The preparation of CuM/SiO₂ (M = Bi, Mg, Mn) catalysts applied in ethynylation of formaldehyde for 1,4-butynediol synthesis: the positive interface effect of CuO and Bi₂O₃

The ethynylation of formaldehyde catalyzed by Cu-based catalysts is an important synthesis method for 1,4-butynediol relating to high-value-added chemicals. In this work, a series of CuM/SiO₂ (M = Bi, Mg, Mn) catalysts were prepared by a deposition-precipitation method and applied in the ethynylation reaction. The effects of different promoters (Bi, Mg, Mn) on the catalytic activity were investigated. The relationship between the catalyst structure and performance is systematically studied using XRD, TEM, SEM mapping, N₂ low-temperature adsorption/desorption, FT-IR, XPS, and TG-DTA characterization analyses. The results show that 30Cu2Bi/SiO₂ exhibits the highest 1,4-butynediol yield (70%) and selectivity (97%) after the ethynylation reaction for 7 h. Furthermore, compared with the commercial catalyst, 30Cu2Bi/SiO₂ shows similar cyclic stability, 47% yield, and 98% selectivity for 1,4-butynediol after 8 times for about 60 h. It is suggested that small CuO particles are uniformly dispersed in 30Cu2Bi/SiO₂ with the biggest specific surface area (446.37 m² g^-1). Moreover, the Cu-Bi interface existing in 30Cu2Bi/SiO₂ plays an important role in stabilizing cuprous, not excessively reduced to metallic Cu. Therefore, during the ethynylation reaction, 30Cu2Bi/SiO₂ has the most active Cu₂C₂ and the least polyacetylene by-products. In addition, the richest oxygen vacancies arising in 30Cu2Bi/SiO₂ also contribute to the ethynylation reaction of formaldehyde.