Importance Of Zinc Oxide In Cu-Based Catalysts For The Ethynylation Of Formaldehyde To 1,4-Butynediol

As more technologies have been developed to produce formaldehyde and acetylene from biomass, the condensation-addition reaction between formaldehyde and acetylene provides a green and atom-economic method to synthesize 1,4-butynediol (BD). It is important to design and construct a new efficient copper-based catalyst for formaldehyde ethynylation with multi-center synergy to improve the reaction efficiency. In this work, a CuO-xZnO composite catalyst with an interface structure was constructed. Compared with a CuO-based catalyst, the yield of BD was increased from 19.07 to 70.9% by introducing an appropriate amount of ZnO, and the reaction activation energy decreased from 28.94 to 16.35 kJ/mol, which improved the catalytic reaction efficiency. The results showed that ZnO in the CuO-xZnO catalyst dispersed the active Cu species and also promoted the conversion of CuO to copper acetylide by electron transfer in the interface structure. Moreover, Zn2+ in ZnO acted as a Lewis acid and adsorbed the carbonyl oxygen of formaldehyde, causing the carbonyl electrons to flow to Zn2+, which enhanced the electropositivity of C+ in the formaldehyde molecule. This resulted in a nucleophilic addition reaction between formaldehyde activated by ZnO and acetylene activated by copper acetylide at the interface, which efficiently generated the target product BD.