Selective liquid-phase oxidation of cyclopentene over MWW type titanosilicate

The epoxidation of cyclopentene has been carried out over titanosilicate catalysts of Ti-Beta, TS-1 and Ti-MWW. Ti-MWW exhibited the highest cyclopentene conversion and epoxide selectivity with either H₂O₂ or tert-butyl hydroperoxide as an oxidizing agent. The cyclopentene conversion depended greatly on the post treatment conditions. Acid-treated but uncalcined Ti-MWW gave cyclopentene conversion twice as high as the calcined one, while the epoxide selectivity was maintained at high levels in both cases. Various techniques such as XRD, UV-vis, ²⁹Si MAS NMR, N₂ adsorption and liquid-phase adsorption, and chemical analyses have verified consistently that the acid treatment removed the organic species located between the layers of MWW sheets, which made the interlayer entrance open and easily accessible to bulky molecules. Nevertheless, a further calcination led to a complete interlayer dehydroxyaltion and made the catalyst to be more effective for the epoxidation of linear alkenes but less active for the epoxidation of cyclic ones.