The Preparation Of Nano-copper Catalysts Supported On Activated Carbon Under Microwave Irridation For The Systhesis Of Dimethyl Carbonate

Dimethyl carbonate (DMC) is an environmentally benign compound and unique intermediate, which is regarded as a new building block of organic synthesis. During several reaction routs for the synthesis of DMC, the oxidative carbonylation of methanol in vapor phase has been considered the most promising way, which has become the predominant exploition technology in many countries.In recent years, since the problem of deactivation caused by loss of Cl related to traditional catalysts can be ultimately avoided, chlorine-free copper catalysts have attracted great attention from researchers all over the world.In this study, nano-copper catalysts supported on activated carbon (Cu/AC) were prepared by microwave irradiation and characterized by XRD, H2-TPR, XPS, and SEM techniques. The Effect of preparation parameters, reaction conditions, and the addition of La and Zr promoters on the oxidative carbonylation of methanol have been investigated. Moreover, the deactivation and regeneration methods of Cu/AC catalysts were discussed. The main content and conclusions are listed as follows.(1) The optimized preparation conditions of Cu/AC catalysts were as follows:vacuum degree,-0.05 Mpa; temperature; 350℃, and Cu content, 16wt%. It is found that the structural properties and the catalytic performance of the catalyst are greatly determined by the calcination temperature. CuO, Cu2O and Cu0 were detected in catalyst prepared at 250℃ due to autoreduction of copper species. For the sample calcined at 350℃, the copper species is mostly in the form of Cu° with particle size of around 40 nm on the surface of the catalyst, and the highest catalytic activity is achieved. When calcination temperature rises to 450℃, the dimension of Cu0 crystal is increased to about 1 OOnm and the catalytic activity is greatly declined.(2) The dispersion reduction of copper species and oxygenation of Cu° by O2 in the feed gases during the reaction resulted in a decreases in the catalytic activity of Cu/AC catalysts in the oxidative carbonylation of methanol. However, the catalytic activity of the catalyst can reached more than 90% of the initial activity after heating at 400℃ for 3 h under H2 flow..(3) The effect of reaction conditions on the oxidative carbonylation of methanol was studied. The optimal conditions were obtained as follows:GHSV, 9720 h-1; reaction temperature,110℃; reaction pressure,1.5 Mpa; and CO/O2 molar ratio,11.(4) The effect of additon of promoters on the catalytic performance of Cu/AC catalysts was studied. It is found that the addition of La and Zr into the catalyst promotes the enrichment of copper species on the surface of the catalyst and the formation of Cu0, therefore lead to an improved catalytic activity.