Rh NPs Immobilized on Phosphonium- based Supported Ionic Liquid Phases (Rh@SILPs) as Hydrogenation Catalysts.

Johannes Zenner,Alexis Bordet,Gilles Moos,Kylie L Luska,Walter Leitner

doi:10.2533/chimia.2021.724

Abstract

A series of phosphonium-based supported ionic liquid phases (SILPs) was prepared for the immobilization of Rh nanoparticles (Rh@SILP). The influence of systematic variations in the structure of the ionic liquid-type molecular modifiers (anion, P-alkyl chain length) on the formation and catalytic properties of Rh nanoparticles (NPs) was investigated. Both the nature of the anion and the length of the P-alkyl chain were found to have a strong impact on the morphology of the NPs, ranging from small (1.2-1.7 nm) and well-dispersed NPs to the formation of large NPs (9.9-16.5 nm) and/or aggregates. The catalytic properties of the resulting Rh@SILP materials were explored using the hydrogenation of benzylideneacetone and biomass-derived furfuralacetone as model reactions. The changes in ring and C=O hydrogenation activity as a function of the SILP structure and the Rh NPs size allowed for the selective synthesis of products with distinct molecular functionalities.

Highlights

With depleting fossil resources, the utilization of renewable resources for the production of fuels and chemicals represents currently one of the biggest challenges for the chemical industry.[1] Extensive efforts are in particular dedicated to the conversion of biomass-derived feedstock into value-added compounds including fuels, bulk and fine chemicals as well as building blocks for the production of pharmaceuticals.[2]
Similar trends could be observed for imidazolium-based ionic liquids (ILs), where the melting point generally decreased with increasing N-alkyl chain length.[16]
In summary, Rh NPs were immobilized on phosphoniumbased supported ionic liquid phases (Rh@SILP) of systematically varied molecular structure (P-alkyl chain length, anion)

Summary

Introduction

The utilization of renewable resources for the production of fuels and chemicals represents currently one of the biggest challenges for the chemical industry.[1] Extensive efforts are in particular dedicated to the conversion of biomass-derived feedstock into value-added compounds including fuels, bulk and fine chemicals as well as building blocks for the production of pharmaceuticals.[2]. 2.1 Synthesis and Characterization Rh@SILP Catalysts A series of phosphonium-based ILs was synthesized by adapting a previously reported procedure.[15] These ILs will be denoted as R -P-X, where R corresponds to the P-alkyl chains (R = Me, Bu, tBu, Oct) and X to the anion (X = I, OTf, PF6, NTf2).

Results

Conclusion