Effects of Hydrophobicity of Group IV and V Framework-Substituted Zeolite Catalysts on Rates and Selectivities for Olefin Epoxidation

Group IV and V transition metal-substituted zeolites have long been used to catalyze olefin epoxidation, and several studies about how metal identity affects rates for epoxidation exist in the current literature. However, little is known about the effects of different catalytic properties, particularly hydrophobicity, on rates and selectivities for such epoxidations. Limited knowledge of these catalysts prevents hydrogen peroxide-oxidized reactions from replacing less-green methods of epoxide synthesis. Here, kinetic and thermodynamic measurements are used to demonstrate that the activity of group IV (i.e. Ti) and V (i.e. Nb and Ta) catalysts is directly related to the hydrophobicity of the catalyst. In particular, more hydrophobic catalysts give better rates for the desired epoxidation pathway and present smaller enthalpic barriers for epoxidation. Furthermore, a relationship between the Lewis acidity of a metal and its affinity to catalyze epoxidation (and the subsequent determination that Ti *BEA is the most active for epoxidation among this group) has been observed, in agreement with previously published work.NSFOpe