M.C. Capel-Sanchez

Soybean oil epoxidation with hydrogen peroxide using an amorphous Ti/SiO2 catalyst

We report a study of the epoxidation of soybean oil and soybean methyl esters with hydrogen peroxide in dilute solution (6 wt%) using an amorphous heterogeneous Ti/SiO2 catalyst in the presence of tert-butyl alcohol. The influence of some relevant process variables such as temperature and the hydrogen peroxide-to-double bond molar ratio on performance is examined. The highest yields of epoxidized olefins were obtained upon using a H2O2 ∶ substrate molar ratio of 1.1 ∶ 1. Higher ratios than this were not effective for speeding up the reaction. Under the experimental conditions employed in this work, no degradation of the oxirane ring was observed.

Grafting Strategy to Develop Single Site Titanium on an Amorphous Silica Surface

Titanium/silica systems were prepared by grafting a titanium alkoxide (titanium isopropoxide and titanium (triethanolaminate) isopropoxide) precursor onto amorphous silica. The grafting process, which consisted of the hydrolysis of the Ti precursor by the hydroxyl groups on the silica surface, yielded samples containing Ti-loadings of 1-1.6 wt %. The as synthesized and calcined TiO(2)-SiO(2) samples were characterized by UV-vis, FTIR, XPS, and XANES spectroscopic techniques. These systems were tested in the liquid-phase epoxidation of oct-1-ene with hydrogen peroxide reaction. Spectroscopic data indicated that titanium anchoring takes place by reaction between the alkoxide precursor and surface OH groups of the silica substrate. The nature of surface titanium species generated by chemical grafting depends largely on the titanium precursor employed. Thus, the titanium isopropoxide precursor yields tetrahedrally coordinated polymeric titanium species, which give rise to a low-efficiency catalyst. However, if an atrane precursor (titanium (triethanolaminate) isopropoxide) is employed, isolated titanium species are obtained. The fact that these species remain isolated even after calcination is due to the protective effect of the triethanolaminate ligand that avoids titanium polymerization. These differences in the titanium environment have a pivotal role in the performance of these systems in the epoxidation of alkenes with hydrogen peroxide.

Effective alkene epoxidation with dilute hydrogen peroxide on amorphous silica-supported titanium catalysts

The use of amorphous silica-supported titanium catalysts in which the titanium ions display a chemical environment similar to that of Ti-substituted zeolites, afforded excellent activity in the epoxidation of terminal linear and bulky alkenes with dilute solutions of hydrogen peroxide.