Study On The Direct Synthesis Of DMC By Supercritical Carbon Dichloride Catalysts Supported On Supported Solid Base Catalysts And CH ₃ OH

Dimethyl carbonate is a kind of widely used and environmental friendly raw chemical materials, which was known as a "new cornerstone" of organic synthesis in21st century. The research and development,of its synthesis and application has drawn wide attention of researchers both at home and abroad. The catalytic activity of supported solid base catalyst was mainly studied in this article on direct synthesis of dimethyl carbonate with supercritical CO2and methanol.. In this reaction process, carbon dioxide gas offers both supercritical CO2atmosphere and a kind of basic raw materials. The joint application of supercritical fluid technology and traditional synthesis process, with the additionof solid base catalyst, makes it easier to get a greater degree of activated CO2, thus the synthesis yield of DMC. was improved.A series of solid base catalysts were prepared for the direct synthesis of dimethyl carbonate(DMC) using CO2and CH3OH as raw materials. KOH was used as active component in these catalysts which were based on silica gel, magnesium oxide, activated carbon and alumina. The iso-volumic impregnation method was adopted during the preparation process. The experimental results showed that the catalytic activity of activated carbon loading KOH performed the most excellent. The catalysts were characterized by Brunauer-Emmett-Teller(BET), X-ray diffraction(XRD) and scanning electron microscope(SEM), and the experimental results show that the activated carbon with large specific surface area tends to be a good carrier. After high temperature calcinations, the KOH loaded on supports decomposes into K2O crystal, which improves the catalytic activation for CO2. The porous catalyst structure makes K2O disperse well on the surface of the catalyst carriers and the inner wall of the holes. The effects of KOH loading amounts, the composition of additives, reaction temperature, pressure and time on the production of DMC were investigated over KOH/C catalysts. Under the optimum conditions, the yield of DMC is7.13%.On the basis of preliminary experiment research, continuous studies on catalytic activity were performed. A series of supported solid base catalyst were got.with coconut shell charcoal, gold charcoal, nut shell charcoal and air purifying carbon four kinds of different specifications of activated carbon as the carrier, respectively by KOH, K2CO3, KI as active componen. The activity evaluation results show that the K2CO3/nut shell charcoal has the highest catalytic activity. The same surface properties of structure of catalyst were studied by BET, XRD, SEM et al. And through the NH3temperature programmed desorption (NH3-TPD) and CO2temperature programmed desorption (CO2-TPD) testing methods, the influence of load type solid alkali catalyst activity and surface acid-base acid-base strength on the catalyst activity were focused on. The investigation results show that the effect of catalyst surface acid active sites and the basic sites make a big difference to the catalytic reaction. Finally, the influences of process conditions of K2CO3loading and catalyst calcination temperature on catalyst activity were studied. With the optimal operating conditions, DMC yield is15.5%. The catalytic effect is obviously better than the previous group of experiments.