Preparation Of Highly Dispersed Ni-baced Montmorillonite Catalyst And Study On Its Performance Of CO/CO₂ Methanation

CO/CO₂ methanation is an important chemical reaction,which is of great significance for clean utilization of coal and environmental protection.Using montmorillonite as support to prepare high dispersion Ni-based methanation catalyst has practical value for resource utilization and scientific significance for methanation research.In this thesis,montmorillonite was used as a support,nickel nitrate,L-lysine,L-alanine,L-serine,and glycine were used as raw materials to prepare a series of nickel-based catalysts using an improved impregnation method.The catalysts were characterized by the X-ray diffraction analysis（XRD）,specific surface and pore structure analysis,H₂ temperature programmed reduction analysis（H₂-TPR）,thermogravimetric analysis（TG）,transmission electron microscopy analysis（TEM）,energy dispersion spectrum analysis（EDX）and mapping etc.The phase,pore structure,elemental composition,distribution of active components,relationship between active components and support,carbon deposition and sintering of catalyst were systematically analyzed.The performance of the catalyst was investigated and a tubular reactor was employed.The Agilent gas chromatography was used to detect the products.CO methanation reaction conditions:atmospheric pressure,temperature 300℃-500℃,space velocity 10000 h^-1,molar ratio H₂/CO=3;CO₂ methanation reaction conditions:atmospheric pressure,temperature 300℃-500℃,space velocity 12000 h^-1.The molar ratio H₂/CO₂=4.The specific research content and research results are as follows:1.The specific surface area of montmorillonite was increased from58.58 m²/g to 411.39 m²/g,and the pore volume was increased from 0.11cm³/g to 0.62 cm³/g after hydrothermal and acid treatment.But the original lamellar structure of montmorillonite was maintained well.2.Using montmorillonite before and after modification as support,methane-based nickel-based catalysts were prepared and characterized according to the design of orthogonal experiments.It was found that nickel in the catalyst mainly existed in the form of Ni O.After modification with acid,the changes of specific surface area and pore structure of montmorillonite affected the dispersion degree of active component and the interaction between the active component and the support.The catalyst prepared with modified montmorillonite has high catalytic activity.The addition of amino acids made the active components of the catalyst highly dispersed and the Ni O nanoparticles significantly smaller.3.The results of orthogonal experiment showed that the optimal catalyst was M_RNi20A₂（1:1）,namely,acid modified clay,20%of the nickel loading,and 1 of the molar ratio of L-alanine to nickel nitrate.The catalytic activity of the catalyst increased first and then decreased at the reaction temperature of 300℃-500℃.In the CO methanation reaction,the CO conversion rate reached 100%and the CH₄ selectivity reached 82%.In the CO₂ methanation reaction,the CO₂ conversion rate reached 90%and the CH₄ selectivity reached 99%.4.The 60 h stability test of catalysts M_RNi20A₂（1:1）,M_RNi20A₃（0:1）and MNi20A₂（1:1）showed that the weight loss rates due to carbon deposition in the CO methanation reaction were 2.07%,1.57%and 2.49%,respectively.In the CO₂ methanation reaction,the weight loss rates due to carbon deposition in the three catalysts were 1.40%,1.67%and 0.86%,respectively.The catalyst M_RNi20A₂（1:1）still maintained good stability and anti-carbon deposition after 60 h stability test.