表面活性剂改性制备负载型聚苯乙烯磺酸催化剂

Preparation of supported polystyrene sulfonate catalyst modified by surfactant

利用表面活性剂对硅胶载体改性可避免载体表面聚苯乙烯的团聚,进而通过磺化得到负载型有机磺酸固体酸催化剂,对所得催化剂进行比表面积检测(BET)、热重分析(TG)、NH_(3)程序升温脱附(NH_(3)-TPD)、扫描电镜(SEM)和元素分析等表征,对催化剂制备条件进行优化,并考察其在柠檬酸三丁酯合成反应中的活性,探讨催化剂失活机制。结果表明:在十六烷基三甲基氯化铵(CTAC)的作用下,聚苯乙烯分子在硅胶表面得到有效地分散,有利于磺化过程的进行,磺酸基数量增加;在最佳的反应条件下,柠檬酸三丁酯收率可达88.1%;催化剂在连续使用6次后催化活性没有出现明显下降,表现出较好的稳定性;所制备催化剂与树脂催化剂具有相同的失活原因,都是由磺酸基团的单独脱落所致,但前者磺酸基流失量要远小于后者。

The modification of silica gel carrier by surfactant can avoid the agglomeration of polystyrene on the surface of the carrier,and then the supported organic sulfonate solid acid catalyst was obtained by sulfonation.The obtained catalyst was characterized by specific surface area detection(BET),thermogravimetric analysis(TG),NH_(3)temperature programmed desorption(NH_(3)-TPD),scanning electron microscopy(SEM)and elemental analysis.The preparation conditions of the catalyst were optimized and the performance in the synthesis of tributyl citrate was investigated.The deactivation mechanism of the catalyst was discussed as well.The results show that the polystyrene molecules are effectively dispersed on the surface of silica gel under the action of cetyltrimethylammonium chloride(CTAC),which is beneficial to the sulfonation process and the number of sulfonic acid groups increases.Under the optimum reaction conditions,the yield of tributyl citrate can reach 88.1%.The catalytic activity did not decrease significantly after six consecutive cycles,exhibiting good stability.The prepared catalyst has the same deactivation reason with the resin catalyst,which is caused by the loss of sulfonic acid group alone,and the loss of sulfonic acid groups in the prepared catalyst is much lower than that in the resin catalyst.