Дисертації з теми "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.
Повний текст джерелаTitle from document title page. Document formatted into pages; contains x, 174 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 155-166).
Ewbank, Jessica Lee. "Rational synthesis of novel reforming catalysts." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54850.
Повний текст джерелаChristensen, 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.
Повний текст джерелаThe 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
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.
Повний текст джерелаSitompul, 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.
Повний текст джерелаCRISTIANO, 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.
Повний текст джерелаDi, 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.
Повний текст джерелаAlbarazi, Abdulkader. "Development of Ni-based catalysts for methane dry reforming application." Paris 6, 2013. http://www.theses.fr/2013PA066814.
Повний текст джерелаBlaylock, 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.
Повний текст джерелаCataloged 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.
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.
Повний текст джерелаMcFarlane, Andrew Robert. "The application of inelastic neutron scattering to investigate methane reforming catalysts." Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/4098/.
Повний текст джерелаRamirez-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.
Повний текст джерелаCao, Pengfei. "The development of Ni based catalysts for carbon dioxide reforming of methane." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/46876/.
Повний текст джерелаRicca, 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.
Повний текст джерелаIn 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.
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.
Повний текст джерелаDarujati, 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.
Повний текст джерелаSuhartanto, 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.
Повний текст джерелаNardi, 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.
Знайти повний текст джерелаPegios, Nikolaos [Verfasser], Regina [Akademischer Betreuer] Palkovits, and 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.
Повний текст джерелаJabbour, 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.
Повний текст джерелаDry 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
Pegios, Nikolaos Verfasser], Regina [Akademischer Betreuer] [Palkovits, and 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.
Повний текст джерелаNajfach, 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.
Повний текст джерелаDaoura, 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.
Повний текст джерелаDry 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
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.
Повний текст джерелаKaydouh, 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.
Повний текст джерелаAlthough 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
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.
Повний текст джерелаNorris, 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/.
Повний текст джерелаLaycock, 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.
Повний текст джерелаLiu, 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.
Повний текст джерелаThe 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
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.
Повний текст джерелаDry 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
Littlewood, Patrick [Verfasser], Reinhard [Akademischer Betreuer] Schomäcker, Reinhard [Gutachter] Schomäcker, and 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.
Повний текст джерелаPapargyriou, 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.
Повний текст джерелаBobin, 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.
Повний текст джерелаOxygen 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
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/.
Повний текст джерелаZirconium 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.
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/.
Повний текст джерелаNowadays, 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.
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/.
Повний текст джерелаNowadays, 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.
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/.
Повний текст джерелаDue 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.
Mette, Katharina [Verfasser], Malte [Akademischer Betreuer] Behrens, Robert [Akademischer Betreuer] Schlögl, Thorsten [Akademischer Betreuer] Ressler, and 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.
Повний текст джерелаSwirk, Katarzyna. "Design of new catalysts for chemical CO2 utilization." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS367.
Повний текст джерелаReforming 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
Beheshti, Askari Abbas [Verfasser], Serena [Gutachter] DeBeer, Martin [Gutachter] Muhler, and 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.
Повний текст джерелаBerrocal, 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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FAPESB
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.
Salvador
Tillmann, Lukas [Verfasser], Martin [Gutachter] Muhler, and 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.
Повний текст джерелаEl, 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.
Повний текст джерелаRêgo, 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.
Повний текст джерелаAmong 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
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.
Повний текст джерелаNo 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
Kumarasamy, Puvaneswary. "Heterogeneous catalysis for methane oxidation." Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326890.
Повний текст джерелаLiu, James. "Kinetics, catalysis and mechanism of methane steam reforming." Digital WPI, 2007. https://digitalcommons.wpi.edu/etd-theses/68.
Повний текст джерелаGallon, 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.
Повний текст джерелаBerrocal, 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
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.
Повний текст джерелаVehicles 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