Manganese-containing MCM-41 for epoxidation of styrene and stilbene

Mn-MCM-41 is found to be the most effective heterogeneous catalyst for the epoxidation of styrene with tert-butyl hydroperoxide (TBHP) among several metal ion-containing mesoporous molecular sieves including Mn-, V-, Cr-, Fe-, and Mo-MCM-41. ESR, XANES, diffuse reflectance UV-VIS, UV-Raman and XPS are used to characterize the Mn-MCM-41 synthesized by both direct hydrothermal (DHT) and template ion exchange (TIE) methods. The results suggest that Mn2+ and Mn3+ coexist in the Mn-MCM-41 samples synthesized by both methods and a large part of manganese atoms could be incorporated into the framework, of MCM-41 obtained by the DHT method. The oxidation of either styrene or stilbene with TBHP as the oxidant over the Mn-MCM-41 produces corresponding epoxide as the main products the reaction probably proceeds through a radical intermediate. The TIE catalyst shows higher activity, while the DHT catalyst gives higher TBHP efficiency for the epoxidation reactions. (C) 2002 Elsevier Science B.V. All rights reserved.