固体碱催化碳酸二甲酯和3-戊酮合成丙酸甲酯

以碳酸二甲酯(DMC)和3-戊酮为原料,以固体碱为催化剂合成了丙酸甲酯,并考察了反应温度、反应时间、催化剂用量和原料配比等因素对合成反应的影响。实验结果表明,固体酸催化剂不利于丙酸甲酯的生成,而具有中强碱位的MgO对该反应具有较好的催化性能。当以MgO为催化剂时,反应的最佳条件为:反应温度260℃、反应时间5h、催化剂用量占反应物总质量的1.5%、n(DMC)∶n(3-戊酮)=6,在该反应条件下,3-戊酮的转化率和丙酸甲酯的选择性分别达到40.9%和53.9%。同时,反应主要副产物为3-戊酮缩合产物(4-甲基-5-乙基-4-庚烯-3-酮)、甲基化产物(2-甲基-3-戊酮和3-甲氧基-2-戊烯)及中间产物2-甲基丙酰乙酸甲酯等。

Synthesis of Methyl Propionate from Dimethyl Carbonate and 3-Pentanone over Solid Base Catalyst

A convenient and simple way for synthesis of methyl propionate from 3-pentanone and dimethyl carbonate(DMC)was exploited in the presence of solid base catalysts.No product was detected in the absence of the catalyst.If only solid acid Al2O3 was in use,only self-condensation products of 3-pentanone were detected,which suggested that solid acid catalyst was inactive to synthesis of methyl propionate.In comparing with solid bases ZrO2,La2O3 and CaO being tested,MgO with moderate strength,when used as catalyst,facilitated the formation of methyl propionate.Under optimal reaction conditions:temperature 260 ℃,time 5 h,MgO as catalyst and its mass fraction(based on total mass of reactants)1.5%,and n(DMC)∶ n(3-pentanone)6,conversion of 3-pentanone was 40.9% and selectivity to methyl propionate was 53.9%.The main by-products of the reaction were self-condensation products of 3-pentanone(5-ethyl-4-methyl-4-hepten-3-one),methylation products(2-methyl-3-pentanone and 3-methoxy-2-pentene)and the intermediate(methyl 3-oxopentanoate).