8-磷钨酸催化羧酸酯化反应的研究

由于硫酸作催化剂合成羧酸酯副产物多、产率低、且腐蚀设备、造成环境污染。因此 ,人们对可代替硫酸的催化剂作了大量的研究。以杂多酸中的 8-磷钨酸为催化剂 ,制备了一系列羧酸酯 ,讨论了催化酯化的各种影响因素。并与 1 2 -磷钨酸 ,硫酸做催化剂进行比较 ,8-磷钨酸与 1 2 -磷钨酸活性相似 ,收率能达到或超过用硫酸催化的水平。与浓硫酸、硫酸铁等催化剂相比较 ,杂多酸催化羧酸酯化反应具有较好的活性。由于杂多酸特殊的Keggin结构 ,使杂多酸易溶于水和醇7] ,反应为均相反应 ,杂多酸用量少 ,反应时间短 ,产率高。杂多酸无毒 ,易于回收 ,后处理简单。不腐蚀设备和污染环境。杂多酸催化剂用量为反应液的 1 % ,醇酸摩尔比为 1 :1 ,反应时间 1 .5h。可替代硫酸催化酯化反应。

Study on Esterification of Carboxylic Acid Using the PW8 as Catalyst

Sulfuric acid was used as a catalyst to prepare acetic esters with more by-product, low yield, equipment corrosion and acid wastewater. Different catalyst was used instead of sulfuric acid. Heteroply acid was one of them. PW_8 was used as a catalyst for preparing acetic esters and comparing with PW_12 and H_2SO_4. The activity of PW_8 is similar to PW_12, but the yield is more than that of using H_2SO_4. The experimental result indicated that, in comparison with other catalysts such as H_2SO_4, Fe_2(SO_4)_3·xH_2O etc, the heteropoly acid catalysts showed shorter reaction time, higher yield of end-product, less quantity of catalyst to be used, and the post-treating was unnecesary. Because of its “Keggin” structure heteropoly acid can be resolve in water and alcohol easily. The reaction was one phase. The reaction conditions are that the quantity of the catalyst is 1%(wt), of the feedstock, mol ratio of alcohol to carboxylic is 1:1, and the reaction time is 2 h.