DFT investigations on the conversion of acetylene to undesired vinyl acetylene during vinyl acetate synthesis

•CHCH physically adsorbs on Zn(Ac)2/AC catalyst.•The generation of CHC is the rate-limiting step.•CHCH prefers to undergo hydrogenation rather than dehydrogenation.

Density functional theory was employed to investigate the alternative mechanisms of vinyl acetylene formation on zinc acetate/activated carbon catalyst, aiming to better understand the deactivation behaviour and illustrate the plausible vinyl acetylene formation routes during vinyl acetate synthesis. The structural and energetic properties of relevant species were calculated and discussed in details. Two possible pathways for vinyl acetylene formation were proposed and they both are characterized by the generation of CHC as the rate-limiting step. It seems that CHCH prefers to undergo hydrogenation rather than dehydrogenation because of the lower barrier calculated for acetylene hydrogenation. Path2 (CHCH + H → CH2CH; CHCH → CHC + H; CH2CH + CHC → CH2CHCCH) is identified as the predominant pathway for vinyl acetylene formation on Zn(Ac)2-COOH-AC surfaces.

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