Complexation effect of copper(ii) with HEDP supported by activated carbon and influence on acetylene hydration

Heterogeneous catalysts based on Hg are found to be highly active for the acetylene hydration reaction with a very high yield of acetaldehyde, but severe toxicity limits its application. Herein, HEDP was selected as a polydentate phosphonate ligand to synthesize novel green Cu-based catalysts by a simple impregnation method. The prepared catalyst with the best ratio of Cu/ligand of 1 : 1 and 4 wt% Cu loading can achieve >82.9% selectivity of the aldehyde with 99% conversion of acetylene after 8 h compared to the ligand-free catalyst. The effect of the ligand and the active component on the catalytic performance was evaluated in detail by several characterization methods. XRD, TPR, and HRTEM coupled with EDS analysis revealed that the introduction of HEDP could enhance the dispersion of Cu species and decrease the particle sizes of Cu. XPS indicated strong interaction of the coordination compound formed by the coordination of Cu2+ with HEDP molecules, which effectively inhibited the reduction of Cu ions during the reaction process. TGA revealed that this complex could inhibit the coking deposition produced during the reaction. The novel perspective will provide the potential of using HEDP as a metal chelating agent to stabilize the active components and increase the dispersion for the heterogeneous catalyst.