接枝型三相转移催化剂的制备及其催化作用

将苯乙烯(St)接枝聚合在微米级硅胶表面,制备了接枝微粒PSt/SiO2;使用新型氯甲基化试剂1,4-二氯甲氧基丁烷,对接枝在硅胶表面的聚苯乙烯进行了氯甲基化(CM)反应,制得了氯甲基聚苯乙烯/硅胶(CMPS/SiO2)接枝微粒;使三乙胺与CMPS分子链上的苄氯基团发生季铵化反应,制得了固载有季铵盐(Quaternary salt)的接枝微粒QPSt/SiO2,即制得了接枝型三相相转移催化剂.将此相转移催化剂用于氯化苄与乙酸钠合成乙酸苄酯的相转移催化反应,考察了催化活性、各种因素对相转移催化反应的影响及催化剂的重复使用性能.实验结果表明,接枝型三相相转移催化剂QPSt/SiO2对乙酸苄酯的合成具有较高的催化活性,在液-固-液之间即可有效地实现反应物种乙酸根的转移,在60℃的较低温度下反应7 h,氯化苄的转化率可达66.1%;研究发现,固体催化剂QPSt/SiO2表面接枝聚合物PSt的季铵化程度对其催化活性有很大的影响,季铵化程度过大与过小催化活性都较低,当季铵化程度为20%左右时,催化剂的活性最高.

Preparation of Tricatalyst with Graft-Type and its Catalytic Activity

Polystyrene was grafted on the surface of silica gel particles,and grafting particles PSt/SiO2 were prepared.Then the grafted polystyrene was chloromethylated by using a novel chloromethylation reagent,1,4-bis(chloromethoxy) butane,and grafting particles CMPS/SiO2 were obtained.Finally,the quaternization between benzyl chlorides on the macromolecular chains of CMPS and triethylamine was carried out,and graft type tricatalyst QPSt/SiO2 was obtained.QPSt/SiO2 was used in the phase transfer catalytic reaction of benzyl chloride and sodium acetate to form benzyl acetate,and the catalytic activity of QPSt/SiO2 was examined.The experimental results show that QPSt/SiO2 has higher catalytic activity in the synthesis of benzyl acetate,and it can effectively transfer acetic acid radical among tri-phases of liquid-solid-liquid.It was found that the quaternization degree of polystyrene grafted on SiO2 has a great effect on the catalytic activity of QPSt/SiO2.QPSt/SiO2 has the highest catalytic activity as the quaternization degree of polystyrene grafted on SiO2 is about 20%,whereas the catalytic activity is lower as the quaternization degree is too great or small.