice non poreuse via la formation de phyllosilicates de Ni. Au final, les monolithes de type SBA-15 incluant Ni par voie « one-pot » et les particules de Ni0 issues de la réduction des phyllosilicates se sont avérés être les catalyseurs les plus performants
Dry reforming of methane is a process for the conversion of CH4 and CO2 into “syngas”, a gaseous mixture of H2 and CO (with a molar ratio value of 1) that can serve as feedstock for the production of liquid fuel by the mean of Fischer-Tropsch procedure. Nickel-based catalysts are promising candidates for this reaction displaying high activity, lower cost and wider availability than noble metal-based materials but deactivating by sintering and/or coke deposition. Stabilization of Ni0 nanoparticles within siliceous supports either by confinement and/or by improving their dispersion and interaction with the support are among the best and the less expensive methods to overcome the deactivation in dry reforming which represents the main objective for this work. Here, new stable nickel-based catalysts were synthesized, characterized and tested in dry reforming. Three main issues were examined: (i) Testing the efficiency of new mesoporous supports (mesocellular silica foams) using different nickel precursors (salt or colloidal form) incorporated by impregnations or pH adjustment assisted one-pot methods, (ii) designing highly dispersed nickel-based mesoporous monoliths through an original sol-gel method (iii) controlling the nickel size, dispersion and therefore its interaction with the support onto non-porous silica carriers by the mean of phyllosilicates. Monoliths of the SBA-15 type incorporating Ni0 by a one-pot method, and Ni0 obtained through the reduction of nickel phyllosilicates turned out to be the most stable and efficient catalysts

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Homsi, Doris. "Steam reforming of methane ans ethanol over CoₓMg₆₋ₓAl₂, Ru/CoₓMg₆₋ₓAl₂ and Cu/CoₓMg₆₋ₓAl₂ catalysts". Phd thesis, Université du Littoral Côte d'Opale, 2012. http://tel.archives-ouvertes.fr/tel-00920778.

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This work focuses on methane and ethanol conversion to hydrogen in the presence of a catalyst in order to increase the selectivity of the desired product (H₂) and reduce carbon monoxide emission and coke formation. Two kinds of active phase were used (copper and ruthenium) and impregnated on calcined hydrotalcites CoₓMg₆₋ₓAl₂ in order to be evaluated in the methane and ethanol steam reforming reactions. For both reactions, the influence of several factors was evaluated in order to adjust the reaction parameters. It has been shown that catalysts performances for the reforming reactions depend on the content of cobalt and magnesium. High cobalt content enhanced the catalytic activity. 1Ru/Co₆Al₂ catalyst presented the highest activity and stability in the methane steam reforming reaction among the other industrial and prepared catalysts even under a low GHSV and with no hydrogen pretreatment. Reduced ruthenium and cobalt were detected after the reaction by XRD. EPR technique was able to detect negligible amount of two kinds of carbonaceous species formed during the reaction : coke and carbon. On the other hand, 5Cu/Co₆Al₂ catalyst revealed the highest hydrogen productivity in the ethanol steam reforming reaction. However, it suffers from coke formation that deactivated the catalysts after few hours. 5Cu/Co₂Mg₄Al₂ catalyst showed a much lower quantity of carbonaceous species with no deactivating during 50 hours due to the basic character of the magnesium oxide phase present in the support.

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Kaydouh, Marie-Nour. "Confinement effect of Nickel in mesoporous silica-based catalysts for syngas production by reforming of methane with CO2". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066425/document.

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Malgré ses avantages économiques et environnementaux, le procédé de reformage à sec du méthane sur des catalyseurs au nickel supporté se heurte encore à des problèmes de frittage de la phase active (un métal de transition) et de dépôt de carbone, ce qui entraîne une diminution de l'activité catalytique. Cette thèse porte sur l'étude de l'effet de confinement du nickel dans des catalyseurs à base de silice mésoporeuse pour la production de gaz de synthèse par reformage du méthane par le CO2. Dans cette étude, les échantillons ont été caractérisés par physisorption de N2, DRX, MET/MEB, RTP, et, en plus, par Raman, SPX, HTP/SM, ATG/SM pour les catalyseurs après test catalytique. Les résultats montrent qu'un support mésoporeux bien structuré ayant une grande surface spécifique et un grand volume poreux est important pour une meilleure dispersion et stabilisation de la phase active à l'intérieur de la porosité. La silice mésoporeuse de SBA-15 (préparée en grande quantité), composée de grains allongés, semble être appropriée pour atteindre cet objectif. Il est de plus démontré que la formation de petites particules bien confinées à l'intérieur des pores favorise la résistance au dépôt de carbone. Ceci peut être obtenu en imposant un traitement hydrothermal au support, en utilisant la méthode deux solvants pour le dépôt de Ni, en passant à une réduction directe des échantillons non calcinés, en ajoutant du Rh en faibles quantités ou en utilisant du Ce comme promoteur, à condition que le Ni et Ce soient en interaction
Although economically and environmentally advantageous, the methane dry reforming process using supported nickel based catalysts still faces problems of active phase (a transition metal) sintering and of carbon deposition, which result in catalytic activity loss. This thesis is focused on the study of the confinement effect of nickel in mesoporous silica-based catalysts for syngas production by reforming of methane with CO2. In this study, the samples were characterized by N2 sorption, XRD, TEM/SEM, TPR, in addition to Raman, XPS, TPH/MS, TGA/MS for the spent catalysts. The results indicate that a well-structured mesoporous support with high surface area and large pore volume is important for better dispersion and stabilization of the active phase inside the porosity. The mesoporous SBA-15 silica support (prepared in large quantity), composed of elongated grains, appear to be suitable for the purpose. Moreover, it is demonstrated that the formation of small nickel particles well-confined inside the pores favors carbon resistance. This can be achieved by applying hydrothermal treatment to the support, using two solvents method for Ni deposition, using direct reduction of uncalcined samples, adding Rh in small quantities or promoting with Ce, provided that Ni and Ce are in interaction

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Charlesworth, R. J. "The steam reforming and combustion of methane on micro-thin catalysts for use in a catalytic plate reactor". Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246682.

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Norris, Elizabeth L. "Steam reforming of methane over alumina supported nickel catalysts : influence of calcination temperature, gold doping and sulfur addition". Thesis, Keele University, 2013. http://eprints.keele.ac.uk/3817/.

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Alumina supported nickel and gold-doped nickel catalysts have been investigated for their use as hydrocarbon steam reforming catalysts. The influence of calcination temperature during preparation has been investigated using a variety of techniques including X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area analysis, scanning electron microscopy (SEM) and temperature-programmed reduction (TPR). It has been shown that the nickel phases present and their subsequent reducibility are strongly dependent upon the calcination temperature during preparation. As the calcination temperature is increased nickel aluminate (NiAl2O4) is formed and nickel oxide–support interactions increase. The addition of gold to the catalyst increases nickel oxide–support interactions, lowering the sample reducibility and increasing formation of NiAl2O4 at lower calcination temperatures. The calcination temperature significantly influences the steam methane reforming characteristics under both stoichiometric and methane-rich reaction conditions and the presence of unreduced NiAl2O4 significantly alters catalytic activity. Under the reaction conditions employed, the presence of gold provides no long-term benefit towards catalyst performance, resulting in a reduced reforming activity, especially at lower reaction temperatures, and in certain cases an increase in carbon laydown. Sulfur addition to the reaction mixture results in catalyst poisoning and in some cases complete deactivation, particularly at low reaction temperatures. However, sulfur addition does significantly increase resistance to carbon deposition. The addition of sulfur to the reaction mixtures and gold-doping of catalysts provides an increase in carbon resistance, whilst significantly reducing the rate of sulfur poisoning and increasing catalyst lifetime. This research discusses the influence of calcination temperature on steam methane reforming activity, catalyst resistance towards carbon formation and sulfur tolerance under variable reforming conditions over alumina supported nickel and gold-doped alumina supported nickel catalysts.

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Laycock, Christian J. "Studies into carbon deposition and sulphur tolerance of nickel catalysts for carbon dioxide reforming of methane : Implications for biogas utilisation". Thesis, Keele University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.530766.

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Liu, Hongrui. "CO2 Chemical Utilization through Dry Reforming of Methane : Development of Non-Noble Metals Catalysts Supported on Natural and Synthetic Clays". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS480.

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Notre stratégie de développement «croissance à tout prix» a causé de nombreux problèmes environnementaux. Ainsi, la dépendance vis-à-vis des combustibles fossiles tels que le pétrole est encore plus élevée. On se doit de réduire cette dépendance. Parmi les stratégies permettant de réduire cette dépense on peut citer la production d'hydrogène, de gaz de synthèse ou d'autres produits utilisant du CO2 et/ou du CH4. L’utilisant de ces derniers est l'un des moyens prometteurs de convertir les gaz à effet de serre en produits chimiques est le procédé de reformage à sec du méthane. Ainsi, cette thèse vise à proposer de nouveaux supports utilisant de différents promoteurs pour améliorer la sélectivité et la stabilité des catalyseurs à base de nickel pour le reformage à sec du méthane ; et à analyser les performances catalytiques des catalyseurs préparés en associant les effets de température avec des caractérisations physico-chimiques telles que la mesure de surface, la diffraction des rayons X, et la désorption programmée à la température du CO2. Tout d'abord, différents promoteurs avec du nickel ont été imprégnés sur une argile naturelle ou de l’argile modifiée Fe/Cu de Tunisie. Deuxièmement, les catalyseurs dérivés de l'argile synthétique ont été préparés par une méthode de co-précipitation pour rechercher les influences de la structure sur le DRM. Enfin, les catalyseurs ayant la même composition que d'excellents catalyseurs dérivés de Ni-hydrotalcite ont été synthétisés mécaniquement par broyage planétaire pour comparer l'effet de la vitesse de rotation et de la préparation à des synthèses classiques
The development strategy of “growth-at-any-cost” has not been applied to the current development with the increased attention of various countries to environmental issues. But the dependence on fossil fuels such as petroleum will be still high in a short period of time based on the consideration of economic and social development. Thus, the focus on the production of hydrogen, syngas or other products using CO2 and/or CH4 that has attracted more attention in chemical products is the process of dry reforming of methane. Thus, this research focuses on proposing new supports loaded with different promoters to enhance the catalytic selectivity and stability of nickel-based catalysts for dry reforming of methane, and analyze the catalytic performance of prepared catalysts by associating temperature effects with multiple characterizations such as Brunauer-Emmett-Teller, X-ray diffraction, and CO2-temperature programmed desorption. First, different promoters with nickel are impregnated on natural clay or Fe/Cu-modified clay from Tunisia. Second, the synthetic clay derived catalysts are prepared by co-precipitation method to research the influences of structure on the DRM. In the end, the catalysts having the same composition as excellent Ni-hydrotalcite derived catalysts are further synthesized by ball milling to compare the effect of rotational speed and preparation

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Karam, Leila. "New routes of preparation of active and stable mesoporous Ni-alumina based catalysts for methane dry reforming and CO2 methanation". Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS163.pdf.

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Le reformage à sec du méthane (DRM) est un processus qui convertit simultanément CH4 et CO2 en un mélange gazeux de H2 et de CO appelé syngas. Les catalyseurs à base de Ni sont particulièrement prometteurs mais ils ne sont pas stables en raison du frittage du Ni et du dépôt de coke. Dans cette thèse, nous avons développé deux voies de synthèse de catalyseurs mésoporeux à base de Ni-Al2O3 dans lesquels Ni est stabilisé dans l'oxyde, ce qui donne une activité et une stabilité élevées en DRM. Des techniques physicochimiques complémentaires ont été appliquées pour identifier les propriétés des matériaux à toutes les étapes de préparation et d'activation. La première approche comprend la synthèse « EISA one-pot » de matériaux mésoporeux Ni-Mg-Al2O3. L’échantillon à base de 15% en poids de Mg (charge optimale) contribue à une dispersion élevée et homogène de Ni et de Mg tout en préservant la qualité structurale de la matrice Al2O3 mésoporeuse. La basicité accrue renforce l'activité et la stabilité. La seconde méthode consiste à synthétiser des matériaux mésoporeux Ni-Al2O3 innovants en utilisant une structure organométallique (MOF) comme matrice sacrificielle. Cette procédure permet la formation de petites nanoparticules de Ni stabilisées de manière homogène dans le support de grande surface spécifique, insensibles au frittage et à la formation de nanotubes de carbone lors de la réaction de DRM. Les tests catalytiques complétés par des calculs thermodynamiques montrent l’efficacité des matériaux synthétisés non seulement pour le reformage à sec du méthane, mais également pour la méthanation du CO2 et le reformage à sec de biogaz issu de pyrolyse
Dry reforming of methane (DRM) is a process that converts CH4 and CO2 gases into syngas, a gaseous mixture of H2 and CO. Ni based catalysts proved to be suitable for the reaction due to their good activity, wider availability and lower cost than noble-based materials. However, these catalysts are not stable due to Ni sintering and coke deposition. In this thesis we developed two different synthesis routes of mesoporous Ni-Al2O3 based catalysts that can occlude Ni inside the pores achieving high activity and stability in DRM. A set of complimentary physicochemical techniques was systematically applied to thoroughly investigate the materials properties at all steps of preparation and activation. The first approach embraces synthesis of mesoporous Ni-Mg-Al2O3 materials by one-pot EISA strategy. Results demonstrate that 15 wt% Mg (optimum loading) based sample contribute to high and homogenous dispersion of both Ni and Mg, preserving ordered mesoporous Al2O3 walls. The good structural and textural characteristics in addition to the enhanced basicity reinforce activity and stability. The second method involves synthesizing new mesoporous Ni-Al2O3 materials using metal-organic framework as sacrificial template. This procedure results in small Ni nanoparticles homogeneously dispersed and stabilized within the high surface area support resisting sintering and inhibiting carbon nanotubes formation during reforming reaction. Based on catalytic tests completed by thermodynamics calculations, the synthesized materials proved to be eficient not only for dry reforming of methane, but also for CO2 methanation reaction and dry reforming of waste pyrolysis products

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Littlewood, Patrick [Verfasser], Reinhard [Akademischer Betreuer] Schomäcker, Reinhard [Gutachter] Schomäcker i Ulrich [Gutachter] Nieken. "Low temperature dry reforming of methane with nickel manganese oxide catalysts / Patrick Littlewood ; Gutachter: Reinhard Schomäcker, Ulrich Nieken ; Betreuer: Reinhard Schomäcker". Berlin : Technische Universität Berlin, 2016. http://d-nb.info/1156017491/34.

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Papargyriou, Despoina. "Materials and catalysts incorporation for the fuel oxidation layer of oxygen transport membranes". Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/12113.

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Oxygen Transport Membranes (OTMs) can drastically reduce the energy and cost demands of processes that require pure oxygen, as they offer the possibility to combine a separation unit with a chemical reactor. One of the most commercially viable applications of OTMs is the partial oxidation of hydrocarbons for syngas production. A typical OTM configuration is a sequential arrangement of layers, i.e. an inactive support, a fuel oxidation layer, a dense layer and an oxygen reduction layer. However, one of the limitations of the OTM system is the low catalytic activity and stability of the materials currently used for the fuel oxidation layer. Moreover, the traditional deposition techniques that are used for the catalysts preparation are difficult to perform, as the fuel oxidation layer is buried deeply in the structure of the OTM. To simplify the OTM fabrication and improve the catalysts activity and stability, this thesis explores the exsolution of Ni nanoparticles from two different host lattice compositions, as potential materials for the fuel oxidation layer of OTMs. The (La₀.₇₅Sr₀.₂₅)(Cr₀.₅Mn₀.₄₅Ni₀.₅)O₃ (LSCMNi5) perovskite was selected, as the first candidate material for the OTMs. During reduction, the exsolution of Ni nanoparticles from the perovskite lattice took place and enhanced significantly the catalytic activity of the material regarding methane conversion. However, these nanoparticles were oxidised during the first hours of the testing and slowly reincorporated into the perovskite structure, leading to drop in the performance. Thereafter, the (La₀.₇₅Sr₀.₂₅)(Cr₀.₅Mn₀.₄₅Ni₀.₅)O₃ (LSCMNi5) perovskite was selected as an alternative composition. When the oxide lattice was sufficiently reduced, the exsolution of Fe-Ni alloy nanoparticles occurred. The catalytic testing suggested that the Fe-Ni alloy nanoparticles on LSCFNi5 presented lower activity for methane conversion comparing to the Ni nanoparticles on LSCMNi5, but higher stability in oxidising conditions. By increasing the Ni doping on the B-site of LSCF to 15 mol%, the catalytic activity of the material regarding methane conversion was increased and exceeded that of LSCMNi5. A CH₄ conversion of 70% was achieved, which was 20 times higher than that of the initial LSCF perovskite. Therefore, by tailoring the perovskite composition and the exsolution of the Fe-Ni alloy nanoparticles, it was possible to synthesize a material for the fuel oxidation layer of OTMs, which combined the high catalytic activity of Ni and the good redox stability of Fe.

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Bobin, Alexey. "Methane reforming by carbon dioxide over metal supported on nanocrystalline mixed oxides : mechanism and transient kinetics for relating catalysts structure and performance". Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10164/document.

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L'énergie de liaison, la mobilité et la réactivité de l'oxygène dans des matériaux nanocristallins de type cérine-zircone dopée aux terres rares (La, Gd, Pr, Sm) supportant des métaux (Pt, Ni, Ru) ont été étudiées par échange isotopique en réacteurs statiques et traversés (18O2 and C18O2), DTP d'O2, RTP d'H2 et CH4, microcalorimétrie pulsée et réacteur TAP. La mobilité d'oxygène de coeur apparait comme contrôlée par le réarrangement des sphères de coordination des cations Ce et Zr et par des chemins préférentiels le long de chaines Pr3+/Pr4+. En surface et subsurface, ce contrôle se ferait par des interactions fortes métal/support avec l'incorporation de cations métalliques. Cette mobilité de l'oxygène limiterait le vieillissement et le frittage en conditions réalistes de reformage par le gaz carbonique. Des études cinétiques non stationnaires et par marquage isotopique ont permis de proposer un mécanisme bi-fonctionnel fondé sur des étapes rédox indépendantes pour l'activation du méthane et du dioxyde de carbone. L'étape limitante serait l'activation du méthane tandis que l'activation du gaz carbonique s'opérerait plus rapidement sur des sites réduits du support, générant de l'oxygène diffusant aisément vers l'interface métal/support (enthalpie de désorption 600-650 kJ/mol) pour oxyder les fragments du méthane en CO et H2. Dans les meilleures formulations catalytiques, des agrégats Ni-Ru faciliteraient l'activation du CO2 dans son état de transition, en marge de carbonates stables qui restent "spectateurs" de la réaction. Pour le Pt/PrCeZrO, il existerait une autre voie d'activation de carbonates faiblement adsorbés sur des ions Pt+ stabilisés par des cations Pr4+. Cette spécificité confère à cette formulation des perspectives très intéressantes en reformage à sec, notamment sur des supports structurés de type alumine corindon, bien adaptés à des réacteurs compacts à temps courts pour des ressources en gaz dispersées et de capacité limitée
Oxygen bonding strength, mobility and reactivity in nanocrystalline Ln-doped ceria-zirconia (Ln=La, Gd, Pr, Sm) with supported Pt, Ni, Ru were studied by state-of-the-art techniques such as isotopic exchange in static and flow reactors with 18O2 and C18O2, O2 TPD, H2 and CH4 TPR, pulse microcalorimetry and TAP reactor. Bulk oxygen mobility is found controlled by a rearrangement of Ce and Zr cations coordination sphere with doping as well as by fast oxygen migration along Pr3+/Pr4+ cationic chains. Surface and near-surface oxygen mobility appears controlled by a strong metal-support interaction with incorporation of metallic ions into surface layers and domain boundaries. In realistic feeds, the catalytic activity in dry reforming of methane correlates with oxygen mobility, required to prevent coking and metal sintering.Transient kinetic studies (non steady-state and SSITKA) allowed us to propose a bi-functional reaction mechanism corresponding to independent redox steps of CH4 and CO2 activation. The rate- limiting step is shown to be the irreversible activation of CH4 on metal sites, while CO2 dissociation on reduced sites of oxide supports proceeds much faster (being reversible for the steady-state surface) followed by a fast oxygen transfer along the surface/domain boundaries to metal sites where CH4 molecules are transformed to CO and H2. The CH4 selective conversion into syngas would involve strongly bound bridging oxygen species with heat of desorption ::600-650 kJ/mol O2. For optimized formulations, Ni+Ru clusters could be involved in CO2 activation via facilitating C-O bond breaking in the transition state, thus increasing the rate constant of the surface reoxidation by CO2, while strongly bound carbonates behave as spectators. For Pt/PrCeZrO, an additional fast route to syngas would occur on Pt ions with participation of weakly bound carbonates stabilized by neighboring Pr4+ ions. Such specificity makes this system highly promising for methane oxi-dry reforming, especially on structured corundum supports for short contact time compact reactors, well adapted to stranded and limited gas resources

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Bellido, Jorge David Alguiar. "Estudo de catalisadores de níquel suportados em ZrO2 modificados aplicados em reações de reforma". Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-05122008-113631/.

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O óxido de zircônio (ZrO2) é um material com características físicas e químicas que pode ser aplicado em vários campos, tanto de interesse industrial como acadêmico. Dentro da catálise, sistemas baseados em ZrO2 estão ganhando um crescente interesse, seja como suportes ou como catalisadores, tendo em vista que é possível alterar suas propriedades pela adição de diversos cátions. Este trabalho teve por objetivo o estudo de catalisadores de níquel suportados em ZrO2 modificados com os cátions, Mg2+, Ca2+, La3+ e Y3+ em diferentes proporções, e a aplicação dos mesmos nas reações de reforma seca de metano, reforma a vapor de metano, oxidação parcial de metano e reforma a vapor de etanol. Os suportes foram sintetizados pelo método de polimerização para a diluição dos cátions dentro da rede cristalina do ZrO2. A adição do níquel foi feita via impregnação úmida em uma proporção de 5% em massa para todos os suportes. Os suportes e catalisadores foram caracterizados por área superficial especifica, pelo método B.E.T., difração de raios-X, redução a temperatura programada, espectroscopia UV-Vis, ressonância paramagnética eletrônica e condutividade elétrica. A partir das caracterizações verificou-se que os suportes formaram soluções sólidas entre o ZrO2 e os cátions adicionados, em todas as proporções utilizadas. Também se observa que houve a estabilização da fase tetragonal do ZrO2, acompanhado de um aumento na área superficial, quando comparado ao ZrO2 puro, que apresentou uma mistura de fases tetragonal e monoclínica e uma baixa área superficial. As medidas de EPR mostraram a presença de radicais oxigênio cuja proporção aumentou em função do teor de aditivo utilizado no ZrO2, este efeito foi atribuído à presença de vacâncias de oxigênio. Nas medidas de RTP, observou-se uma variação no perfil de redução em função destas vacâncias, onde se identificou um efeito promotor na redução do NiO para menores temperaturas com o aumento do teor dos aditivos no ZrO2. Este efeito pode ser atribuído a interações entre as vacâncias de oxigênio nos suportes e espécies de níquel em contato com elas. Medidas de UV-Vis confirmaram a presença destas interações, que são dependentes tanto do cátion adicionado ao ZrO2, quanto do teor utilizado. As medidas de condutividade elétrica confirmaram a presença de vacâncias de oxigênio nos suportes. Nos ensaios de reforma seca de metano observou-se uma relação entre o comportamento catalítico e a condutividade elétrica dos suportes, sugerindo, assim, a participação das vacâncias de oxigênio na ativação das moléculas oxigenadas. Nos ensaios de reforma a vapor de metano e oxidação parcial de metano esta relação direta não foi observada, o que sugere diferentes mecanismos de ativação das moléculas oxigenadas por parte das vacâncias de oxigênio, além da influência de outros fatores. Nos ensaios de reforma a vapor de etanol, observou-se semelhança entre o comportamento catalítico desta reação e das reações de reforma seca, indicando similaridade na influência das modificações catalíticas no comportamento destas reações.
Zirconium dioxide is a material with physics and chemical characteristics that can be applied in many fields, as academic as industrial. In the catalysis, the interest in systems based on zirconia (ZrO2) are growing- up quickly, as a catalyst as a support, considering that ZrO2 properties can be changed by the addition of different cations. The objective of this work was the study of nickel catalyst supported on ZrO2, modified with the cations: Mg2+, Ca2+, La3+ and Y3+ in different proportions and their performance on catalytic tests of dry reforming of methane, steam reforming of methane, partial oxidation of methane and steam reforming of ethanol. The supports were prepared by the polymerization method for the dilution of the cations in the zirconia lattice. The nickel addition was made wet impregnation in a proportion of 5wt% for all the catalysts. Supports and catalysts were characterized by specific surface area (B.E.T method), Xray diffraction, temperature-programmed reduction, UV-Vis spectroscopy, electronic paramagnetic resonance and electrical conductibility. In the characterizations was observed the formation of solid solutions between the ZrO2 and the cations added in all proportions used. Also, it was observed the stabilization of tetragonal phase of ZrO2, accompanied by an increase in the surface area when compared to the pure ZrO2, which is a mixture of tetragonal and monoclinic phases with low surface area. The EPR measurements showed the presence of oxygen radicals whose proportion increased in function of the additive content in ZrO2, this effect was attributed to the presence of oxygen vacancies. In the TPR measurements, a variation on reduction patterns was observed in function of the oxygen vacancy presence, where is possible to identify a promoter effect on NiO reduction to lower temperature with the additive load increase in ZrO2. This effect can be attributed to interactions between the oxygen vacancies of support and nickel species close to them. UV-Vis measurements confirmed these interactions presence that are dependent both of the cation added as well the load used. The electrical conductivity measurements confirm the presence of oxygen vacancies in the supports. In the dry reforming of methane was observed a relation between the catalytic behavior and the electrical conductivity of the supports. This observation suggests the oxygen vacancies participation on oxygenates molecules activation. In the steam reforming of methane and the partial oxidation of methane this relation was not found, suggesting different ways for oxygenates molecules activation by the oxygen vacancies, besides other factors. In the steam reforming of ethanol, it was observed relation between the catalytic behavior of this reaction and the dry reforming of methane, indicating similarity on the influence of the catalyst modifications on the catalytic behavior of these reactions.

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Abreu, Amanda Jordão de. "Efeito da adição de CeO2 no catalisador Ni/Al2O3 aplicado durante as reações de reforma a vapor e com dióxido de carbono do metano". Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-18042008-152035/.

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Na atualidade, a reforma do metano é de grande interesse industrial para o aproveitamento deste gás na produção de hidrogênio e de gás de síntese. Entre as reações de reforma do metano, destacam-se as reações de reforma a vapor e a reação com dióxido de carbono.O catalisador comumente utilizado nos processos re reforma do metano é Ni/Al2O3. Porém durante este processo, ocorre uma indesejada formação de depósitos de espécies carbonáceas na superfície deste catalisador, os quais levam a sua destruição mecânica e conseqüentemente sua desativação. Por isso, uma das propriedades mais importantes de um bom catalisador para as reações de reforma do metano é a sua resistência à desativação. Entre as propostas para melhorar o desempenho do catalisador encontra-se a incorporação do óxido de céria junto ao suporte alumina.Catalisadores 5%Ni/xCeO2/Al2O3 (x = 0, 1, 5, 10, 20 e 100%) forma preparados, caracterizados e submetidos a ensaios catalíticos nas reações de reforma a vapor e com dióxido de carbono de metano com objetivo de avaliar o efeito da adição de céria ao suporte.Os suportes e os catalisadores forma obtidos pelo método de impregnação e calcinados a 500ºC. Estes compostos foram caracterizados por Fisissorção de Nitrogênio pelo método B. E. T., Espectroscopia dispersiva de raios-X (EDX), espectroscopia de na região do ultra violeta e do visível (UV-vis-NIR) e Redução à Temperatura Programada (RTP). Após todas as reações catalíticas verificou-se que a adição de céria é benéfica ao catalisador Ni/Al2O3 e entre todos os catalisadores avaliados, o melhor desempenho obtido foram dos catalisadores contendo 20% de céria em massa, seguido do catalisador contendo 10%.
Nowadays, the methane reforming is large interest industrial for the take advantage of these gas in production the hydrogen and synthesis gas (syngas). Among in the reactions of methane stand of the reactiosn steam reformig and carbon dioxide reforming of methane. The main catalysts uses in the methane reforming is Ni/Al2O3. However, the supported-nickel catalyst is susceptible to the deactivation or the destruction by coke deposition. The carbon dissolves in the nickel crystallite and its diffuses through the nickel, leading for formation of the carbon whiskers, which results in fragmentation of the catalyst. Modification of such catalysts, like incorporation of suitable promoters, is desirable to achieve reduction of the methane hydrogenolysis and/or promotion of the carbon gasification. Catalysts 5%Ni/xCeO2/Al2O3 (x = 0, 1, 5, 10, 20 e 100%) were prepared, characterized and evalueted in reactions steam and carbon dioxide refoming of methane with objetive the value effect loading oxide ceria in support. The suppots and catalysts were prepared by impregnation method and calcined at 500ºC. The supports and catalysts were characterized by X Nitrogen Adsorption by B.E.T., method -rays diffraction (XRD), , Xrays dispersive spectroscopy (XDS), to spectroscopy in the region of the ultraviolet and the visible (UV-vis NIR) to and temperature programmed reduction (TPR). After all the catalytic reactions check which the addition of cerium is beneficial for Ni/Al2O3 catalysts and the best catlysts is 5%Ni/20%CeO2/Al2O3 following 5%Ni/10%CeO2/Al2O3.

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Abreu, Amanda Jordão de. "Desenvolvimento e caracterização de catalisadores de níquel suportados em matrizes CeO2-ZrO2-Al2O3, CeO2-La2O3-Al2O3 e ZrO2-La2O3-Al2O3 avaliados para as reações de reforma do metano". Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-24072012-135713/.

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A reforma do metano é um processo de grande interesse industrial para a produção de hidrogênio e de gás de síntese. Entre as reações de reforma do metano, destacam-se as reações de reforma a vapor e a reação com dióxido de carbono. O catalisador comumente utilizado nos processos e Ni/Al2O3. Porém, durante este processo, ocorre uma indesejada formação de depósitos carbonáceos na superfície do catalisador, os quais levam a sua destruição mecânica e, consequentemente, sua desativação. Por isso, uma das propriedades mais importantes de um bom catalisador para as reações de reforma do metano é a sua resistência a desativação. Entre as propostas para melhorar o desempenho do catalisador encontra-se a incorporação do óxido de cério junto ao suporte alumina. Catalisadores Ni/Al2O3 incorporados em soluções sólidas formadas por CeO2-ZrO2, ZrO2-La2O3 e CeO2-La2O3 foram preparados, caracterizados e submetidos a ensaios catalíticos nas reações de reforma a vapor e com dióxido de carbono e oxidação parcial do metano com objetivo de avaliar o efeito da adição da solução sólida ao suporte. Os suportes foram preparados pelo método da co-precipitação e os catalisadores foram obtidos pelo método de impregnação e calcinados a 500°C. Estes compostos foram caracterizados por Fisissorção de Nitrogênio, Difração de Raios X (DRX), Espectroscopia dispersiva de raios X (EDX), espectroscopia de na região do ultra violeta e do visível (UV-vis-NIR), Redução à Temperatura Programada (RTP), Espectrocopia RAMAN, Espectroscopia fotoeletrônica de Raios X (XPS), Espectroscopia de absorção de Raios X (XAS) e Análise termogravimétrica. Os ensaios catalíticos mostraram que a adição de solução sólida melhorou o desempenho do catalisador Ni/Al2O3 e, dentre todos os catalisadores avaliados, os melhores desempenhos obtidos foram com os catalisadores suportados em Ni/CeO2-La2O3-Al2O3.
Nowadays, the methane reforming is large interest industrial for the take advantage of these gas in production the hydrogen and synthesis gas (syngas). Among in the reactions of methane stand of the reactions steam reforming and carbon dioxide reforming of methane. The main catalysts uses in the methane reforming is Ni/Al2O3. However, the supported-nickel catalyst is susceptible to the deactivation or the destruction by coke deposition. The carbon dissolves in the nickel crystallite and its diffuses through the nickel, leading for formation of the carbon whiskers, which results in fragmentation of the catalyst. Modification of such catalysts, like incorporation of suitable promoters, is desirable to achieve reduction of the methane hydrogenolysis and/or promotion of the carbon gasification. Catalysts 5% Ni/Al2O3 supported on solid solutions formed by ZrO2-CeO2, La2O3 and CeO2-ZrO2-La2O3 were prepared, characterized and evalueted in reactions steam and carbon dioxide refoming and partial oxidation of methane with objetive the value effect loading solution solid in support. The supports were prepared by co-precipitation method and catalysts were prepared by impregnation method and calcined at 500°C. The supports and catalysts were characterized by Nitrogen Adsorption, method -rays diffraction (XRD), X-rays dispersive spectroscopy (XDS), spectroscopy in the region of the ultraviolet and the visible (UV-vis NIR) to and temperature programmed reduction (TPR), RAMAN Spectrocopy, X-ray absorption spectroscopy and Termogravimetric Analysis. After all the catalytic reactions check which the addition of solid solution is beneficial for Ni/Al2O3 catalysts and the best catalysts are Ni/CeO2-La2O3-Al2O3.

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Ferreira, Orlando Lima de Sousa. "Conversão de biogás em gás de síntese via reações de reforma do metano com CO2 e a vapor sobre catalisadores de Ni-Y-Al". Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-26072010-140022/.

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Devido a crescente busca por fontes de energia que utilizem combustíveis renováveis, a utilização do biogás (mistura de gases produzida durante a digestão de matéria orgânica) proveniente do tratamento anaeróbio de águas residuárias e esgotos, surge como um processo promissor para a produção de gás de síntese (mistura de H2 e CO), contribuindo para a geração de produtos de maior valor agregado e para o aproveitamento de rejeitos industriais e domésticos. O biogás normalmente é composto de 60-65% de CH4 e 30-35% de CO2 e, de acordo com a composição do biogás, pode-se combinar processos de reforma do metano com CO2 e reforma a vapor do metano de modo a maximizar o consumo do CH4 excedente presente no biogás, para a geração de gás síntese. Catalisadores baratos e eficientes devem ser desenvolvidos para estas aplicações. Este trabalho tem como objetivo o estudo das melhores combinações destas reações em função da composição de alimentação do reator, aliado ao desenvolvimento de catalisadores de níquel, ítrio e alumínio, buscando minimizar a deposição de carbono, que é o principal problema encontrado nestes processos. Os catalisadores foram preparados pela técnica de coprecipitação de óxido de ítrio e alumínio, no qual se impregnou o óxido de níquel. Os catalisadores foram caracterizados por diversas técnicas: EDX, método B.E.T., DRX, RTP, XAS, além dos ensaios catalíticos para as reações de reforma do metano: com CO2, a vapor e oxidativa. Os resultados mostraram que é possível a preparação de catalisadores de níquel suportado em mistura de Y2O3-Al2O3, e que eles são ativos para as reações de reforma do metano.
Due to the considerable growth in the demand for energy sources that use renewable fuels, the use of biogas (a mixture of gases produced during digestion of organic matter) from the anaerobic treatment of wastewater and sewage, appears as a promising process for the production of synthesis gas (mixture of H2 and CO), contributing to the generation of products with higher value and the use of industrial wastes and domestic. Biogas is typically composed of 60-65% of CH4 and 30-35% of CO2 and, according to the composition of biogas, it can combine the reform processes of methane with CO2 and steam reforming of methane to maximize the consumption of CH4 excess present in the biogas to the production of the synthesis gas. Cheap and efficient catalysts must be developed for these applications. This paper aims to study the best combinations of these reactions depending on the feed composition of the reactor, coupled with the development of catalysts of nickel, yttrium and aluminum in order to minimize the carbon deposition, which is the main problem in these processes. The catalysts were prepared by the technique of co-precipitation of yttrium oxide and aluminum, which is impregnated nickel oxide. The catalysts were characterized by different techniques: EDX, BET method, XRD, TPR, XAS, and catalytic tests for methane reforming reactions: CO2, steam and oxidative. The results showed that it is possible to prepare nickel catalysts supported on mixed Y2O3-Al2O3, and they are active for the methane reactions.

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Mette, Katharina [Verfasser], Malte [Akademischer Betreuer] Behrens, Robert [Akademischer Betreuer] Schlögl, Thorsten [Akademischer Betreuer] Ressler i Martin [Akademischer Betreuer] Muhler. "Development of hydrotalcite-derived Ni catalysts for the dry reforming of methane at high temperatures / Katharina Mette. Gutachter: Robert Schlögl ; Thorsten Ressler ; Martin Muhler. Betreuer: Malte Behrens". Berlin : Technische Universität Berlin, 2015. http://d-nb.info/1075807751/34.

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Swirk, Katarzyna. "Design of new catalysts for chemical CO2 utilization". Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS367.

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Le reformage de CH4, qui fait partie des technologies de valorisation du CO2, est considéré comme une voie intéressante pour la production de gaz de synthèse. Les hydroxydes à double couche (HDC) contenant du Ni, Al2O3, MgO ont des propriétés prometteuses. Le dopage par Y, Zr ou Ce a également montré une influence positive sur l’activité catalytique. L’objectif de cette thèse était donc d’évaluer des HDC Ni/Mg/Al dopés par Y, et Zr ou Ce dans la réaction de reformage à sec du méthane (DRM), l’oxydation partielle du méthane (POM), l’oxydation partielle combinée au reformage du méthane (CRPOM) et le tri-reformage du méthane (TRM). Les catalyseurs ont été caractérisés par XRD, XRF, N2-sorption, TPR-H2, TPD-CO2, chimisorption d’H2, TEM, HRTEM, TGA et spectroscopie Raman et testés en TPSR de 600 à 850 °C et à 700 °C pendant 5h. En DRM, en présence de Y, la dispersion de Ni et la SBET ont augmenté. La co-imprégnation de Zr et Y a conduit à une meilleure stabilité due à la formation d’une phase YSZ. L'addition de Zr et Y par co-précipitation a permis d’augmenter la dispersion de Ni et la basicité totale. En reformage « oxydant », HTNi et HTNi-Y2.0 ont été testés. En POM, HTNi et HTNi-Y2.0 sont actifs et stables avec H2/CO≈2.0. En CRPOM, on observe une conversion plus élevée de CH4, mais moins importante pour le CO2 comparée au DRM. L'ajout d'O2 dans le mélange réactionnel a donc contribué à l'élimination du carbone. La formation de carbone est limitée avec un rapport CO2/H2O=1 (TRM). Cependant, avec CO2/H2O = 0,5, une grande quantité de C est toujours présente et la stabilité structurelle de HTNi-Y2.0 est influencée négativement lorsque la périclase est transformée en hydroxyde
Reforming of methane, belonging to the Carbon Capture and Utilization technologies, is considered an attractive route for syngas production. Double-layered hydroxides (DLHs) with Ni, Al2O3, MgO components were reported to have promising properties. Promotion with yttrium, zirconium or cerium also positively influence the catalytic performance. Thus, the goal of this PhD thesis was to evaluate the catalytic behavior of Ni/Mg/Al DLHs promoted with Y, and Zr or Ce in dry reforming of methane (DRM), partial oxidation of methane (POM), partial oxidation combined with methane reforming (CRPOM), and tri-reforming of methane (TRM). The catalysts were characterized by XRD, XRF, N2 sorption, TPR-H2, TPD-CO2, H2 chemisorption, TEM, HRTEM, TGA and Raman spectroscopy and tested in TPSR from 600 to 850°C, and at 700°C for 5h. In DRM, the Y promotion increased Ni dispersion and SBET, especially with 2 wt.%. Zr and Y co-impregnation resulted in the YSZ phase formation leading to better stability. The Zr and Y introduction during co-precipitation step increased the Ni dispersion and the total basicity, similarly as for Ce and Y promoted materials. In the oxidative reforming, HTNi and HTNi-Y2.0 were tested. In POM, both were active and stable with H2/CO≈2.0. CRPOM tests showed higher CH4 conversion, but lower for CO2 as compared to DRM. Addition of O2 in the gas feed greatly contributed to the C removal. The carbon formation was inhibited when CO2/H2O=1 during TRM tests. However, with CO2/H2O=0.5, a high amount of C was formed, and the structural stability of Y-catalyst was negatively influenced as periclase was transformed into hydroxides

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Beheshti, Askari Abbas [Verfasser], Serena [Gutachter] DeBeer, Martin [Gutachter] Muhler i Wolfgang [Gutachter] Kleist. "In-situ scanning transmission x-ray microscopic study of dry methane reforming catalysts / Abbas Beheshti Askari ; Gutachter: Serena DeBeer, Martin Muhler, Wolfgang Kleist ; Fakultät für Chemie und Biochemie". Bochum : Ruhr-Universität Bochum, 2020. http://d-nb.info/121266423X/34.

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Berrocal, Guillermo José Paternina. "Desenvolvimento de catalisadores baseados em níquel e rutênio para a reforma do metano". reponame:Repositório Institucional da UFBA, 2009. http://www.repositorio.ufba.br/ri/handle/ri/11735.

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Níquel suportado em alumina tem sido reconhecido como um catalisador efetivo das reações de reforma de metano. No entanto, ele apresenta desativação por coque e problemas de estabilidade térmica, em altas temperaturas, principalmente devido à transição de fase do suporte e sinterização do metal. Uma opção atrativa, para obter suportes mais adequados para esses catalisadores, é a combinação da alumina com a zircônia que possui elevada estabilidade térmica, dureza e propriedades anfotéricas. Por outro lado, a adição de metais nobres ao catalisador de níquel usado na reforma de metano poderia evitar a desativação por formação de coque, assim como conduzir a atividades mais elevadas. Desta forma, neste trabalho, foram estudados catalisadores de níquel associados, ou não, ao rutênio suportados em óxidos de alumínio e zircônio, destinados à reforma a vapor e reforma autotérmica de metano. . Foram sintetizados catalisadores monometálicos de níquel (15 %) e bimetálicos de níquel (15 %) e rutênio (razão molar Ru/Ni = 0,1), por impregnação em óxidos de alumínio e/ou zircônio. Estes sólidos foram preparados por métodos de precipitação à temperatura ambiente, a partir de soluções de oxicloreto de zircônio e nitrato de alumínio, obtendo-se materiais com razões molares Al/Zr = 1, 2, 5 e 10 além do óxido de zircônio e de alumínio puros. As amostras foram caracterizadas por espectroscopia no infravermelho com transformadas de Fourier, termogravimetria, análise térmica diferencial, difração de raios X, redução a temperatura programada e medidas de área superficial específica e porosidade. Os catalisadores foram testados na reação de reforma a vapor e autotérmica de metano na faixa de 450 a 750 ºC. . Observou-se a formação da fase γ-Al2O3 na alumina pura e a fases tetragonal e monoclínica na zircônia pura. Com a adição de alumínio à zircônia houve a estabilização da fase tetragonal em todos os casos, em detrimento da monoclínica. A adição de pequenas quantidades de zircônio ao óxido de alumínio produziu um aumento na área superficial especifica da alumina, associado à ação textural do zircônio como espaçador entre as partículas de óxido de alumínio ou à geração de tensões no sólido, causando o deslocamento do equilíbrio para a formação de partículas menores. A adição dos metais (níquel e rutênio) ao suporte causou diminuição da área superficial específica, o que pode estar associado ao bloqueio de alguns poros por esse metal e/ou à sinterização da amostra após a impregnação e calcinação ou a uma combinação desses efeitos. A redução do níquel foi facilitada pela presença do zircônio e/ou do rutênio. Todos os catalisadores foram ativos na reação de reforma a vapor e na reforma autotérmica de metano, observando-se aumento na conversão de metano com a temperatura. Na reação de reforma a vapor e na reforma autotérmica, observouse, que em temperaturas típicas dessas reações, o catalisador de níquel impregnado no suporte com razão molar Al/Zr =10 levou às conversões mais elevadas. O rutênio produz um efeito similar, em catalisadores de níquel isentos de zircônio. Dessa forma, as amostras mais promissórias são aquelas contendo níquel suportado em alumina contendo zircônio ou rutênio.
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Tillmann, Lukas [Verfasser], Martin [Gutachter] Muhler i Wolfgang [Gutachter] Kleist. "Kinetic studies on the dry reforming of methane applying heterogeneous Nickel catalysts with controlled metal dispersion and active supports / Lukas Tillmann ; Gutachter: Martin Muhler, Wolfgang Kleist ; Fakultät für Chemie und Biochemie". Bochum : Ruhr-Universität Bochum, 2020. http://d-nb.info/1204258465/34.

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El, Solh Tarek. "Heterogeneous catalyst for methane reforming". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0007/MQ30748.pdf.

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Rêgo, de Vasconcelos Bruna. "Phosphates-based catalysts for synthetic gas (syngas) production using CO2 and CH4". Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2016. http://www.theses.fr/2016EMAC0004/document.

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Parmi les produits issus de la biomasse ou de la transformation des déchets organiques, le CO2 et le CH4 sont des intermédiaires chimiques importants qui ont de forts impacts environnementaux. En effet, ils sont les principaux gaz responsables de l'effet de serre et leur atténuation est un enjeu majeur. Une voie intéressante pour la valorisation de ces gaz est le reformage à sec du méthane (DRM), qui convertit le CO2 et le CH4 en gaz de synthèse (mélange d'hydrogène et de monoxyde de carbone). Ce mélange peut être utilisé pour plusieurs applications telles que la production de méthanol, d'éther diméthylique, d'hydrogène et des hydrocarbures liquides. Malgré cet intérêt, l'exploitation du DRM à l'échelle industrielle n'a pas encore vu le jour. La raison principale est la désactivation rapide des catalyseurs en raison des conditions sévères de fonctionnement du procédé (température élevée, dépôt de carbone). Cette thèse porte sur le développement de nouveaux catalyseurs à base de phosphate de calcium (CaP) dopés avec des métaux de transition pour la valorisation du CO2 et du CH4 en gaz de synthèse par DRM. Les CaP sont utilisés car ils possèdent des propriétés avantageuses en catalyse hétérogène comme la présence simultanée de sites acides et basiques, bonne stabilité thermique, large gamme de surface spécifique ... Dans un premier temps, des études sur les méthodes de synthèse de catalyseurs et sur la performance de différents métaux de transition (Zn, Fe, Co, Cu, Ni) ont été effectuées dans le but de sélectionner le catalyseur et sa méthode de préparation. Un réacteur à lit fixe capable de fonctionner à hautes température et pression a ensuite été testé pour un long temps de réaction afin d'évaluer correctement la performance des catalyseurs préparés. Ensuite, une étude paramétrique détaillée a été menée. L'influence des paramètres tels que le prétraitement des catalyseurs, la température (T = 400-700°C) et la pression (P = 1-25bar) de la réaction et les différents supports (hydroxyapatite, alumine) ont été étudiés. Enfin, la stabilité thermique et catalytique a été étudiée durant 300h de réaction. Les catalyseurs à base de CaP ont montré des rendements plus élevés en gaz de synthèse en comparaison aux catalyseurs commerciaux. Ces catalyseurs sont donc compétitifs dans les mêmes conditions opératoires (T = 700°C, P = 1bar, WHSV = 12272mLh-1gcat-1, t = 300h). Ce travail a montré l'intérêt des catalyseurs à base de CaP pour des processus à haute température, tel que le reformage à sec du méthane
Among the products resulting from biomass or organic waste transformation, CO2 and CH4 are important chemical intermediates. They also have a strong environmental impact since they are primarily responsible for the greenhouse effect and their mitigation is a key issue. An attractive way of valorization of such gases is the dry reforming of methane (DRM), which converts CO2 and CH4 into syngas (mixture of hydrogen and carbon monoxide). This mixture can be used for several applications, such as the production of methanol, dimethyl ether, hydrogen and liquid hydrocarbons. Despite such interest, the exploitation of DRM on industrial scale has not emerged yet. The main reason is the rapid deactivation of the catalysts due to the severe operating conditions of the process (high temperature, carbon deposition). This thesis focuses on the development of new catalysts based on calcium phosphate (CaP) doped with transition metals for the valorization of CO2 and CH4 through DRM. Actually,CaP has advantageous properties in heterogeneous catalysis, as the simultaneous presence of acid and basic sites, good thermal stability, and wide range of surface area... Initially, a study on the catalyst synthesis methods and an investigation of the performance of different transition metals (Zn, Fe, Co, Cu, Ni) were carried out in order to select the catalyst system and the preparation method. Secondly, a fixed-bed reactor capable of operating at high temperature and pressure and for log time on stream was built and implemented during this work in order to properly evaluate the performance of the preparedcatalysts. Then, a detailed parametric study was conducted. The influence of parameters such as catalyst pre-treatment, temperature (T = 400-700°C) and pressure (P = 1-25bar) of the reaction and support (hydroxyapatite, alumina-based supports) were investigated. Finally, the catalytic stability was studied for 300h of time on stream (TOS). The CaP catalysts showing higher yields on syngas were compared to commercial catalysts. Our catalysts showed to be competitive in the same operating conditions (T = 700°C, P = 1bar, WHSV = 12272mLh-1gcat-1,TOS = 300h). This work shows the interest of CaP catalysts for high temperature process, such as dry reforming of methane

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Xavier, Thiago Padovani. "Reforma de biogás para produção de hidrogênio usando catalisadores tipo perovskitas a base de lantânio e níquel, dopados com cério". Universidade Federal de Uberlândia, 2011. https://repositorio.ufu.br/handle/123456789/15208.

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In the present study, the behavior of La1-xCexNiO3 (x = 0; 0.05 and 0.10) perovskite-type oxides catalysts was investigated, acting as catalysts, in reactions of dry reforming of methane (DRM) and biogas reforming (BR). The catalysts were synthesized by sol-gel method (or citrate) and by combustion with urea. Later, they were structurally evaluated and studied on the catalytic performance. The synthesized perovskite-type oxides were characterized by X-ray diffraction, nitrogen adsorption temperature programmed reduction and thermal gravimetric analysis. The catalysts showed low values of specific area (< 10 m2 g-1). The LaNiO3 phase present in all the calcined samples was converted into La2O3, Ni0 and La(OH)3 after reduction, keeping the phase CeO2 in the doped samples with cerium. It was observed more evident La(OH)3 phase in the samples synthesized by combustion method. The average crystallite sizes, on the main stage LaNiO3, remained between 13 to 17 nm. La0,90Ce0,10NiO3 synthesized by combustion had the lowest average crystallite size whereas La0, 95Ce0,05NiO3 and La0,90Ce0,10NiO3 synthesized by sol-gel method has the highest value. The sol-gel method produced NiO grains (20-25 nm) smaller than those produced by the combustion method (31 - 38 nm). But for all samples is observed a decrease in average Ni0 grain sizes after reduction. In the samples synthesized by combustion method the mean Ni0 crystallite size were similar (20, 19 and 21 nm), whereas the values increased with Ce addition (13 21 nm) in the samples synthesized by sol-gel method. All samples with 1:9 dilution (catalyst/ inert SiC) were active, stable and resistant to deactivation by coke deposition after 24 h of DRM and BR reactions, but with molar ratio H2/CO < 1. The La0,90Ce0,10NiO3 catalyst synthesized by sol-gel method, with 1:1 dilution (catalyst/ inert SiC) showed the greatest resistance to the carbon formation (1,06 mg Carbon / gcat h). The catalysts synthesized by the combustion method, when 1:9 diluted, showed TOFCH4 values between 13 - 16 in the DRM and between 15 - 19 in BR, with molar ratio H2/CO next 1. The catalysts synthesized by combustion method, with 1:1 dilution (catalyst/inert SiC) were more active (TOFCH4 8 13 h-1) in BR reaction than the catalysts synthesized by sol-gel method (TOFCH4 3 4 h-1). The lower values for the stoichiometric H2/CO <1 indicate favoring the reverse reaction of water-gas shift in catalytic tests, supported by the fact that higher CO2 conversion in all reactions usin catalysts with 1:9 dilution. There was a molar ratio H2/CO increase in the RB, especially when used as the catalyst with 1:1 dilution (catalyst/inert SiC), indicating that reverse water-gas shift reaction is less favored when feed CH4: CO2 = 2 and using a larger amount of catalyst.
No presente trabalho, foi avaliado o comportamento de óxidos do tipo perovskitas La1-xCexNiO3 (x = 0; 0,05 e 0,10), atuando como catalisadores, frente às reações de reforma seca do metano (RSM) e reforma de biogás (RB). Os catalisadores foram sintetizados pelo método sol-gel (ou citrato) e pelo método de combustão com uréia. Posteriormente, foram avaliados estruturalmente e quanto ao seu desempenho catalítico. Os precursores catalíticos foram caracterizados por difração de raios X, medidas de área específica BET, redução a temperatura programada e análise termogravimétrica. Todos os catalisadores apresentaram baixos valores de área específica (< 10 m2 g-1). A fase principal LaNiO3, presente em todas as amostras calcinadas, foi convertida em La2O3, Ni0 e La(OH)3 após redução, sendo observada a fase CeO2 nas amostras dopadas com cério. A presença da fase La(OH)3 foi mais evidente nas amostras sintetizadas pelo método de combustão. Os tamanhos médios de cristalito, referentes à fase principal LaNiO3, se mantiveram entre 13 17 nm. A amostra La0,90Ce0,10NiO3 sintetizada pelo método de combustão apresentou o menor tamanho médio de cristalito enquanto que as amostras La0,95Ce0,05NiO3 e La0,90Ce0,10NiO3 sintetizadas pelo método sol-gel tem o maior valor. O método sol-gel produziu tamanhos médios de cristalito do NiO (20 25 nm) menores do que os produzidos pelo método de combustão (31 38 nm). Porém, para todas as amostras, é observada uma diminuição nos tamanhos médios de cristalito de Ni0 após a redução/passivação. Nas amostras sintetizadas pelo método de combustão os tamanhos médios de cristalito do Ni0 foram semelhantes (20, 19 e 21 nm), enquanto que nas amostras sintetizadas por sol-gel os valores cresceram com a adição de Ce (13 21 nm). Todas as amostras com diluição de 1:9 (catalisador/inerte SiC) foram ativas, estáveis e resistentes à desativação pela deposição de coque após as 24 h das reações RSM e RB, porém com razão molar H2/CO < 1. O catalisador La0,90Ce0,10NiO3 sintetizado pelo método sol-gel, com diluição 1:1 (catalisador/inerte SiC) apresentou a maior resistência à formação de carbono (1,06 mg Carbono / gcat h). Os catalisadores sintetizados pelo método de combustão, quando diluídos 1:9 (catalisador/inerte SiC), apresentaram valores de TOFCH4 entre 13 16 h-1 na RSM e entre 15 - 19 h-1 na RB com razões molares H2/CO próximas de 1. Os catalisadores sintetizados pelo método de combustão com diluição de 1:1 (catalisador/inerte SiC) se mostraram mais ativos (TOFCH4 8 13 h-1) na RB do que os catalisadores sintetizados pelo método sol-gel (TOFCH4 3 4 h-1). Os valores menores que o estequiométrico para H2/CO < 1 indicam o favorecimento da reação reversa de deslocamento gás-água nos testes catalíticos, fato suportado pela maior conversão de CO2 em todas as reações utilizando catalisadores com diluição 1:9. Na condição de RB houve um aumento da razão molar H2/CO, especialmente quando forma utilizados os catalisadores com diluição 1:1 (catalisador/inerte SiC), indicando que reação reversa de deslocamento gás-água é menos favorecida quando a razão de alimentação é de CH4:CO2 = 2 e utilizando uma maior quantidade de catalisador.
Mestre em Engenharia Química

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Kumarasamy, Puvaneswary. "Heterogeneous catalysis for methane oxidation". Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326890.

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47

Liu, James. "Kinetics, catalysis and mechanism of methane steam reforming". Digital WPI, 2007. https://digitalcommons.wpi.edu/etd-theses/68.

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The search for an alternative clean and renewable energy source has become an urgent matter. One such energy-saving technology is a fuel cell; it uses fuel as the source of energy to produce electricity directly and the byproducts formed are not as voluminous and environmentally harmful. The conventional low temperature fuel cells use hydrogen as the fuel which is produced from conventional fuels via reforming. However, developing reformers for hydrocarbon fuels requires AN understanding of the fundamental mechanisms and kinetics studies. In this study, simple hydrocarbon fuel, namely methane, in external reforming or internal reforming within a solid oxide fuel cell has been studied because of its importance and with the hope that it will ultimately lead to an understanding of reforming of higher hydrocarbons, such as logistic fuels like JP-8. For this purpose, methane was used the starting point and building block for the progressive understanding of reforming of complex hydrocarbons. Methane steam reforming (MSR), CH4 + 2H2O = CO2 + 4H2 is, in fact, the most common method of producing commercial bulk hydrogen along with the hydrogen used in ammonia plants. United States alone produces 9 million tons of hydrogen per year. The overall MSR reaction CH4 + 2H2O = CO2 + 4H2 is in fact composed of two reactions, the water gas shift reaction, CO + H2O = CO2 + H2, which has recently been investigated by a former Ph.D. student in our group, Caitlin Callaghan. Here, the first reaction CH4 + H2O = CO + 3H2, i.e., methane reforming, is analyzed using a reaction route network approach to obtain the overall methane steam reforming network and kinetics. Kinetics providing detailed information of elementary reaction steps for this system, namely micro-kinetics, has not yet been fully addressed. Employing the theory of Reaction Route Network Theory, recently developed by Fishtik and Datta, and using the Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) method of Shustorovich to predict elementary step kinetics coupled with transition-state theory, a detailed microkinetic model of steam and dry reforming of methane has been developed for Rh(111) and Ni(111) in this thesis. While there is extensive literature on it, the standard reference on the mechanism and kinetics of MSR is that of Xu and Froment, who proposed a 13 step mechanism. Based on the assumption of rate limiting steps for these overall reactions, Xu and Froment derived rate expressions for overall kinetics with fitted parameters. Here a more detailed micro-kinetic model of steam reforming of methane has been developed by adding 3 steps pertinent to carbon formation on the catalyst to Xu and Froment's mechanism. The complete set as well as the dominant reaction routes has been identified. This was accomplished first by enumerating the list of reaction routes and drawing this network. A program was written in Maple and was used to assist in creating the list of full routes, empty routes and intermediate nodes. This program reduces the amount of repetitive work that was needed in an earlier Matlab program when computing the list. After drawing the complete reaction network it was than converted into an equivalent electrical circuit and Multisim analysis was performed. Further, the resistances of various reaction steps were compared. From the reduced graph, it was determined that reaction steps pertaining to desorption of carbon dioxide, i.e., step s4, and intermediate methylene forming intermediate methylidyne, s11, are the rate limiting steps. Further, through simulation with Multisim, it was determined that in fact only 2 overall reactions are needed. Adding a third overall reaction results in a nodal balance error. A rate expression was developed based on assuming the above two rate determining steps, with remaining steps at pseudo equilibrium along with the quasi-steady state approximation. The rate expression however produced a substantial error in conversion when compared to the overall microkinetic model. In addition to computing the micro-kinetic model, experimental work for methane steam reforming was conducted. A steam to carbon ratio of 2:1 was fed to the packed bed reactor, where experimental conversion data were obtained. These data points for Ni and Rh catalyst were plotted against the model to see how well the simulation predicted the experimental results. Reasonable agreement was obtained.

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48

Gallon, Helen Jennifer. "Dry reforming of methane using non-thermal plasma-catalysis". Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/dry-reforming-of-methane-using-nonthermal-plasmacatalysis(3d260efa-9f5a-4151-bdeb-14d92ea66f4a).html.

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This thesis has studied CO2 reforming of CH4 in atmospheric pressure, non-thermal plasma discharges. The objective of this research was to improve the current understanding of plasma-catalytic interactions for methane reforming. Chapter 1 introduces the existing and potential applications for methane reforming products. The industrial approaches to methane reforming and considerations for catalyst selection are discussed. Chapter 2 introduces non-thermal plasma technology and plasma-catalysis. An introduction to the analytical techniques used throughout this thesis is given. Chapter 3 investigates the effects of packing materials into the discharge gap. The materials were found to influence the reactant conversions for dry reforming of methane in the following order: quartz wool > no packing > Al2O3 > zeolite 3A > BaTiO3 > TiO2. In addition to the dielectric properties, the morphology and porosity of the materials was found to influence the reaction chemistry. The materials also affected the electrical properties of the plasma resulting in surface discharges, as opposed to a filamentary discharge mode. Chapter 4 investigates the effects of variation in CH4/CO2 ratios on plasma-assisted dry reforming of CH4. Differences in the reaction performance for different feed gas compositions are explained in terms of the possible reaction pathways and the electron energy distribution functions. A NiO/Al2O3 catalyst is introduced for plasma-catalytic dry reforming of CH4, which was found to have no significant effect on the reaction performance at low specific input energies. Chapter 5 presents the plasma-assisted reduction of a NiO/Al2O3 catalyst by CH4 and H2/Ar discharges. When reduced in a CH4 discharge, the active Ni/Al2O3 catalyst was effective for plasma-catalytic methane decomposition to produce H2 and solid carbon filaments. A decrease in the breakdown voltage was observed, following the catalyst reduction to the more conductive Ni phase. Chapter 6 investigates the performance of the plasma-reduced Ni/Al2O3 catalysts for plasma-catalytic dry reforming of methane. Whilst the activity towards dry reforming of CH4 was low, the CH4 plasma-reduced catalyst was found to be effective for catalysing the decomposition of CH4 into H2 and solid carbon filaments; both potentially useful products. Chapter 7 discusses further work relevant to this thesis.

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Berrocal, Guillermo José Paternina. "Preparação e caracterização de catalisadores de níquel suportado em óxido de zircônio e aluminio". Programa de Pós-Graduação em Química da UFBA, 2005. http://www.repositorio.ufba.br/ri/handle/ri/9996.

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Níquel suportado em alumina tem sido extensivamente usado para catalisar a reforma a vapor do metano, devido ao seu baixo custo, quando comparado a outros catalisadores, à base de metais nobres. Entretanto, ele não é estável durante a reação principalmente devido à transição de fase e à sinterização do suporte. Isto requer o desenvolvimento de novos catalisadores. Uma opção atrativa seria usar suportes baseados em zircônia, que possui diversas vantagens, tais como estabilidade térmica, dureza e propriedades anfotériças, mas esse sólido possui baixa área superficial específica, quando comparado a suportes catalíticos convencionais. Uma provável solução para esse problema é combinar as propriedades da alumina e da zircônia. Com este objetivo foi estudada, neste trabalho, a preparação e caracterização de catalisadores de níquel suportado em zircônia e alumina. Os suportes foram preparados por métodos de precipitação à temperatura ambiente, a partir de soluções aquosas de oxicloreto de zircônio e de nitrato de alumínio, seguido de calcinação a 500 oC. Foram obtidos sólidos com razões molares Zr/Al (molar) = 10; 5; 2; 1; 0,5; 0,2 e 0.1, além de alumina e zircônia puras. Os catalisadores foram preparados por métodos de impregnação de soluções de nitrato de níquel, seguido de calcinação a 500 oC. As amostras foram caracterizadas por energia dispersiva de raios X, termogravimetria, análise térmica diferencial, espectroscopia no infravermelho, com transformadas de Fourier, difração de raios X, redução termoprogramada, medidas de área superficial específica e porosidade e espectroscopia fotoeletrônica de raios X. O efeito da temperatura sobre a cristalização dos suportes foi estudada "in situ" por difração de raios X, usando uma câmara de aquecimento. Observou-se a presença das fases tetragonal e monoclínica na zircônia pura e g-Al2O3 na alumina pura. A adição de pequenas quantidades de alumínio estabilizou a fase tetragonal da zircônia, enquanto quantidades mais elevadas de alumínio levaram à produção de sólidos mal cristalizados. As amostras ricas em alumínio (Zr/Al= 0,1; 0,2 e 0,5) também produziram g-Al2O3. A altas temperaturas, os sólidos mal cristalizados formaram aluminato de níquel. A área superficial específica aumentou com a adição de alumínio, o que foi atribuído à presença desse metal na superfície do sólido, onde ele atua como espaçador. A amostra pobre em alumínio (Zr/Al= 0,1) mostrou a área superficial específica mais elevada. Entretanto, a área superficial específica decresceu devido à adição de níquel, provavelmente devido ao bloqueio de alguns poros por esse metal. As amostras apresentaram poros com diferentes formas e tamanhos e produziram isotermas dos Tipos II e III com "loops" de histerese, típicas de materiais mesoporosos. A adição de alumínio também afetou a redução de níquel, tornando esse processo mais difícil; este efeito aumentou com a quantidade de níquel nos sólidos. Entre as amostras à base de alumínio e zircônio, o sólido com quantidades iguais desses metais (Zr/Al (molar)= 1) apresentou o teor mais elevado de níquel na superfície. Ele apresenta área superficial específica elevada e pode ser facilmente reduzido, permitindo a formação da fase ativa do catalisador, na reforma a vapor do metano. Portanto, esse sólido é o catalisador mais promissor para essa reação.
Salvador

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50

Agrell, Johan. "Development of Methanol-Reforming Catalysts for Fuel Cell Vehicles". Doctoral thesis, KTH, Chemical Engineering and Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3669.

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Vehicles powered by proton exchange membrane (PEM) fuelcells are approaching commercialisation. Being inherently cleanand efficient sources of power, fuel cells constitute asustainable alternative to internal combustion engines to meetfuture low-emission legislation. The PEM fuel cell may befuelled directly by hydrogen, but other alternatives appearmore attractive at present, due to problems related to theproduction, transportation and handling of hydrogen.

Fuelling with an alcohol fuel, such as methanol, which isoxidised directly at the anode, offers certain advantages.However, the efficiency of the direct-methanol fuel cell (DMFC)is still significantly lower than that of the conventionalhydrogen-fuelled PEM fuel cell, due to some technical problemsremaining unsolved. Hence, indirect fuelling by a reformedliquid fuel may be the most feasible option in the early stagesof the introduction of fuel cell vehicles.

The work presented in this thesis concerns the developmentof catalysts for production of hydrogen from methanol bypartial oxidation, steam reforming or a combination thereof.The work contributes to the understanding of how thepreparation route affects catalyst morphology and howphysicochemical properties determine catalytic behaviour andreaction pathways.

The thesis is a summary of seven papers published inscientific periodicals. The first paper (Paper I) reviews thecurrent status of catalytic hydrogen generation from methanol,focusing on the fuel cell application. Paper II investigatesthe partial oxidation of methanol over Cu/ZnO catalystsprepared in microemulsion and by a conventionalco-precipitation technique. The activity for methanolconversion in the low-temperature regime is found to besignificantly higher over the former materials and the workcontinues by determining the nature of possible Cu-ZnOinteractions in the catalysts by studying their physicochemicalproperties more thoroughly (Paper III). In Paper IV, thepathways for methanol conversion via both partial oxidation andsteam reforming are elucidated.

In Paper V, partial oxidation of methanol is studied overPd/ZnO catalysts prepared by microemulsion technique and againcompared to conventional materials. This investigationdemonstrates that although possessing high methanol conversionactivity, palladium-based catalysts are not suitable forreforming in fuel cell applications due to the considerableamounts of carbon monoxide formed.

In Paper VI, methanol reforming is investigated over acommercial Cu/ZnO/Al2O3 catalyst. The mechanisms for carbonmonoxide formation and strategies for its suppression arediscussed, as well as reactor design aspects. The study alsoincludes some simple kinetic modelling. Finally, Paper VIIdescribes the optimisation of catalyst composition and processconditions to reach high hydrogen production efficiency at lowoperating temperatures and with minimum carbon monoxideformation.

Keywords:PEM fuel cells, hydrogen, methanol, reforming,(partial) oxidation, reaction pathways, carbon monoxide,catalyst, microemulsion, Cu/ZnO, Pd/ZnO, copper, redoxproperties, oxidation state

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