Selective hydrogenation of acetylene on Pd/SiO2 in bulk liquid phase: A comparison with solid catalyst with ionic liquid layer (SCILL)

• Both SCILL and bulk liquid modification enhance ethylene selectivity.
• Bulk liquid modification in NMP outperforms SCILL in selectivity and stability.
• The highest ethylene selectivity is 97% at acetylene conversion of 96%.
• Bulk-liquid-phase hydrogenation prevents “run-away” of temperature.

Selective hydrogenation of acetylene is usually a gas-phase reaction. In this work, liquid phase was introduced as a selective solvent to improve the selectivity to ethylene by coupling absorption to the reaction. N-methyl-2-pyrrolidone (NMP) and 1,3-dimethylimidazolium methylphosphite ([DMIM][MeHPO3]) were used as selective solvents in two types of liquid modification (in bulk liquid phase and on SCILL). Both types of modification significantly enhanced the ethylene selectivity compared with the gas-phase reaction. The mass transfer could be eliminated almost completely in bulk NMP, slightly on SCILL, but could not be eliminated in bulk [DMIM][MeHPO3]. Among the reactions with liquid introduction, the reaction in bulk NMP could increase the ethylene selectivity to the greatest extent, which had a highest ethylene selectivity of 96.6% at conversion of 96.1%, and outperformed SCILL in catalyst stability.

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