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1
Herauville, Virginie Marie Therese. "Catalytic Dehydrogenation of Propane : Oxidative and Non-Oxidative Dehydrogenation of Propane." Thesis, Norges Teknisk-Naturvitenskaplige Universitet, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-21096.
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The dehydrogenation of propane has a great interest, due to a global growing demand in propene. This reaction needs a catalyst, high temperature and low propane partial pressure. During this work, platinum hydrotalcite-supported was used as catalyst. First, three different kinds of support were tested: the hydrotalcite 30 (30% MgO, 70% Al2O3), the hydrotalcite 63 and the hydrotalcite 70. The catalysts were prepared with 1 or 2 % mass platinum, by a kind of colloid method. They were characterized by BET, XRD, and chemisorption, and activity tests were performed. The catalytic tests were performed in a fix bed reactor in a temperature range from 350 °C to 650 °C. The propane conversion and selectivity were not really different between the three supports. For example, the selectivity to propene reached a maximum between 50 % and of 55 % at 550 °C for all the catalysts. Then, the catalyst HT 63 with 1 % Pt was selected for further experiments. The feed gas composition was varied, to see the influence of the ratio Propane/Oxygen/Hydrogen. Some experiments involved oxidative dehydrogenation of propane, whereas some others were non-oxidative dehydrogenation of propane. The propane conversion was better when the reaction took place simultaneous with oxidative reactions. The system is complex, but some feed gas compositions favor the conversion of propane and the selectivity of propane to propylene. The influence of pressure on the reaction was also investigated. Oxidative dehydrogenation of propane was studied at low (1.1 bar) and high pressure (above 3 bar). When the pressure in the reactor during the experiment was above 2 bar, the propane conversion, the propane selectivity to propene and the propene yield are improved.
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Jibril, Baba El-Yakubu. "Catalytic oxidative dehydrogenation of propane." Thesis, University of Salford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248905.
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Mandani, Faisal Mohammad. "Kinetic and deactivation studies during catalytic dehydrogenation." Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305913.
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Mpuhlu, Batsho. "Vapour phase dehydrogenation of cyclohexane on microstructured reactors." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/8661.
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The work that is described in this thesis forms part of the research and development projects at InnoVenton: NMMU Institute of Chemical Technology in collaboration with Sasol Technologies. The broader view of the project was testing on the so-called “Small Production Platforms” (SPP’s). In particular the main aim of this study was to investigate the effect of micro-structuring on the heterogeneous catalysed, vapour-phase oxidative dehydrogenation of cyclohexane in the presence of air. Ground work studies were done to provide a proper comparison of the micro-structured reactor with a traditional fixed-bed reactor. These included evaluation of a proper vanadium pyrophosphate catalyst for the reaction, testing of reaction parameters for the oxidative dehydrogenation reaction on a fixed-bed reactor and lastly comparing the performance of the micro-structured reactor to that of the fixed-bed reactor Various vanadium pyrophosphate catalysts that were tested for activity included: bulk (VO)2P2O7, bulk (VO)2P2O7 promoted with Fe, (VO)2P2O7 supported on -Al2O3 and Fe promoted (VO)2P2O7 supported on -Al2O3. These catalysts showed significant differences in TOF, however it was not conclusive from the results whether these differences may be traced to increased activity for dehydrogenation for different catalysts since all reactions were run under conditions of oxygen deficiency. It is, however, clear that Fe promotion significantly increase activity, irrespective of the relative degrees of oxidative dehydrogenation and normal dehydrogenation. The Fe promoted catalyst was further tested for long term stability in-view of using it as the catalyst in the micro-structured reactor. These studies showed the catalyst to have a high degree of stability with minimal structural changes under the reaction conditions used. Various response surface models describing the variation in each of the cyclohexane conversion, cyclohexene selectivity, and benzene selectivity, respectively when changing reaction condition, were derived by means of multiple regression. To obtain some idea of the degree and nature of the normal dehydrogenation reaction, the amount of deficit oxygen was estimated from the measured results for cyclohexane conversion and cyclohexene and benzene selectivities. These estimated values were also modelled as described above. The regression models were used to interpret specific trends in the responses for the oxidative dehydrogenation of cyclohexane and account for the oxygen deficit in the system. The performance of a fixed bed tubular reactor (FBR) and micro-structured sandwich reactor (MSSR) were compared over an Fe promoted vanadium pyrophosphate. Reactor performance was evaluated by varying specific reaction conditions (temperature and space velocity). Subsequently the turn-over frequencies, conversion and selectivities from the two reactors were compared. The conversion achieved in the micro-structured reactor was observed to be significantly higher than that achieved in the fixed-bed reactor at all reaction parameters. This is despite the fact that the total amount of catalyst in the micro-structured reactor is approximately 5 times less than that used in the fixed bed reactor. In addition, the contact time (1/MHSV) in the micro-structured reactor is also significantly shorter than in the fixed-bed reactor.
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Hiltzik, Laurence Howard. "Characterization of a catalyst regeneration process for metals fouled CoMo/Al[subscript]2O[subscript]3 catalysts." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/10974.
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Ismail, Manal. "Dehydrogenation of isobutane using a structured adsorptive reactor." Thesis, Imperial College London, 2006. http://hdl.handle.net/10044/1/8223.
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Levin, Doron P. "Novel transition metal molybdates for catalytic oxidative dehydrogenation." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/37037.
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Talwar, Dinesh. "Hydrogenation and dehydrogenation with cyclometalated iridium (III) complexes." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2003856/.
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The selective hydrogenation and dehydrogenation of organic molecules is a fundamentally challenging and an attractive transformation for both, industry and academia. However, catalysts capable of undergoing both transformations under environmentally benign conditions are rare. In this thesis, our contribution to the development of a “universal” catalyst capable of achieving both hydrogenation and dehydrogenation of a wide range of organic compounds under mild conditions is presented. A general introduction covering the recent developments in the area of transfer hydrogenation of C=X (X = O, N) bonds, relevant applications of cyclometalated half-sandwich complexes and previous work in the area developed within our group is described in Chapter 1. In Chapter 2, Cyclometalated iridium complexes are shown to be highly efficient and chemoselective catalysts for the transfer hydrogenation of a wide range of carbonyl groups with formic acid in water. Examples include α-substituted ketones (α-ether, α-halo, α-hydroxy, α-amino, α-nitrile, α-ester), α-keto esters, β-keto esters, and α,β-unsaturated aldehydes. The reduction was carried out at substrate/catalyst ratios of up to 50000 at pH 4.5, requiring no organic solvent. The protocol provides a practical, easy and efficient way for the synthesis of β-functionalised secondary alcohols, such as β-hydroxyethers, β-hydroxyamines and β-hydroxyhalo compounds, which are valuable intermediates in pharmaceutical, fine chemical, perfume and agrochemical synthesis. In Chapter 3, the cyclometalated iridium complexes are shown to catalyse the transfer hydrogenation of various nitrogen heterocycles, including but not limited to quinolines, isoquinolines, indoles and pyridiniums, in aqueous solution under mild conditions. The catalyst shows excellent functional group compatibility and high turnover number (up to 7500), with loading as low as 0.01% being feasible. In Chapter 4, cyclometalated iridium complexes are found to be versatile catalysts for the direct reductive amination of carbonyls to give primary amines under transfer hydrogenation conditions with ammonium formate as both the nitrogen and hydrogen source. The activity and chemoselectivity of the catalyst towards primary amines is excellent, with a substrate to catalyst ratio of 1000 being feasible. Both aromatic and aliphatic primary amines were obtained in high yields. Moreover, a first example of a homogeneously catalysed transfer hydrogenative direct reductive amination (DRA) has been achieved for -keto ethers, leading to the corresponding -amino ethers. In addition, non-natural -amino acids could also be obtained in excellent yields with this method. Following the success of hydrogenation, cyclometalated iridium complexes were also found to be versatile catalysts for the oxidant-free, acceptorless dehydrogenation of various N-heterocycles, including tetrahydroquinolines, tetrahydroisoquinolines, tetrahydroquinoxalines and indolines. This protocol was also successfully applied to the total synthesis of alkaloids as presented in Chapter 5. Chapter 6 describes the development of a new strategy for the oxidant- and base-free dehydrogenative coupling of N-heterocycles at mild conditions. Under the action of an iridium cyclometalated catalyst, N-heterocycles undergo multiple sp3 C-H activation, generating a nucleophilic enamine that reacts in situ with various electrophiles to give highly functionalised products. The dehydrogenative coupling can be cascaded with Friedel-Crafts addition, resulting in double functionalisation of the N-heterocycles. The dehydrogenation products could also be saturated under either hydrogenation or transfer hydrogenation conditions, giving rise to structurally diverse products. Final conclusion and perspectives of the research covered in this PhD thesis are presented in Chapter 7.
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V, Ashok Kumar. "Oxidative dehydrogenation of hydrocarbons over mixed metal oxides." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2017. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/5889.
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Wang, Bo. "Applications of hydrogenation and dehydrogenation on noble metal catalysts." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1446.
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Lee, Won Jae. "Ethylbenzene dehydrogenation into styrene: kinetic modeling and reactor simulation." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4847.
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A fundamental kinetic model based upon the Hougen-Watson formalism was
derived as a basis not only for a better understanding of the reaction behavior but also
for the design and simulation of industrial reactors.
Kinetic experiments were carried out using a commercial potassium-promoted
iron catalyst in a tubular reactor under atmospheric pressure. Typical reaction conditions
were temperature = 620oC, steam to ethylbenzene mole ratio = 11, and partial pressure
of N2 diluent = 0.432 bar. Experimental data were obtained for different operating
conditions, i.e., temperature, feed molar ratio of steam to ethylbenzene, styrene to
ethylbenzene, and hydrogen to ethylbenzene and space time. The effluent of the reactor
was analyzed on-line using two GCs.
Kinetic experiments for the formation of minor by-products, i.e. phenylacetylene,
ñ-methylstyrene, ò-methylstyrene, etc, were conducted as well. The reaction conditions
were: temperature = 600oC ~ 640oC, a molar ratio of steam to ethylbenzene = 6.5, and partial pressure of N2 diluent = 0.43 bar and 0.64 bar. The products were analyzed by
off-line GC.
The mathematical model developed for the ethylbenzene dehydrogenation
consists of nonlinear simultaneous differential equations in multiple dependent variables.
The parameters were estimated from the minimization of the multiresponse objective
function which was performed by means of the Marquardt algorithm. All the estimated
parameters satisfied the statistical tests and physicochemical criteria. The kinetic model
yielded an excellent fit of the experimental data.
The intrinsic kinetic parameters were used with the heterogeneous fixed bed
reactor model which is explicitly accounting for the diffusional limitations inside the
porous catalyst. Multi-bed industrial adiabatic reactors with axial flow and radial flow
were simulated and the effect of the operating conditions on the reactor performance was
investigated.
The dynamic equilibrium coke content was calculated using detailed kinetic
model for coke formation and gasification, which was coupled to the kinetic model for
the main reactions. The calculation of the dynamic equilibrium coke content provided a
crucial guideline for the selection of the steam to ethylbenzene ratio leading to optimum
operating conditions.
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McGregor, James. "Heterogeneous catalytic hydrogenation and dehydrogenation : catalysts and catalytic processes." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612796.
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Al-Anazi, Flaiyh Farhan N. "Propane oxidative dehydrogenation to propene using molybdenum phosphate catalysts." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/56052/.
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Molybdenum based catalysts have been used successfully as catalysts for the oxidative dehydrogenation of propane to propene. Metal phosphate catalysts have also been reported to exhibit high yields of propene in the oxidative dehydrogenation of propane to propene. Therefore, MoO2HPO4.H2O was used as a precursor to prepare different bulk and supported molybdenum phosphate phases based on the methodology used in the preparation of vanadium phosphate (VPO) catalysts which are used commercially for selective butane oxidation. The materials obtained were tested as catalyst for propane oxidative dehydrogenation. MoOPO4 was prepared by a novel procedure. The unsupported molybdenum phosphates were not active for propane oxidative dehydrogenation to propene. However, the activity of the molybdenum phosphates was significantly enhanced after being impregnated on the supports (Al2O3, SiC2, TiO2 and MoO). The enhancement of the activity was attributed to the enhancement of the reducibility of the supported molybdenum phosphates. The more reducible the catalyst the more active it is. Moreover, these supported catalysts exhibited high selectivity at the initial reaction temperature. However, the selectivity decreases as the reaction temperature increases, which was attributed to a consecutive oxidation of formed propene. No crystalline phase has been detected by XRD in all supported molybdenum phosphates, which is attributed to a strong interaction between the impregnated molybdenum phosphate material and the supports. Niobia-supported molybdenum phosphate (heated in nitrogen at 500 C) exhibited the highest alkene selectivity of 51.7% (propene selectivity = 42.5% and ethene selectivity = 9.2%) at a propane conversion as high as 20%. Therefore, the propene and total alkene yield are 8.5 and 10.3%, respectively, which are comparable to that reported in the literature. Therefore, supported molybdenum phosphate catalysts are promising for propane oxidative dehydrogenation to propene. The relative performance of molybdenum phosphate supported on different supports at 500 C (heated in nitrogen to 500 C) is as follows: 20% MoPO/TiO2> 20% MoPO/Al2O3=20% MoPO/SiO2>20% MoPO/Nb205 While the selectivity to propene is as follows: 20% MoPO/Nb2O5> 20% MoPO/SiO2>20% MoPO/Al2O3>20% MoPO/TiO2. This indicates that the higher the activity the lower the selectivity, except for the silica-supported molybdenum phosphate and the alumina-supported molybdenum phosphate. They exhibited the same activity, but the silica-supported molybdenum phosphate was more selective to propene. The in situ XRD confirmed the formation of a stable amorphous phase of molybdenum phosphate when the molybdenum precursor (MoO2HPO4.H2O) was heated in nitrogen up to 400 C. Moreover, heating the amorphous phase formed up to 500 C resulted in the formation of a stable crystalline phase at 500 C. According to the JCPDS data this crystalline phase was molybdenum pyrophosphate ((MoO2)2P2O7).
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Stubbs, Naomi E. "Metal-catalysed and metal-free dehydrogenation of amine-boranes." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.686189.
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Gianotti, Elia. "High purity hydrogen generation via partial dehydrogenation of fuels." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20078/document.
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Ces travaux de thèse ont été développés dans un contexte de motivation générale de développement de modes de transport plus électrifiés et plus respectueux de l'environnement, dans le but de réduire considérablement les émissions de gaz à l'effet de serre. Plus particulièrement l'objectif de ce projet de thèse a été d'étudier la faisabilité d'un concept de génération d'hydrogène à bord, par déshydrogénation catalytique partielle (PDh) du carburant, permettent d'obtenir de l'hydrogène pour alimenter une pile à combustibles embarquée en replacement des unités de puissance auxiliaires. Dans un même temps le combustible qui n'est que partiellement déshydrogéné conserve ses propriétés et peut être réinjecté dans le pool de carburant. Cette thèse est divisée en deux grandes parties. Une première partie décrit les travaux de recherche sur la déshydrogénation partielle du kérosène pour la production d'hydrogène à bord d'un avion. Le choix du catalyseur est crucial, il doit permettre de produire de l'hydrogène de haute pureté sans compromettre les propriétés d'origine du kérosène. Des matériaux avancés, composés de métaux imprégnés sur des nouveaux supports ont été développés, caractérisés et évalués en tant que catalyseur dans la réaction de PDh. L'influence de la composition du catalyseur sur son activité, sélectivité et durée de vie ainsi que les mécanismes de désactivation ont été étudiés. Un matériau catalytique optimisé composé d'une phase active de 1% Pt - 1 % Sn (m/m) supporté sur une γ-alumine à porosité contrôlée, a permis une production d'hydrogène de 3500 NL•h-1•kgcat-1, avec une pureté de 97,6% vol. et un temps de vie de 79 h, ce qui correspond à une puissance électrique fournie par une pile à combustible de 3,5 kW.La deuxième partie du manuscrit décrit une étude sur le diesel et l'essence et sur la faisabilité de la génération d'hydrogène par PDh des carburants autres que le kérosène. Les résultats obtenus avec le même matériau sont encourageants et montre une application possible dans des domaines de transports autres que l'aviation. Les résultats les plus significatifs obtenus avec des substituts de gasoil et d'essence sont respectivement des valeurs de productivité d'hydrogène de 3500 et 1800 NL•h-1•kgcat-1 avec des temps de vie de 29 et 376 h et une pureté supérieur à 99 % vol. pour le deuxThis thesis work have been developed in the general context of the development of more electrified and environmentally friendly means of transport, in order to significantly reduce greenhouse gases emissions. More specifically, the objective of this thesis project was to study the feasibility of the concept of on-board hydrogen generation by catalytic partial dehydrogenation (PDh) of fuel. The hydrogen produced serves to power a fuel cell system that replaces vehicles auxiliary power units. At the same time the fuel, that is only partially dehydrogenated, maintains its properties and can be re-injected into the fuel pool.This thesis is divided into two main parts. The first part describes the research on the PDh of kerosene to produce hydrogen on-board an aircraft. The choice of the catalyst is crucial: it should allow to produce high purity hydrogen without compromising the original properties of kerosene. Advanced materials, composed by metals impregnated on different supports, have been developed, characterized and evaluated as a catalysts in the reaction of PDh. The influence of catalyst composition on the activity, selectivity and stability as well as the deactivation mechanisms were studied. One of the optimized catalytic materials, composed of a 1% Pt - Sn 1% (w/w) active phase supported on a γ-alumina with controlled porosity, allowed a hydrogen production of 3500 NL•h-1•kgcat-1, with a purity of 97.6% vol. and a lifetime of 79 h, which corresponds to 3.5 kW of electric power supplied by fuel cells.The second part of the manuscript describes a study on diesel and gasoline and asses the feasibility of hydrogen generation by PDh of fuels different from kerosene. The results obtained with the previously mentioned catalyst are encouraging and show the possibility of applying this concept to other fields of transportation beside the aviation. The most significant results obtained with gasoline and diesel surrogates are respectively a hydrogen productivity value of 3500 et 1800 NL•h-1•kgcat-1 with lifetimes of 29 and 376 h and a purity that exceeds 99% vol. in both cases
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Tanniru, Mahesh. "Hydrogenation and dehydrogenation characteristics of electrodeposited Mg-Al alloys." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0041120.
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Taylor, David J. "Metal catalysed transfer hydrogenation, dehydrogenation and racemisation of amines." Thesis, University of York, 2010. http://etheses.whiterose.ac.uk/1473/.
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This thesis describes the study of the fundamental mechanisms relating to asymmetric transfer hydrogenation (ATH) of imines and the transfer dehydrogenation and racemisation of secondary amines by Cp*Rh and Cp*Ir complexes. A series of 16-electron complex of the type Cp*M(XNC6H4NX’) (where M = Rh or Ir and X, X’ = H or Ts) have been synthesised, fully characterised and demonstrated to be active catalysts for the transfer hydrogenation of imines. The crystal structures of the complexes reveal structural features that are important in understanding their unique ability to act as transfer hydrogenation catalysts including a remarkable trend in the M-N bond lengths, indicative of M-NH π-bonding and the absence of M-NTs π-bonding which has several implications for catalysis. The complexes allowed catalytic studies without the need for 18-electron precursors, as is the case for the more widely used Noyori-type Cp*M(Cl)(TsNCHPhCHPhNH2) (where M = Rh or Ir) ATH complexes. We observed key intermediates in the mechanism by NMR spectroscopy such as an 18-electron formate complex, Cp*Rh(OCHO)(TsNC6H4NH2) and the 18-electron Rh(III) hydride complex, Cp*Rh(H)(TsNC6H4NH2). An 18-electron chloride precursor complex, Cp*Rh(Cl)(TsNC6H4NH2) was also characterised by X-ray crystallography. DFT calculations were used to support our observations and an “outer-sphere” mechanism for the transfer hydrogenation of imines is proposed. We also studied the mechanism of a dimeric Cp*Ir diiodide complex, [Cp*Ir(I)2]2 that is capable of amine racemisation under mild conditions and characterised several key intermediates including an ammine-coordinated complex, Cp*Ir(I)2(NH3) which itself was demonstrated to be equally active for the racemisation process under identical conditions; amine bound complexes of the type Cp*M(X)2(PhCH2NHMe) (where M = Rh, Ir and X = Cl, I) proposed to be the first step in the mechanism; an imine-coordinated Cp*Ir diiodide complex characterised by 1H/15N HSQC and the reversible hydrogenation of this complex by addition of molecular hydrogen to form the corresponding amine. A mechanism based on the current evidence for the racemisation of amines using the [Cp*Ir(I)2]2 catalyst is proposed. Finally, we describe a method for producing hyperpolarised carbon dioxide gas by using the Cp*Rh(Cl)(TsNCHPhCHPhNH2) ATH catalyst to catalytically decompose a pre-hyperpolarised solution of natural abundance formic acid, which was observed by 13C NMR spectroscopy.
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Bowman, Amber Suzanne. "ENHANCED ANALYSIS OF LIGNIN DEHYDROGENATION OLIGOMERS VIA MASS SPECTROMETRY." UKnowledge, 2018. https://uknowledge.uky.edu/chemistry_etds/104.
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Effective analytical techniques need to be developed to characterize the products of lignin degradation experiments to be able to generate renewable products from lignin. Mass spectrometry is an valuable analytical approach for lignin characterizaion, but it is hindered by lignin’s poor ionization efficiency, especially in the positive ion mode. In this work, we attempt to improve lignin’s ionization by utilizing electrospray and laser desorption mass spectrometry coupled with the addition of cations and chemical derivatives. We confronted the ionization problem from both a top-down and bottom-up analytical approach by analyzing synthesized monomers, dimers, and polymers along with natural lignin extracts from switchgrass. We also utilized tandem mass spectrometry to sequence lignin dimers and determine their bonding motifs from their fragmentation patterns. We believe that resolving the ionization issues with lignin will open the door for easier and more efficient lignin break-down techniques and ultimately more accessible renewable products from lignin.
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Dai, Hongxing. "The oxidative dehydrogenation of ethane over alkaline earth halide-promoted rare earth oxide and perovskite-type halo-oxide catalysts." HKBU Institutional Repository, 2001. http://repository.hkbu.edu.hk/etd_ra/293.
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Lilac, W. Douglas. "Controlled depolymerization of polypropylene via selective partial oxidation in a supercritical water medium /." free to MU campus, to others for purchase, 1999. http://wwwlib.umi.com/cr/mo/fullcit?p9962539.
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Karamullaoglu, Gulsun. "Dynamic And Steady-state Analysis Of Oxidative Dehydrogenation Of Ethane." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606269/index.pdf.
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In this research, oxidative dehydrogenation of ethane to ethylene was studied over Cr-O and Cr-V-O mixed oxide catalysts through steady-state and dynamic experiments. The catalysts were prepared by the complexation method. By XRD, presence of Cr2O3 phase in Cr-Oand the small Cr2O3 and V2O4 phases of Cr-V-O were revealed. In H2-TPR, both catalysts showed reduction behaviour. From XPS the likely presence of Cr+6 on fresh Cr-O was found. On Cr-V-O, the possible reduction of V+5 and Cr+6 forms of the fresh sample to V+4, V+3 and Cr+3 states by TPR was discovered through XPS. With an O2/C2H6 feed ratio of 0.17, Cr-O exhibited the highest total conversion value of about 0.20 at 447°
C with an ethylene selectivity of 0.82. Maximum ethylene selectivity with Cr-O was obtained as 0.91 at 250°
C. An ethylene selectivity of 0.93 was reached with the Cr-V-O at 400°
C. In the experiments performed by using CO2 as the mild oxidant, a yield value of 0.15 was achieved at 449°
C on Cr-O catalyst. In dynamic experiments performed over Cr-O, with C2H6 pulses injected into O2-He flow, the possible occurrence of two reaction sites for the formation of CO2 and H2O was detected. By Gaussian fits to H2O curves, the presence of at least three production ways was thought to be probable. Different from Cr-O, no CO2 formation was observed on Cr-V-O during pulsing C2H6 to O2-He flow. In the runs performed by O2 pulses into C2H6-He flow over Cr-V-O, formation of CO rather than C2H4 was favored.
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Creaser, Derek Claude. "The role of oxygen in the oxidative dehydrogenation of propane." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq22197.pdf.
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Davies, Aled Mathew. "Selective oxidation and oxidative dehydrogenation reactions using niobium based catalysts." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54882/.
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The selective oxidation of methanol to formaldehyde, the oxidative dehydrogenation of ethane and the oxidative dehydrogenation of propane have been investigated using niobium based catalysts. It has been shown that niobium oxides prepared by different methods show in general a low conversion of reactant in all probe reactions investigated. However, high selectivity to the desired products are maintained (i.e. formaldehyde, ethylene and propene) at elevated temperatures. The introduction of phosphorus into niobium based catalysts enhanced the catalytic performance of the catalyst The aim was to maintain a high selectivity of desirable products whilst increasing conversion. Two sets on niobium and phosphorus based catalysts were investigated. The first set of catalyst was niobium oxide phosphates, NbOPC>4, prepared from a method which was analogous to VPO work. Catalytic testing of the niobium oxide phosphates showed an increased conversion in both methanol oxidation and ethane oxidative dehydrogenation. However, there was little effect in using niobium oxide phosphates for the oxidative dehydrogenation of propane. Comparing niobium oxide phosphates to niobium oxides, the conversion doubled with respect to oxidative dehydrogenation of ethane and increased 18-fold with respect to methanol oxidation. The second set of niobium and phosphorus based catalysts were niobium phosphates, NbPOs. These were prepared from the reduction of niobium oxide phosphates. Catalytic testing showed an increased conversion in both methanol oxidation and ethane oxidative dehydrogenation. This is the first time that niobium phosphates and oxyphosphates have been investigated as catalysts and they demonstrate appreciable activity for a range of selective oxidation reactions.
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Robertson, Alasdair P. M. "Amine-borane dehydrogenation : catalyst development, novel materials and mechanistic insight." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.559079.
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This Thesis describes investigations into the dehydrogenation of amine-borane adducts and hydrogenation of aminoboranes via metal-catalysed and thermolytic routes. Chapter 1 provides a general introduction to the area of metal-catalysed dehydrocoupling reactions of main-group compounds. Specific emphasis is placed upon amine-borane adducts, for which the physical and chemical properties are also discussed in detail. Chapter 2 describes the identification and application of skeletal Ni as an effective heterogeneous catalyst for the dehydrocoupling of amine-boranes. The optimisations of catalyst formulation and reaction conditions are presented, together with studies of the catalytic dehydrogenation of a series of amine-boranes. Investigations into the mechanism of the catalytic transformation are presented in addition to studies of potential surface poisoning processes. Chapter 3 describes the synthesis of a novel amine-borane / aminoborane pair, iPr2NH'BH(C6F5)2 and iPr2N=B(C6Fs)2. The interconversion of the two species through dehydrogenation and hydrogenation respectively via metal-mediated and thermolytic protocols is described. A DFT study of the thermodynamics of the interconversion is also presented and the thermodynamic parameters for the related phosphine-borane / phosphinoborane pair, iPr2PH'BH(C6F5)2 and iPr2P-B(C6F5)2 are also elucidated. Chapter 4 describes the development of a general route to linear diborazanes, RR'R"N-BH2-NRR' -BH3, with the spectroscopic and crystallographic characterisation of a series of novel compounds presented. The thermal and Ir-catalysed redistributions of these species are investigated in detail, and the formation of transient aminoboranes demonstrated in some cases to result in complex hydrogen transfer reactions. The novel hydrogen transfer reactivity is exemplified by a further study of reactions between amine-boranes and aminoboranes. Chapter 5 describes the development of synthetic routes to amine-thioborane adducts R2NH' BH2SR'. A variety of possible routes to such species are presented, with a broad series of tertiary and secondary amine-thioborane adducts characterised. Studies of the thermal and metal-catalysed dehydrogenation of the secondary amine-thioboranes are also presented. Chapter 6 describes possible future, or indeed ongoing, work based upon the results presented in chapters 2-5.
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Pearson, Karolina [Verfasser]. "Hydrogen Production by Partial Catalytic Dehydrogenation of Kerosene / Karolina Pearson." München : Verlag Dr. Hut, 2016. http://d-nb.info/110096794X/34.
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Crabb, Eleanor Mary. "An investigation of the oxidative dehydrogenation of ethane and propane." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304514.
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Vance, James R. "Iron-catalysed dehydrocoupling/ dehydrogenation of amine- and phosphine-borane adducts." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681991.
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This Thesis describes the investigations of iron-catalysed dehydrocoupling/dehydrogenation of various amine- and phosphine-borane adducts. Chapter 1 gives a general introduction to mam group element-element bond forming reactions, focusing on transition metal-catalysed dehydrocoupling under mild conditions. Chapter 2 describes the use of a series of iron precatalysts in the dehydrocoupling of Me2NRBH3. Analysis by liB NMR spectroscopy allowed the identification of various intermediates to be made. Furthermore, it was found that in the case of dinuclear Fe(I) complexes that they reduced in situ to afford Fe(O) nanoparticles which were the active catalyst. Interestingly, a related mononuclear Fe(II) complex was found to generate a homogeneous catalyst which, while also dehydrocoupling Me2NRBH3 to produce [Me2N-BH2h as the final product, favoured the formation of a different intermediate than was detected in the case of the Fe nanoparticles. Chapter 3 describes the use of the same iron precatalysts in the dehydrocoupling of MeNH2·BH3 and H3N·BH3. It was found that they were all active towards these adducts which demonstrated the versatility of the Fe catalysts. FUlihermore, various polymeric and oligomeric products were formed depending on which precatalysts were employed. Chapter 4 describes the synthesis of a series of Fe-phosphidoborane complexes. These were then employed as dehydrocoupling catalysts for a variety of phosphine-borane adducts. Although they were shown to be poor catalysts for the dehydrocoupling of secondary phosphine-boranes, increased catalytic activity was observed in the analogous reactions with primary phosphine-boranes. Polyphosphinoboranes of high molecular weight were yielded as the sole products. Chapter 5 describes the on-going investigation and possible future work based on the research described in Chapters 2-4.
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Whittemore, Sean M. "Efforts Toward the Site-Selective Dehydrogenation of Saturated Fatty Acids." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366198700.
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Tan, Ping Lian. "Methane dehydrogenation and aromatization over Mo(Re, Mn)/HZSM-5 in the absence/presence of an oxidant." HKBU Institutional Repository, 2004. http://repository.hkbu.edu.hk/etd_ra/582.
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Bayraktar, Oguz. "Effect of pretreatment on the performance of metal contaminated commercial FCC catalyst." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2071.
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Thesis (Ph. D.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains xvi, 214 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 199-208).
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Soole, Kathleen Lydia. "Characterisation of the NADH dehydrogenases associated with isolated plant mitochondria /." Title page, contents and summary only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09phs711.pdf.
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Cabús, Llauradó Maria Clara. "Catalytic non-oxidative dehydrogenation and reactivity of biobased fatty acid derivatives." Doctoral thesis, Universitat Rovira i Virgili, 2007. http://hdl.handle.net/10803/8595.
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Los compuestos tipo omega-3 son compuestos que han adquirido un especial interés en los últimos años debido a los importantesbeneficios que aportan si son incluidos en la dieta humana. Representan una fuente de energía para las personas que debe de ser necesariamente ingerida, dado que nuestro organismo no es capaz de sintetizarlos. La naturaleza nos ofrece diferentes fuentes de omega-e como el pescado azul y el aceite de linaza. La deshidrogenación de compuestos tipo omega-6 como el linoleato de etilo, puede dar lugar a dichos compuestos.
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Sotoodeh, Farnaz. "Hydrogenation and dehydrogenation kinetics and catalysts for new hydrogen storage liquids." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/35863.
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Due to the very low density of H₂, practical storage and recovery of H₂ has been
a challenge in utilizing H₂ as an alternative fuel. Organic heteroaromatics have
attracted interest because of their thermal stability and high storage capacity. In
this study, H₂ storage and recovery from these compounds were investigated. The
kinetics of the hydrogenation/dehydrogenation reactions was studied and DFT calculations
were used to understand the dehydrogenation product distribution.
The hydrogenation of N-ethylcarbazole and carbazole at 403-423 K on a supported
Ru catalyst was well described by first-order kinetics. The hydrogenation of
N-ethylcarbazole was significantly faster than the hydrogenation of carbazole, and
>95 % selectivity to dodecahydro-N-ethylcarbazole and dodecahydrocarbazole
was achieved, respectively.
The dehydrogenation kinetics of dodecahydro-N-ethylcarbazole was studied at
101 kPa and 423-443 K over a Pd catalyst prepared by wet impregnation and calcination
in air. The reactions followed first-order kinetics with 100 % conversion but
only 69 % recovery of H₂ was achieved at 443 K, due to minimal selectivity to Nethylcarbazole.
The complete recovery of H₂ from dodecahydro-N-ethylcarbazole
was achieved at 443 K and 101 kPa using Pd/SiO₂ catalysts prepared by incipient
wetness impregnation with calcination in He. The dehydrogenation TOF and selectivity
to N-ethylcarbazole were dependent upon the Pd particle size.
The effect of the N heteroatom on the dehydrogenation of polyaromatics was
studied by comparison of dodecahydro-N-ethylcarbazole, dodecahydrocarbazole
and dodecahydrofluorene dehydrogenation over Pd catalysts. The dehydrogenation
of dodecahydro-N-ethylcarbazole and dodecahydrocarbazole were structure
sensitive. The dehydrogenation rate of dodecahydrocarbazole was slower than
dodecahydro-N-ethylcarbazole. Despite catalyst poisoning through the N atom
in dodecahydrocarbazole, the N heteroatom was found to favor dehydrogenation,
making heteroaromatics better candidates for H₂ storage than aromatics.
The structure sensitivity of the reactions and the observed product distribution
are explained in view of DFT calculations that showed that the adsorption
of dodecahydro-N-ethylcarbazole on Pd required multiple catalytic sites and the
heat of adsorption was dependent upon the surface structure. The effect of the
ethyl group and the N heteroatom on the dehydrogenation rate of dodecahydro-
N-ethylcarbazole was also investigated by comparing the adsorption energies of
dodecahydro-N-ethylcarbazole with dodecahydrocarbazole and dodecahydrofluorene.
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Mouton, Duane Wilmot. "The development of a membrane reactor for the dehydrogenation of isopropanol." Thesis, Stellenbosch : University of Stellenbosch, 2003. http://hdl.handle.net/10019.1/16397.
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Thesis (MScIng)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: Both porous and dense hydrogen selective membranes have recently been an active area of research. The combination of a reactor and a separator in the form of a membrane reactor is seen as a feasible application in which to perform dehydrogenation reactions. These reactions are equilibrium limited so that the removal of the product H2 by a selective membrane can improve the process effectiveness. Early Pd-based membranes were made of thin-walled tubes. In an attempt to increase permeation rates, thin supported Pd membranes have been developed. This study investigated the development and performance of a catalytic membrane reactor. The membrane reactor consists of a tubular alumina membrane support coated on the inside with a film of palladium or a palladium-copper alloy. This reactor was used for the dehydrogenation of isopropanol. The thin film was coated on the alumina support using an electroless plating process. This process occurs in a liquid medium where palladium and copper are deposited by electrolysis or electroless means. With these methods alloys can also be deposited on the support. By plating a thin film of palladium on the alumina membranes, will attract hydrogen molecules from the reaction product, which will increase the reaction rate. The electroless plating process consists of four major components: (i) (ii) (iii) (iv) reducing agent ( 0.04 M hydrazine), temperature bath, stabilised source of metal ions, and support membrane (α-alumina). Heat treatment was carried out on the coated membranes for 5 hours in a hydrogen atmosphere at 450°C. The plated membranes supplied by Atech were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM) and particle induced Xray emission (PIXE) before and after heat treatment. SEM photographs showed that the pore size of the membranes was doubtful and due to that the films were not of a dense nature. XRD results revealed that heat treatment led to the formation of smaller Pd and Cu crystallites. The concentration profiles constructed from the PIXE results indicated that Cu and Pd penetrated deep into the pores of the membrane during film preparation. Different catalysts (Al2O3, MgO and SiO2) were tested and the best one was chosen as catalyst in the membrane reactor. These catalytic runs were done in a plug flow (fixedbed) reactor. Different particle sizes of catalysts were also tested. A 9.2 Cu wt % on silica achieved the highest acetone yields for the temperatures tested. Two different types of alumina membrane reactors were used. These were supplied from SCT. One membrane only coated with palladium and the other coated with palladium and copper. Selectivity and permeability tests were also carried out on these membranes. Selectivities of up to 90.6 could be reached with the palladium coated membrane. The palladium-copper plated membrane only achieved selectivities of up to 13. With heat treatment this value decreased even more. The palladium coated membrane also achieved much better conversion to acetone in the dehydrogenation of 2-propanol. The reason for that is its better selectivity. The palladium-copper membrane reactor did not show much better results than the fixed-bed reactor.
AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die ontwikkeling en werk verrigting van ‘n katalitiese membraan reaktor. Die membraan reaktor bestaan uit ‘n dun film palladium of palladium-koper allooi wat aan die binnekant van ‘n silindriese alumina membraan geplateer word. Die alumina dien as membraanbasis. Hierdie reaktor sal gebruik word vir die dehidrogenering van isopropanol. Die dun films van metaal word neergeslaan op die alumina basis deur ‘n elektrodelose platerings proses. Hierdie proses vind plaas in ‘n vloeistof medium waar palladium en koper neerslag plaasvind op ‘n elektrodelose wyse. Met hierdie metode kan metaal allooie geplateer word op basis membrane. Deur ‘n dun palladium lagie aan die binnekant van die alumina membrane te plateer sal veroorsaak dat waterstof molekules uit die reaksie volume sal weg beweeg. Dit sal ‘n verhoging in reaksie tempo meebring. Die platerings proses bestaan uit vier komponente: (i) reduseermiddel (0.04M Hidrasien), (ii) temperatuur water bad, (iii) stabiliseerde bron van metaal ione (Pd/Cu kompleks oplossing), en (iv) basis membraan (α-alumina). Hittebehandeling vir 5 uur is uitgevoer op hierdie geplateerde membrane by 450°C in ‘n waterstofatmosfeer. Die geplateerde membrane is daarna gekarakteriseer- voor en na hittebehandeling. Dit is gekarakteriseer deur X-straal diffraksie (XRD), skanderings elektron mikroskopie (SEM) en partikel geïnduseerde X-straal emissie (PIXE). XRD eksperimente het gewys dat die koper en die palladium ‘n allooi gevorm het. Veranderinge in kristaltekstuur het voorgekom na hittebehandeling. Tydens hittebehandeling was kleiner palladium en koper kristalle gevorm. SEM resultate het getoon dat die film nie baie dig was nie en die porie grootte van die membrane was ook nie korrek nie. PIXE resultate het die konsentrasieprofiele van beide koper en palladium oor die dikte van die membraan bepaal. Dit het gewys dat die Cu en Pd diep binne die membraan penetreer het tydens voorbereiding van die membraan. Verskillende soorte kataliste (Al2O3, MgO and SiO2) is ondersoek vir die dehidrogenering van isopropanol. Hierdie katalitiese ondersoek is gedoen in ‘n propvloei reaktor. Die beste katalis is gekies om in die membraan reaktor te gebruik. Verskillende partikel groottes is ook ondersoek. ‘n 9.2 Cu massa % koper op silika katalis het die beste omsetting na asetoon verkry vir die temperature waarvoor toetse gedoen is. Twee tipes membraan reaktors is gebruik. Een met net ‘n palladium film, terwyl ‘n palladium-koper allooi op die ander membraan reaktor gedeponeer was. Selektiwiteits- en deurlaatbaarheids toetse is op altwee membrane gedoen. Selektiwiteite van 90.6% kon verkry word met die palladium membraan. Die palladium-koper membraan kon slegs ‘n selektiwiteit van 13% bereik. Met hittebehandeling daarvan het die selektiwiteit selfs meer afgeneem. Die palladium membraan het ook hoër omsettings na asetoon getoon. Die rede hiervoor is die membraan se hoë selektiwiteit. Die palladium-koper membraan het nie veel beter resultate as die propvloei reaktor gelewer nie.
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Hop, Marina. "Dehydrogenation of N-Propanol to Propionaldehyde over a copper chromite catalyst." Master's thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/18796.
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Methyl methacrylate (MMA) is widely used for a range of polymer products. MMA can be produced from propionaldehyde via the BASF process. n-Propanol is readily available 'in South Africa as a byproduct of Fischer-Tropsch synthesis. This prompted an investigation into the production of propionaldehyde by the dehydrogenation of n-propanol. There is presently no established technology for the dehydrogenation of n-propanol to propionaldehyde and there has been very little work carried out on the effect of process variables on propionaldehyde yield. The emphasis of the current work was optimising propionaldehyde production. A commercial copper-chromite catalyst (G-13), for the dehydrogenation of ethanol to acetaldehyde, was used for the purposes of this study.
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Elangovan, Saravanakumar. "Well-defined iron and manganese catalysts for reduction and dehydrogenation reactions." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S008/document.
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La substitution des métaux nobles par des métaux de transition abondants et bon marché est un challenge majeur de ce siècle en chimie de synthèse. Récemment, les métaux abondants tels que le fer et le manganèse (1er et 3ème en abondance dans l'écorce terrestre) ont connu un essor remarquable en catalyse homogène, notamment en réduction. Les travaux de thèse ont portés sur le développement de nouveaux catalyseurs bien-définis efficaces du fer et du manganèse pour effectuer des réactions d'hydrogénation de dérivés carboxyliques, de réduction par prêt d'hydrogène et de déshydratation d'amidesThe substitution of noble metals by abundant and cheap transition metals is a major challenge of this century in synthetic chemistry. Recently, abundant metals such as iron and manganese (1st and 3rd in abundance in the Earth's crust) have seen remarkable growth in homogeneous catalysis, especially in reduction. The thesis work focused on the development of new well-defined efficient catalysts of iron and manganese to carry out reactions of hydrogenation of carboxylic derivatives, reduction by hydrogen and dehydration of amides
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Rallan, Chandni. "Development of novel structured catalysts and testing for dehydrogenation of methylcyclohexane." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/development-of-novel-structured-catalysts-and-testing-for-dehydrogenation-of-methylcyclohexane(8a18f073-74b2-4a3e-9498-344e109f628b).html.
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Hydrogen storage for stationary and mobile applications is an expanding research topic. Using liquid organic hydrides for hydrogen storage is one of the most promising alternatives as it provides simple and safe handling. Liquid organic hydrides are largely compatible with current transport infrastructure, whereas alternatives such as liquid and gaseous hydrogen and metal hydrides would require a completely new infrastructure. An attractive storage system is the so-called MTH system (Methylcyclohexane, Toluene and Hydrogen). The dehydrogenation of methylcyclohexane is a highly endothermic reaction. To improve the reaction kinetics, this research was to develop a structured catalyst with a conductive metal support (Fecralloy) which could hold an adherent catalytic washcoat (γ - Al2O3). The active phase was impregnated onto this support and the developed catalyst was tested for the dehydrogenation of methylcyclohexane. The catalyst preparation involved three key steps which were support oxidation, loading of an adherent washcoat and finally impregnation of the active phase. The oxidation and washcoat stages required significant optimisation. The optimum oxidation conditions were found to be 950 °C for 10 h. The washcoating procedure was optimised by modifying a one-step hybrid washcoating method suggested in patent literature. Characterization techniques including SEM, XRD and EDX were used to study each step of catalyst preparation. In addition the technique of STEM was used to study platinum dispersion on the catalytic washcoat. Finally the catalytic activity of the developed catalyst was compared with an in-house pelleted catalyst based on the material used to prepare the structured catalyst and commercially available platinum on γ - Al2O3. Three key factors: activity, selectivity and stability were evaluated. The activity and selectivity were studied at varied operating conditions of T = 340 °C - 400 °C, W/F = 7345 - 14690 g s/mol, H2/MCH molar ratio = 0 - 9 and P = 1.013 bar. The dehydrogenation reaction of methylcyclohexane was found to be very selective to toluene (above 99%). Compounds, which are considered coke precursors, were identified, to attempt to explain the mechanism of catalyst deactivation. By-product distribution was monitored and possible reaction pathways were postulated. To gauge the stability of the catalyst, long term life tests were also performed on the structured catalyst at 400 °C and W/F = 14690 g s/mol for approximately 400 h. The stability study investigated the different types of deactivation mechanisms. The catalyst evaluation study helped identify the effect of the alloy support, the alumina washcoat and platinum dispersion on the selectivity of the catalyst.
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Li, Zheng. "Phase behavior of iron oxide doping with ethylbenzene dehydrogenation catalyst promoters." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3355517.
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Sahoo, M. K. "Visible light mediated photoredox catalytic dehydrogenation and C-H arylation reactions." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2018. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/4557.
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Unel, Ebru. "Ruthenium(iii) Acetylacetonate As Catalyst Precursor In The Dehydrogenation Of Dimethylamine-borane." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612980/index.pdf.
Full textAbstract:
Amine boranes have recently been considered as solid hydrogen storage materials with high capability of hydrogen storage. Dimethylamine borane is one of the promising amine boranes with high theoretical gravimetric capacity of 16.9 wt%. Dimethylamine borane can undergo dehydrogenation only in the presence of a suitable catalyst at moderate temperature.
In this project, throughout the dehydrogenation of dimethylamine borane (DMAB), the catalytic activity of ruthenium(III) acetylacetonate was examined for the first time. During the catalytic reaction, formation of a new in-situ ruthenium(II) species, [Ru{N2Me4}3(acac)H], is observed. Mercury poisoning experiment indicates that the in-situ ruthenium(II) species is a homogeneous catalyst in the dehydrogenation of dimethylamine borane. Kinetics of catalytic dehydrogenation of dimethylamine borane starting with ruthenium(III) acetylacetonate was investigated depending on catalyst concentration, substrate concentration and temperature. As a result, the hydrogen generation rate was found to be first-order with respect to catalyst concentration and zero-order regarding the substrate concentration. Besides, evaluation of the kinetic data yielded that the activation parameters for dehydrogenation reaction: the activation energy, Ea = 85 ±2 kJ&bull
mol-1
the enthalpy of activation, DH# = 82 ±
2 kJ&bull
mol-1 and the entropy of activation
DS# = -85 ±
5 J&bull
mol-1&bull
K-1. Additionally, before deactivation, [Ru{N2Me4}3(acac)H] provides 1700 turnovers over 100 hours in hydrogen evolution from the dehydrogenation of dimethlyamine borane. [Ru{N2Me4}3(acac)H] complex formed during the dehydrogenation of dimethylamine borane was isolated and characterized by UV-Visible, FTIR, 1H NMR, and Mass Spectroscopy. The isolated ruthenium(II) species was also tested as homogeneous catalyst in the dehydrogenation of dimethylamine borane.
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Hocknull, M. D. "The influence of water-immiscible organic solvents on bacterial steroid Delta2-dehydrogenation." Thesis, University College London (University of London), 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508463.
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Liu, Yining. "Isopropyl alcohol dehydrogenation of CO2 by the utilisation of plasmolysis with fluidics." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19864/.
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One of the greatest challenges currently faced by humanity is the evolution of global environmental trends. Evidence points to the increased greenhouse gas emissions generated by humans as the main cause of these changes. One possible solution to the reduction of CO2 emissions is the production of value-added products or precursors which can be used as the feedstock for the former. In this project, several methods are used to facilitate the hydrogenation of CO2 via reaction with isopropyl alcohol, which acts as a hydrogen source, for the production of formic acid/formate and acetone. Since CO2 is thermodynamically stable, microbubble technology and plasmolysis were hypothesised to reduce the activation energies, even though the literature has only the precedent of catalysis.
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Anghel, Alexandra Teodora. "Surmounting reaction barriers : DFT studies of alkane dehydrogenation on Pt{110}(1x2)." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614861.
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Sharninghausen, Liam S. "Transition Metal Complexes for Glycerol Dehydrogenation and Study of Water Oxidation Catalysis." Thesis, Yale University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10957339.
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This dissertation describes the study of transition metal complexes in relation to two types of oxidation catalysis, namely dehydrogenation and water oxidation.
Chapters 1 and 2 explore dehydrogenation catalysis as a means of glycerol valorization. Glycerol is the major byproduct of biodiesel production (~10%), and there is thus intense interest in developing methods to convert this waste glycerol to more valuable products. One such product is lactic acid, which is commonly used in the food and detergent industries, and is a platform chemical that is seeing increasing demand. All prior methods for convening glycerol to lactic acid employed heterogeneous catalysts, which often require high temperatures and give generally poor selectivity and catalytic activity. In this work, I describe our study of homogeneous catalysts for glycerol conversion to lactic acid. Our Ir bis-NHC (NHC = N-heterocyclic carbene) precatalysts are superior to the previous systems in terms of selectivity and activity, and function in neat glycerol without the need for a co-solvent. These complexes can convert samples of crude glycerol from the biodiesel industry without the need for prior purification, suggesting their possible industrial application. Additionally, hydrogen is produced as a valuable byproduct. Chapter 2, carried out in collaboration with Professor Nilay Hazari (Yale), describes the study of catalysts based on non-precious metals for this reaction. A family of Fe precatalysts with bifunctional PNP pincer ligands give excellent selectivity and activity, and represent the first examples of homogeneous base-metal catalysts for glycerol conversion to lactic acid. In studies of Ir species formed from our Ir bis-NHC precatalysts during glycerol dehydrogenation, we isolated a series of unusual NHC-rich Ir polyhydride clusters (Chapter 3). These compounds are unprecedented in terms of their high NHC content, and were fully characterized using a variety of methods.
Chapters 4 and 5, carried out in collaboration with Shashi Sinha and Dimitar Shopov, joint BrudvigCrabtree students, describe the study of model complexes related to resting states and high oxidation state intermediates in water oxidation catalysis. Water oxidation has garnered intense interest because of its potential application in the production of solar fuels, but effective catalysts are needed to carry out the reaction with low overpotentials. Our group previously found that upon oxidative activation, the Cp*Ir(pyalk)OH precatalyst (pyalk = 2-pyridyl-2-propanolate) generates one of the most active and robust water oxidation catalysts reported to date. Previous spectroscopic characterization and DFT studies revealed that the Cp* ligand is oxidatively degraded, and the catalyst resting state likely consists of a mixture of related species with a (pyalk)2IrIV-O-IrIV(pyalk) core. However, these species completely resisted purification and crystallization by standard methods. Therefore, we developed a protocol to more selectively prepare related CI(pyalk)2IrIV-O-IrIV(pyalk) 2CI complexes, which can be isolated and crystallographically characterized. These complexes are unusual examples of well-defined Ir(IV,IV) mono-μ-oxo dimers, and are stable under ambient conditions, in contrast to previous examples of Ir(IV,IV) mono-μ-oxo dimers containing organometallic ligands. Our study of these complexes sheds light on the resting state of our Ir water oxidation catalyst, and opens the door to future development of well-defined Ir-oxo dimers for water oxidation catalysis.
In a related study (Chapter 5), we use techniques and insights that build on our Ir oxo-dimer study to synthesize unprecedented Ir(V) coordination complexes with organic ligands. Study of such well-defined high oxidation state complexes is of interest in relation to oxidation catalysis, where Ir(V) species have been proposed as key intermediates. In order to access Ir(V), we developed the ligand dpyp, an N,O,Odonor analogue of pyalk. Importantly, dpyp forms coordination complexes with four coplanar alkoxogroups, an arrangement that favors attainment of high oxidation states based on our previous work. Indeed, oxidation of IrIV(dpyp)2gives IrV(dpyp) +2+, which was fully characterized including by X-ray crystallography and DFT methods.
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Kazmierczak, Kamila Maria. "Heterogeneous catalysts for acceptor-less alcohol dehydrogenation - joined experimental and theoretical studies." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEN045.
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La déshydrogénation d’alcool sans accepteur est une réaction extrêmement intéressante du point de vue de la chimie verte. Dans celle-ci, les alcools (dérivés de la biomasse) sont transformés en produits carbonylés, qui sont des produits chimiques à haute valeur ajoutée. De plus, de l’hydrogène est produit hautement énergétique, sous forme gazeuse, comme seul sous-produit de la réaction. La présence de catalyseur facilite le processus. Des catalyseurs hétérogènes au cobalt supportés et des nanoparticules façonnées sans support ont été étudiés dans cette réaction. Pour comprendre leurs performances catalytiques, les approches expérimentales et théoriques ont été reliées. Les tests catalytiques visaient à évaluer l'activité et la sélectivité des catalyseurs vis-à-vis de la déshydrogénation de mono- et polyalcools (diols) possédant des groupes hydroxyle primaires et secondaires. Une caractérisation poussée a permis d’evaluer les propriétés intrinsèques des matériaux. La réductibilité du cobalt sur des supports de nature différente a été examinée. Pour les nanoparticules non supportées, la forme, le type de facettes métalliques exposées et l'épaisseur de la couche de ligand protégeant les nanoparticules ont été analysés. Les calculs de la théorie fonctionnelle de la densité (DFT) ont permis de comprendre le comportement catalytique au niveau moléculaire. L'activité catalytique et la sélectivité, ont été étudiées pour des surfaces de Co de différentes natures ainsi que l'influence des ligands co-adsorbés. En combinant tous les résultats, il a été possible d'identifier les facteurs guidant l'activité du catalyseurAcceptor-less alcohol dehydrogenation is a highly interesting reaction from the green chemistry point of view. In it, the (biomass derived) alcohols are transformed into carbonyl products, which are high value-added chemicals. Moreover, highly-energetic H2 in gaseous form is produced as the only by-product in the reaction. The presence of catalyst facilitates the process. Cobalt heterogeneous supported catalysts and unsupported shaped nanoparticles were investigated in this reaction. To understand their catalytic performance, the experimental and theoretical approaches were joined. Catalytic testing was aiming to assess the activity and selectivity of the catalysts, towards the dehydrogenation of mono- and polyalcohols (diols) possessing primary and secondary hydroxyl groups. Extensive characterization allowed to investigate the intrinsic properties of the materials. In between the reducibility of cobalt supported on materials of different nature was examined. For unsupported nanoparticles the shape, type of exposed metal facets, and also thickness of the ligand layer protecting the nanoparticles were analyzed. Density Functional Theory (DFT) calculations gave the opportunity to understand the catalytic behavior on the molecular level. The catalytic activity and selectivity, and the influence of the co-adsorbed ligands on the catalytic performance of metal, were studied for Co surfaces of different nature. By combining all the results it was possible to identify the factors guiding the catalyst activity
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Usman, Muhammad Rashid. "Kinetics of methylcyclohexane dehydrogenation and reactor simulation for 'on-board' hydrogen storage." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/kinetics-of-methylcyclohexane-dehydrogenation-and-reactor-simulation-for-onboard-hydrogen-storage(dfd62a36-75a7-4de6-96fa-3f30ecdff9a7).html.
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Today's transportation system is contributing to increasing air pollution and lack of future fuel for a growing number of vehicles. Over the years, many alternate solutions have been proposed to replace or to assist conventional fuels in order to alleviate the environmental damage and future fuel shortage. One such solution is to use hydrogen gas as fuel in an internal combustion engine or a fuel cell. Hydrogen being light, flammable and having very low critical temperature has associated problems of storage, transportation and utilisation. The methylcyclohexane-toluene-hydrogen (MTH)-system is a safe and economical way of storage and 'on-board' hydrogen generation. The dehydrogenation reaction of MCH is highly endothermic and suffers from equilibrium limitations. Therefore, success of the MTH-system for 'on-board' applications lies in the development of a highly active, selective and stable catalyst as well as a reactor supplying high rates of heat transfer to the catalytic bed. A review of the literature has shown that there is a huge disagreement in describing the kinetic mechanism of the dehydrogenation reaction of MCH. There is no consensus on the rate-determining step and the inhibition offered by the products. Moreover, there is no detailed kinetic investigation over a wide range of operating conditions including experiments without H2 in the feed and under integral conditions.The present study is designed to conduct a detailed kinetic investigation over a wide range of operating conditions including experiments without hydrogen in the feed for the most promising catalyst developed to date. The reaction kinetics are incorporated into a two-dimensional pseudo-homogeneous model to predict observed longitudinal temperature profiles. Alternative configurations and schemes for 'on-board' hydrogen generation based on the MTH-system are compared and a prototype reactor, suitable for 'on-board' hydrogen generation, is designed and simulated in detail, exchanging heat with the engine exhaust gas. Kinetic experiments were performed in a laboratory fixed bed tubular reactor under integral conditions. A 1.0 wt% Pt/Al2O3 catalyst was prepared and a wide range of experimental conditions were studied. A number of kinetic models were applied based on the power law, Langmuir-Hinshelwood-Hougen-Watson (LHHW) and Horiuti-Polanyi (HP) mechanisms. A kinetic model based on LHHW single-site mechanism with loss of the first H2 molecule the rate rate-controlling step was found to best fit the data. Analyses of the products show that the dehydrogenation of MCH is very selective towards toluene. As well as the main product toluene, a number of condensable by-products were also identified. Benzene, cyclohexane and ring-closed products (ethylcyclopentane and dimethylcyclopentanes) are the major by-products.Laboratory experimental data for the 12 experimental runs made under varying conditions of pressure, space velocity and feed composition were simulated and good agreement between predicted and observed centreline temperatures was found. A hybrid MTH-gasoline-system is a viable option. Using titanium aluminide as the material of construction, the dynamic (start up) time requirement for the prototype reactor may be halved over that required for a stainless steel construction.
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Mohamed, Dzahir Mohd Irfan Hatim. "Pd based inorganic hollow fibre membranes for H2 permeation and methylcyclohexane dehydrogenation." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6919.
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The availability of inorganic membranes which can withstand high temperatures and harsh chemical environments has resulted in a wide range of opportunities for the application of membranes in chemical reactions and separations. In particular, the combination of membrane separation and catalytic reaction into a single operating unit is an attractive way to increase conversions, improve yields and more efficient use of natural resources in many reactions. In this study, asymmetric alumina hollow fibres with different macrostructures consisting of finger-like macrovoids and a sponge-like packed pore structure in varying ratios have been prepared by a combined phase inversion/sintering technique. The asymmetric membranes in hollow fibre geometry possess superior surface area to volume ratios with less gas permeation resistance in comparison to commercial symmetric membranes in tubular and disk configurations. Such asymmetric hollow fibres are used as substrates onto which a Pd membrane is directly deposited by an electroless plating (ELP) technique without any pre-treatment of the substrate surface. A systematic study of the electroless plating of Pd and Ag onto an asymmetric alumina hollow fibre substrate has been carried out by direct measurement of one of the gaseous products, i.e. N2, using gas chromatography (GC). In addition, the influences of the substrate macrostructure on hydrogen permeation through the Pd/Al2O3 composite membranes have been investigated both experimentally and theoretically. Furthermore, a multifunctional Pd/alumina hollow fibre membrane reactor (HFMR) has been developed and employed for the catalytic dehydrogenation of methylcyclohexane (MCH) to toluene (TOL). The developed HFMR consists of a thin and defect-free Pd membrane coated directly onto the outer surface of an asymmetric alumina hollow fibre substrate. 50 wt% Ni/Al2O3 nano-sized catalysts were directly impregnated into the substrate. The performance of HFMR has also been compared with several different reactor configurations.
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Park, Justin Lane. "The Investigation of Nickel-Based Catalysts for the Oxidative Dehydrogenation of Ethane." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7393.
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The Investigation of Nickel-Based Catalysts for the Oxidative Dehydrogenation of Ethane Justin Lane ParkDepartment of Chemistry & Biochemistry, BYU Doctor of Philosophy Chemistry The advancement of creating ethylene from ethane via oxidative dehydrogenation (ODH) rather than the traditional direct dehydrogenation is right on the cusp of commercialization. The oxidative pathway provides a novel route that reduces the operating temperature of this reaction by 400-500°C. A variety of metals including Mo, V, and Ni that have redox properties suitable for the partial oxidation of small chain alkanes have been investigated. Currently, a MoVNbTe oxide is the most promising catalyst but it suffers from a long and difficult preparation method and the combination of four expensive metals. Nickel based catalysts have also shown great promise but are limited by the reactivity of the oxygen species on the surface of the catalyst. In this manuscript, the details for improving the activity of the nickel and altering the activation mechanism are outlined.Bulk CeNiNb oxide catalysts were shown to almost double the rate of ethylene yields at temperatures as low as 300°C. This is partially related to the improved rate of oxygen adsorption and transfer to the active oxygens on the nickel oxide via the ceria additive. However, with further characterization of these materials, it was shown that there is likely an interaction between the Ce and Nb, forming a Ce-O- Nb linkage that is also selective towards ethylene. This facilitates a higher activity of the catalyst by creating two redox active sites. The improved rates of ethylene formation observed with these catalysts led to the initial development of a commercially viable nickel based catalyst. The support interactions of NiO with a novel silica doped alumina support show higher yields than previously reported studies of NiO on alumina for ODH. These initial metal support interactions show that the addition of the niobium and ceria to this catalyst should give ethylene yields that are satisfactory for the commercialization of this catalyst.
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Pickard, Simeon. "The Vapor-Phase Dehydrogenation of Ethylbenzene Using Polymeric & Polymer-Supported Quinones." TopSCHOLAR®, 1986. https://digitalcommons.wku.edu/theses/2710.
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Polymer-supported and polymeric quinones were synthesized and evaluated in their ability to dehydrogenate ethylbenzene in the vapor phase. The polymeric quinones were found to be more useful agents for dehydrogenation than the polymer-supported quinones, probably due to the higher concentration of quinone per given mass of polymer.
The factors that affected the yield of styrene using the polymeric quinone were the nature of the polymer, the space velocity in the column, and the reaction temperature. The space velocity was evaluated by holding constant the flow rate of the carrier gas and varying the concentration of ethylbenzene in the gas stream. The best yields were obtained by introducing 0.25 ml of reactant into the column every ten minutes. Using this process the yield of styrene varied from 2.73% at 200°C to 6.90% at 250°C. Both nitrogen and air were used as the carrier gas in this process, and there was no significant difference in the yield of styrene. However, the ability of air to re-oxidize the quinone or its tendency to form undesirable oxidation by-products was not evaluated.
The effect on the ease of vapor-phase dehydrogenation of adding an electron-donating or an electron-withdrawing substituent to ethylbenzene was evaluated. The electrondonating substituent appeared to have little effect upon the dehydrogenation, but the electron-withdrawing substituent had a negative effect.
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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 - 2013In 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]
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