Study On Carbon Deposition Resistance Of The Ni-based Molecular Catalyst And Its Structure-activity Relationship For CO₂ Reforming

In recent years,with the increase of greenhouse gas emissions,global warming has become increasingly serious,and restrictions on greenhouse gas emissions have also received widespread attention.The CH₄/CO₂ reaction can effectively utilize two greenhouse gases,CH₄ and CO₂,and has received widespread attention.At present,noble metal catalysts have high catalytic activity and carbon deposition resistance,but they are also costly at the same time,which is not conducive to industrial applications.The non-precious metal Ni catalytic activity is comparable to precious metals,and the cost is low,which is very advantageous for industrial applications.However,it is also easy to cause catalyst loss due to high temperature sintering and carbon deposition,thereby affecting the activity and stability of the catalyst,which is also a major problem to be solved by the current Ni-based catalyst.The purpose of this paper is to reduce the Ni particle size,improve the dispersion of the catalyst and the interaction between Ni and the support by modifying the catalyst,thereby improving the sintering resistance of the catalyst and preventing carbon deposition,so as to achieve high activity and stability,and analysis the structure-performance relationship.Therefore,the paper mainly adopts three modification methods,one is alcohol modification,one is plasma modification,and the other is plasma combined with alcohol modification to obtain a catalyst,and used for carbon dioxide reforming.In the methane reaction,the catalytic activity was tested.The results and physicochemical properties of the catalyst were characterized by XRD,BET,TPR,TG and other characterization methods.The research contents and results are as follows:?1?First,the surface modification of the alcohol of the Ni-based molecular sieve catalyst and the performance evaluation of the catalyst.The carrier and the catalyst were respectively modified to optimize the process parameters of the optimal alcohol-modified catalyst.The results show that 10%Ni/MCM-41-BA-Sup?n-butanol-treated support?and 10%Ni/MCM-41-BA?n-butanol?catalysts have the best catalytic activity,the conversion of CH₄ and CO₂ are 90%,92%and 85%,86%,respectively.The XRD results show that alcohol modification has a great influence on the particle size and dispersion of Ni in the catalyst;H₂-TPR results show that the interaction between the alcohol modified catalyst Ni and the support is enhanced;The TG results show that the alcohol modification can effectively inhibit the carbon deposition of the catalyst.?2?The plasma modifies the catalyst and optimizes the plasma processing parameters.The optimal parameters for plasma treatment are:treatment atmosphere is N₂;treatment power is 5W/200 W;treatment time is 24 min.The results show that10%Ni/MCM-41-P-24min-N₂ catalysts have the best catalytic activity,the conversion of CH₄ and CO₂ are 90%and 86%.XRD characterization results show that the dispersion of the active component Ni of the catalyst after plasma treatment is improved,and the grain size of Ni is decreased;H₂-TPR characterization results show that the interaction between Ni and the support can be enhanced after plasma treatment;TG characterization results show that the carbon deposition resistance of the catalyst is significantly improved after the plasma treatment,because the plasma treatment can change the type of carbon generated by the catalyst in the reaction,thereby improving the carbon deposition resistance of the catalyst,which is related to XRD and TPR.This is consistent with XRD and TPR results.?3?Plasma modification combined with alcohol modification and screening of the optimal alcohols.Among the catalysts modified by plasma treatment,the prepared MCM-41-EA-Sup-Cat-P?first treated with ethanol to treat the carrier MCM-41,then loaded with Ni to obtain a catalyst,obtained by plasma treatment?and 10%Ni/MCM-41-EA-P?the catalyst was treated with ethanol and then treated with a plasma?catalyst had the best catalytic activity,and the conversion rates of CH₄ and CO₂ were 89%,90%,87%,and 87%,respectively.The XRD characterization results show that the dispersion of the active component Ni of the plasma-treated alcohol-modified catalyst is improved,and the grain size of Ni is decreased;H₂-TPR characterization results show that the interaction between Ni and the carrier can be enhanced after plasma treatment;TG characterization results show that the plasma-treatedand alcohol-modified catalyst has significantly improved carbon deposition resistance,because both plasma treatment and alcohol modification are beneficial to inhibit the formation of carbon on the catalyst,thereby increasing the carbon deposition resistance of the catalyst,which is consistent with the XRD and TPR results.?4?Plasma modification combined with alcohol modification and optimization of plasma parameters.The optimal parameters for plasma treatment in ethanol atmosphere are:treatment method is plasma treatment and then roasting;roasting temperature is 500?;treatment power is 160 W;treatment time is 64 min.The optimum catalyst was 10%Ni/MCM-41-P?EA?-500°C-160W-64min,and the conversion rate to CH₄ and CO₂ reached 89%and 87%.XRD characterization results show that the dispersion of the active component Ni of the catalyst after plasma treatment is improved,and the grain size of Ni is lowered;BET characterization results show that the catalyst still maintains a good mesoporous structure after plasma treatment and has a pore-expanding effect.H₂-TPR characterization results show that the interaction between Ni and the carrier can be enhanced after plasma treatment;TG characterization results show that the carbon deposition resistance of the catalyst is obviously improved after the plasma treatment,because the type of carbon formed by the catalyst in the reaction can be changed after the plasma treatment,thereby improving the carbon deposition resistance of the catalyst,which is consistent with the XRD and TPR results.