Highly effective synthesis of dimethyl carbonate from methanol and carbon dioxide using a novel copper–nickel/graphite bimetallic nanocomposite catalyst

A novel graphite supported Cu–Ni bimetallic nanocomposite catalyst for direct synthesis of dimethyl carbonate (DMC) from CH3OH and CO2 has been synthesized and investigated. The support and the synthesized catalysts were fully characterized using BET surface area, TG–DSC, Raman spectra, FTIR, SEM–EDX, TEM, XRD, TPR and XPS techniques. The catalytic activities were investigated by performing micro-reactions. It has been found that the nitrogen adsorption isotherm of graphite oxide support showed a typical Type II features. The layered structure of graphite was well maintained in the synthesized catalysts. Metal particles with an average size of 15.8 nm were uniformly dispersed on the support surface. Metal phase and alloy phase of Cu and Ni in the catalyst were partially formed during the reduction and activation step. The Cu–Ni/graphite nanocomposite catalyst exhibited remarkably high activity, selectivity and stability for the direct synthesis of DMC. The highest DMC yield was higher than 9.0% at 378 K and 1.2 MPa and the selectivity of DMC was higher than 88.0%. The high catalytic activity of Cu–Ni/graphite nanocomposite catalyst in DMC synthesis could 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 graphite and the interaction between the metal particles and the supports.