一步酯交换法合成碳酸酯

Synthesis of Carbonates by One-Step Transesterification

以甲醇、CO_2、环氧乙烷(EO)为原料通过一步酯交换法合成碳酸酯,考察了多种酯化及醇解催化剂的活性。对于季铵盐、季鏻盐催化剂,阳离子基团活性高低顺序为:[Pr_4N]^+>[Et_4N]^+>[Me_4N]^+>[PPh_3Me]^+>[Bu_4N]^+;阴离子活性高低顺序为:Br^->I^-;其中,[Et_4N]^+基团的目标产物选择性最好。因此选择Et_4NBr作为一步酯交换反应的催化剂,确定了较佳的反应条件:温度150℃、压力4MPa、催化剂用量0.22mol/L、甲醇与EO的摩尔比4、反应时间4h。在此条件下,EO转化率达到97.22%,产物中碳酸二甲酯与碳酸乙烯酯的总选择性为86.54%。

Synthesis of carbonates from methanol, CO2 and ethylene oxide （EO） through one-step transesterification was studied and various catalysts used in alcoholysis and esterification were investigated. The results indicated that in the presence of quaternary ammonium salt or quaternary phosphonium salt catalysts, the reaction activity order for the cationic groups was： [ Pr4N ]＋ 〉 [ Et4N]＋ 〉 [Me4N] ＋ 〉 [PPh3Me] ＋ 〉 [Bu4N] ＋ and the order for the anionic groups was Br- 〉 I- Thereinto[Et4N] ＋ showed the best target product selectivity, so it was selected as catalyst used in the one-step transesterification. Under the optimum conditions of temperature 150 ℃, pressure 4 MPa, the catalyst dosage 0.22 mol/L, mole ratio of methanol to EO 4 and time 4 h, EO conversion could reach 97.22% and total selectivity to both dimethyl carbonate and ethylene carbonate could be 86.54%.