Dissertation > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalytic reaction

New Carbon Materials Based Nano-composites for Preferential Oxidation of Co to H2-Rich Gases and CO Oxidation

Author ZhangCheng
Tutor LiuYuan
School Tianjin University
Course Industrial Catalysis
Keywords Graphene Graphite oxide Nanotube composites Composites Carbon monoxide Preferential oxidation CO oxidation
CLC O643.32
Type PhD thesis
Year 2011
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Both of the CO oxidation and preferential oxidation are exothermic reactions, for these rections, hot pots was easily formed during heat transfers on the traditional oxides catalyst and played a positive role on the Reversed water gas shift reaction, and finally effects the purification of CO. theoretically, the number of hot pots on the traditional CO oxidation catalysts can be decreased after the addition of graphene, carbon nanotubes and other carbon materials with good thermal performance. Such complexes would be a potential catalyst for CO oxidation and CO oxidation.Graphite oxide (GO) was prepared by an improved Hummers method from natural graphite and turned to graphene sheets (Gs) through low-temperature thermal expansion method and chemical reduction method, and was then characterized by SEM, TEM and XRD. A series of graphite oxide and graphene supported nanometal catalysts were synthesized by wetness impregnation method and then used in the CO oxidation reaction. Preliminary research on the interactions between metal nano-particles and graphene support was also studied.The results show that, carbon materials such as of Gn and GO showed their inertance for CO oxidation reaction under250℃, while the supported carbon-metal complex catalysts prepared by wetness impregnation showed a certain amount of CO oxidation activity, following in this order:PtNi/Gs (GO)> Pt/Gs (GO)> Ni/Gs (GO)> Gs (GO). TPR, TEM, XPS and other characterization results showed that the formation of Pt-Ni alloy phase on the catalyst surface played a key role.A series of Pt, PtNi supported graphene catalysts were prepared by wetness impregnation, citric acid complex and chemical reduction methods. In this study, preparation conditions of these catalysts was studied in order to see the metal loading or metal oxide loading on those carbon materials, and the relationship between the structure of the catalyst and catalyst performance for the CO preferential oxidation was also studied. Detailed studies of catalyst preparation conditions such as preparation methods, precursor concentration, addition of Ni additives and surfactants was also carried out.Due to the good thermal conductivity of CNTs, the composite catalyst mixed with Co3O4-CeO2and CNTs can reduce the formation of hot spot on the catalyst surface, inhibit reversed water-gas shift reaction occurs and reduce the negative impact of CO2. In this paper, CNTs supported CO3O4and Co3O4-CeO2composite catalysts were prepared by mechanical mixing and impregnation, by increasing the active component dispersion of Co3O4on the CNTs support to improve their catalytic performance.In this text, a new way of preparing the macro-meso porous material with a CNTs template has been built. A series of meso-macro porous Ru/α-Al2O3catalysts with different Ru loading conents were prepared and used in the PROX reaction and showed good catalytic activities. Among these Ru/α-Al2O3catalysts,2wt.%Ru/CNTs-α-Al2O3-750showed the best ability of CO elimination, and under a space velocity of60,000ml·gcat-1·h-1and the reactant feed gas of1vol.%CO,1vol.%O2,50vol.%H2,48vol.%N2, the conversion of CO reached to100%at the range of100-150℃.

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