Various zinc halide-based ionic liquids were prepared from zinc halides and onium halides as catalysts for the synthesis of styrene carbonate (SC) from styrene oxide and carbon dioxide.The effects of the ionic liquid catalyst composition (types of onium cation and halide, onium cation/zinc ratio) and CO 2 pressure on the reaction were investigated. The effectiveness of the onium cation as the active catalyst component was in the order of tetrabutylammonium > 1-butylpyridinium > 1-butyl-3-methylimidazolium >> choline. The type of halide atom originating from the zinc salt affected the catalytic activity of the ionic liquid more significantly than that of the one originating from the onium salt. The onium cation/zinc ratio also affected the SC yield, but its manner was different depending on the type of onium cation.Influence of CO 2 pressure was not significant.
Diphenyl carbonate (DPC) was synthesized from phenol and dense phase CO 2 in the presence of CCl 4 and K 2 CO 3 using different catalysts of ZnCl 2 , ZnBr 2 , Lewis acid ionic liquids including 1-butyl-3-methylimidazolium chloride (BMIMCl) and bromide (BMIMBr). It was found that K 2 CO 3 was not required, ZnCl 2 and ZnBr 2 were similar in the catalytic performance, and the use of BMIMCl and BMIMBr was not effective for the production of DPC. For the reactions with ZnCl 2 in CCl 4 , the effects of such reaction variables as temperature, CO 2 pressure, the amount of ZnCl 2 , and the volume of CCl 4 were studied in detail. It was shown that the pressure was less influential while a larger amount of ZnCl 2 , a smaller volume of CCl 4 , and a low temperature of around 100°C were beneficial for the synthesis of DPC. On the basis of the results obtained, possible reaction mechanisms were discussed.
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