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| Three different preparation methods: liquid-phase ion exchange, incipient-wetness- impregnation and the novel method adopted by firstly ion exchange together with Cu(NO3)2- impregnated, are employed to prepare the CuHY catalysts, which are applied in oxidative carbonylation of methanol to dimethyl carbonate (DMC). Characterization of samples by XRD, H2-TPR, DIRFTS of CO adsorption, XPS, AAS and TEM, reveal that the catalyst prepared by liquid-phase ion exchange exhibits low catalytic activity because of the low content of copper and most of Cu species located in the sodalite units or hexagonal prisms, which are difficult to contact with reagent CO and O2. Dispersion of crystalline CuO is the main Cu species of the catalyst prepared by incipient-wetness-impregnation, while 30 percent of Cu2+ of the total amount of Cu is located in the sodalite units or hexagonal prisms, which is not helpful for catalytic activity. However, the catalyst, which is prepared by the novel method, exhibits the remarkable advantages that covers both preparation methods of liquid-phase ion exchange and incipient-wetness-impregnation. This novel method not only obtains CuO species that is beneficial to oxidative carbonylation of methanol to DMC, but also adjusts the location of Cu ions, which makes more Cu2+ locate in the supercages, as a result, Cu2+ can contact with CO and O2. Moreover, Cu2+ located in the supercages have shown the better catalytic performance for oxidative carbonylation compared with CuO species on the surface of the Y zeolites. |
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| Keywords:Catalyst Engineering; CuY catalyst; Cu species; oxidative carbonylation; Methanol |
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