Preparation Of Nickel-based Catalysts By Plasma-induced Micro-combustion Method And Its Performance Evaluation

Nickel-based catalysts are widely used in many gas-solid catalytic processes because of their low cost,easy availability and high activity.However,the Ni-based catalyst is easy to be deactivated by carbon deposition in the system containing CO and CH₄,and is prone to sintering at high temperature,thus affecting its stability.Among many synthesis methods,solution combustion method is a fast and efficient treatment method,but the controllability of combustion process is poor,resulting in the irregular morphology of combustion products,which is not conducive to performance optimization.At the same time,the dielectric barrier discharge plasma technology has high electron energy and strong activation.Moreover,it can be carried out at low temperature,which can effectively prevent the agglomeration and sintering of metal active components.Therefore,in view of the problems encountered by Ni based catalysts,this paper combined the two methods to form a plasma–induced micro-combustion method to prepare Ni/SiO₂ catalyst,in order to improve its catalytic performance,and explore the relationship between structure and performance.Firstly,compared with Ni/SiO₂ catalyst prepared by single solution combustion or plasma treatment,Ni/SiO₂ catalyst prepared by plasma-induced micro-combustion?5%and 10%of Ni content?has better Ni dispersion of metal and stronger metal-carrier interaction force,showing excellent activity and anti-sintering stability in CO methanation evaluation.Secondly,the influence of the amount of fuel?urea?added on the structure and performance of the catalyst is investigated.The Ni/SiO₂ catalyst exhibites excellent catalytic activity when the ratio of the valence of the reducer and the oxidizer is 1.25.Because Ni has the smallest particle size and the best dispersion on the carrier.Under the conditions of 340°C,CO conversion of Ni/Si-1.25 can reach 93.7%in CO methanation,and it shows the best activity in CO₂ methanation.Finally,the catalysts are modified by doping La,Ce and Zr as the second active metal.The results show that the interaction between Ni-La,Ni-Ce and Ni-Zr change the environment around Ni,significantly increased the number of Ni active sites on the catalyst surface,enhanced the adsorption capacity and adsorption amount of H₂ and CO₂ on the catalyst surface,and thus promote the occurrence of CO₂ methanation.The activity sequence of the catalysts in CO₂ methanation are 10Ni-3La/Si>10Ni-3Ce/Si>10Ni-3Zr/Si>10Ni/Si.Among them,the catalyst doped with La element has the best catalyst performance.Under the conditions of 280°C,CH₄ selectivity of Ni/Si-1.25 can reach 94%.