Optimization Of Solid Phase Synthesis And Catalytic Performance Of CH₄/CO₂ Reaction Over Metal Catalyst Supported By Activated Carbon

Global temperatures are rising as greenhouse gas emissions,such as CH4 and CO2,increase year by year.Rational utilization and transformation of greenhouse gases is an important measure to alleviate the current environmental and energy crisis.The preparation of syngas by CH4/CO2 reforming has a broad application prospect.The addition of high efficiency catalyst is the most effective method to solve the high energy consumption of CH4/CO2 reforming reaction.The traditional solution impregnation method can easily lead to the agglomeration of the particles of the metal active components,which can aggravate the carbon deposition and reduce the activity of the catalyst.As an efficient and convenient green synthesis method,solid phase synthesis can be used to prepare nanoscale active metal catalysts.Therefore,this paper carried out the research on the optimization of solid phase synthesis and catalytic CH4/CO2 reaction performance of metal catalysts supported by activated carbon.The main contents and conclusions are as follows:(1)Nickel was loaded onto activated carbon,molybdenum disulfide and carbon nitride by solid phase synthesis.The effects of carrier properties,impregnation solution concentration and solid phase grinding time on metal particle size and distribution were studied,and the optimal carrier type and preparation parameters were determined.The reaction rules,product distribution and carbon deposition characteristics of reforming were studied by using the fixed bed reactor and the optimal catalyst.The experiment confirmed that the abundant pore structure was one of the factors contributing to the uniform metal load,and the optimal conditions were determined as:the soaking mass ratio between activated carbon and polyvinyl pyrrolidone was 6:1,the mixing grinding time was 15 min,and the catalyst surface active metal was evenly distributed and the average particle size was minimum 4.69 nm.Results of catalytic performance show that the catalyst has good catalytic performance and anti-carbon deposition effect in reforming experiment.In the catalytic reforming experiment at 900℃ for 9 h,the gas conversion rate took 2 h as the inflection point,showing a trend of decreasing first and then rising.The characterization results show that the reason for the increase of gas conversion rate is that the internal structure of the catalyst tends to be stable and changes under the high temperature reduction atmosphere.(2)Under the optimal preparation conditions and with different properties of activated carbon as the carrier preparation of solid phase load nickel catalyst,the specific surface area and pore structure on the metal particle size of activated carbon,dispersion properties and microscopic characteristics,the influence of catalyst surface functional groups of the different activated carbon load nickel catalyst for reforming reaction of catalytic performance,revealing the nature of the carrier the influence law of the performance of catalyst,get the following conclusion:it was found that the particle size,dispersion status and catalytic activity of the active metal were unified as a whole,which decreased with the decrease of specific surface area.The metal particle size of the catalyst prepared by coconut shell activated carbon with the largest specific surface area was 4.11 nm at the minimum,with the highest catalytic activity.However,the coal activated carbon has a minimum specific surface area and a high volatile component,which can easily lead to the agglomeration of active metals and thus reduce the catalytic activity.(3)Choose coconut shell activated carbon as a carrier,solid phase synthesis of nickel and cobalt catalyst active component,metal bicomponent quality than metal size and distribution rule of the influence of the different types under the action of catalyst reforming reaction characteristics,specific performance and bimetallic catalyst quality than quantitative relationship,reveal the different catalyst activity,summarize activated carbon load mechanism of different metal catalyst for catalytic activity,through the research get the following conclusion:during the preparation of catalysts with the increase of the content of metal elements cobalt catalyst form the surface of the metal particle size increases gradually,nickel and cobalt elements than 1:2,the maximum average particle size was 6.76 nm,and the influence of different metal proportions on metal distribution was weak.By studying the catalytic activity of different catalysts,it was found that when the ratio of ni to co was 1:2,the overall catalytic effect was better than that of single metal and other metal catalysts.And 1:1,2:1 ratio of nickel and cobalt for CH4 conversion rate is about 10%lower than the single metal catalyst,but high CO2 conversion during metal ratio of 1:1,based on the reforming reaction mechanism of summarize,thought to be due to the different metal components for internal promotion mechanism,leading to different metal component gas conversion rate.Through the above research,master the optimized preparation method of solid phase synthesis of metal catalyst supported by activated carbon,reveal the catalytic law of the reaction of metal catalyst supported by activated carbon to methane and carbon dioxide reforming,and master the carbon deposition characteristics under the metal catalyst supported by activated carbon.It provides theoretical basis for efficient emission reduction and resource utilization of methane and carbon dioxide greenhouse gases.