Experimental Study On The Integrated Carbon Dioxide Capture And Methanaton Process Catalyzed By CaO-Ni Materials

The massive emissions of carbon dioxide have brought enormous pressure to the environment,and research on carbon dioxide capture and conversion is of great significance for improving environmental issues.Currently,large-scale carbon dioxide treatment mainly adopts carbon dioxide capture and storage,that is,high concentration carbon dioxide is stored through chemical absorption or mineralization,and then transported to chemical plants for use or stored underground.Although this approach can achieve carbon reduction quickly and economically,the cost issues brought about by its transportation and storage processes cannot be ignored.Based on this,this paper proposes an integrated process of carbon dioxide capture and utilization（ICCU）,which uses Ca O-Ni dual function materials to achieve the collaborative disposal of carbon capture and high value utilization of carbon resources through the capture of carbon dioxide and in-situ methanation conversion.The appropriate reaction conditions（temperature,reaction time,catalyst loading）have a significant impact on the capture and conversion efficiency of carbon dioxide.This paper first studied the effects of different reaction conditions,including methanation temperature（350,400,450,500°C）and reaction time（10,20,30minutes）,on the catalytic performance of Ca O-Ni function materials for carbon dioxide adsorption and methanation.The results indicate that under this experimental environment,methane production first increases and then decreases with increasing temperature.As the reaction time increases,methane production first increases and then stabilizes.When the temperature is 450°C and the reaction time is 30 minutes,the catalytic activity of the function material reaches its maximum,and the cycle stability is good at this time.After 5 cycles,the carbon dioxide conversion and methane production do not significantly decrease.In addition,the effect of nickel loading in the catalyst（2.5%,5%,10%,20%）on the product was studied.With the increase of nickel loading,the adsorption capacity of carbon dioxide and methane production show a trend of first increasing and then decreasing.At a temperature of450°C,a duration of 30 minutes,and a Ni loading of 10%,the Ca O-Ni based function material achieved the best activity,with average adsorption capacity of 0.23mmol/g _DFMs,average methane production of 0.20 mmol/g _DFMs,and average carbon dioxide conversion of 88.4%.In order to enhance the activity and stability of ICCU for dual functional materials,metal based support（Al₂O₃,Ce O₂）and carbon based support（Multi walled carbon nanotubes,Graphene）were selected to load and modify the Ca O-Ni based dual function material,and their effects on carbon dioxide adsorption and methane yield were studied.The results showed that the methane production and carbon dioxide conversion of the dual function materials using metal based supports were higher than those using carbon based supports.The highest methane production of Ca Ni Al and Ca Ni Ce samples reached 0.23 and 0.24 mmol/g _DFMs,respectively,with average carbon dioxide conversion of 95.36and 87.57%.However,Ca Ni M and Ca Ni G samples exhibit better cyclic stability,with methane production decay rates of8.81%and 15.8%.In order to further improve the adsorption performance of dual function materials for carbon dioxide and enhance their catalytic carbon conversion efficiency,this paper uses alkali modification,acid modification,and nitrogen-doped modification to activate and pre-treat the support,and explores the influence of modification methods on the integrated carbon dioxide capture and methanation performance.The results showed that the nitrogen-doped multi walled carbon nanotube support had higher adsorption capacity and methane production,with an average of 0.27 and 0.23mmol/g _DFMs,respectively.On this basis,the influence of different nitrogen doping amounts was explored,and the results showed that as the nitrogen content increased,methane production also increased.When the ratio of nitrogen source to support is 1:4,the formation of carbon monoxide is detected in the product gas after multiple cycles,reducing the selectivity of methane.When the ratio is 1:3,the reactivity of methane is the highest.The average values of carbon dioxide adsorption and methane production reached 0.27 and 0.25 mmol/g _DFMs,respectively.In multiple cycles,the average carbon dioxide conversion reached 90.5%.