Amorphous titania, activity compared

Comparative catalytic activities (turnover numbers and selectivity (in parentheses)) of ordered Ti-MCM-41 (A) and amorphous titania-silica (B-E) catalysts in the epoxidation of unsaturated cyclic terpenes (1-6) using anhydrous TBHP... 

Data for several titania systems are given In Table 1 for the photodegradation of dichloromethane. First of all, data for unsupported titania should be compared. These data suggest that the rutile form of titania is more active than the anatase form which In turn Is more active than the amorphous titania. In general this is also true for the supported analogs. Reasons why an ordered high temperature form Is more active than a low temperature or amorphous form may be due to the propensity of the former to form defect adsorption sites (See below). 

In Table 2, the effect of the addition of Mg citrate on the catalytic activity is compared on the two different types of TiOp supports. While the catalytic activity of Au/titania-A (amorphous) is enhanced by use of Mg citrate, Au/titania-B (anatase) shows a high catalytic activity regardless of the addition of Mg citrate. 

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