Preparation Of Nickel-based Vermiculite Molecular Sieve Material And Its Catalytic Performance For Dry Reforming Of Methane

CH₄ and CO₂ are greenhouse gases that have a significant impact on global warming.Researchers are interested in how to effectively eliminate these two gases to achieve the national goals of"carbon neutrality"and"carbon peak".The dry reforming of methane（DRM）is an important reaction for eliminating these two greenhouse gases,which can effectively utilize CH₄ and CO₂ for beneficial purposes in human living environments,alleviate greenhouse effects and energy shortages,and synthesize gas with an H₂/CO ratio of1 for the preparation of various fuels such as diesel and gasoline through the Fischer-Tropsch synthesis reaction,making it one of the green chemical pathways for sustainable development.Nickel metal has good catalytic performance,but the catalyst is prone to sintering and coking during the reaction process.The zeolite-based carrier is very suitable for loading active nickel metal for the dry reforming of methane due to its good thermal stability and large specific surface area.The catalyst sintering and coking problems in the dry reforming of methane can be solved by effective treatment methods.The main work of this thesis is to prepare mesoporous zeolite-based（VMT-Si O₂）by treating zeolite,which will be used as the carrier for loaded nickel metal.The Ni-active component is prepared by loading,doping,and forming Ni-M（M=Fe,Co,Cu）with transition metals.These catalysts were characterized by XRD,BET,TG,and corresponding activity and stability tests.The conclusions are as follows:（1）Catalysts Ni-oa/VMT-Si O₂,Co-oa/VMT-Si O₂ and Ni-Co-oa/VMT-Si O₂ prepared by oleic acid method and Ni-im/VMT-Si O₂ and Ni-Co-im/VMT-Si O₂ prepared by traditional impregnation method were used for methane carbon dioxide reforming reaction,respectively.At 750℃,36000 m L/(g_cat·h)and atmospheric pressure,the CH₄ conversion rate of Ni-Co-oa/VMT-Si O₂catalyst reaches 72%and the CO₂conversion rate reaches 82%.It is far better than Ni-oa/VMT-Si O₂ and Ni-im/VMT-Si O₂ and Ni-Co-im/VMT-Si O₂ catalysts prepared by traditional methods.This is because compared with the traditional impregnation method,the addition of oleic acid makes the active components in the catalyst more dispersed,preventing the catalyst from rapidly agglutinating in high temperature environment,which leads to the degradation of catalytic performance,and the introduction of transition metal Co further improves the activity of the catalyst.（2）La Ni O₃/VMT-Si O₂ was prepared using mesoporous zeolite as a carrier,and La Ni O₃ and Ni-im/VMT-Si O₂ prepared by a single impregnation method were used as controls.At 750℃and atmospheric pressure with a space velocity of 36000 m L/(g_cat·h),the CH₄ and CO₂ of La Ni O₃/VMT-Si O₂ catalyst reached80%and 88%,respectively,indicating that the mesoporous zeolite carrier can effectively improve the dispersion of the perovskite catalyst.The reduced catalyst contains La₂O₃,which can effectively enhance the CO₂ adsorption capacity and further strengthen the overall anti-sintering performance of the catalyst.（3）La Ni_0.8X_0.2O₃/VMT-Si O₂（X=Fe,Co,Cu）catalysts were prepared by loading transition metal components with a mass fraction of 2wt%on La Ni O₃/VMT-Si O₂ perovskite carriers.The three catalysts with different metal doping were obtained by reduction and used for the dry reforming of methane.At 750℃and atmospheric pressure with a space velocity of 36000 m L/(g_cat·h),the CH₄ and CO₂ of La Ni_0.8 Co_0.2O₃/VMT-Si O₂ perovskite catalyst reached 83%and 91.3%,respectively,showing the best activity and stability.This is because Co does not passivate the Ni active site compared to La Ni0.8Fe_0.2O₃/VMT-Si O₂ and La Ni_0.8Cu_0.2O₃/VMT-Si O₂ perovskite catalysts,and Co can enhance the catalyst’s anti-coking performance by increasing CO₂ adsorption.