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1
Ferrandon, Magali. "Mixed metal oxide - noble metal catalysts for total oxidation of volatile organic compounds and carbon monoxide." Doctoral thesis, Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3156.
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Weeks, Simon A. "Anodes for methanol oxidation." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258023.
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Hoffmann, Jens. "Methanol-Oxidation an getragenen Pd-Modellkatalysatoren." [S.l. : s.n.], 2003. http://www.diss.fu-berlin.de/2003/128/index.html.
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Wawata, Ibrahim. "Methanol oxidation on molybdenum oxide catalysts." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/74613/.
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Alshehri, Abdulmohsen. "Methanol oxidation on transition elements oxides." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/47041/.
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Methanol oxidation to formaldehyde is one of the most important industries in our lives; the reaction occurs on catalyst surface in heterogeneous catalysis. Iron molybdate is the current selective catalyst. However, molybdenum volatilises during methanol oxidation and leaving the catalyst with a low molybdenum ratio, which deactivates the catalyst, a 2.2 Mo: 1Fe iron molybdate catalyst was used instead the stoichiometric catalyst, while yield of formaldehyde cannot be 100%. The goal of this study is to find more selective and more productive catalyst than iron molybdate catalyst, the first step is to find another transition element as selective as molybdenum, because molybdenum is the selective part, and iron is the active part, the resulting iron molybdate catalyst is a selective catalyst to formaldehyde near molybdenum and active near iron. Experimentally, catalysts were prepared using co-precipitation method, however, some doped catalysts were papered by incipient wetness impregnation, also sol-immobilization was used to prepare nano-gold particles on the surfaces of few supports. Catalysts characterizations were carried out within several techniques for the surface analysis (XPS) and bulk analysis (XRD), also the surface area was measured by BET equipment. Raman too was used in this study, while micro-reactor was the reactor to determine selectivity and activity of each catalyst. When molybdenum replaced by vanadium, the catalyst yielded 100% formaldehyde at 200 oC; moreover, tungsten was selective. Likewise, iron was replaced by other active metals such as manganese, copper and bismuth, which are active. Nano-gold improved activity when doped on molybdenum oxide and iron molybdate supports.
6
Long, Antony Richard. "The oxidation of methanol in methylotrophic bacteria." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304611.
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Spagnolo, David. "Low temperature oxidation of methanol using hydrophobic catalysts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21640.pdf.
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Yaseneva, Polina. "Selective oxidation of methanol on mixed oxide catalysts." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/54464/.
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In the present work selective oxidation of methanol over the model Mo/Fe2O3 and Mo/Co(Zn) Fe2O4 systems has been investigated. It was shown that pure iron oxide and cobalt ferrite combust methanol to carbon dioxide and water. When molybdenum is loaded on the surface of iron oxide and calcined at 500 C, this leads to the formation of iron molybdate surface layer over Fe2C>3 core, which significantly changes selectivity in methanol oxidation towards partial oxidation products. The neighbouring Fe-Mo and Mo-Mo pairs of iron molybdate layer are responsible for the formation of carbon monoxide and formaldehyde respectively. According to XRD, Raman and XPS data, dosing of molybdenum onto the cobalt ferrite surface results in the formation of a mixed layer consisting of cobalt molybdate, iron molybdate and molybdena phases. Oxidation of methanol over Mo/CoFe2O4 results in the formation of a mixture of CO and CO2 with small traces of formaldehyde. CO is produced on mixed Fe-Mo and Co-Mo sites at temperatures above 220 C, whereas CO2 is mainly produced at lower temperatures and low oxygen conversion due to oxidation of CO by highly reactive traces of pure cobalt ferrite or cobalt molybdate present on the surface. Methanol oxidation was used as a model reaction to establish whether there is a relationship between catalytic activity and selectivity, and magnetic properties of catalysts. The catalytic behaviour of the pure and Mo impregnated ZnxCoi-xFe2O4 systems in the vicinity of Curie point was studied. Curie temperature of the material and the nature of Curie transition were adjusted varying Zn content and sample calcination temperature.
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Squire, Gavin Daniel. "Partial oxidation of methane to methanol and formaldehyde." Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278072.
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House, Matthew Peter. "Selective oxidation of methanol over iron molybdate catalysts." Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/56182/.
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The selective oxidation of methanol to formaldehyde over iron molybdate catalysts has been investigated. It has been shown that when Fe2C 3 is present at the surface CO2 and H2 are observed from surface formates, while neighbouring pairs of molybdena sites leads to the production of formaldehyde and water from surface methoxys. When molybdenum sites are isolated then the surface methoxy is stabilised and a direct pathway to CO and H2 is created. On molybdena rich surfaces the production of CO is observed, but as a secondary oxidation product following the linear pathway: CH3OH → CH2O → CO → CO 2, established by varying bed lengths. Catalysts with addition of small amounts of molybdena added to the surface of Fe2O 3, are similar to those with a low bulk ratio of Mo:Fe showing increased activity over Fe2O3. Selectivity is dictated by the presence of isolated or pairs of molybdena sites, which guide the reaction to the primary products of CO and formaldehyde respectively. Structural analysis showed the phases of a-Fe2O3, (X-MoO3 and a-Fe2(MoO4)3, depending on the ratio of the cations present. Molybdenum has been shown to concentrate at the surface of iron molybdates by reactor results from low ratio catalysts, Raman spectroscopy, XP spectroscopy and STEM/EEL spectroscopy. The normal reaction of iron molybdates is via the Mars-van Krevelen mechanism, so tests were made without the presence of gaseous oxygen. The reduction of the surface layer can occur at temperatures as low as 200°C. At temperatures above 250°C diffusion of lattice oxygen to replace the lost surface oxygen can occur, leading to the production of further oxidised products. If the oxidation state of surface molybdenum drops below +6 then formaldehyde selectivity drops markedly, with direct production of CO and secondary production of CO2 observed.
11
Zheng, Sisi. "Methanol partial oxidation and dehydration over silver catalyst." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/11622.
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This thesis describes an experimental and modelling study of the kinetics of silver-catalysed formaldehyde production via methanol partial oxidation and dehydrogenation. In methanol oxidation, the reaction is controlled by the gas phase diffusion of reactants towards the catalyst surface. The methanol-to-oxygen ratio at the catalyst wall is 100-200 times higher than that in the feed, which means that the reaction operates with large excess of methanol and therefore is solely controlled by the availability of O2 at the surface. A constant stoichiometry = 2.25 is found. In methanol dehydrogenation, the strongly-bound surface oxygen (Oγ) catalyses the formation of CH2O and H2 without any by-product. The decline in methanol conversion over time is attributed to the gradual consumption of Oγ due to the thermal decomposition. During the surface pre-oxidation, the surface oxygen penetrates into the silver bulk and diffuses back to the surface after O2(g) is withdrawn. The H2 production during methanol oxidation is solely via the dehydrogenation channel occurring on the whole catalyst surface independently but concurrently with the oxidation, which only happens on the surface that is in contact with O2(g). Without pre-treatment, the “oxidation surface” is the only active surface for both oxidation and dehydrogenation. A transient penetration layer of active oxygen species is formed and catalyses the methanol dehydrogenation. The near constant stoichiometry is a fundamental constant describing the ratio of the dehydrogenation channel over the oxidation channel on the same surface area. Surface characterization (ex-situ XPS and SEM analysis) were performed over silver foil showing the dynamic picture of oxygen evolution and further supporting the proposed reaction mechanisms in this work.
12
Zhou, Ling. "Model studies of methanol selective oxidation over copper catalysts." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976146614.
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Shan, Jingning. "Polymer-supported catalysts for oxygen reduction and methanol oxidation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0017/MQ55541.pdf.
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Gilmour, Marie Naomi. "Oxidation of propane and methanol using metal oxide catalysts." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54964/.
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The selective and nonselective oxidation of propane was investigated using a range of metal oxide catalysts. Total oxidation of propane was studied using Nb and W supported on Pd/Ti02- The addition of Nb or W to Pd/TiO<sub> 2</sub> promoted the activity of the catalyst to give 100% conversion by 450°C. The only reaction product observed was carbon dioxide. The addition of Nb and W significantly changed the nature of the palladium and oxygen mobility, from XPS studies. Niobium and tungsten exhibited the highest activity with a 6% loading with the best catalyst being 0.5%Pd/6%Nb<sub>2</sub>O<sub>5</sub>/TiO<sub> 2</sub>. Oxidative dehydrogenation of propane was studied using vanadium on a ceria support and also with cobalt, iron and manganese oxides. Ceria on its own was very active for the total oxidation of propane, under the conditions used for oxidative dehydrogenation, but the sole reaction product was carbon dioxide. The addition of vanadium switched the activity of the ceria to give appreciable selectivity to propene of around 90%. The formation of a mixed cerium vanadium phase was of the most interest for future work where conditions could be optimised to give improved yields. Cobalt, iron and manganese oxides were prepared by grinding the corresponding nitrate with ammonium bicarbonate and their activity tested in propane oxidative dehydrogenation. The yields of propene were higher than the V/CeO<sub>2</sub> catalysts with the most active oxide being cobalt with a yield of 3.8%. The activity of cobalt was attributed to a small crystallite size, high reducibility and high ratio of O/Co. Methanol oxidation was also investigated using the cobalt, iron and manganese oxides. The main reaction product was formaldehyde and the highest yield, of 23%, was obtained for the manganese oxide. The activity was attributed to a high O/Mn ratio of 3.03 and an optimal particle size of 54nm.
15
Zhang, Meng. "Regulation of methanol oxidation genes in Methylobacterium extorquens AM1 /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/9847.
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Matthews, Terry. "The Partial Oxidation of Methane to Methanol & Formaldehyde." TopSCHOLAR®, 1987. https://digitalcommons.wku.edu/theses/2602.
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The conversion of methane into methanol is viewed as one approach to utilizing the vast reserves of natural gas.
One such prospect for the utilization of natural gas is the partial oxidation of methane to methanol. Methanol ranks high on the commodity market. As a liquid it is easily transportable and therefore skirts the issue of vast amounts of a gas having to be transported either by pipeline or by liquifying.
The catalytic partial oxidation of methane to methanol is investigated. Two different reactor systems are employed. The first system is a fixed bed system. The second is a fluid bed system.
Areas to be addressed are different catalyst systems, different loading rates, elemental promotion, different supports, surface area, catalyst particle mesh size, and effects of preparation.
17
Yu, Eileen Hao. "Development of direct methanol alkaline fuel cells." Thesis, University of Newcastle Upon Tyne, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289171.
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Day, Darren John. "The methanol : cytochrome c oxidoreductase of Methylobacterium extorquens AM1." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293714.
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Qian, Min. "Technical study of the silver catalyzed methanol oxidation to formaldehyde /." Berlin : Logos Verlag Berlin, 2004. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014188297&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Lee, Christopher. "Computer simulation of ethylene glycol oxidation and methanol-water interactions." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/51368/.
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In this project, density functional theory calculations were performed to study the adsorption of ethylene glycol to the MgO (100), MgO (130), Al2O3 (0001), PdO (101) surfaces, as well as Au38 and Au38O16 nanoparticles. Adsorption of ethylene glycol is favourable to all of these surfaces with Al2O3 (0001) and PdO (101) showing the most favourable adsorption at -168 kJ mol-1 and -135 kJ mol-1 respectively. The MgO surfaces showed adsorption energies between -80 kJ mol-1 and -100 kJ mol-1, and the gold nanoparticles showed lower adsorption energies at approximately -35 kJ mol-1. Barriers to O-H activation and C-H activation of ethylene glycol were also studied on these surfaces. The barriers to O-H activation were small over each of the surfaces (between 8 and 46 kJ mol-1) and large for the gold nanoparticles (108 kJ mol-1). The barriers to C-H activation were very large over the MgO surfaces (>300 kJ mol-1), and lower over the PdO (101) surface (63 kJ mol-1) and the gold nanoparticles (68 kJ mol-1). C-H activation was found to not be possible over the Al2O3 (0001) surface. Classical molecular dynamics studies were performed on various water and methanol mixtures as well as in the presence of a hydroxylated Al2O3 (0001) surface. It was found that in methanol there are on average 1.1 oxygen – oxygen close contacts with other methanol molecules in pure methanol, and water has on average between 2.03 and 2.86 oxygen – oxygen close contacts, with more being present at higher temperatures. The presence of a hydroxylated aluminium oxide surface induces local ordering in the methanol molecules resulting in an increase in methanol – methanol and water – methanol oxygen – oxygen contacts, however there is a decrease in water oxygen – water oxygen contacts.
21
Amaratunga, Karen. "Molecular biology of the methanol oxidation system in Methylobacterium extorquens." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307151.
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Mensch, Michael W. "The Oxidation of Methanol on Cr2O3 (1012) Single Crystal Surfaces." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31546.
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The reaction of methanol with the nearly-stoichiometric and oxygen-terminated surfaces of Cr2O3 (1012) was studied using thermal desorption spectroscopy and x-ray photoelectron spectroscopy. Dissociative adsorption of methanol occurs on the nearly-stoichiometric surface and is attributed to the presence of cation/anion site-pairs. An array of products including CH4, CH2O, CO, CO2, and H2 are produced above 550 K on the nearly-stoichiometric surface. Monolayer coverage of methanol yields a 58% conversion to products. Of these products, selectivity to CO is the highest (41%), followed by CH2O (28%), CH4 (24%), and CO2 (7%). At higher temperatures methoxides reversibly undergo dehydrogenation and nucleophilic from lattice oxygen to form dioxymethylene. Hydrogenation of methoxides leads to the formation of CH4 and CH3OH above 550 K. Formate is formed as a surface intermediate by reversible dehydrogenation of dioxymethylene. Formaldehyde is produced via C-O bond cleavage of dioxymethylene, and the decomposition of formate yields CO, CO2, and H2. The oxygen-terminated surface is unreactive for methanol dissociation due cation site blocking by terminal chromyl oxygen.<br>Master of Science
23
Morimoto, Yu. "Electrochemical oxidation of methanol on platinum and platinum based electrodes." Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1058206604.
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Yang, Yuqing. "Electrochemical and Surface-enhanced Raman Spectroscopic Studies of CO and Methanol Oxidation." Miami University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1218126135.
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25
Schlunke, Anna Delia. "Mechanism and Modelling of the Partial Oxidation of Methanol over Silver." Thesis, The University of Sydney, 2007. http://hdl.handle.net/2123/2013.
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This work involves an experimental and kinetic modelling study of the silver catalysed reaction of methanol to formaldehyde. The motivation for this was the desire to investigate the potential for Process Intensification in formaldehyde production. Formaldehyde production from methanol over silver catalyst is a fast, exothermic process where dilution is used to control heat release, and these properties are both indicators of Process Intensification potential. The process is run adiabatically and produces hydrogen (which is currently burnt). Oxygen is consumed during the reaction but is also required to activate the catalyst and is fed in understoichiometric quantities. The central overall reactions in the silver catalysed process for formaldehyde production are oxydehydrogenation CH3OH + ½ O2 -> CH2O + H2O (DH = -159kJ/mol) and dehydrogenation CH3OH <-> CH2O + H2 (DH = 84kJ/mol). When sufficient oxygen is available, formaldehyde can be further oxidised to carbon dioxide CH2O + O2 -> CO2 + H2O (DH = -519kJ/mol). Formaldehyde can decompose to carbon monoxide and hydrogen CH2O <-> CO + H2 (DH = 12.5kJ/mol). Oxidation of methanol and hydrogen also occurs and other minor products of the reaction are methyl formate, methane and formic acid. These overall reactions do not adequately describe the silver catalysed reaction mechanism. In particular, the overall dehydrogenation reaction does not include oxygen as a reactant, but it will not occur over silver that does not have active atomic oxygen species adsorbed on the surface, and these atomic oxygen species are formed from gas phase oxygen. In the absence of a complete mechanism for silver catalysed formaldehyde production, the intensification of the process was investigated using a thermodynamic model (based on the overall oxydehydrogenation and dehydrogenation reactions, not reaction kinetics). It was found that by using heat exchange (rather than heat generated from the exothermic oxydehydrogenation path) and a lower oxygen concentration in the feed stream, hydrogen selectivity could be increased while maintaining the required methanol conversion. Before this iv opportunity could be further investigated, a complete reaction mechanism that would allow the requirement of oxygen for catalyst activation to be included was required. There is agreement in the literature that two active atomic oxygen species react with methanol on silver. These are weakly bound atomic oxygen (Oa) and strongly bound atomic oxygen (Og). The location of Oa is on the surface of the silver, while the location of Og has been described as being in the silver surface (where it substitutes for silver atoms). Both species react with methanol to form formaldehyde. When the concentration of Oa is high enough, Oa will also react with formaldehyde forming carbon dioxide (while Og will not). The literature presents differing views on the extent of involvement of each atomic oxygen species in industrial formaldehyde production. There is also disagreement on the pathways for water and hydrogen formation. An extensive experimental investigation of the partial oxidation of methanol to formaldehyde was carried out using a flow reactor. The effect of temperature (250- 650°C), reactant concentration (7000-40000ppm methanol) and the feed ratio of methanol to oxygen (2.5-5.5) were studied. The extreme case of methanol reaction with Og in the absence of gas phase oxygen was also investigated. To isolate the effect of secondary reactions, the oxidation of formaldehyde, carbon monoxide and hydrogen were investigated, both in the presence and absence of silver catalyst. When methanol was exposed to silver catalyst that had been activated by being covered in Og (with this being the only source of oxygen) the catalytic nature of Og was demonstrated by the high selectivity to formaldehyde and hydrogen that was achieved (with very little carbon dioxide or water production). When gas phase oxygen was fed to the reactor along with methanol, hydrogen selectivity over silver increased up to about 40% as the concentration of reactants was increased. This result is consistent with the general rule of thumb from industrial practice that hydrogen selectivity is about 50%. When formaldehyde and oxygen were exposed to silver in the flow reactor, the only reaction products were carbon v dioxide and water and the combination of high temperature and excess oxygen was required for complete conversion of formaldehyde. A pseudo-microkinetic model (based on a Langmuir-Hinshelwood mechanism) for the partial oxidation of methanol to formaldehyde (over silver) was taken from the literature and investigated. This model predicts formaldehyde production using only Oa (no other active atomic oxygen species are included) but lacks pathways for reactions between Oa and adsorbed hydrogen or hydroxyl (so the only possible fate of adsorbed H atoms is to desorb as H2). The Oa model was combined with literature models for hydrogen desorption and the reactions involving adsorbed hydroxyl (desorption, self reaction, decomposition and reaction with adsorbed hydrogen). Comparison of this Hybrid model with experimental data showed that reactions involving Oa will predict formaldehyde formation and oxidation, but not hydrogen formation (because the rate of hydrogen desorption is too slow compared with the rate of water formation). It is concluded that any detailed model must include the reaction between methanol and Og (producing hydrogen). Although the reaction between two adsorbed OgH species has been suggested as the pathway for hydrogen formation from Og, this is not certain and so all possible reactions involving Og and hydrogen need be investigated and the appropriate pathways added to the Hybrid model. Once a complete microkinetic mechanism for the partial oxidation of methanol to formaldehyde over silver is available it can be used to further investigate the process intensification of this process. In particular, the use of staged addition of oxygen (to keep the catalyst active) combined with heat exchange (to replace the heat normally supplied by the oxydehydrogenation path) with the aim of simultaneously maximizing methanol conversion and selectivity to formaldehyde and hydrogen.
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Schlunke, Anna Delia. "Mechanism and Modelling of the Partial Oxidation of Methanol over Silver." University of Sydney, 2007. http://hdl.handle.net/2123/2013.
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Doctor of Philosophy (PhD)<br>This work involves an experimental and kinetic modelling study of the silver catalysed reaction of methanol to formaldehyde. The motivation for this was the desire to investigate the potential for Process Intensification in formaldehyde production. Formaldehyde production from methanol over silver catalyst is a fast, exothermic process where dilution is used to control heat release, and these properties are both indicators of Process Intensification potential. The process is run adiabatically and produces hydrogen (which is currently burnt). Oxygen is consumed during the reaction but is also required to activate the catalyst and is fed in understoichiometric quantities. The central overall reactions in the silver catalysed process for formaldehyde production are oxydehydrogenation CH3OH + ½ O2 -> CH2O + H2O (DH = -159kJ/mol) and dehydrogenation CH3OH <-> CH2O + H2 (DH = 84kJ/mol). When sufficient oxygen is available, formaldehyde can be further oxidised to carbon dioxide CH2O + O2 -> CO2 + H2O (DH = -519kJ/mol). Formaldehyde can decompose to carbon monoxide and hydrogen CH2O <-> CO + H2 (DH = 12.5kJ/mol). Oxidation of methanol and hydrogen also occurs and other minor products of the reaction are methyl formate, methane and formic acid. These overall reactions do not adequately describe the silver catalysed reaction mechanism. In particular, the overall dehydrogenation reaction does not include oxygen as a reactant, but it will not occur over silver that does not have active atomic oxygen species adsorbed on the surface, and these atomic oxygen species are formed from gas phase oxygen. In the absence of a complete mechanism for silver catalysed formaldehyde production, the intensification of the process was investigated using a thermodynamic model (based on the overall oxydehydrogenation and dehydrogenation reactions, not reaction kinetics). It was found that by using heat exchange (rather than heat generated from the exothermic oxydehydrogenation path) and a lower oxygen concentration in the feed stream, hydrogen selectivity could be increased while maintaining the required methanol conversion. Before this iv opportunity could be further investigated, a complete reaction mechanism that would allow the requirement of oxygen for catalyst activation to be included was required. There is agreement in the literature that two active atomic oxygen species react with methanol on silver. These are weakly bound atomic oxygen (Oa) and strongly bound atomic oxygen (Og). The location of Oa is on the surface of the silver, while the location of Og has been described as being in the silver surface (where it substitutes for silver atoms). Both species react with methanol to form formaldehyde. When the concentration of Oa is high enough, Oa will also react with formaldehyde forming carbon dioxide (while Og will not). The literature presents differing views on the extent of involvement of each atomic oxygen species in industrial formaldehyde production. There is also disagreement on the pathways for water and hydrogen formation. An extensive experimental investigation of the partial oxidation of methanol to formaldehyde was carried out using a flow reactor. The effect of temperature (250- 650°C), reactant concentration (7000-40000ppm methanol) and the feed ratio of methanol to oxygen (2.5-5.5) were studied. The extreme case of methanol reaction with Og in the absence of gas phase oxygen was also investigated. To isolate the effect of secondary reactions, the oxidation of formaldehyde, carbon monoxide and hydrogen were investigated, both in the presence and absence of silver catalyst. When methanol was exposed to silver catalyst that had been activated by being covered in Og (with this being the only source of oxygen) the catalytic nature of Og was demonstrated by the high selectivity to formaldehyde and hydrogen that was achieved (with very little carbon dioxide or water production). When gas phase oxygen was fed to the reactor along with methanol, hydrogen selectivity over silver increased up to about 40% as the concentration of reactants was increased. This result is consistent with the general rule of thumb from industrial practice that hydrogen selectivity is about 50%. When formaldehyde and oxygen were exposed to silver in the flow reactor, the only reaction products were carbon v dioxide and water and the combination of high temperature and excess oxygen was required for complete conversion of formaldehyde. A pseudo-microkinetic model (based on a Langmuir-Hinshelwood mechanism) for the partial oxidation of methanol to formaldehyde (over silver) was taken from the literature and investigated. This model predicts formaldehyde production using only Oa (no other active atomic oxygen species are included) but lacks pathways for reactions between Oa and adsorbed hydrogen or hydroxyl (so the only possible fate of adsorbed H atoms is to desorb as H2). The Oa model was combined with literature models for hydrogen desorption and the reactions involving adsorbed hydroxyl (desorption, self reaction, decomposition and reaction with adsorbed hydrogen). Comparison of this Hybrid model with experimental data showed that reactions involving Oa will predict formaldehyde formation and oxidation, but not hydrogen formation (because the rate of hydrogen desorption is too slow compared with the rate of water formation). It is concluded that any detailed model must include the reaction between methanol and Og (producing hydrogen). Although the reaction between two adsorbed OgH species has been suggested as the pathway for hydrogen formation from Og, this is not certain and so all possible reactions involving Og and hydrogen need be investigated and the appropriate pathways added to the Hybrid model. Once a complete microkinetic mechanism for the partial oxidation of methanol to formaldehyde over silver is available it can be used to further investigate the process intensification of this process. In particular, the use of staged addition of oxygen (to keep the catalyst active) combined with heat exchange (to replace the heat normally supplied by the oxydehydrogenation path) with the aim of simultaneously maximizing methanol conversion and selectivity to formaldehyde and hydrogen.
27
Afolabi, Paul Remi. "The active site of methanol dehydrogenase from Methylobacterium extorquens." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327335.
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Lee, Jaeyoung. "Electro-oxidation of small organic molecules kinetic instabilities and spatiotemporal pattern formation /." [S.l.] : [s.n.], 2001. http://www.diss.fu-berlin.de/2001/210/index.html.
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Lin, Yu-Chuan. "Methanol : a chemical probe and hydrogen source by catalytic partial oxidation /." Search for this dissertation online, 2006. http://www.lib.umi.com/cr/ksu/main.
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Seland, Frode. "Electrochemical Oxidation of Methanol and Formic Acid in Fuel Cell Processes." Doctoral thesis, Norwegian University of Science and Technology, Department of Materials Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-697.
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<p>The main objectives of the thesis work were: (1), to study the oxidation of methanol and formic acid on platinum electrodes by employing conventional and advanced electrochemical methods, and (2), to develop membrane electrode assemblies based on polybenzimidazole membranes that can be used in fuel cells up to 200 °C.</p><p>D.c. voltammetry and a.c. voltammetry studies of methanol and formic acid on polycrystalline platinum in sulphuric acid electrolyte were performed to determine the mechanism and kinetics of the oxidation reactions.</p><p>A combined potential step and fast cyclic voltammetry experiment was employed to investigate the time dependence primarily of methanol oxidation on platinum. Charge measurements clearly demonstrated the existence of a parallel path at low potentials and short times without formation of adsorbed CO. Furthermore, experimental results showed that only the serial path, via adsorbed CO, exists during continuous cycling, with the first step being diffusion controlled dissociative adsorption of methanol directly from the bulk electrolyte. The saturation charge of adsorbed CO derived from methanol was found to be significantly lower than CO derived from formic acid or dissolved CO. This was attributed to the site requirements of the dehydrogenation steps, and possibly different compositions of linear, bridged or multiply bonded CO. The coverage of adsorbed CO from formic acid decreased significantly at potentials just outside of the hydrogen region (0.35 V vs. RHE), while it did not start to decrease significantly until about 0.6 V vs. RHE for methanol. Adsorbed CO from dissolved CO rapidly oxidized at potentials above about 0.75 V due to formation of platinum oxide.</p><p>Data from a.c. voltammograms from 0.5 Hz up to 30 kHz were assembled into electrochemical impedance spectra (EIS) and analyzed using equivalent circuits. The main advantages of collecting EIS spectra from a.c. voltammetry experiments are the ability to directly correlate the impedance spectra with features in the corresponding d.c. voltammograms, and the ability to investigate conditions with partially covered surfaces that are inaccessible in steady-state measurements.</p><p>A variety of spectral types were observed, and for methanol these showed only a single adsorption relaxation aside from the double-layer/charge-transfer relaxation, though some structure in the phase of the latter relaxation hints at another process. The charge-transfer resistance showed Tafel behaviour for potentials in the rising part of the oxidation peak consistent with a one-electron process in the rate-determining step. The rate limiting step was proposed to be the electrochemical reaction between adsorbed CO and OH at the edge of islands of OH, with competition between OH and CO adsorption for the released reaction sites. Only a single adsorption relaxation in methanol oxidation was observed, implying that only one single coverage is required to describe the state of the surface and the kinetics. It was assumed that this single coverage is that of OH, and all the surface not covered with OH is covered with CO so that the coverage of CO is not an independent variable. Inductive behaviour and negative relaxation times in the methanol oxidation were attributed to nucleation and growth behaviour. Linear voltammetry reversal and sweep-hold experiments also indicated nucleation-growth-collision behaviour in distinct potential regions, both in the forward and reverse potential scan for methanol oxidation on platinum.</p><p>In both methanol oxidation and formic acid oxidation, a negative differential resistance (NDR) was observed in the potential regions that possess a negative d.c. polarization slope, and was attributed to the formation of surface oxide which inhibited the oxidation of methanol or formic acid.</p><p>EIS spectra for formic acid clearly showed the presence of an additional low frequency relaxation at potentials where we expect adsorbed dissociated water or platinum oxide to be present, implying that more than one single coverage is required to describe the state of the surface and the kinetics. Two potential regions with hidden negative differential resistance (HNDR) behaviour were identified in the positive-going sweep, one prior to platinum oxide formation, assumed to involve adsorbed dissociated water, and one just negative of the main oxidation peak, assumed to involve platinum oxide. Oscillatory behaviour was found in the formic acid oxidation on platinum by adding a large external resistance to the working electrode circuit, which means that there is no longer true potentiostatic control at the interface. By revealing the system time constants, impedance measurements can be used to assist in explaining the origin of the oscillations. In the case of formic acid, these measurements showed that the oscillations do not arise from the chemical mechanism alone, but that the potential plays an essential role.</p><p>Preparation and optimization of gas-diffusion electrodes for high temperature polymer electrolyte fuel cells based on phosphoric acid doped polybenzimidazole (PBI) membranes was performed. This fuel cell allows for operating temperatures up to 200 °C with increased tolerance towards catalytic poisons, typical carbon monoxide. In this work we employed pure hydrogen and oxygen as the fuel cell feeds, and determined the optimum morphology of the support layer, and subsequently optimized the catalytic layer with respect to platinum content in the Pt/C catalyst and PBI loading. A smooth and compact support layer with small crevices and large islands was found to be beneficial with our spraying technique in respect to adhesion to the carbon backing and to the catalyst layer. We found that a high platinum content catalyst gave a significantly thinner catalyst layer (decreased porosity) on both anode and cathode with superior performance. The PBI loading was found to be crucial for the performance of the electrodes, and a relatively high loading gave the best performing electrodes.</p>
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Ozturk, Zafer. "Carbon Supported Platinum-palladium Catalysts For Methanol And Ethanol Oxidation Reactions." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613008/index.pdf.
Full textAbstract:
In this work, two groups of carbon supported Pt-Pd catalysts have been prepared in order to investigate the effect of Pd, as a second metal, and surfactants on the catalytic activity towards methanol and ethanol oxidation reactions used in the direct methanol and ethanol fuel cells. In the first group (group a), 1- hexanethiol was used as a stabilizing agent while in the second group (group b), 1,1 dimethyl hexanethiol was utilized. Cyclic voltammetry (CV), chronoamperometry (CA), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used in order to determine the nature of the catalysts.
The average crystalline size of the metal particles in the catalysts was explored by XRD and TEM. TEM results revealed the uniform distribution of the metal nanoparticles on carbon support with a narrow size distribution in the range of 3.0 to 3.7 nm and the average crystalline sizes of metal particles for group &ldquo<br>b&rdquo<br>catalysts were larger than that of group &ldquo<br>a&rdquo<br>catalysts which can be explained by the surfactant effect. These results were in good agreement with XRD data.
The oxidation states of platinum (Pt(0) and Pt(IV)) and palladium (Pd(0) and Pd(II)) and their ratios were investigated by XPS and for the most active catalyst, catalyst Ib, these ratios were found to be as 6.94 and 13.7, respectively.
Electrochemical activities of the catalysts towards methanol and ethanol oxidation reactions were recorded and compared with that of Pt/C and the commercial Pt (ETEK 20 %wt) catalysts. The results indicated that the group &lsquo<br>b&rsquo<br>catalyst has greater catalytic activities than that of group &lsquo<br>a&rsquo<br>catalysts. Catalyst Ib comes into prominence as the most active catalyst due to its superior characteristics that it possess such as highest extent of alloying with respect to the palladium amount used, active surface area, CO-tolerance, stability and Pt (0) to Pt (IV) and Pd (0) to Pd (II) ratios.
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Díaz, Real Rafael Alfredo. "Partial oxidation of methanol to formaldehyde over Sb-Mo oxide catalysts." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7465.
Full textAbstract:
The kinetics of the vapor phase air oxidation of methanol to formaldehyde over molybdenum oxide catalysts, antimony oxide catalyst, and their mixtures (both supported and unsupported), at atmospheric pressure and different operating conditions, have been studied in a fixed-bed integral reactor heated by a fluidized sand bath. The effect of various process variables, namely the process temperature (T), the ratio of catalysts to feed flow rate or space time (W/F), and the ratio of methanol fed to air (R), on conversion and yield have been determined. A screening study at varying operating conditions was performed to determine the optimum composition of a Sb$\sb2\rm O\sb4$-MoO$\sb3$ mixture. On the basis of this study a catalyst containing 67% $\rm Sb\sb2O\sb4$-33% MoO$\sb3$ was selected for the detailed kinetic study of oxidation of methanol to formaldehyde. The operating conditions studied were as follows: temperature in the range 623 to 698 K, space times from 5 to 50 $\rm g\sb{cat}/mol\sb{CH\sb3OH}h\sp{-1},$ and methanol to air ratios in the range 0.04 to 0.10 mol$\rm\sb{CH\sb3OH}h\sp{-1}/mol\sb{air}h\sp{-1}.$ This catalyst proved to be highly active and selective to formaldehyde formation. Yields up to $\sim$100% were obtained. Best operating conditions found were obtained at a space time of 27.5 for a methanol/air ratio of 0.06 and a temperature of 698 K. The rate equation for the oxidation of methanol to formaldehyde was derived on the basis of a two-stage redox mechanism$$\eqalign{\rm CH\sb3OH\sb{(g)} + S\sb{ox}\ {\buildrel{k\sb1}\over{\to}}\ &\rm HCHO\sb{(g)} + H\sb2O\sb{(g)} + S\sb{red}\cr\rm O\sb{2\sb{(g)}} + &\rm S\sb{red}\ {\buildrel{k\sb2}\over{\to}}\ S\sb{ox}\cr}$$where S$\rm\sb{ox}$ represents an active site of lattice oxygen and S$\rm\sb{red}$ represents a reduced site of lattice oxygen. The rate equation for the temperature of 648 to 698 K which correlated the data was$$\rm r = {k\sb1P\sb{M}\over 1+{k\sb1P\sb{M}\over 2k\sb2P\sb{O\sb2}}}$$where k$\sb1$ and k$\sb2$ are the temperature dependent rate constants of steps one and two. The equations relating k$\sb1$ and k$\sb2$ with temperature were$$\eqalign{&\rm ln\ k\sb1 = -6.4039-{6.9153\times10\sp3\over T}\cr&\rm ln\ k\sb2 = -3.0154 + {1.8809\times10\sp3\over T}\cr}$$ Several spectroscopic and analytical techniques, viz, electron spin resonance (ESR), x-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), and adsorption studies were used to characterize the catalysts. The surface are of the catalyst used in the kinetic study was 6.1 m$\sp2$/g as determined by the BET method. A preliminary study of the Sb-Mo oxide mixture (load of $\sim$5 wt%) supported on Y zeolite was also carried out. Maximum yield obtained was comparable to that obtained with pure MoO$\sb3.$ A new catalyst has been developed that gave nearly 100% conversion and 100% yield. The industrial potential of this catalyst is very promising.
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Zoumot, Rowaida George. "Partial oxidation of methanol to formaldehyde over molybdenum-tin oxide catalysts." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/11094.
Full textAbstract:
The vapor phase air oxidation of methanol to formaldehyde was investigated over molybdenum oxide, tin oxide and their mixtures in an integral flow reactor at atmospheric pressure between temperature of 513 and 573 K, a space time of 10-40 hr g-cat/g-mol methanol and a molar ratio of 0.04-0.1 mol CH3OH/mol air. Experiments were done under such conditions that the effects of internal and external heat and mass transfer effects were negligible. The effects of several process variables, temperature, space time and methanol/air ratio on the conversion of methanol and the selectivity of the catalyst for formaldehyde production were determined. The results indicated that the impact of the process variables on the conversion, selectivity and yield of formaldehyde were in the following decreasing order T > W/F > R. A screening study indicated the optimum catalyst composition to be 50% SnO2 and 50% MoO3, while conversion increased with temperature and W/F selectivity decreased. This catalyst proved to be highly active and selective to formaldehyde production. Selectivity and yield of up to about 100% were obtained at 100% conversion at a temperature of 553 K, a space time (W/F) of 40 g-cat/g-mol methanol per hour and a molar ratio (R) of 0.04 mol CH3 OH/mol air. The rate expression r=k1P2M 1+k1P2M2k 2PO2 was deduced assuming a steady-state involving two-stage irreversible oxidation-reduction process. It represented the experimental data satisfactorily. Arrhenius plots of the two rate constants gave activation energies of 31.7 and 18.1 kcal/g-mol.
34
Hammond, Charles Rhodri. "Partial oxidation of methane to methanol using modified mixed metal oxides." Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/54537/.
Full textAbstract:
The current steam reforming process for the production of CH<sub>3</sub>OH is complicated and difficult, and therefore the direct partial oxidation of CH<sub>4</sub> to CH<sub>3</sub>OH would be economically desirable. In previous work a design approach for a selective partial oxidation catalyst has been investigated, which comprises the combination of components with a desired reactivity, producing a successful selective partial oxidation catalyst. In this approach, it is considered a successful partial oxidation catalyst must activate methane, activate oxygen and not destroy the desired product, methanol. All these properties could not be found in a single catalyst, so it was proposed that two synergistic components could be combined, one responsible for methane activation and the other for oxygen activation/insertion. Previous work has studied the CH<sub>4</sub>/D<sub>2</sub> exchange reaction as an indication of the ability of a metal oxide surface to activate CH<sub>4</sub>. Two metal oxides demonstrated appreciable activity for the activation of CH<sub>4</sub>, these being Ga<sub>2</sub>C<sub>3</sub> and ZnO. These oxides were then doped with different metals in order to try and increase the activity of the catalyst. The doping of Ga<sub>2</sub>O<sub>3</sub> with Zn or Mg did not improve the methane oxidation properties of Ga<sub>2</sub>C<sub>3</sub>, and the doping of ZnO with Ga significantly lowered the light off temperature, the temperature at which CH<sub>4</sub> was first detected, and increased its oxidative capacity. The addition of precious metals significantly affected the catalysts ability to activate CH<sub>4</sub>. The addition of Au to the Ga and Zn catalysts dramatically reduced the light off temperature, and increased its rate of oxidation at lower temperatures, with the optimum loading 2% for both catalysts. For GaO(OH) and ZnO, the addition of 1%Au and l%Pt by coprecipitation produced a synergistic effect, producing lower light offs and higher CH<sub>4</sub> conversion than the singly doped catalysts with Au and Pt separately. When the methane activation catalysts were combined with MoO<sub>3</sub> in a physical mixture, a number of the mixtures produced higher methanol per pass percentage yields than its constituent parts. It is concluded that the increased methane activation properties beneficially interact with the oxygen activation and insertion properties of MoO<sub>3</sub>. However, none of the yields reported were significantly higher. A dual bed system, with the lower layer comprising the methane activation catalysts, and the upper layer consisting of MoO<sub> 3</sub> was tested. The results for this system were promising, with the low temperature activation of CH<sub>4</sub>, combined with the oxygen insertion ability of MoO<sub>3</sub>, producing high selectivities of CH<sub>3</sub>OH at much lower temperatures. The best results were obtained when the ratio of the two layers was 50:50 with respect to 2%Au ZnO and MoO<sub>3</sub>. In previous work a design approach for a selective partial oxidation catalyst has been investigated, by combining components with a desired reactivity to produce a successful selective partial oxidation catalyst, which must activate methane and oxygen, and not destroy methanol. All these properties could not be found in a single catalyst, so it was proposed that two synergistic components could be combined, one responsible for methane activation and the other for oxygen activation/insertion. The doping of ZnO with Ga significantly lowered the light off temperature, and increased its oxidative capacity, an effect which was not seen with the doping of Ga<sub>2</sub>O<sub>3</sub> with Zn or Mg. The addition of Au to the Ga and Zn catalysts dramatically reduced the light off temperature, and increased its rate of oxidation at lower temperatures, both with optimum loading of 2%. The addition of l%Au and l%Pt produced a synergistic effect, producing lower light offs and higher CH<sub>4</sub> conversion than the singly doped catalysts with Au and Pt separately. When the methane activation catalysts were combined with MoO<sub>3</sub> in a physical mixture, a number of the mixtures produced higher methanol per pass percentage yields than its constituent parts. It is concluded that the increased methane activation properties beneficially interact with the oxygen activation and insertion properties of MoO<sub>3</sub>. The dual bed system, with the lower layer comprising the methane activation catalysts, and the upper layer consisting of MoO<sub> 3</sub> produced promising results, with the low temperature activation of CH<sub>4</sub>, combined with the oxygen insertion ability of MoO<sub>3</sub>, producing high selectivities of CH<sub>3</sub>OH at much lower temperatures. The best results were obtained when the ratio of the two layers was 50:50 with respect to 2%Au ZnO and MoO<sub>3</sub>. (Abstract shortened by UMI.).
35
Dales, Simon Leslie. "The structure, function and biosynthesis of proteins involved in methanol oxidation." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296270.
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Javu, Bulelwa Patricia. "Multi-component Platinum Group Metals for the methanol electro-oxidation process." University of the Western Cape, 2018. http://hdl.handle.net/11394/6571.
Full textAbstract:
>Magister Scientiae - MSc<br>The purpose of this study was to develop a high performance-lower cost catalyst
to be applied in Direct Methanol Fuel Cells (DMFC). The study also aimed to
prepare plurimetallic supported platinum (Pt), platinum-ruthenium (PtRu),
platinum-ruthenium-vanadium (PtRuV) and platinum ruthenium-vanadium-iron
(PtRuVFe) upon multi-walled carbon nanotube (MWCNT) as well as upon multiwalled
carbon nanotube-titanium oxide (MWCNT/TiO2) supports. Platinum is
very active but prone to poisoning by carbon monoxide (CO), which may be
present in the fuel used in fuel cells. The focus on the use of methanol was
because of its better reaction kinetics, and better performance in direct methanol
fuel cells (DMFC) better than proton exchange membrane fuel cell (PEMFC).
When Pt is alloyed with another platinum group metals (PGM) the alloying
decreases the over-potential for reactions critical in the fuel cells. Proton exchange
membrane fuel cell (PEMFC) performance may be improved at low metal
loading, when supported pluri-metallic catalysts are applied since the trimetallic
catalysts may promote high catalyst utilisation. In practice, DMFC require
electrodes with a Pt loading to achieve acceptance fuel cell (FC) power
performance. The aim of this study was therefore the reduction of the catalyst
loading through further improvement of mass activity of Pt based catalysts by
partial substitution of the noble metal/metals, and the use of a carbon support that
will provide high surface area, good electrical conductivity and high stability.
MWCNT supported pluri-metallic (PtRuVFe,) and bimetallic (PtRu)
nanoparticles possessed characteristic of increased surface area, improved
electron transfer rate, enhance electro-catalytic activity and promoted stability.
37
Leke, Luter. "Methanol oxidation over copper and silver monometallic and bimetallic supported catalysts." Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=227099.
Full textAbstract:
The partial oxidation of methanol to formaldehyde with air as oxidant has been studied with supported monometallic and bimetallic catalysts of copper and silver over a range of temperature and contact times. This was done to investigate the influence the bimetallics could possibly have on either the reaction pathways and/or the product(s) selectivity of the oxidation of methanol. Characterisation of these catalysts was performed by nitrogen adsorption and porosity measurements, XRD, and IR spectroscopy of adsorbed methanol and of adsorbed CO. These results indicated no crystalline phases of the loaded metals to be present. CO adsorption showed the presence of small cluster metal atoms on the surface of the catalysts. The reduction peaks from TPR also revealed the presence of partially oxidised and dispersed metal atoms. Infra-red studies of methanol adsorbed on these sample catalysts revealed the presence of intermediate methoxy and formate species which are believed to be formed in the course of the reactions. Results showed the monometallic copper and silver catalyst to be more active than the bimetallics. Although formaldehyde selectivities and yields were generally low, they were highest for the bimetallics supported on the silica catalyst than the monometalics and alumina supported samples. Copper-silver interaction in the bimetallic was proposed to enhance the reduction of the silver that enhanced the selectivity to formaldehyde. In particular under conditions, low conversions of methanol saw highest selectivities to formaldehyde. There was also a pronounced effect of the supports on product distribution and activities with the alumina based samples being more active than the silica supported ones, with the product distributions on the alumina supported significantly showing high yields of DME while the silica showed high yield for methyl formate with COx and CH4 detected in small quantities on all the catalysts within the parameters investigated.
38
Baldwin, Ian Robert. "Total synthesis of acetoxyodontoschismenol." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284653.
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Chellappa, Anand S. "Methane conversion to methanol : homogeneous and catalytic studies /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9842517.
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Naylor, Philip David. "The electrochemical oxidation of methanol in acid and alkaline fuel cell environments." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/31970.
Full textAbstract:
The electrochemical oxidation of methanol as applicable to low temperature fuel cell environments, has been investigated. The case for the use of methanol as a directly oxidisable fuel in alkaline electrolyte is presented. Initial work was targeted at establishing a non-noble metal electrode at which methanol could be oxidised in an aqueous alkaline electrolyte. Nickel, as an established electrode material for alkaline cells, was investigated by cyclic voltammetry and potentiostatic polarisation in both hydroxide and carbonate electrolytes, and noted features studied. The relative methanol oxidation performance of a selection of potential electrocatalysts, introduced through surface modification of porous and non-porous nickel structures, was later demonstrated.
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Narsimhan, Karthik. "Catalytic, low temperature oxidation of methane into methanol over copper-exchanged zeolites." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109671.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 135-147).<br>As production of shale gas has increased greatly in the United States, the amount of stranded shale gas that is flared as carbon dioxide has become significant enough to be considered an environmental hazard and a wasted resource. The conversion of methane, the primary component of natural gas, into methanol, an easily stored liquid, is of practical interest. However, shale wells are generally inaccessible to reforming facilities, and construction of on-site, conventional methanol synthesis plants is cost prohibitive. Capital costs could be reduced by the direct conversion of methane into methanol at low temperature. Existing strategies for the partial oxidation of methane require harsh solvents, need exotic oxidizing agents, or deactivate easily. Copper-exchanged zeolites have emerged as candidates for methanol production due to high methanol selectivity (> 99%), utilization of oxygen, and low reaction temperature (423-473 K). Despite these advantages, three significant shortcomings exist: 1) the location of surface intermediates on the zeolite is not well understood; 2) methane oxidation is stoichiometric, not catalytic; 3) there are few active sites and methanol yield is low. This work addresses all three shortcomings. First, a new reaction pathway is identified for methane oxidation in copper-exchanged mordenite zeolites using tandem methane oxidation and Koch carbonylation reactions. Methoxy species migrate away from the copper active sites and adsorb onto Bronsted acid sites, signifying spillover on the zeolite surface. Second, a process is developed as the first instance of the catalytic oxidation of methane into methanol at low temperature, in the vapor phase, and using oxygen as the oxidant. A variety of commercially available copper-exchanged zeolites are shown to exhibit stable methanol production with high methanol selectivity. Third, catalytic methanol production rates and methane conversion are further improved 100- fold through the synthetic control of copper speciation in chabazite zeolites. Isolated monocopper species, directed through the one-pot synthesis of copper-exchanged chabazite zeolites, correlates with methane oxidation activity and is likely the precursor to the catalytic site. Together, these synthetic methods provide guidelines for catalyst design and further improvements in catalytic activity.<br>by Karthik Narsimhan.<br>Ph. D.
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Xin, Jiayu. "Oxidation stability and improvement of biodiesel as prepared by supercritical methanol method." Kyoto University, 2009. http://hdl.handle.net/2433/126409.
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Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(エネルギー科学)<br>甲第14960号<br>エネ博第203号<br>新制||エネ||46(附属図書館)<br>27398<br>UT51-2009-M874<br>京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻<br>(主査)教授 坂 志朗, 教授 塩路 昌宏, 准教授 河本 晴雄<br>学位規則第4条第1項該当
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Pinnell, Rebecca. "Cobalt oxide catalysts for the total oxidation of propane." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/73543/.
Full textAbstract:
The three-way catalyst (TWC) greatly reduces emissions of hydrocarbons, carbon monoxide and nitrogen oxides from gasoline powered vehicles. However up to 80% of all hydrocarbons are emitted in the first 120 seconds after the engine is started, before the TWC achieves light-off. Catalysts which are active at lower temperatures offer a potential solution to this ‘cold-start’ problem. Co3O4 is one of the most active transition metal oxide catalysts for the total oxidation of hydrocarbons. In this work the synthesis of bulk and supported cobalt oxide catalysts has been investigated. The catalysts were thoroughly characterised and tested for the total oxidation of propane, a model hydrocarbon. Variables in the mechanochemical synthesis and precipitation of bulk Co3O4 were studied. Cobalt hydroxycarbonate hydrate synthesised by both techniques was found to give rise to active and stable Co3O4 catalysts upon calcination. Small Co3O4 crystallites, high surface areas, weak Co3+-O bonds, and the absence of contaminants were found to be required for high propane oxidation activity. Deposition precipitation, wet impregnation and powder blending methods were investigated for supporting Co3O4 on a high surface area, non-porous silica. Wet impregnation from cobalt nitrate was found to be the most effective method of synthesising supported Co3O4 with minimal formation of undesired cobalt silicates. Activity increased with increased cobalt weight loading but supported catalysts displayed lower activity than bulk catalysts.
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Modibedi, Remegia Mmalewane. "The catalytic membrane reactor for the conversion of methane to methanol and formaldehyde under mild conditions." Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&.
Full textAbstract:
This thesis described the development of new catalytic system for the conversion of natural gas (methane) to liquid products such as methanol and formaldehyde. This technology can allow the exploitation of small and medium size gas fields without the need to build an expensive gas to liquid plants or long pipelines. The technology is based on a concept of non-separating membrane reactor where an inorganic membrane paper serves as a catalyst support through which a reaction mixture is flowing under mild conditions and short residence times.
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Arvindan, Nallakkan Subbiah. "Development of microreactor systems for electrocatalytic studies of methanol oxidation at elevated temperatures /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/9914.
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Götz, Michael. "Katalysatorentwicklung für die anodische Oxidation von Methanol und CO-haltigem Wasserstoff in Membranbrennstoffzellen." [S.l. : s.n.], 2000. http://elib.tu-darmstadt.de/diss/000069.
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Rai, Yasuhiro. "Reaction Characteristics of Methanol Partial Oxidation Using Thermal Effects of a Porous Material." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/174921.
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Taylor, Stuart Hamilton. "The design of new catalysts for the partial oxidation of methane to methanol." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260339.
Full textAbstract:
The direct partial oxidation of CH4 to CH30H would offer considerable economic advantages over the current two stage process. It would also facilitate the utilisation of natural gas reserves in remote locations. To date, the catalytic partial oxidation of CH4 to CH30H has been extensively studied, however, it has proved to be an extremely demanding reaction which has met with little success. This study has adopted a design approach for the identification of new catalysts by considering the efficacy of single oxides for CH4 activation, CH30H oxidation and 02 isotope exchange activity. On the basis of CH30H stability Sb203 was the best oxide, showing only 3 % CH30H conversion at 500°C. The majority of oxides totally combusted CH30H below 400°C. Mo03, Nb20S, Ta20S and W03 showed high selectivity to HCHO and (CH3hO with low levels of COx throughout the range of conversion. These oxides were not considered unsuitable from the perspective of CH30H stability as the products HCHO and (CH3hO are not considered undesirable by products from a CH4 partial oxidation process. A weak but significant correlation was observed between the combustion activity of the oxides and the oxygen exchange rate. Using CH4/D2 exchange as an indication of CH4 activation it has been shown that Ga203 was a particularly good catalyst, followed by ZnO and Cr203. A relationship between exchange activity and oxide basicity was established for the rare earth sesquioxides, MgO and CaO. This relationship indicak:d that CH4 activation took place by H+ abstraction to form a surface CH3- species. From these results and literature studies of oxygen isotope exchange, dual component oxides have been formulated as catalysts for CH4 partial oxidation. The best catalysts was Ga203/Mo03, prepared by a physical mixing process. This catalyst showed an increased yield of CH30H over the homogeneous gas phase oxidation of CH4 in a quartz chips packed reactor. This increased yield has been attributed to the development of a cooperative effect between the two component oxides. Comparison of the catalytic data with the homogeneous reaction in the empty reactor tube showed that the presence of a catalyst had a detrimental effect on the CH30H yield.
49
Schwiedernoch, Renate [Verfasser]. "Partial and total oxidation of methane in monolithic catalysts at short contact times / vorgelegt von Renate Schwiedernoch." 2005. http://d-nb.info/976886464/34.
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Górecka, Sylwia. "Wieloskładnikowe układy tlenkowe pochodzenia hydrotalkitowego w roli katalizatorów wybranych procesów środowiskowych." Praca doktorska, 2019. https://ruj.uj.edu.pl/xmlui/handle/item/73235.
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