Ni-based Bimetallic Catalysts Prepared By Micro-combustion Method For Methane Dry Reforming

Natural gas,as an important clean energy,is more and more favored by people with the increasing attention to environmental protection.Converting CH₄from natural gas to syngas to produce high value-added products or liquid fuels for easy transportation can save the cost of long-distance pipeline transportation.In addition,the rapid consumption of fossil fuels has resulted in excessive CO₂emissions,which has threatened the survival and development of human beings.The reduction and utilization of CO₂is extremely urgent.Methane dry reforming can simultaneously convert two greenhouse gases（CH₄and CO₂）into syngas,and subsequently produce chemical products with high commercial value,such as methanol.The research and development of this technology can help us achieve the grand goal of"carbon peak and carbon neutrality".However,current nickel-based catalysts are prone to sintering and carbon deposition at high temperature,which thus leads to the aggregation of nickel particles and deteriorates the catalytic effect.On the basis of analyzing the characteristics of solution combustion method and non-equilibrium cold plasma technology,this paper adopts a new strategy combining the two emerging technologies,that is,introducing plasma into the combustion process,called micro-combustion.The Ni-based bimetallic catalysts were prepared and the structure-performance relationship in the bimetallic catalysts were explored by XRD,TEM,H₂-TPR,XPS,TG,CO₂-TPD and DRIFTs.Firstly,Ni-Cu,Ni-Co and Ni-Fe bimetallic catalysts were prepared by solution combustion and micro-combustion method,and their catalytic performance in CH₄-CO₂reforming were studied.The catalyst prepared by the micro-combustion method exhibited better catalytic activity.In addition,we optimized the ratios of bimetallic catalysts respectively and explored the influence of different Ni/M ratios on the catalytic performance.Adding a small amount of Fe to the mono-metal catalyst could significantly enhance its activity and resistance to carbon deposition.Among them,5Ni-0.1Fe/Si O₂-P catalyst displayed excellent catalytic performance.In 30 h stability test,the CH₄conversion and CO₂conversion were maintained at 80%and91%,respectively,without any deactivation.Secondly,the catalysts prepared by solution combustion and micro-combustion were characterized by XRD,TEM,H₂-TPR,XPS and TG.The bimetallic catalysts prepared by micro-combustion method had smaller active metal particles,more uniform dispersion,closer metal-support interaction,higher electron density and lattice oxygen mobility on metal surface,thus performing better performance in methane dry reforming.Finally,the reaction kinetics and mechanism analysis of the catalysts prepared by solution combustion and micro-combustion method were carried out,respectively.The surface of the catalyst prepared by micro-combustion method was mainly activated by CO₂,so that more oxygen-containing species for carbon oxidation were generated on the surface of the catalyst,which effectively inhibited the formation of carbon deposition,and lowered the activation energy of DRM reaction.In addition,the high lattice oxygen mobility of the bimetallic catalyst prepared by micro-combustion promoted the cleavage of C-H bond in CH₄,and accelerated the combination of activated CO₂and H atoms generated by CH₄decomposition into HCOO^-intermediates,thus exhibiting excellent catalytic performance.