Study Of The Liquid-phase Catalytic Oxidative Carbonylation Of Methanol By Cu/M-OMS-2 Catalysts

Dimethyl carbonate (DMC) is an environmental friendly building block. DMC has show bright future in the non-reactive fields in recent years. It can be used as an additive to gasoline and a green solvent in medicine, pesticide, dyestuff, flavoring agent of foodstuff and electronic chemical, thus DMC synthsis has attracted more attention for its growing market. The clean technology to synthesize DMC by liquid-phase oxidative carbonization of methanol attracted more and more attention worldly. This method is the most valuable industrial route because of the following advantages: cheap raw materials and high atom utilization.In this study, CuCl catalysts supported on manganese oxide octahedral molecular sieves (OMS) were firstly prepared and were used to synthesize DMC in oxidative carbonylation reaction. Then the effect of preparation methods of carriers, different copper source, preparation mehtods of catalyst and different metal dopants on catalytic activity were investigated, and XRD,SEM,H₂-TPR,XPS and BET technices was used to charactrize the properties of catalysts. Finally, the operating parameters in batch reactors was optimized. The conclusion was obtained as follows:1. It chose different Cu sources to prepare Cu-OMS-2 catalysts. CuCl was the best active substance among the selected Cu source .2. The activity and selectivty of catalysts supported on OMS synthesized by a reflunt method was better than that by sol-gel method and no-solvent method.3. The Cu-OMS-2 catalyst with 25% CuCl loading, calcination temperature of 500℃and calcination time of 5 hours had shown the best catalytic performance with the yield of 84.6%. This could be attributed to the appropriate proportion of Cu²⁺ and Cu+ in catalyst, which is favor to form the intermediate of Cu(COOCH₃)Cl. Meanwhile, CuCl existed in thin slice form had dispersed well on the surface, it is advatage to the adsorption of reactant.4. Investigate the catalytic activity of Cu/M-OMS-2(Ag⁺,Ce³⁺,Sr²⁺,Pb²⁺,Zn²⁺,La⁺), the results suggest that Cu-Ag-OMS-2 show the best catalytic activity with the yield of 89.7%. The doping of Ag changes the fiber topography of Cu-OMS-2. Meanwhile the adding of Ag⁺ produce compound of AgCl,which will contribute to fix the anion of Cl. The catalyst of Cu/Ag-OMS-2 with the appropriate proportion of Cu²⁺ and Cu+ is favourable to synthesize the DMC as well.5. The yield and selectivity of dimethyl carbonate reached 92.5% and 98.5%, respectively, under optimized conditions: catalyst 3g , methanol 50mL, reaction temperature 130℃, reaction total pressure 4.0MPa, reaction time 4h and the volume concentration of O2 5% ,600 r/min .