Cu nanoparticles encapsulated with hollow carbon spheres for methanol oxidative carbonylation: Tuning of the catalytic properties by particle size control

Abstract

Cu nanoparticles (NPs) encapsulated within a hollow carbon spheres (Cu@HCS) is an effective catalyst with optimal structural design for the oxidative carbonylation of methanol to dimethyl carbonate (DMC). Control of the structural properties of both the shell and the core plays a vital role in determining the catalytic properties. In this study, mesoporous HCS with an average diameter of 190 nm and a shell thickness of 15 nm were obtained using silica micropheres as a hard template and by tuning the amount of resorcinol and formaldehyde. Cu@HCS catalysts were fabricated by hydrothermal impregnation followed by hydrogen reduction, and the size of Cu NPs was delicately controlled by varying heating rate of reduction process. The results show that a thin mesoporous carbon shell of Cu@HCS is beneficial to the diffusion of reactants and products, and that Cu NPs with very small size can provide a large active specific surface area. In comparison with the commercial CuCl catalyst, the Cu@HCS-5 catalyst displays superior catalytic activity; its turnover frequency and apparent activation energy reaches 23.1 h−1 and 20.5 kJ·mol−1, respectively. In addition, it exhibits higher stability than that of CuCl because the carbon shell prevents the aggregation and leaching of copper NPs during the reaction. With the advantages in catalytic activity, corrosion effect, and recovery performance, the Cu@HCS catalyst has a promising potential for realizing the cleaner production of DMC.