Epoxidation of crotyl alcohol using Ti-containing heterogeneous catalysts: Comments on the loss of Ti by leaching

被引:66
作者
Davies, LJ
McMorn, P
Bethell, D
Page, PCB
King, F
Hancock, FE
Hutchings, GJ
机构
[1] Cardiff Univ, Dept Chem, Cardiff CF10 3TB, S Glam, Wales
[2] Univ Liverpool, Dept Chem, Leverhulme Ctr Innovat Catalysis, Liverpool L69 3BX, Merseyside, England
[3] Loughborough Univ Technol, Dept Chem, Loughborough LE11 3TU, Leics, England
[4] Synetix, Billingham TS23 1LB, Cleveland, England
基金
英国工程与自然科学研究理事会;
关键词
epoxidation of allylic alcohols; heterogeneous epoxidation using TS-1; heterogeneous epoxidation using Ti-beta; heterogeneous epoxidation using Ti-MCM-41; heterogeneous epoxidation using Ti-xerogel; Ti-leaching;
D O I
10.1006/jcat.2000.3139
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The leaching of Ti from the redox molecular sieve TS-1 is compared and contrasted with Ti leaching from Ti-Al beta, Ti-MCM-41, and a Ti-xerogel under both batch and continuous flow reaction conditions for the oxidation of crotyl alcohol with hydrogen peroxide. The product distributions for the catalysts are similar, with epoxide being formed initially and, subsequently, the secondary reaction products of the trial and ether dials. Ti leaching is more pronounced under continuous flow conditions and the order of stability is TS-1 > Ti-Al beta > Ti-MCM-41 > Ti-xerogel, for both continuous flow and batch reaction conditions. TS-1 leaching is shown to be caused by the reaction of trial with TS-1 in the presence of hydrogen peroxide. A possible mechanism in which the triol byproduct chelates the Ti and breaks the Ti-O-Si framework bonds, leading in turn to the formation of a Ti species in solution, is proposed. The soluble Ti species is found to be an active homogeneous catalyst giving triol as the major product from crotyl alcohol. Under batch reaction conditions, it is possible that an equilibrium is established between the solution Ti species and Ti on the catalyst surface. This equilibrium is perturbed when continuous flow conditions are used, and this leads to increased Ti leaching. (C) 2001 academic Press.
引用
收藏
页码:319 / 327
页数:9
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