反应控制相转移催化剂催化氯丙烯环氧化合成环氧氯丙烷

Synthesis of Epichlorohydrin by Epoxidation of Allyl Chloride on Reaction-Controlled Phase-Transfer Catalyst

以 H_2O_2为氧化剂,用反应控制相转移催化剂(磷钨杂多酸季铵盐)催化氯丙烯进行环氧化反应合成了环氧氯丙烷,考察了反应条件对环氧化反应的影响。结果表明,在乙腈溶剂中,催化剂回收困难,而在氯仿溶剂中,催化剂容易回收。在氯仿溶剂中环氧氯丙烷的选择性较低,通过加入适量的助剂 K_2HPO_4能抑制环氧氯丙烷的水解而提高环氧氯丙烷的选择性。氯丙烯环氧化反应的适宜条件为:以氯仿为溶剂,K_2HPO_4用量(相对于总反应物的质量分数)0.04%,反应温度50℃,反应时间4 h,m(氯内烯):m(H_2O_2)=5.0,m(催化剂):m(H_2O_2)=1.0。在此条件下,H_2O_2的转化率为96.4%,环氧氯丙烷的选择性和收率分别为89.4%和86.2%。该催化剂的稳定性好,回收的催化剂性能接近新鲜催化剂。

Epoxidation of allyl chloride to epichlorohydrin catalyzed by a reaction-controlled phasetransfer catalyst（ quaternary ammonium heteropolyphosphotungstate） was investigated, using aqueous hydrogen peroxide as oxidant. Effects of solvent, additives, catalyst dosage, reaction temperature, reaction time on the reaction were studied. It is easy to separate catalyst from reaction solvent chloroform but difficult from acetonitrile. However, selectivity to epichlorohydrin （ECH） is lower in chloroform. As compensation, addition of KiHPO4 can improve selectivity to ECH due to inhibition of ECH hydrolysis. Suitable catalyst dosage can improve both conversion of hydrogen peroxide and selectivity to ECH, but excess of catalyst will on the contrary accelerate decomposition of H2O2 and hydrolysis of ECH, so selectivity drops. Conversion of hydrogen peroxide increases with the increases of temperature and reaction time, but higher temperature or longer reaction time than the appropriate will decrease the selectivity. The recycled catalyst keeps similar catalytic activity to the fresh after 4 times of recycling. Under optimal conditions ： 50 ℃, reaction time 4 h, m （ allyl chloride ） ： m（H2O2） 5.0, m（ catalyst） ： m（H2O2） 1.0, K2HPO4 as additives and chloroform as solvent, H2O2 conversion is 96.4%, selectivity to ECH is 89.4% and yield to ECH is 86.2%.