The Effect of Coating Pd/Al2O3 and PdAg/Al2O3 Catalysts with [BMIM][DCA] for the Selective Hydrogenation of 1-Octyne in 1-Octene

The selective hydrogenation of octyne in a mixed 1-octyne/1-octene feed was investigated by employing Pd/Al2O3 and PdAg/Al2O3 catalysts coated with 1-butyl-3-methylimidazolium dicyanamide ([BMIM][DCA]) as SCILLs (Solid Catalysts with an Ionic Liquid Layer). All SCILLs were compared to an organically modified, 1-ethylimidazole (EIM) coated catalyst to determine if there is a SCILL effect. Results of the catalysis showed that both uncoated catalysts were highly active (100 % 1-octyne and 1-octene conversion) in the hydrogenation reactions with dominant selectivity towards octane. No increase of 1-octene in the reactor outflow (octene gain) was noted. Coating 1Pd/Al2O3 with [BMIM][DCA] at four monolayers (ML) corresponding to a surface loading of 45 wt% still gave 100 % octyne conversion but now with a 54 % 1-octene gain, as no octene was converted. Coating 1Pd9Ag/Al2O3 with only a single monolayer of [BMIM][DCA] (14 wt%) was sufficient to give a 1-octene gain of 84 % at an octyne conversion of 91 %. Time-on-stream reactions for the uncoated and SCILL systems showed stable operation during the experiments.