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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。
As a catalyst for the synthesis of carboxylic acid ester by-products and more, low yield, and corrosion of equipment, resulting in environmental pollution. Therefore, a great deal of research has been done on catalysts that can replace sulfuric acid. A series of carboxylic acid esters were prepared from 8-phosphotungstic acid in heteropolyacids. Various influencing factors of esterification were discussed. Compared with 1 2 - phosphotungstic acid and sulfuric acid, the activity of 8 - phosphotungstic acid is similar to that of 1 2 - phosphotungstic acid, and the yield can reach or exceed the level catalyzed by sulfuric acid. Compared with the catalysts such as concentrated sulfuric acid and ferric sulfate, heteropolyacid catalyzed carboxylic acid esterification has good activity. Due to the special Keggin structure of heteropolyacid, heteropolyacid is easily soluble in water and alcohol [7], the reaction is homogeneous, the amount of heteropoly acid is less, the reaction time is short, and the yield is high. Heteropoly acid non-toxic, easy to recycle, post-processing simple. Do not corrode the equipment and pollute the environment. The amount of heteropoly acid catalyst is 1% of the reaction solution, the molar ratio of alkyd is 1: 1, and the reaction time is 1.5 h. An alternative to sulfuric acid esterification reaction.