Recently, it has been widely reported that CO2 was utilized to produce valuable chemical feedstock with copper/zinc and metal oxide based catalysts, yet harsh conditions (high pressure and high temperature, etc.) are still essential for the activity and selectivity. Compared with the harsh conditions required in the direct conversion of CO2 to achieve high selectivity and activity, mild conditions in the indirect conversion of CO2 through the carbonate intermediate provides an alternative. Since CO2 can be easily transferred to carbonate under mild and even atmospheric pressure of CO2 in many reports, hydrogenation of carbonates to methanol at ambient condition presents an attractive strategy for the indirect conversion of CO2 with higher catalytic activity. In our previous work, we have reported that Cu/SiO2 catalyst achieved satisfying performance for the hydrogenation of diethyl carbonate with poor stability at long term running due to the agglomeration of active metal. Herein, we present that the catalytic activity and stability of the catalysts in the hydrogenation of carbonates could be efficiently improved by the addition of Cr.
In this research, various Cr-promoted Crx-Cu/SiO2 catalysts were synthesized through an ammonia evaporation method. The effect of added Cr on the catalytic performance was investigated by the hydrogenation of diethyl carbonate (DEC) as a probe reaction system. The results showed that the Crx-Cu/SiO2 catalyst with 3 w% Cr performed the preferable activity. Under the reaction conditions of temperature of 503 K, hydrogen pressure of 2.5 MPa and liquid hourly space velocity (LHSV) of 1.0 h-1, the conversion of DEC could be 99%, while the selectivity of product methanol (86.2%) and space-time yields (STY) of methanol (5.6 mmolMeOH·gcat-1·h-1) were enhanced significantly. The physicochemical properties Crx-Cu/SiO2 catalysts were characterized by X-ray diffraction (XRD), N2 physical adsorption and desorption, transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR) and in-situ diffuse reflection infrared Fourier transform spectroscopy (In-situ DRIFTS). The results revealed that the dispersion of active copper species was significantly improved. The copper chromite species formed by the interaction of copper and chromium could optimize the distribution of Cu(0) and Cu(I) and regulate adsorption construction of reactant, efficiently improving the catalytic performance and stability for the hydrogenation of diethyl carbonate to methanol.
李华博, 崔园园, 刘逸心, 戴维林. 助剂Cr对Cu/SiO2催化碳酸酯加氢制甲醇性能的影响[J]. 化学学报, 2014, 0(0): 0-0.
Li Huabo, Cui Yuanyuan, Liu Yixin, Dai Wei-Lin. Promotional effect of Cr on Cu/SiO2 catalyst for the production of methanol from carbonate hydrogenation. Acta Chim. Sinica, 2014, 0(0): 0-0.