Influence of dehydrating agents on the oxidative carbonylation of methanol for dimethyl carbonate synthesis over a Cu/Y-zeolite catalyst

The influence of the dehydration by metal oxides on the synthesis of dimethyl carbonate (DMC) via oxidative carbonylation of methanol was studied.A Cu/Y-zeolite catalyst was prepared by the ion exchange method from CuCl2·2H2O and the commercial NH4-form of the Y type zeolite.The catalyst was characterized by X-ray fluorescence (XRF),N2 adsorption (BET method),X-ray diffraction (XRD),and temperature-programmed desorption of ammonia (NHs-TPD) to evaluate its Cu and Cl content,surface area,structure,and acidity.Reaction tests were carried out using an autoclave (batch reactor) for 18 h at 403 K and 5.5 MPa (2CH3OH + 1/2O2 +CO (=) (CH3O)2CO + H2O).The influence of various dehydrating agents (ZnO,MgO,and CaO) was examined with the aim of increasing the methanol conversion (XMeOH,MeOH conversion).The MeOH conversion increased upon addition of metal oxides in the order CaO ＞＞ MgO ＞ ZnO,with the DMC selectivity (SDMC) following the order MgO ＞ CaO ＞ ZnO.The catalysts and dehydrating agents were characterized before and after the oxidative carbonylation of methanol by thermogravimetric and differential thermogravimetric (TG/DTG),and XRD to confirm that the dehydration reaction occurred via the metal oxide (MO + H2O → M(OH)2).The MeOH conversion increased from 8.7％ to 14.6％ and DMC selectivity increased from 39.0％ to 53.1％,when using the dehydrating agent CaO.