The influence of the pore structure in ordered mesoporous carbon over the formation of Cu species and their catalytic activity towards the methanol oxidative carbonylation

Abstract

Two ordered mesoporous carbon (OMC) materials with different structures were prepared and used as supports for Cu catalysts. One is prepared by soft-template method (denoted as SOMC), and the other is by hard-template method (donated as HOMC). The microstructures of OMC and Cu/OMC were characterized by XRD, H2-TPR, BET, and TEM. The catalytic activity in oxidative carbonylation of methanol to dimethyl carbonate (DMC) was evaluated in a fixed-bed reactor under atmosphere pressure. Both OMC materials own highly ordered mesostructures, but their pore structure differences have remarkable influences on Cu dispersion, location, valence, as well as the corresponding contents. SOMC has long hollow interiors 3.6 nm in diameter, and most Cu particles are located on its outer surface. By contrast, HOMC is made up of ordered arrays of carbon nanorods, and most Cu particles are homogeneously distributed inside the interconnected 3.6 nm mesoporous among the nanorods. Stronger interaction between Cu particles and HOMC and better Cu dispersion of Cu/HOMC resulted in easier autoreduction of CuO to Cu2O compared with that of Cu/SOMC. As a result, Cu/SOMC exhibited better stability, while Cu/HOMC performed better in terms of the methanol conversion and DMC space–time yield. Besides, increasing the copper loading moderately could be considered as a good option to improve the methanol conversion and space–time yield of DMC.