Study Of Dimethyl Carbonate Synthesis By Methanol And Triphosgene

Dimethyl carbonate is a new green compound that is produced from methanol. As an important chemical product, it has already attracted much attention in the world to study the preparation and the application technology. Recently, a lots of research work have been carried out to develop dimethyl carbonate synthesis. The synthesis by reaction between methanol and triphosgne is a new promising way but it has not been reported in the literature. In this paper, the reaction conditions including reaction temperature, reaction time, mole ratio of methanol/triphosgene, organic solvent and initiator etc. have been studied. The main conclusions were obtained as follows:(1) The product produced from methanol and triphosgene are complicated and dissolve lots of HC1. The aciding of solvent made the injector hard to work. The test can be carried out after adding NaOH to the product solvent.(2) With the temperature increased, the yield of DMC increased and reached maxium 63.52% at 313K, and then decreased. The reaction is complexed with the time running.(3) When the mole ratio of methanol and triphosgene was 25:1, the selectivity and the yield of dimethyl carbonate were relatively lower. With the ratio decreasing, the selectivity and the yield of dimethyl carbonate are increasing; The impact of solvent to yield of triphosgene is following: tetrachloride > chlorobenzene > toluene > benzene.(4) The organic alkali as the initiator is better than the solid akali which is propitious to synthesize DMC but the effect is limited. The order of effect of the solid alkali to promote the reaction is following: MgO/SiO₂>MgO/Al₂O₃>MgO/ZnO₂ >MgO/TiO₂ >KNO₃/ZrO₂.(5) After investigated simply, We presumed two reaction mechanism for the synthesis: 1) Triphosgene is decomposed into diphosgene,phosgene in the present of methanol which is weak nucleophilic reagent. And then diphosgene,phosgene would be react with methanol to dimenthyl carbonate and some by-products. The product of dimethyl carbonate is decomposed in the effect of chloride ions; 2) Triphosgene react with methoxyl of methanol directly. Lots of chloride ions are produced when the reaction progressed to a certain extent. Triphosgene is decomposed into phosgene on the effect of chloride ions, and the phosgene react with methanol to products, accompanying with the products reaction.