Дисертації: "Gas oxidations"

1

Malibo, Petrus Molaoa. "Development of heterostructured tin oxide nanocatalysts for the synthesis of bio-based maleic acid." University of Western Cape, 2021. http://hdl.handle.net/11394/8438.

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Philosophiae Doctor - PhD
Maleic acid (MA) is a key intermediate for the synthesis of polyester resins, surface coatings, lubricant additives, plasticizers, copolymers, pharmaceuticals and agricultural chemicals. The current industrial production of MA is an energy-intensive gas-phase oxidation process of n-butane. The dwindling fossil resources and environmental issues have brought about a worldwide paradigm shift from fossil feedstocks to biomass resources for the sustainable production of fuel and chemicals. Furfural (FFR) and 5-hydroxymethylfurfural (HMF) are excellent biomass-derived platform chemicals, which present an alternative route for the production of renewable bio-based MA. There has been considerable success achieved in the oxidation of furfural and HMF to maleic acid and maleic anhydride with different catalysts in recent years.

2

Luciani, Silvia <1981&gt. "Structural changes and dynamic behaviour of vanadium oxide-based catalysts for gas-phase selective oxidations." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1724/.

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Selective oxidation is one of the simplest functionalization methods and essentially all monomers used in manufacturing artificial fibers and plastics are obtained by catalytic oxidation processes. Formally, oxidation is considered as an increase in the oxidation number of the carbon atoms, then reactions such as dehydrogenation, ammoxidation, cyclization or chlorination are all oxidation reactions. In this field, most of processes for the synthesis of important chemicals used vanadium oxide-based catalysts. These catalytic systems are used either in the form of multicomponent mixed oxides and oxysalts, e.g., in the oxidation of n-butane (V/P/O) and of benzene (supported V/Mo/O) to maleic anhydride, or in the form of supported metal oxide, e.g., in the manufacture of phthalic anhydride by o-xylene oxidation, of sulphuric acid by oxidation of SO2, in the reduction of NOx with ammonia and in the ammoxidation of alkyl aromatics. In addition, supported vanadia catalysts have also been investigated for the oxidative dehydrogenation of alkanes to olefins , oxidation of pentane to maleic anhydride and the selective oxidation of methanol to formaldehyde or methyl formate [1]. During my PhD I focused my work on two gas phase selective oxidation reactions. The work was done at the Department of Industrial Chemistry and Materials (University of Bologna) in collaboration with Polynt SpA. Polynt is a leader company in the development, production and marketing of catalysts for gas-phase oxidation. In particular, I studied the catalytic system for n-butane oxidation to maleic anhydride (fluid bed technology) and for o-xylene oxidation to phthalic anhydride. Both reactions are catalyzed by systems based on vanadium, but catalysts are completely different. Part A is dedicated to the study of V/P/O catalyst for n-butane selective oxidation, while in the Part B the results of an investigation on TiO2-supported V2O5, catalyst for o-xylene oxidation are showed. In Part A, a general introduction about the importance of maleic anhydride, its uses, the industrial processes and the catalytic system are reported. The reaction is the only industrial direct oxidation of paraffins to a chemical intermediate. It is produced by n-butane oxidation either using fixed bed and fluid bed technology; in both cases the catalyst is the vanadyl pyrophosphate (VPP). Notwithstanding the good performances, the yield value didn’t exceed 60% and the system is continuously studied to improve activity and selectivity. The main open problem is the understanding of the real active phase working under reaction conditions. Several articles deal with the role of different crystalline and/or amorphous vanadium/phosphorous (VPO) compounds. In all cases, bulk VPP is assumed to constitute the core of the active phase, while two different hypotheses have been formulated concerning the catalytic surface. In one case the development of surface amorphous layers that play a direct role in the reaction is described, in the second case specific planes of crystalline VPP are assumed to contribute to the reaction pattern, and the redox process occurs reversibly between VPP and VOPO4. Both hypotheses are supported also by in-situ characterization techniques, but the experiments were performed with different catalysts and probably under slightly different working conditions. Due to complexity of the system, these differences could be the cause of the contradictions present in literature. Supposing that a key role could be played by P/V ratio, I prepared, characterized and tested two samples with different P/V ratio. Transformation occurring on catalytic surfaces under different conditions of temperature and gas-phase composition were studied by means of in-situ Raman spectroscopy, trying to investigate the changes that VPP undergoes during reaction. The goal is to understand which kind of compound constituting the catalyst surface is the most active and selective for butane oxidation reaction, and also which features the catalyst should possess to ensure the development of this surface (e.g. catalyst composition). On the basis of results from this study, it could be possible to project a new catalyst more active and selective with respect to the present ones. In fact, the second topic investigated is the possibility to reproduce the surface active layer of VPP onto a support. In general, supportation is a way to improve mechanical features of the catalysts and to overcome problems such as possible development of local hot spot temperatures, which could cause a decrease of selectivity at high conversion, and high costs of catalyst. In literature it is possible to find different works dealing with the development of supported catalysts, but in general intrinsic characteristics of VPP are worsened due to the chemical interaction between active phase and support. Moreover all these works deal with the supportation of VPP; on the contrary, my work is an attempt to build-up a V/P/O active layer on the surface of a zirconia support by thermal treatment of a precursor obtained by impregnation of a V5+ salt and of H3PO4. In-situ Raman analysis during the thermal treatment, as well as reactivity tests are used to investigate the parameters that may influence the generation of the active phase. Part B is devoted to the study of o-xylene oxidation of phthalic anhydride; industrially, the reaction is carried out in gas-phase using as catalysts a supported system formed by V2O5 on TiO2. The V/Ti/O system is quite complex; different vanadium species could be present on the titania surface, as a function of the vanadium content and of the titania surface area: (i) V species which is chemically bound to the support via oxo bridges (isolated V in octahedral or tetrahedral coordination, depending on the hydration degree), (ii) a polymeric species spread over titania, and (iii) bulk vanadium oxide, either amorphous or crystalline. The different species could have different catalytic properties therefore changing the relative amount of V species can be a way to optimize the catalytic performances of the system. For this reason, samples containing increasing amount of vanadium were prepared and tested in the oxidation of o-xylene, with the aim of find a correlations between V/Ti/O catalytic activity and the amount of the different vanadium species. The second part deals with the role of a gas-phase promoter. Catalytic surface can change under working conditions; the high temperatures and a different gas-phase composition could have an effect also on the formation of different V species. Furthermore, in the industrial practice, the vanadium oxide-based catalysts need the addition of gas-phase promoters in the feed stream, that although do not have a direct role in the reaction stoichiometry, when present leads to considerable improvement of catalytic performance. Starting point of my investigation is the possibility that steam, a component always present in oxidation reactions environment, could cause changes in the nature of catalytic surface under reaction conditions. For this reason, the dynamic phenomena occurring at the surface of a 7wt% V2O5 on TiO2 catalyst in the presence of steam is investigated by means of Raman spectroscopy. Moreover a correlation between the amount of the different vanadium species and catalytic performances have been searched. Finally, the role of dopants has been studied. The industrial V/Ti/O system contains several dopants; the nature and the relative amount of promoters may vary depending on catalyst supplier and on the technology employed for the process, either a single-bed or a multi-layer catalytic fixed-bed. Promoters have a quite remarkable effect on both activity and selectivity to phthalic anhydride. Their role is crucial, and the proper control of the relative amount of each component is fundamental for the process performance. Furthermore, it can not be excluded that the same promoter may play different role depending on reaction conditions (T, composition of gas phase..). The reaction network of phthalic anhydride formation is very complex and includes several parallel and consecutive reactions; for this reason a proper understanding of the role of each dopant cannot be separated from the analysis of the reaction scheme. One of the most important promoters at industrial level, which is always present in the catalytic formulations is Cs. It is known that Cs plays an important role on selectivity to phthalic anhydride, but the reasons of this phenomenon are not really clear. Therefore the effect of Cs on the reaction scheme has been investigated at two different temperature with the aim of evidencing in which step of the reaction network this promoter plays its role.

3

Guidetti, Stefania <1982&gt. "Catalytic liquid- and gas-phase oxidations for the synthesis of intermediates and specialty chemicals: some examples of industrial relevance." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2673/.

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Nowadays, it is clear that the target of creating a sustainable future for the next generations requires to re-think the industrial application of chemistry. It is also evident that more sustainable chemical processes may be economically convenient, in comparison with the conventional ones, because fewer by-products means lower costs for raw materials, for separation and for disposal treatments; but also it implies an increase of productivity and, as a consequence, smaller reactors can be used. In addition, an indirect gain could derive from the better public image of the company, marketing sustainable products or processes. In this context, oxidation reactions play a major role, being the tool for the production of huge quantities of chemical intermediates and specialties. Potentially, the impact of these productions on the environment could have been much worse than it is, if a continuous efforts hadn’t been spent to improve the technologies employed. Substantial technological innovations have driven the development of new catalytic systems, the improvement of reactions and process technologies, contributing to move the chemical industry in the direction of a more sustainable and ecological approach. The roadmap for the application of these concepts includes new synthetic strategies, alternative reactants, catalysts heterogenisation and innovative reactor configurations and process design. Actually, in order to implement all these ideas into real projects, the development of more efficient reactions is one primary target. Yield, selectivity and space-time yield are the right metrics for evaluating the reaction efficiency. In the case of catalytic selective oxidation, the control of selectivity has always been the principal issue, because the formation of total oxidation products (carbon oxides) is thermodynamically more favoured than the formation of the desired, partially oxidized compound. As a matter of fact, only in few oxidation reactions a total, or close to total, conversion is achieved, and usually the selectivity is limited by the formation of by-products or co-products, that often implies unfavourable process economics; moreover, sometimes the cost of the oxidant further penalizes the process. During my PhD work, I have investigated four reactions that are emblematic of the new approaches used in the chemical industry. In the Part A of my thesis, a new process aimed at a more sustainable production of menadione (vitamin K3) is described. The “greener” approach includes the use of hydrogen peroxide in place of chromate (from a stoichiometric oxidation to a catalytic oxidation), also avoiding the production of dangerous waste. Moreover, I have studied the possibility of using an heterogeneous catalytic system, able to efficiently activate hydrogen peroxide. Indeed, the overall process would be carried out in two different steps: the first is the methylation of 1-naphthol with methanol to yield 2-methyl-1-naphthol, the second one is the oxidation of the latter compound to menadione. The catalyst for this latter step, the reaction object of my investigation, consists of Nb2O5-SiO2 prepared with the sol-gel technique. The catalytic tests were first carried out under conditions that simulate the in-situ generation of hydrogen peroxide, that means using a low concentration of the oxidant. Then, experiments were carried out using higher hydrogen peroxide concentration. The study of the reaction mechanism was fundamental to get indications about the best operative conditions, and improve the selectivity to menadione. In the Part B, I explored the direct oxidation of benzene to phenol with hydrogen peroxide. The industrial process for phenol is the oxidation of cumene with oxygen, that also co-produces acetone. This can be considered a case of how economics could drive the sustainability issue; in fact, the new process allowing to obtain directly phenol, besides avoiding the co-production of acetone (a burden for phenol, because the market requirements for the two products are quite different), might be economically convenient with respect to the conventional process, if a high selectivity to phenol were obtained. Titanium silicalite-1 (TS-1) is the catalyst chosen for this reaction. Comparing the reactivity results obtained with some TS-1 samples having different chemical-physical properties, and analyzing in detail the effect of the more important reaction parameters, we could formulate some hypothesis concerning the reaction network and mechanism. Part C of my thesis deals with the hydroxylation of phenol to hydroquinone and catechol. This reaction is already industrially applied but, for economical reason, an improvement of the selectivity to the para di-hydroxilated compound and a decrease of the selectivity to the ortho isomer would be desirable. Also in this case, the catalyst used was the TS-1. The aim of my research was to find out a method to control the selectivity ratio between the two isomers, and finally to make the industrial process more flexible, in order to adapt the process performance in function of fluctuations of the market requirements. The reaction was carried out in both a batch stirred reactor and in a re-circulating fixed-bed reactor. In the first system, the effect of various reaction parameters on catalytic behaviour was investigated: type of solvent or co-solvent, and particle size. With the second reactor type, I investigated the possibility to use a continuous system, and the catalyst shaped in extrudates (instead of powder), in order to avoid the catalyst filtration step. Finally, part D deals with the study of a new process for the valorisation of glycerol, by means of transformation into valuable chemicals. This molecule is nowadays produced in big amount, being a co-product in biodiesel synthesis; therefore, it is considered a raw material from renewable resources (a bio-platform molecule). Initially, we tested the oxidation of glycerol in the liquid-phase, with hydrogen peroxide and TS-1. However, results achieved were not satisfactory. Then we investigated the gas-phase transformation of glycerol into acrylic acid, with the intermediate formation of acrolein; the latter can be obtained by dehydration of glycerol, and then can be oxidized into acrylic acid. Actually, the oxidation step from acrolein to acrylic acid is already optimized at an industrial level; therefore, we decided to investigate in depth the first step of the process. I studied the reactivity of heterogeneous acid catalysts based on sulphated zirconia. Tests were carried out both in aerobic and anaerobic conditions, in order to investigate the effect of oxygen on the catalyst deactivation rate (one main problem usually met in glycerol dehydration). Finally, I studied the reactivity of bifunctional systems, made of Keggin-type polyoxometalates, either alone or supported over sulphated zirconia, in this way combining the acid functionality (necessary for the dehydrative step) with the redox one (necessary for the oxidative step). In conclusion, during my PhD work I investigated reactions that apply the “green chemistry” rules and strategies; in particular, I studied new greener approaches for the synthesis of chemicals (Part A and Part B), the optimisation of reaction parameters to make the oxidation process more flexible (Part C), and the use of a bioplatform molecule for the synthesis of a chemical intermediate (Part D).

4

Smith, David Andrew. "Oxidation of alkenes in the gas phase." Thesis, University of York, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341095.

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5

Vernon, Patrick D. F. "Heterogeneous catalytic oxidation reactions of methane." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308602.

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6

Fathi, Marcus. "Catalytic partial oxidation of methane to synthetis gas." Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2000. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1831.

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7

Olsen, Susanne Kelly. "Catalytic membrane reactors for synthesis gas production from natural gas via partial oxidation." Thesis, Robert Gordon University, 2004. http://hdl.handle.net/10059/626.

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Natural gas obtained during the extraction of liquid hydrocarbons is often undesired due to the lack of infrastructure to transport the natural gas to an onshore location. As a result the natural gas is often flared causing economic waste and environmental concern. It would therefore be desirable to either convert the natural gas into some other substance which can be transported easily, or transport the natural gas in a liquid state. In that way, new field development will be more financially viable through the use of the extensive infrastructure and technology already in place in the offshore industry for transporting liquid hydrocarbons. It is considered that one feasible way of utilising offshore produced natural gas, is to convert it into synthetic gas (syngas) which can in turn be used to produce gases and fluids such as methanol, ammonia or a synthetic crude oil that can be readily pumped through the same pipelines as the produced oil. For the production of synthetic gas, membrane technology presents an attractive advantage improving conversion efficiency by operating as catalyst support, which then also increases the catalyst dispersion, resulting in optimal catalyst load and complete consumption of oxygen and methane in the partial oxidation. In the present investigation, an enhanced catalyst-dispersed ceramic membrane for low-cost synthesis gas production suitable for gas-to-liquids has been prepared, characterised and tested in a self-designed membrane reactor. The effect of temperature and feed flow rates has been studied and a kinetic model has been developed. In the novel membrane reactor, an active porous layer is located on both sides facing the oxygen and methane containing gas, adjacent is a second active porous layer and is supported by layers with increasing pore radii. Here the active porous layer on the bore side enhances the reaction between permeated oxygen and fuel species. In this study, it has also been demonstrated that the oxygen is activated prior to contacting the methane inside the membrane. This often results in 100% oxygen conversion, CO selectivity higher than 96% and syngas ratio (1-1/2 C O) of 2.2 to 1.8. Another advantage of the developed membrane system is that it can be used in high temperatures (> 1273.15K) and high pressure (80bars) processes with no variation on the flow rates, due to the mechanical strength of the ceramic support used.

8

Krothapalli, Deep. "Gas-liquid Mass Transfer in Oxygen Delignification Systems." Fogler Library, University of Maine, 2004. http://www.library.umaine.edu/theses/pdf/KrothapalliD2004.pdf.

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9

Kahnt, Ariane. "Semivolatile compounds from atmospheric monoterpene oxidation." Doctoral thesis, Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-93492.

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This PhD thesis aims to improve the knowledge on the processes and chemical species in the gas- and particle-phases that are involved in the production of secondary organic aerosol (SOA) from monoterpene oxidation in the atmosphere. A denuder/filter technique that enabled the simultaneous sampling of gaseous and particulate compounds was applied in the present study. The sampling technique was comprehensively characterised and optimised using twelve atmospherically relevant carbonyl compounds. The present study improved the denuder coating procedure and the sampling performance. An additional coating with the derivatisation reagent, 2,4‑dinitrophenylhydrazine (DNPH), reduced the break-through potential (e.g., from 98% to 0.9% for methyl vinyl ketone) and the fraction of carbonyl compounds on the filter material (e.g., from 8.7% to 0% for acetone). Calibration experiments against an aerosol chamber were performed to reduce the relative standard deviation (RSD) of the calibration points in the denuder measurements. The RSDs were reduced by half for acetone, acetaldehyde, methyl vinyl ketone, glyoxal, benzaldehyde and campholenic aldehyde using a XAD‑4/DNPH denuder, and the quantification error was also reduced. This sampling technique was then applied to a series of α- and β-pinene ozonolysis experiments. The present study examined the influence of an OH radical scavenger (CO), and hence the HO2/RO2 ratio, on the SOA formation, product distribution and partitioning behaviour of selected oxidation products in conjunction with different seed particle acidities. It was shown that SOA yields increased by about 8% in α-pinene ozonolysis when CO and acidic seed particles co-existed, whereas only a marginal difference was observed (increase of 2%) for β-pinene compared to neutral seed particles. From the denuder/filter sample analysis, it was possible to tentatively identify a new compound from the α-pinene ozonolysis, i.e., terpenylic aldehyde. Gas- and particle-phase yields were estimated for the first time for this compound (i.e., 1% and 0.4%, respectively). The atmospheric relevance of terpenylic aldehyde was demonstrated based on ambient filter measurements and a possible formation pathway was suggested. Furthermore, the present study provided an additional explanation for enhanced SOA formation when acidic seed particles are used in monoterpene ozonolysis. It was demonstrated that the isomerisation of monoterpene oxides on acidic seed particles leads to the formation of highly reactive SOA precursors, whose subsequent reaction with ozone contributes significantly to SOA formation.

10

Hoorn, Johannes Adriaan Aris. "Aspects of mass transfer in gas-liquid oxidation reactions." Enschede : University of Twente [Host], 2005. http://doc.utwente.nl/50858.

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11

Cawthorne, R. N. "The oxidation chemistry of alcohols in the gas phase." Thesis, University of York, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381359.

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12

Oliveira, Luciana C. "Gas-phase surface oxidation and chlorination of carbon nanotubes /." Online version of thesis, 2009. http://hdl.handle.net/1850/10931.

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13

Eriksson, Sara. "Development of catalysts for natural gas-fired gas turbine combustors." Doctoral thesis, Stockholm : Department of Chemical and Engineering and Technology, School of Chemical Science and Engineering, KTH - Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4239.

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14

Hughes, Dimitri. "Facilitated characterization of a catalytic partial oxidation fuel reformer using in situ measurements." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31646.

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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010.
Committee Co-Chair: Haynes, Comas; Committee Co-Chair: Wepfer, William; Committee Member: Jeter, Sheldon. Part of the SMARTech Electronic Thesis and Dissertation Collection.

15

Mirzaei, Ali Akbar. "Low temperature carbon monoxide oxidation using copper containing catalysts." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266493.

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16

Carruth, Martin. "Corrosion of silicon based ceramics in simulated gas turbine environments." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248736.

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17

Brandstadt, Katrina L. "Thermal oxidation of fine aluminum powders in carbon dioxide gas." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81530.

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The thermal oxidation of fine aluminum (Al) powders in carbon dioxide (CO2) gas was investigated for the purpose of metal-based propulsion fuel development. The thermal behavior and reaction energy was studied using simultaneous thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). The reactivities of Al powders with nanometer and micrometer-scale average particle sizes were compared. The particle morphology was examined at different stages of the process using field emission gun scanning electron microscopy (FEG-SEM) and transmission electron microscopy (TEM). The corresponding chemical changes were analyzed by X-ray diffraction spectrometry (XRD) and energy dispersion X-ray spectrometry (EDS).
Nano- and micrometer-scale Al powders exhibited different calorimetric behaviour. The primary oxidation occurred at around 533°C for the nanopowders and at 1045°C for the micropowders. The mechanism of the oxide growth, particle deformations, and hollow oxide shells are discussed. A low-temperature transformation of the amorphous Al2O3 coating to crystalline gamma-Al 2O3 is identified as a trigger to the exothermic reaction in the case of the Al nanopowders. Carbon was also shown to be involved in the reaction.

18

Calavia, Boldú Raúl. "Gas sensor microsystems based on nanostructured layers via anodic oxidation." Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/96314.

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En aquesta tesi es detalla la metodologia per obtindre sensors de gasos basats en òxid de tungstè nanoestructurat sobre suports micromecanitzats de silici. Aquesta nanoestructuració s’ha fet mitjançant una capa d’alúmina porosa como a motlle, pel que s’ha desenvolupat una metodologia per a compatibilitzar l'anodització de l’alumini, i altres metalls com el tungstè, amb els processos estàndards del silici. S’han desenvolupat dos tipus de capes nanoestructurades, nanotubs i nanopunts de WO3. Els nanotubs s’han obtingut depositant mitjançant polvorització catòdica reactiva la capa sensible sobre alúmina porosa recobrint les parets dels pors. Els nanopunts s’han obtingut anoditzant una bicapa d’alumini i tungstè, on la primera anodització crea la alúmina porosa i la segona fa créixer els nanopunts d’òxid de tungstè en la base dels pors. S’ha analitzat la composició, morfologia i funcionament com a sensors de gasos d’ambdós materials nanoestructurats i s’han comparat els resultats amb sensors basats en materials sense nanoestructuració.
En esta tesis se detalla la metodologia para obtener sensores de gases basados en óxido de tungsteno nanoestructurado sobre soportes micromecanizados de silicio. Dicha nanoestructuración se ha obtenido empleando una capa de alúmina porosa como molde, por lo que se desarrolla una metodología para compatibilizar la anodización del aluminio, y otros metales como el tungsteno, con los procesos estándares del silicio. Se han desarrollado dos tipos de capas nanoestructuradas, nanotubos y nanopuntos de WO3. Los nanotubos se han obtenido depositando por pulverización catódica reactiva la capa sensible sobre alúmina porosa recubriendo las paredes de sus poros. Los nanopuntos se han obtenido anodizando una bicapa de aluminio y tungsteno, donde la primera anodización crea la alúmina porosa y la segunda hace crecer los nanopuntos de óxido de tungsteno en la base de los poros. Se ha analizado la composición, morfología y funcionamiento como sensores de gases en ambos casos y se han comparado los resultados con los de sensores sin nanoestructuración.
This thesis shows the methodology to obtain nanostructured tungsten oxide layer as sensing material on silicon micromachined gas sensor devices. A porous anodised alumina layer was used as pattern to obtain it, so a technique has been developed to make compatible the anodising of aluminium and other metals like tungsten with the standard silicon processes. Two different nanostructuring approaches were developed, nanotube and nanodot based tungsten oxide layers. The WO3 nanotube layer has been obtained by the tungsten oxide deposition using reactive sputtering on the porous alumina layer. As a result a continuous sensing layer coats the pores without clogging them. WO3 nanodot layers were obtained by the anodising of an aluminium and tungsten bilayer, where the first anodising process grows the porous alumina layer and the second one generates the tungsten oxide nanodots in the end of the pores. Compositional and morphological studies and the study of their behaviour as gas sensors where conducted for the two nanomaterials. The results have been compared with the flat tungsten oxide layers on micromachined gas sensors.

19

Tranter, Robert Simon. "The gas phase oxidation of ethers, ketones and branched hydrocarbons." Thesis, University of Hull, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262426.

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20

Schuster, Ute. "Microbial methane oxidation in marine sediment around intertidal gas seeps." Thesis, University of Essex, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241218.

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21

Roden, Peter John. "The gas-phase oxidation of unsaturated compounds at elevated temperatures." Thesis, University of York, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338552.

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22

Morgan, Michelle Marie. "Oxidation of mercury in flue gas streams via gold catalysis." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677959.

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Mercury emission from coal-fired power plants is a global problem that has garnered attention due to regulations limiting the emission from anthropogenic sources. The three forms of mercury that are all emitted include: elemental mercury (HgO), oxidized mercury (Hg2+), which can both then form particulate mercury. Since current HgO removal technology is not effective, and HgO is extremely toxic, new catalytic solutions are necessary to allow complete oxidation of HgO. The aim of the project was to understand the mechanism of heterogeneous catalyzed mercury oxidation from simulated flue gas streams using supported gold catalysts. It has been proposed in the literature that three mechanisms could potentially be responsible for mercury oxidation: the Langmuir-Hinshelwood, the Eley-Rideal, and the Mars-Maessen mechanisms. To investigate the possible reactions, the mercury saturator was placed either before or after the catalyst bed and in some experiments, the gold catalyst was pre-saturated with mercury. Numerous characterization and gas-phase analysis techniques were used to identify surface changes and species present at both the surface and in the gas stream. For the gold catalysts, it was found that pre-saturating the catalyst with mercury improved mercury oxidation. Based on this data, mercury adsorption is necessary to promote the reaction, not mercury in the gas phase. In addition, the catalysts more efficient at oxidizing mercury generally had increased CI2 production. The gold-mercury amalgam was seen in the STEM images, but only in the more complex gas compositions, not in the N2/Hg gas mixture. In addition to the gold catalysts, ruthenium catalysts supported on titania were tested due to their promotion of the Deacon process. Mercury oxidation and CI2 production was as high with the ruthenium catalysts as with the gold supported catalysts. It is possible that the titania supports are better at producing an oxidized form of mercury, such as HgCI2.

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Liu, Zhouyang. "Heterogeneous Catalytic Elemental Mercury Oxidation in Coal Combustion Flue Gas." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512045805884364.

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24

Muziki, Sibongile. "Carbon monoxide clean-up of reformate gas by preferential oxidation." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/20090.

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The preferential oxidation (PrOx) activity of two Ru/Al2O3 catalysts prepared using different methods was tested. The first catalyst was prepared by wetness impregnation at a high pH and the second was prepared by incipient wetness impregnation. Catalytic activity was measured at varying temperatures, space velocities as well as O2/CO ratio. The Ru catalyst catalyst prepared using wetness impregnation at high pH was found to exhibit higher CO conversion despite having a lower Ru dispersion compared to the Ru catalyst prepared using incipient wetness impregnation at the tested temperature range. For both Ru catalysts the trends observed with varying temperature, space velocity as well as O2/CO ratio were similar. Increasing temperature increased CO conversion up to a maximum after which a further increase in temperature led to a decrease in CO conversion. At low temperatures, increasing space velocity resulted in a decrease in CO conversion. An increase in CO conversion was observed with increasing space velocity at higher temperatures. Increasing space velocity led to a decrease in CH4 formation at high temperatures. Furthermore it was determined that mass transfer limitations played a role during the catalytic process. The effects of mass transfer limitations could be reduced by increase the linear space velocity. A Pt-Fe/mordenite catalyst was prepared in this study using solid state ion exchange to deposit Fe and competitive ion exchange to deposit Pt. This method was proposed in order to try and improve the preparation method reported in literature. The synthesised catalyst did not perform as well as the Pt-Fe/Mordenite reported in literature. A maximum CO conversion of 99 % with 47 % CO2 selectivity at 180 °C, 120 000 ml/(h gcat) and O2/CO ratio of 1 was achieved.

25

Salomon, de Friedberg Adam Maciej. "Kinetics of lead concentrate oxidation in a stagnant gas reactor." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/28516.

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The behaviour of lead concentrate particles oxidizing in a stagnant gas reactor has been examined and a mathematical model which predicts the kinetics of galena particles developed. The effects of oxygen concentration, particle size, furnace temperature and concentrate composition were studied. The results showed that the concentrates all exhibited sharply defined ignition points. The ignition points were found to be strongly dependent on oxygen concentration. Reductions in ignition temperature of up to 100 K were observed when the concentrates were reacted in pure oxygen rather than in air. Iron composition was found to have a similar effect on ignition temperature. The modelling results predict short reaction times for ignited particles (less than 100 milliseconds). Particles which ignited in air attained predicted temperatures in excess of 2600 K. In oxygen, particle temperatures were calculated to be greater than 2800 K. Good agreement was found between experimental results and model predictions.
Applied Science, Faculty of
Materials Engineering, Department of
Graduate

26

Kalitan, Danielle Marie. "A Study of Syngas Oxidation at High Pressures and Low Temperatures." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2422.

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Ignition and oxidation characteristics of CO/H2, H2/O2 and CO/H2/CH4/CO2/Ar fuel blends in air were studied using both experimental and computer simulation methods. Shock-tube experiments were conducted behind reflected shock waves at intermediate temperatures (825 < T < 1400 K) for a wide range of pressures (1 < P < 45 atm). Results of this study provide the first undiluted fuel-air ignition delay time experiments to cover such a wide range of syngas mixture compositions over the stated temperature range. Emission in the form of chemiluminescence from the hydroxyl radical (OH*) transition near 307 nm and the pressure behind the reflected shock wave were used to monitor reaction progress from which ignition delay times were determined. In addition to the experimental analysis, chemical kinetics calculations were completed to compare several chemical kinetics mechanisms to the new experimental results. Overall, the models were in good agreement with the shock-tube data, especially at higher temperatures and lower pressures, yet there were some differences between the models at higher pressures and the lowest temperatures, in some cases by as much as a factor of five. In order to discern additional information from the chemical kinetics mechanisms regarding their response to a wide range of experimental conditions, ignition delay time and reaction rate sensitivity analyses were completed at higher and lower temperatures and higher and lower pressures. These two sensitivity analyses allow for the identification of the key reactions responsible for ignition. The results of the sensitivity analysis indicate that the ignition-enhancing reaction H + O2 = O + OH and hydrogen oxidation kinetics in general were most important regardless of mixture composition, temperature or pressure. However, lower-temperature, higher-pressure ignition delay time results indicate additional influence from HO2- and CO- containing reactions, particularly the well-known H + O + M = HO2 + M reaction and also the CO + O + M = CO2 + M and CO + HO2 = CO2 + OH reactions. Differences in the rates of the CO-related reactions are shown to be the cause of some of the discrepancies amongst the various models at elevated pressures. However, the deviation between the models and the experimental data at the lowest temperatures could not be entirely explained by discrepancies in the current rates of the reactions contained within the mechanisms. Additional calculations were therefore performed to gain further understanding regarding the opposing ignition behavior for calculated and measured ignition delay time results. Impurities, friction induced ionization, static charge accumulation, boundary layer effects, wall reaction effects, and revised chemical kinetics were all considered to be possible mechanisms for the model and measured data disparity. For the case of wall-reaction effects, additional shock-tube experiments were conducted. For the remaining effects listed above, only detailed calculations were conducted. Results from this preliminary anomaly study are at this time inconclusive, but likely avenues for future study were identified. Additional kinetics calculations showed that the large difference between the experimental data and the chemical kinetics models predictions at low temperatures can be explained by at least one missing reaction relevant to low-temperature and high-pressure experimental conditions involving the formation of H2O2, although further study beyond the scope of this thesis is required to prove this hypothesis both theoretically and experimentally.
Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering PhD

27

Zhu, Jian N. "A feasibility study of methane reforming by partial oxidation." Curtin University of Technology, Department of Chemical Engineering, 2001. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=12764.

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Utilisation of natural gas (mainly methane, CH[subscript]4), a clean and abundant resource, is of great importance. Conventional method, steam reforming, though still dominant, requires a considerately high capital investment and an intensive energy input. Reforming natural gas by partial oxidation, potentially one of the most attractive alternatives, has been investigated vigorously for decades, mainly focusing on looking for suitable catalyst and understanding of the mechanisms of methane partial oxidation. This work focuses on the feasibility of methane partial oxidation reforming from gas phase reaction under fuel-rich conditions.Firstly, a detailed thermodynamic analysis has been conducted, which covers a broad range of operation conditions of temperature up to 2073 K, pressure up to 100 atm and initial O(subscript)2/CH(subscript)4 ratio of 0 to 2.5. It has been found that high syn-gas (H(subscript)2 and CO) yields can be achieved when the temperature is above 1073 K and the initial O(subscript)2/CH(subscript)4 ratio close to 0.5. High pressure is not favoured. However, high temperatures can suppress the effect of high pressures.Carbon deposition, a crucially important factor in methane partial oxidation, is mainly examined by means of thermodynamic analysis. Solid carbon was identified the major carbon deposition form, which could severely happen if the initial O(subscript)2/CH(subscript)4 ratio is less than 0.5. This feature was also indirectly proven during the experimental tests.Secondly, a series of CHEMKIN simulations were performed using various CH(subscript)4 oxidation reaction mechanisms. The general trend of the CH(subscript)4 partial oxidation reforming was revealed by simulations using the GRI, NIST and Konnov mechanisms. A new concept characterising CH(subscript)4 partial oxidation was conceived. i.e., a fast oxidation zone and a slow conversion ++
zone, the reaction is under chemical control that requests high operating temperatures, and the reaction can be accelerated by using relatively high initial 0(subscript)2/CH(subscript)4 ratios.Experimental tests were performed to verify the findings obtained in thermodynamic and kinetic studies, and to identify appropriate reaction schemes for further analysis. Prediction from the NIST mechanisms has shown to be in good agreement with experimental observation when the temperature is less than 1273 K. For higher temperatures the NIST under-predicts the H(subscript)2 yield caused by the lack of carbon formation mechanisms. Two other mechanisms (Konnov and GRI) predicted similar trends but the reaction predicted commenced earlier. Therefore, the NIST was identified to be the best.NO(subscript)x catalytic effect on CH4 oxidation at fuel-rich conditions was confirmed experimentally. However, this effect only exists where the oxygen is available. Therefore, employing NO(subscript)x cannot help the CH(subscript)4 partial oxidation in the second reaction zone. Solely relying on NO(subscript)x to speed up the process or lower the operating temperature is not possible. However, employing NO(subscript)x to initiate the reaction at lower temperatures is viable. The possibility of taking the advantage of NOx catalytic effect for direct synthesis of CH3OH (methanol) has been shown feasible and, more attractively, the operating temperatures required are much lower than that for syn-gas production.Among three reaction schemes, i.e., the Glarborg, Bromly and Dagaut, which are able to account for the NO(subscript)x catalytic effect, the Glarborg mechanism proved to be the best in reproducing experimental measurements for syn-gas production tests. However, none available mechanisms can predict similar magnitude of the direct synthesis of CH(subscript)3OH. To understand the mechanisms ++
of NO(subscript)x catalytic effect, a reaction scheme, Partial Oxidation Mechanisms (POM), has been composed successfully adding five additional reactions into the NIST. The POM can reveal the major catalytic reaction pathways and it is suitable for CH(subscript)4 partial oxidations both with and without NO(subscript)x addition.Finally, a series of simulations were conducted to conservatively estimate the feasibility of CH(subscript)4 partial oxidation using POM. High syn-gas yield is achievable within a reasonable residence time using adiabatic reactor. The variables significantly affecting the syn-gas yield, are preheating temperature, operating pressure, inert dilution, initial ratio of O(subscript)2/CH(subscript)4 and residence time. If NO(subscript)x is used as a catalyst, the preheating temperature can be further reduced.

28

Starr, Sean Michael. "Microbial methane oxidation in the marine and estuarine environment." Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313378.

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29

Benyahia, F. "Gas phase oxidation of iso-butylene over bismuth molybdate based catalysts." Thesis, University of Newcastle Upon Tyne, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382943.

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30

Eriksson, Sara. "Development of methane oxidation catalysts for different gas turbine combustor concepts." Licentiate thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-311.

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31

Awosope, Iyiola Olumide. "Flameless oxidation combustion modelling and application to a gas turbine combustor." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419936.

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32

Bronson, Tyler Mark. "Oxidation and condensation of zinc fume in steelmaking off-gas systems." Thesis, The University of Utah, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10000283.

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Off-gas dust wastes from steelmaking processes contain a number of by-product metals, which are hazardous to dispose of by landfill. With the increased use of electric arc furnaces, zinc has become a significant by-product in the off-gas dust and a main inhibiter of off-gas dust disposal as common waste. Zinc’s low vaporization temperature (907 °C) causes the zinc to evaporate from the melt and become entrained in the off-gas stream. Zinc then deposits as zinc, zinc oxide, and zinc ferrite spinel, which are difficult to separate postprocess from ferrous and other entrained oxides. If the zinc could be separated from the residual entrained particulates through an in-process method, the cost of processing the dust for recycling would go down. In addition, if the zinc-rich portion of the separated dust has high enough zinc content the dust could be sold for a profit. Zinc recovery could increase the steelmaker’s profitability while reducing the environmental toll.

The focus of this research was the condensation of zinc vapor to elemental zinc and zinc oxide solid under varying environments in order to investigate the feasibility of in-process separation of zinc from steelmaking off-gas dusts. Water vapor content, temperature, degree of cooling, gas composition, and initial zinc partial pressure were varied in order to simulate the possible conditions that can occur within steelmaking off-gas systems. Temperature of deposition and the effect of rapidly quenching the gas was specifically studied. Postexperimental analysis included the Zn:ZnO ratio in the condensate; homogeneous nucleation of zinc particles; and developing kinetic rate expressions that correlate condensation rates to gas composition, water content, temperature, and zinc partial pressure.

It was determined that oxidation by H₂O or CO₂ does not occur below 835 °C for highly oxidizing streams (CO₂:CO = 40/7). The rate of oxidation of zinc vapor by carbon dioxide and water vapor were determined. It was proven that cooling rate significantly increased the ratio of elemental zinc to zinc oxide, as well as increased the number of particles produced in the system. SEM analysis was performed of the zinc and zinc oxide samples collected. Homogeneous nucleation was modeled using Matlab and was compared to experimental data, proving that elemental zinc formation within the reactor was homogeneous in origin. The model was expanded to include the rates of oxidation by CO₂ and H₂O; the experimental data had a relatively good fit to the model. For the conditions used in this study, the reaction rates for both carbon dioxide and water vapor oxidation of zinc as well the homogeneous nucleation model of elemental zinc held true for various temperatures, zinc partial pressures, CO₂:CO ratios, and H₂O partial pressures.

33

Askey, Susan. "The photo-oxidation of simple carbonyl compounds in the gas phase." Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241152.

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34

Dale, Alan David. "The oxidation of highly polar stationary phases in gas-liquid chromatography." Thesis, University of Hertfordshire, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254484.

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35

Kumar, Sachin. "Gas Phase Oxidation of Dimethyl Sulfide by Titanium Dioxide Based Catalysts." Miami University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=miami1081780904.

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36

Makgwane, Peter Ramashadi. "Immobilization of catalyst in a wall-coated micro-structured reactor for gas/liquid oxidation of p-cymene." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1182.

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The selective, liquid phase oxidation of p-cymene is an important synthetic route for the production of p-cresol via the tertiary cymene hydroperoxide (TCHP). The industrial-scale oxidation process is characterised by slow oxidation rates due to limitations in the mass transfer of oxidant (gaseous oxygen) into the liquid phase. However, like all other autoxidation reactions, the oxidation reaction is exothermic, following the typical free radical autoxidation reaction mechanism, which implies that careful temperature control is critical in order to prevent the further reaction of the initially formed hydroperoxide species. In the presence of metal catalysts, the limiting oxidation rate is the transfer of oxygen from the gas to liquid boundary interface. As a result, low product yields and poor productivity space-time yield are typically experienced. At high substrate conversions, by-products resulting from the decomposition of the formed hydroperoxides predominate. For this reason, the conversion of substrate is restricted to preserve the TCHP selectivity. The slow rates in industrial-scale p-cymene oxidations results in long oxidation times, typically 8-12 h. Substrate conversions are typically between 15-20 percent, and the TCHP selectivity ranges between 65-70 percent. The work described in this thesis concerns the oxidation of p-cymene in a microstructured falling film reactor (FFMSR). These reactor systems facilitate chemical reactors to have high mass and heat transfer rates because of high surface area-to-volume ratios. Due to their small internal volumes, these reactors are inherently safe to operate. These properties were exploited to improve the p-cymene oxidation rate and, consequently, the space-time yield. In order to evaluate the suitability of vanadium phosphate oxide (VPO) catalysts for use as supported catalyst in the FFMSR, different catalysts prepared from VOHPO4∙0.5H2O and VO(H2PO4)2 precursors was first evaluated for the oxidation of p-cymene in a well-stirred batch reactor. The results of the two activated catalysts, (VO)2P2O7 and VO(PO3)2 when used as powders in their pure form, showed a significant improvement in p-cymene oxidation rates with conversions up to 40 percent in 3-4 h reaction time with a TCHP selectivity of 75-80 percent. The (VO)2P2O7 catalyst showed better oxidation rates and selectivity when compared to the VO(PO3)2 catalyst obtained from the VO(H2PO4)2 precursor. The (VO)2P2O7 catalyst was supported on a stainless steel plate and the coated plate used to study the long-term stability and catalytic perfornance of the catalyst during p-cymene oxidations in a batch reactor. Comparable oxidation rates and TCHP selectivity were obtained with the stainless steel coated VPO catalyst when compared to the “free powder” (VO)2P2O7 catalyst. The results also showed that the stainless steel coated catalyst displays a slow, yet significant deactivation over extended reaction periods (250 h onstream). Characterization of the exposed (VO)2P2O7 catalyst to p-cymene oxidation conditions by powder XRD, SEM and TGA-MS showed that (VO)2P2O7 phase undergoes structural transformation back to VOHPO4∙0.5H2O phase over time. The (VO)2P2O7/-Al2O3 catalyst was used to coat the micro-channel reaction plates of the FFMSR. Both uncoated and coated micro-channel reaction plates were evaluated in the FFMSR for the oxidation of p-cymene. The FFMSR showed effective improvement of oxidation rates in terms of productivity space-time-yield at comparable batch p-cymene conversions. A Typical 10 percent conversion in catalysed batch oxidations at 1-2 h reaction time was achieved in few seconds (19 s) reaction time in FFMSR. The comparison of uncoated (i.e. uncatalysed) and coated (i.e. catalysed) FFMSR oxidations showed slight differences in oxidation rates. No clear explanation could be established with the present results for the observed same behaviour. However, the insufficient contact time between the gas and liquid reactants with the wall-coated solid catalyst is one of the possible causes for the observed behaviour of the coated and uncoated micro-channel plates. A simple developed kinetic model was used to confirm the obtained batch oxidation results using cumene as probe compound due to its similarity to p-cumene oxidation and extensive studied kinetics. With the estimated K values and available rate constants from literature, it was possible to predict the conversions in a batch reactor at the same typical micro-structured reactor residence time (i.e. of 19 s). The predicted conversions in the batch reactor were less than 0.1 percent even at harsh conditions such as 170 oC when compared to about 10 percent achieved in the micro-structured reactor at the same reaction temperature, reactants concentration and reaction time of 19 s. This difference in the reactor systems performance indicates the unique advantages offered by micro-structured reactors (e.g. improved mass transfer, temperature management and high surface-to-volume ratios) to perform typical gas/liquid mass transfer limited reactions such as cumene and p-cymene autoxidations.

37

Johnsson, Lars. "Phytosterol oxidation products : formation, analysis and occurrence /." Uppsala : Dept. of Food Science, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/a490.pdf.

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38

Stein, Vincent Bradley. "Methane oxidation in soils as a tool for reducing greenhouse gas emissions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0021/MQ49688.pdf.

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39

Jin, Lei. "Catalytic oxidation of 1, 4-dichlorobenzene in gas phase and supercritical water /." Access abstract and link to full text, 1991. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9136877.

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40

Xuan, Zheng-Qian. "Gas-phase selective oxidation of C3-C4 hydrocarbon using only molecular oxygen." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54871/.

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The gas-phase epoxidation of propylene to propylene oxide (PO) has been investigated over a series of supported copper-based bimetallic (Cu-Ni, Cu-Ag and Cu-Au) or even trimetallic (Cu-Ag-Ni) alloy catalysts using only molecular oxygen as oxidant. Supported single metal (Cu, Ag and Au) catalysts have been tested for contrast. Zinc oxide and nano powder of silica have been applied as two main supports. It has been found that support has a significant effect on the catalytic performances of final catalysts. For the single metal support on zinc oxide, Cu presents better selectivity than that of Ag or Au. Cu-Ag supported on zinc oxide pre-treated in 5% F/Ar has exhibited very high selectivity to PO (ca. 81%) propylene conversion (ca. 0.011%) at comparatively low temperature, 210 °C. The observation of high selectivity to PO only at low temperature correlates to the intrinsic instability of PO. However, other alloys supported on zinc oxide did not show better selectivity than Cu-Ag. Particularly for Cu-Ni catalysts, the addition of nickel poisons the catalysts so that poor selectivity is obtained. For the support of nano-SiO₂, the copper catalyst can offer both better selectivity (63%) and higher conversion (0.014%) than that supported on zinc oxide (selectivity to PO, ca. 60%, at propylene conversion, ca. 0.007%). A variety of alloy catalysts have shown very good reactivity and selectivity to PO. Typically, Cu-Ni pre-treated in 5% F/Ar can give high selectivity to PO, ca. 78%, as a propylene conversion, ca. 0.018%, at low temperature, 210 °C. Cu-Ag catalysts have also shown stable performance with high selectivity to PO above 70% and propylene conversion of 0.020% at low temperature. On the other hand, gold plays the similar role in Cu-Au/nano-SiO₂ as nickel in Cu-Ni/ZnO catalyst. Cu-Au/nano-SiO₂ is even worse than copper only supported nano-SiO₂. The XPS analysis of Cu-Ag catalysts implies that Cu should be active in propylene epoxidation to PO over catalysts not only on nano-SiO₂ but also zinc oxide. These results suggest that there is a great potential to develop copper-based materials as an inexpensive catalyst for propylene epoxidation. The gas-phase selective oxidation of w-butane to maleic anhydride has also been studied and performed in a gas-gas periodic flow reactor under aerobic and anaerobic environments. Under anaerobic conditions, the catalytic performances of VPD and phase E are worse than that in aerobic conditions. Some vanadia supported on alumina have been loaded in both aerobic and anaerobic flow. The high loading (3.5%) vanadia supported on alumina is more reactive than the lower one (1%).

41

Cobb, Stephen Hal. "Gas-phase characterization of the molecular electronic structure of metal clusters and metal cluster oxidation." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/30417.

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42

Enin-Okut, Edu Owominekaje. "The effect of alumina coatings on the oxidation behavior of nickel-base alloys." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/20226.

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43

Dever, Stuart Anthony Civil &amp Environmental Engineering Faculty of Engineering UNSW. "Passive drainage and biofiltration of landfill gas: behaviour and performance in a temperate climate." Publisher:University of New South Wales. Civil & Environmental Engineering, 2009. http://handle.unsw.edu.au/1959.4/43769.

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Microbial oxidation of methane has attracted interest as an alternative process for treating landfill gas emissions. Approaches have included enhanced landfill cover layers and biocovers, passive gas drainage and biofiltration, and active gas extraction and biofiltration. Previous research has shown that microbial methane oxidation is affected by a number of factors, many of which are dependent on the environment in which the process is occurring. The aim of this research was to evaluate the behaviour and performance of a passive landfill gas drainage and biofiltration system operating in a temperate climate, and to identify and quantify the factors that determine the behaviour and performance of the system under such conditions. To achieve this a series of field trials were undertaken in Sydney, Australia, over a period of 4 years. The trials were designed to evaluate the effect of a range of factors, including landfill gas loading rate, temperature and moisture content of the biofilter media, biofilter media characteristics, and climatic conditions. The results of the field trials showed that a passive gas drainage and biofiltration system operating in a temperate climate can achieve methane oxidation efficiencies > 90% and that the behaviour and performance of a passive gas drainage and biofiltration system is primarily dependent on 3 factors: the landfill gas loading rate, which varies; the temperature of the biofilter media, which is affected by the temperature of the landfill gas being treated, the level of microbial activity occurring in the biofilter, and local climatic conditions; and the moisture conditions within of the biofilter media, which is affected by local climatic conditions and the characteristics of the biofilter media. Relationships between these factors and the performance of a passive biofilter operating in a temperate climate were developed, where able. A number of design concepts for passive landfill gas drainage and biofiltration were developed. A process for assessing the feasibility of applying the concepts and designing a passive landfill gas drainage and biofiltration system was also developed. In addition, guidelines and recommendations for the design of a passive landfill gas drainage and biofiltration system operating in temperate climate were developed.

44

Vereb, Heather A. "Biomarkers of Lipid Oxidation in the Oral Cavity." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76887.

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Measuring lipid oxidation is useful as a means of monitoring oxidative stress, such as that induced by clinical conditions or environmental exposure. Characteristic volatile compounds, often with low threshold odors, are secondary products of lipid oxidation reactions. Metallic flavor in food and beverages has been linked with oxidation of lipids in the oral cavity. Breath, an emerging medium for analysis of internal condition, is one means of measuring the metal-induced lipid oxidation responsible for this flavor. This project analyzes the breath of human subjects, as well as lipid oxidation of in vitro samples to identify compounds responsible for producing metallic flavor, which result from the oxidation of lipids in the oral cavity. Because these analytes are found at extremely low (picomolar to nanomolar) concentrations, preconcentration of samples prior to gas chromatography-mass spectrometry analysis is crucial. This study utilizes both solid phase microextraction (SPME) and micromachined silicon micropreconcentrators to concentrate compounds in breath to optimize analysis.
Master of Science

45

Geck, Christoph [Verfasser], and Eva-Maria [Akademischer Betreuer] Pfeiffer. "Temporal and spatial variability of soil gas transport parameters, soil gas composition and gas fluxes in methane oxidation systems / Christoph Geck ; Betreuer: Eva-Maria Pfeiffer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2017. http://d-nb.info/1137323728/34.

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46

Rankin, Bret A. "Design and development of a microwave enhanced diesel soot oxidation system." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1058.

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Thesis (M.S.)--West Virginia University, 1999.
Title from document title page. Document formatted into pages; contains xiv, 347 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 272-276).

47

Chemweno, Maurice K. "TiO₂ photocatalyst deactivation by gas-phase oxidation of polydimethylsiloxane (PDMS) and silicone sealant off-gas in a recirculating batch reactor /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1421122.

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48

Evans, Jason Carter. "Influence of fuel sulfur content on emissions from diesel engines equipped with oxidation catalysts." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1594.

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Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains xii, 140 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 83-84).

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Hanaki, Yasunari, and Kazuhiro Yamamoto. "Microfluidic Simulation of Diesel Exhaust Gas and Soot Oxidation in Diesel Particulate Filter." SAE International, 2013. http://hdl.handle.net/2237/20341.

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Singh, Rahul. "Electrochemical and Partial Oxidation of CH4." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1208025200.

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