Influencing the Product Distribution in Citral Hydrogenation Using Ionic Liquid Modified Cu Catalysts

Abstract This work shows the effect of selected ionic liquids on the catalytic performance of a Cu/Al 2 O 3 catalyst towards citral hydrogenation. The Cu/Al 2 O 3 was prepared using a combination of wet impregnation and strong electrostatic interaction technique. The catalyst was coated with three ionic liquids, namely: [C 4 C 1 Pyrr][OTf], [C 2 C 1 C 1 Im][NTf 2 ], and [C 2 C 1 Im][NTf 2 ] resulting in Cu‐based SCILL catalysts (solid catalyst with an ionic liquid layer). The fresh and used SCILL catalysts were characterized using FT‐IR spectroscopy and thermal gravimetric analysis. All Cu‐SCILL catalysts were stable throughout the liquid‐phase reactions with no leaching of ionic liquid being detectable by means of TGA. All ionic liquids investigated prevented the formation of undesired isopulegol compared to the 30 % isopulegol selectivity obtained over the bare Cu/Al 2 O 3 catalyst. The Cu‐SCILL (coated with 15 wt% [C 2 C 1 Im][NTf 2 ]) increased the selectivity towards geraniol and nerol by 340 %.