The Prins condensation of formalin with styrene to 4-phenyl-1, 3-dioxane catalyzed by different catalysts, namely concentrated sulfuric acid, HZSM-5 zeolite, sulfonated resin CT-252, ammonium phosphotungstate and phosphotungstic acid, was studied, among which phosphotungstic acid was the most effective catalyst. Under the optimal reaction conditions of mass ratio of catalyst to total reaction mixture 12.0%, styrene 20 mmol, molar ratio of formalin to styrene 4, heating temperature 90 ℃ and reaction time 3.0 h, the conversion of styrene and selectivity to 4-phenyl-l, 3-dioxane can reach 87.3% and 98.9%, respectively. Via extraction and dehydration after the reaction, the phosphotungstic acid could be reused at least three times without evidently decreasing the activity and selectivity.%比较了浓硫酸、HZSM-5分子筛、磺酸型CT-252树脂、磷钨酸铵和磷钨酸催化剂对甲醛水溶液与苯乙烯的Prins缩合反应的催化效果.实验结果表明,磷钨酸的催化性能最佳.以磷钨酸为催化剂,优化了甲醛水溶液与苯乙烯通过Prins缩合反应合成4苯基-1,3-二氧六环的实验条件.实验结果表明,适宜的反应条件为:磷钨酸用量(基于反应体系的质量)12.0％,苯乙烯20 mmol,n(甲醛):n(苯乙烯)=4.0∶1,90 ℃下反应3.0h在此条件下,苯乙烯转化率达到87.3％,4-苯基-1,3-二氧六环的选择性为98.9％.使用后的磷钨酸催化剂经萃取蒸馏处理后,可循环使用3次,催化活性基本不变.该反应具有效率高且成本低的特点.
展开▼
