Carbon nanotubes supported Cu–Ni bimetallic catalysts and their properties for the direct synthesis of dimethyl carbonate from methanol and carbon dioxide

Multi-walled carbon nanotubes (MWCNTs) supported Cu–Ni bimetallic catalysts for the direct synthesis of dimethyl carbonate (DMC) from CH3OH and CO2 were synthesized and investigated. The supporting materials and the synthesized catalysts were fully characterized using FTIR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), X-ray diffraction (XRD) and X-ray photoelectron spectrum (XPS) techniques. The catalytic activities were investigated by performing micro-reactions. The experimental results showed that the metal phase and Cu–Ni alloy phase in the catalyst were partially formed during the calcination and activation step. Active metal particles were dispersed homogeneously on the surface of the MWCNTs. Cu–Ni/MWCNTs catalysts were efficient for the direct synthesis of DMC. The highest conversion of CH3OH was higher than 4.3% and the selectivity of DMC was higher than 85.0% under the optimal catalytic conditions of 120 °C and around 1.2 MPa. The high catalytic activity of Cu–Ni/MWCNTs in DMC synthesis can be attributed to the synergetic effects of metal Cu, Ni and Cu–Ni alloy in the activation of CH3OH and CO2, the unique structure of MWCNTs and the interaction between the metal particles and the supports.