乙酸苄酯合成中接枝型三相相转移催化剂的活性及催化反应动力学

Catalytic activity of tricatalyst with graft-type and catalysis dynamics in synthesis of benzyl acetate

采用"接出(grafting from)"方式,将苯乙烯(St)接枝聚合在微米级硅胶表面,然后对接枝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/硅胶微粒(CMPS/SiO2);使三丁胺与三苯基膦分别与CMPS大分子链上的苄氯基团发生季铵化与季鏻化反应,分别制得了固载有季铵盐与季鏻盐的接枝微粒QN-PSt/SiO2与QP-PSt/SiO2,即制得了两种接枝型三相相转移催化剂.将该催化剂用于苄氯与乙酸钠合成乙酸苄酯的相转移催化反应,并重点考察了催化剂的活性与催化动力学.实验结果表明,两种接枝型三相相转移催化剂QN-PSt/SiO2与QP-PSt/SiO2对乙酸苄酯的合成都具有明显的催化活性,在液-固-液之间可有效地实现反应物种乙酸根的转移;两者相比,季鏻盐型的催化剂QP-PSt/SiO2的催化活性更高;当水相中乙酸钠用量大大过量时,在有机相中苄氯与乙酸根的反应属准一级反应;两个相转移反应体系相比,以QP-PSt/SiO2为催化剂时反应的表观活化能更低.

Polystyrene was grafted on the surface of silica gel particles in ＂grafting from＂ manner,and then the grafted polystyrene was chloromethylated using 1,4-bis （chloromethoxy） butane as chloromethylation reagent, resulting in the grafting particles CMPS/ SiO2. Finally, the quatemarization and quaternary phosphine reaction were carried out using tributylamine and triphenyl phosphine as the reagents, respectively, and two kinds of tricatalysts, QN-PSt/SiO2 and QP-PSt/SiO2, were prepared. The tricatalysts were used in the phase transfer catalytic reaction between benzyl chloride in aqueous solution and sodium acetate in organic phase,leading to the formation of benzyl acetate. The catalytic activities of the tricatalysts were examined, and the catalysis dynamics was studied. The experimental results show that the two kinds of tricatalysts, QN-PSt/SiO2 and QP-PSt/SiO2, have obvious catalytic activity in the synthesis of benzyl acetate, and can efficiently transfer acetates from aqueous phase into organic phase. The catalyst QP-PSt/SiO2 with quaternary phosphine salt-type has higher catalytic activity than QN-PSt/SiO2. When NaAC in the aqueous phase is in excess, the phase transfer catalysis reaction has a characteristic of pseudo first order reaction. The reaction system with QP-PSt/SiO2 as the catalyst has lower active energy.