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/Al2O3 catalyst towards citral hydrogenation. The Cu/Al2O3 was prepared using a combination of wet impregnation and strong electrostatic interaction technique. The catalyst was coated with three ionic liquids, namely: [C4C1Pyrr][OTf], [C2C1C1Im][NTf2], and [C2C1Im][NTf2] 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/Al2O3 catalyst. The Cu‐SCILL (coated with 15 wt% [C2C1Im][NTf2]) increased the selectivity towards geraniol and nerol by 340 %.

Adsorption and thermal evolution of [C1C1Im][Tf2N] on Pt(111)

“…More importantly, the IL also interacts directly with the solid catalyst. [10][11][12][13] Hereby, the IL can modify sites by ligand-like interactions or block less selective sites of the solid catalyst and thus increase the selectivity of the catalytic process. Such SCILL systems are already commercially available by Clariant for the selective hydrogenation of unsaturated hydrocarbons.…”

Structure and Reactivity of the Ionic Liquid [C1C1Im][Tf2N] on Cu(111)

“…In SILP, an IL film containing dissolved transition metal complexes is coated onto a porous support, whereas in SCILL a thin IL film is coated onto the active metal surface of a heterogeneous catalyst [24]. Both SILP and SCILL systems are already in use commercially [26][27][28]. For example, Petronas employs a SILP system to capture mercury (Hg) from natural gas [29], while Clariant employs SCILL systems for the selective hydrogenation of unsaturated hydrocarbons [30].…”

Ionic Liquids in Metal, Photo-, Electro-, and (Bio) Catalysis

“…342 For instance, selectivity to the intermediate is favored if the intermediate is less soluble in the IL than the reactant (Figure 21). Typical examples involve the selective partial hydrogenations of benzene to cyclohexene, 343,344 dienes to monoalkenes, 53,345,346,347 and alkynes to alkenes. 348 The same catalytic performance trend is also observed for related "naked" NPs embedded in bare ILs.…”