Preparation of an Unsupported Copper-Based Catalyst for Selective Hydrogenation of Acetylene from CuO Nanocubes.

Designing cheap, earth-abundant, and nontoxic metal catalysts for acetylene hydrogenation is of pivotal importance, but challenging. Here, a nonprecious metal catalyst for selective hydrogenation of acetylene in excess ethylene was prepared from CuO nanocubes. The preparation includes two steps: (1) thermal treatment in acetylene-containing gas at 160 °C and (2) hydrogen reduction at 180 °C. The resultant catalyst showed outstanding performance at low temperature (80-100 °C) and 0.1-0.5 MPa pressure, completely converting acetylene with a low selectivity to undesired ethane (<20%). The characterization results of high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy corroborated that the formation of an interstitial copper carbide (CuC) might give rise to significantly enhanced hydrogenation activity. Preliminary density functional theory calculation demonstrated that the lattice spacing of CuC was nearly identical to that of the new CuC crystallite measured in HRTEM and determined by XRD. The calculated dissociation energy of hydrogen on CuC(0001) was considerably lower than that on Cu(111), suggesting superior hydrogenation activity of CuC(0001). It is experimentally verified that copper(I) acetylide (CuC) might be the precursor of CuC. CuC underwent partial hydrogenation to fabricate CuC crystallites and the thermal decomposition to Cu and carbon materials in parallel.