Facile one-pot synthesis of CuO–Bi2O3/MgAl2O4 catalyst and its performance in the ethynylation of formaldehyde

The CuO-Bi₂O₃/MgAl₂O₄ catalyst was synthesized via one-pot synthesis and used to catalyze formaldehyde (HCHO) ethynylation. Coprecipitation using Cu²⁺, Bi³⁺, Mg²⁺, and Al³⁺ nitrates and NaOH generated Cu and Bi oxides and spinel MgAl₂O₄ phase. The catalyst precursor was calcined at 450 °C. The catalytic performance of CuO-Bi₂O₃/MgAl₂O₄ in the synthesis of 1,4-butynediol via HCHO ethynylation was investigated. The presence of a new spinel phase enhanced the acid-base properties on the catalyst surface and prevented the aggregation of CuO particles. These properties resulted in improved CuO dispersion during calcination and CuO particle growth suppression, affording smaller CuO crystals. The MgAl₂O₄ support facilitated the reduction of Cu²⁺ to Cu⁺ and formation of abundant active species during the reaction. The catalyst exhibited abundant weakly basic, fewer strongly basic, and least acidic sites, which facilitated the adsorption of HCHO and acetylene. The catalytic performance of CuO-Bi₂O₃/MgAl₂O₄ demonstrated 97 % conversion and 80 % selectivity after the online monitoring of the ethynylation reaction for 6 h. The leaching of Cu during the reaction, as analyzed by inductively coupled plasma spectroscopy, was extremely low. Moreover, conversion and selectivity did not substantially change after eight cycles. In addition, the catalyst exhibited superior activity and long-term stability in the ethynylation reaction.