The effect of ionic liquid on alumina supported copper catalysts for the competitive hydrogenation of octanal in the presence of octene.

The influence of 1-butyl-3-methylimidazolium bis(trifluromethanesulfonyl)imide ([BMIM][NTf 2 ]) on Cu/γ-Al 2 O 3 was investigated for the competitive hydrogenation of octanal in the presence of octene in a continuous flow reactor. The role of the solid catalyst was investigated by comparing the activities of one-step (N15Cu) vs two step (2N15Cu) wet impregnated catalyst. Characterization techniques included nitrogen physisorption, temperature programmed studies, electron microscopy and X-Ray Photoelectron Spectroscopy which were used to determine the catalyst properties and metal-ionic liquid interaction of the uncoated and IL coated catalysts. The Cu SCILL catalyst (solid catalyst with an ionic liquid layer) showed enhanced catalytic performance as compared to the uncoated catalyst. Under optimized conditions, the 2N15Cu SCILL catalyst favoured the desired hydrogenation of the octanal, whilst minimizing the undesired octene hydrogenation. The octene conversion decreased from 26% to 6% over the SCILL catalyst. The presence of the ionic liquid also increased the selectivity towards the desired product, 1-octanol, from 93.5% over the uncoated catalyst to 99.8% over the SCILL catalyst. Investigation into the interaction between the copper and the ionic liquid revealed that the ionic liquid is physically adsorbed onto the catalyst’s surface, and induced changes in the SCILL catalysts surface acidity, BET surface area and hydrogen-metal interaction. It seems likely that the thermal and chemical properties of the ionic liquid also contributed to the SCILL catalyst behaviour, for example, the polar nature of the ionic liquid favours the diffusion of octanal as opposed to octene within the ionic liquid layer. This results in a greater selectivity towards C O hydrogenation which is desired. [ABSTRACT FROM AUTHOR]