Coating of Pd/C catalysts with Lewis-acidic ionic liquids and liquid coordination complexes – SCILL induced activity enhancement in arene hydrogenation

Martin Lijewski,Małgorzata Swadźba-Kwaśny,James M Hogg,Peter Wasserscheid,Marco Haumann

doi:10.1039/c7ra03295a

Abstract

Acid doping – coating of Pd/C catalysts with Lewis-acidic liquid films results in increased hydrogenation activity at very mild reaction conditions.

Highlights

The hydrogenation of aromatic compounds is of major importance for the chemical industry, leading to a plethora of important intermediates and products.[1]
In 2008, Song and co-workers demonstrated that the addition of the Lewis-acidic ionic liquid [BMIM]Cl/AlCl3 to a nely dispersed Pd on activated carbon (Pd/C) resulted in full hydrogenation of benzene, naphthalene, anthracene and naphthacene under very mild conditions.[7]
The same activity was observed for a Pd-solid catalysts with ionic liquid layer (SCILL) catalyst, but a much smaller amount of 140 mg [BMIM]Cl/AlCl3 coating (Pd-SCILL-1) was required, containing only 12.5% of AlCl3 compared to the addition of pure AlCl3

Summary

Introduction

The hydrogenation of aromatic compounds is of major importance for the chemical industry, leading to a plethora of important intermediates and products.[1]. We have utilized both chloroaluminate ionic liquids and LCCs as coating materials for the Pd/C catalyzed hydrogenation of toluene (see Fig. 2). In both cases, the coating introduces Lewis acidity, aiming at the activation of the aromatic ring structure in accordance with Fig. 1. In order to prepare the Pd-SCILL catalyst, the desired amount of Lewis acidic ionic liquid (13 wt% loading) or LCC (10 wt% loading) was added to a round bottom ask with the heterogeneous catalyst Pd/C (10 wt% Pd) and the solvent cyclohexane (7 mL).

Results and discussion

Findings

13.8 Â 10À5

Conclusions