Study On Activated Carbon Supported Copper Catalysts For Dimethyl Carbonate Synthesis By Oxidative Carbonylation Of Methanol

Dimethyl carbonate?DMC? is a green chemical,which has been widely utilized in chemical synthesis and solvents.Vapor-phase oxidative carbonylation of methanol which utilizes methanol,O₂ and CO as reactants to synthesize DMC has become a research hotspot,according to the principles of green chemistry.As a kind of chloridefree catalyst,CuO_x/AC can resolve catalyst deactivation and facility corrosion caused by chlorine loss and thus has attracted much attention.This dissertation focuses on the catalyst preparation,support modification and the role of AC support over CuO_x/AC catalyst in the methanol oxidative carbonylation reaction.CuO_x nanoparticles dispersed on activated carbon?AC?were fabricated by reducing Cu?CH₃COO?₂ supported on AC using gas-phase methanol as reducing agent.The preparation process was facile and could be accomplished in situ at mild condition.The catalytic performance was significantly influenced by reduction conditions including temperature and time.With the similar selectivity of DMC,the space time yield?STY?under optimal reduction conditions reached up to 408 mg/?gcat·h?,which was superior to conventional methods such as thermolysis and solvothermal reduction.Based on the characterization results of XRD,TEM and XPS,the good copper dispersion and high Cu⁺ content obtained by vapor-phase methanol reduction were mainly responsible for the high catalytic activity.The surface properties of activated carbon play an important role in the reaction of oxidative carbonylation of methanol.Characterizations such as N₂ adsorption,IR,Raman,H₂-TPR and TEM were carried out to investigate the effects of nitrogen modification on support properties and catalyst microstructure.Under appropriate temperature,the nitrogen modification led to the increase of the surface area,nitrogen containing groups and defects.As a result,the interaction between support and metal was enhanced and the dispersion of copper species was improved which eventually favored the yield of DMC.In order to further explore the support effects in the reaction of methanol oxidative carbonylation,Cu⁰ catalysts supported on different carriers?i.e.SiO₂,Al₂O₃,AC?were prepared.Activity evaluation results demonstrated that only the catalyst supported on AC possessed the catalytic capacity for the DMC formation.Based on the characterization results of TPD-MS and EPR,it proved that the AC support had the ability to adsorb methanol as well as activate oxygen molecules.Thus,it was inferred that AC worked as a constituent part of the active site which was responsible for the formation of methoxy groups.