Synthesis of Dimethyl Carbonate by Oxidative Carbonylation Using an Efficient and Recyclable Catalyst Co-Schiff Base/Zeolite

Dimethyl carbonate (DMC) has been synthesized by oxidative carbonylation of methanol over the Co-Schiff base complexes, which have been encapsulated in situ in zeolite Y by a ship-in-the-bottle approach. These hybrid materials Co-Schiff base/zeolite Y have been characterized by FT-IR, UV-vis, XRD, BET, and TG/DTA techniques. Analysis of the hybrid materials indicates the formation of complexes in the cavity without affecting the zeolite framework structure. The catalytic activities and corrosion behavior of the encapsulated complexes and their homogeneous analogues were examined. Zeolite-encapsulated Co complexes were found to be more active and stable than the neat Co complexes. When the reaction was carried out using 1.0 g of encapsulated catalyst, 40 mmol of methanol, CO/O-2 ratio of 2:1, and at 3.0 MPa and 120 degrees C for 4 h, zeolite-encapsulated Co-salophen shows the highest activity; and the conversion of methanol and selectivity to DMC were 25.4 and 99.5%, respectively. It was also demonstrated that zeolite-encapsulated Co-salophen catalyst can be reused five times without loss of activity. Both neat and encapsulated Co-salophen exhibit noncorrosive behavior to the reactor made by stainless steel.