Abstract: In the preparation of CuY catalysts by ion-exchange of NaY zeolite with aqueous solution of copper nitrate, ammonia was added to the ion-exchange solution to adjust the pH and the ion-exchanged CuY was activated by high temperature calcination.The prepared CuY catalysts exhibited high catalytic active in the oxidative carbonylation of methanol to dimethyl carbonate. Compared with Cu catalysts prepared by solid-state ion-exchange, precipitation and impregnation, CuY catalysts loaded less Cu but showed good catalytic performance. Based on the characterization of the microstructure of CuY catalysts by XRD, XPS, AES, H2-TPR and elementary analysis, it was shown that by adding ammonia into the ion-exchange solution，the ion-exchanged reaction was promoted, resulting in the increase of the ion-exchanged Cu2+ and the most of Cu2+ in the supercage of CuY catalyst. In the process of calcinating activation of CuY catalysts in inert atmosphere, Cu2+ was auto-reduced to Cu+ and ammonia promoted the auto-reduction, which was conducive to the improvement of catalytic activity. The high activating temperature facilitated the auto-reduction progress of Cu2+ to Cu+ located in the supercage of zeolite, Cu+ content in the supercage of zeolite increased more quickly and the catalytic activity of CuY catalysts increased in the meantime. It was concluded that Cu+ in the supercage of Y zeolite was the main catalytic active center.

Key words: methanol, oxycarbonylation, solution ion-exchange, CuY catalyst, catalysis