Study On The Preparation Of Bochar-based Materials And Its Catalytic Carbon Dioxide Conversion

As a clean,cheap,and directly available C1 resource,carbon dioxide could be converted into high value-added chemicals.Biomass has attracted widespread attention due to its renewable,degradable and various characteristics.The porous carbon materials prepared from biomass had excellent thermal and chemical stability,strong hydrophobicity,large specific voids and pore volume,were applied in various fields such as adsorption and catalysis.In this paper,we used biomass chitosan to prepare biochar-based materials as catalysts to catalyze the conversion of carbon dioxide into cyclic carbonate,carbon monoxide and other high value-added chemicals.A series of nitrogen-doped porous carbon materials was prepared at different temperatures as catalysts to synthesize cyclic carbonates by pyrolyzing chitosan and niacin.Then,the nitrogen-doped porous carbon material was loaded with ruthenium metal by impregnation method to obtain Ru/C catalyst,and the"Ru/C-Bmim Cl-Bmim PF₆"catalytic system was constructed.Last,the synergy between Ru/C and ionic liquids Bmim Cl and Bmim PF₆ was used to catalyze the reverse water gas reaction of carbon dioxide and hydrogen to produce carbon monoxide.Modern analysis and testing techniques such as SEM,TEM,XPS,XRD,FT-IR,TGA,OEA,CO₂-TPD,and specific surface area and pore size analysis were used to characterize the structure of different nitrogen-doped porous carbon materials and the interaction research of material and substrates.For the"Ru/C-Bmim Cl-Bmim PF₆"catalytic system,in addition to the above analysis and testing techniques,¹³C NMR was also applied to study the interaction between ionic liquids and carbon dioxide.The catalytic performance of different nitrogen-doped porous carbon materials was characterized by thermally catalyzing carbon dioxide and epoxides to prepare cyclic carbonates.The results showed that the catalytic properties of the different materials were different,and the material synthesized at 600 ^oC had the best performance.It could achieve high-efficiency catalytic conversion of epoxide and CO₂ into cyclic carbonates at 130 ^oC and 1.5 MPa CO₂pressure,metal-free and halide-free additives,and the yield could be as high as 90%after 2 h.Mechanism studies showed that pyrrole N in nitrogen-doped porous carbon materials was the main active site for the reaction,which could adsorb and activate carbon dioxide.Moreover,the catalyst had good substrate universality and stability.The catalytic performance of Ru/C materials was characterized by reverse water gas reaction.The study found that Ru/C could efficiently produce carbon monoxide by hydrogenation and reduction of carbon dioxide under relatively mild conditions.The catalytic system of“Ru/C-Bmim Cl-Bmim PF₆”was hydrogenated and reduced for 24 h at 160 ^oC and a total pressure of 6 MPa,the output of carbon monoxide was 2.88 mmol,the yield was 120mmol·g^-1·h^-1and the TON value was 291.Mechanism studies showed that Bmim Cl and Bmim PF₆ played important roles in the reaction process.They could absorb and activate carbon dioxide through a joint action.The Ru nanoparticles loaded on carbon materials dissociated hydrogen and converted the activated carbon dioxide into carbon monoxide.