La_2-xCe_xCoO₄ And Mesoporous Ni/Ce_xZr_1-xO₂ Catalysts For The Research Of Dry Reforming Of Methane

In the latest years, efficient utilizating of renewable energy and decreasing carbon emission has been the research hotpot due to the changing of energy structure and environmental degradation.Carbon dioxide and methane as the major componets of both shale gas and nature gas, indirect transferring them to syngas such as dry reforming of methane is considered to doubly meaning of atom economy and weaking, global worming based on the existing industrial technology. Pursing the high dispersion of active metal and anting carbon formation are the uiltimate purpose of developing the catalysts for dry reforming of methane.In this paper we aimed to the weakness of existing catalyst systems,designed and prepared 2 series of Ni/Ce_xZr_1-xO₂ and provkside La_2-xCe_xCoO₄ catalysts. Effects on the stability and anting carbon formation by doping Ceria were researched, the effects of WHSV and temperature on the catalytic performance were also investigated. Several tests like XRD,BET, SEM,TGA, TEM were used to characterize the samples,and the results were also analysied.The consequences were listed below:?1? The catalysts prepared by one-pot co-precipitation and one-pot Pechini method behaved vary catalytic performance. From the comparison of XRD patterns we found the co-precipitation sample display higher and sharped peaks at each phase, which indicated bigger crystallize size of support and active metal.Bigger crystallize size would make lower catalytic performance due to the uniform dispersity.?2?The catalytic performance of NiCe_xZr_1-xO₃?x=0.1,0.3,0.5,0.7,0.9? series of catalysts on dry reforming of methane was investigated.Under the reaction condition of WHSV=22000 mL/?h-g?,1073K,0.3g catalyst, NiCe_xZr_1-xO₃ ?x=0.3,0.5,0.7? behaved high conversion ?more than 90%?of methane and carbon dioxide. NiCeo.7Zr_0.3O₃ behaved highest catalytic activity with methane and carbon dioxide conversions of 94.3% and 99.8% respectively.?3?Characterization results of N₂ adsorption-desorption presented all NiCe_xZr_1-xO₃ ?x=0.1,0.3,0.5,0.7,0.9? catalysts mesoporous structure, and comparing the isotherms of 10%Ni-Ce_0.5Zr_0.5O₂ and NiCe_0.5Zr_0.5O₃ we found that the mesoporous structure was created by CeO₂-ZrO₂ binary oxide. NiCe_0.5Zr_0.5O₃ displayed the biggest bet surface area and minal average pore size. XRD patterns of samples exhibited the nano-sized NiO on the calcined catalysts, which indicated high dispersion of active metal NiO.The crystallize size of Ce_xZr_1-xO₂ solid solution on spent catalysts after 6h reaction grown bigger than that of fresh, and the size increased with the rise of ceria content, which revealed the sintering of support Ce_xZr_1-xO₂ solid solution. It can be observed clearly that NiO nano particles were immobilized in the mesoporous pores on the TEM images. Carbon nano tubes were also found on the TEM images of spent catalysts. Whisker carbon was evidently displayed on the spent NiCe_0.1Zr_0.9O₃ and graphical carbon peak was found on the XRD of spent NiCe_0.1Zr_0.9O₃.TGA results showed minimal amount of carbon formation 4.0% on 10%Ni-Ce_0.5Zr_0.5O₂ and maximal 10.7% on NiCe_0.1Zr_0.9O₃ after 6h reaction respectively.?4? The catalytic performance of perovskite oxides La_2-xCe_xCoO₄ was investigated, and the results showed the conversion increase with the doping of ceria content, under the reaction condition of WHSV=22000 mL/?h · g?,1073K,0.3g catalyst, CH₄ and CO₂ conversions of LaCeCoO₄ were 86.0% and 89.0% respectively. Characterization results of BET analysis reflected that doping ceria would shrink the average pore size and improve the surface area greatly, and the surface area changed slightly with the constantly increasing of ceria content. XRD patterns of calcined samples of La_2-xCe_xCoO₄ behaved weak phase peak which illustrated the high dispersion of particles. Perovskite oxides LaCoO₃ peak at 2?=58.0° was also found on the samples which indicated the existing of synthesis of perovskite oxides during the preparation.