Unraveling high alkene selectivity at full conversion in alkyne hydrogenation over Ni under continuous flow conditions

Abstract

Selective hydrogenation of alkynes into alkenes under continuous flow conditions over non-precious metal catalysts is an attractive prospect for the chemical industry, especially for the petrochemical and polymer industry. Achieving high alkene selectivity at full alkyne conversions is an ongoing challenge. To address this, we dissolved carbon into Ni lattices by treating Ni@C material derived from MOF-74(Ni) with H₂ at 300 °C and the resultant material is explored as a catalyst for selective styrene synthesis from phenylacetylene (PA) under fixed bed flow conditions. The designed catalyst exhibited a rare combination of sustained high styrene (ST) selectivity (92 ± 1%) and full phenylacetylene (PA) conversion (>99%). Density functional theory (DFT) calculations predict that the carbon incorporation decreases the interaction energy between ST and the catalyst surface, and this increased the reaction barrier for further hydrogenation. Time on stream data showed a 13 h stable performance and the catalyst is regenerable for 4 cycles without a loss of activity. Further, PA is completely removed (by semi-hydrogenation) from the styrene stream even when it is present in low quantities (1.8%).