SO_4~(2-)／TiO_2固体超强酸催化合成氯乙酸酯

以SO42-／TiO2型固体超强酸为催化剂,用氯乙酸与醇反应合成了氯乙酸酯。考察了催化剂的制备条件、醇酸摩尔比、催化剂用量、反应时间及带水溶剂对氯乙酸仲丁酯收率的影响。初步探索了SO42-／TiO2型固体超强酸催化氯乙酸和其他饱和烷基醇的酯化反应。结果表明,将TiO2用0．8 mol／L的硫酸浸渍14～16 h后,再经500℃焙烧3 h可制得催化活性最高的催化剂。优化的反应条件为:n(醇):n(酸)=2．5:1,固体超强酸用量为氯乙酸质量的3％,带水溶剂为环己烷,加热回流分水3 h,氯乙酸仲丁酯的收率为75％,并用同样方法合成了其他氯乙酸烷基酯,收率为63％～85％。催化剂可回收再生,重复使用。

SYNTHESIS OF CHLOROACETATES CATALYZED BY SOLID SUPERACID SO_4~(2-)/TiO_2

Solid superacid SO42- /TiO2 was used for catalyzing the synthesis of chloroacetates. The reaction of chloroacetic acid and isobutanol was studied in detail. It was found that the esterification yield mainly depended on the preparation conditions and the amount of superacid catalyst, molar ratio of alcohol to acid, water-carrying agents and reaction time. In addition, the reactions of chloroacetic acid and other alkyl alcohols were also explored with the superacid as catalysts. The results showed that the optimal conditions for the preparation of the catalysts were: TiO2 being immersed in 0. 8 mol/ L sulfuric acid for 14-16 h, then filtered and heated at 500℃for 3 h. The optimal conditions for the preparation of isobutyl chloroacetate were: superacid 3% of chloroacetic acid, the molar ratio of alcohol to chloroacetic acid 2. 5, cyclohexane as water-carrying agent, reaction time 3 h. Under these conditions, the yield was 75%. The catalyst can be recovered, reactivated and reused. Furthermore, a series of alkyl chloroacetic acetates were prepared under the similar reaction conditions with the yield of 63%-85%.