Bimetallic Nanoparticles in Supported Ionic Liquid Phases as Multifunctional Catalysts for the Selective Hydrodeoxygenation of Aromatic Substrates

Abstract

Bimetallic iron-ruthenium nanoparticles embedded in an acidic supported ionic liquid phase (FeRu@SILP+IL-SO₃ H) act as multifunctional catalysts for the selective hydrodeoxygenation of carbonyl groups in aromatic substrates. The catalyst material is assembled systematically from molecular components to combine the acid and metal sites that allow hydrogenolysis of the C=O bonds without hydrogenation of the aromatic ring. The resulting materials possess high activity and stability for the catalytic hydrodeoxygenation of C=O groups to CH₂ units in a variety of substituted aromatic ketones and, hence, provide an effective and benign alternative to traditional Clemmensen and Wolff-Kishner reductions, which require stoichiometric reagents. The molecular design of the FeRu@SILP+IL-SO₃ H materials opens a general approach to multifunctional catalytic systems (MM'@SILP+IL-func).

Keywords: bimetallic nanoparticles; hydrodeoxygenation; iron; ruthenium; supported ionic liquid phases.

Scheme 1

Selective catalytic hydrodeoxygenation of aromatic carbonyl compounds as a possible route to alkyl‐substituted aromatics, opening new synthetic pathways, for example, from Friedel–Crafts acylation products or lignin derivatives.

Scheme 2

The complex reaction network to be controlled for selective deoxygenation of aromatic substrates, exemplified for benzylideneacetone (1).

Figure 1

Schematic of iron–ruthenium nanoparticles immobilized on a sulfonic acid‐functionalized supported ionic liquid phase (Fe₂₅Ru₇₅@SILP+IL‐SO₃H) as a bifunctional catalyst for the hydrodeoxygenation of carbonyl‐substituted aromatic substrates.

Figure 2

Scanning transmission electron microscopy with energy dispersive X‐ray spectroscopy (STEM/EDS) elemental mappings of Fe₂₅Ru₇₅@SILP+IL‐SO₃H. a) STEM‐HAADF image of Fe₂₅Ru₇₅@SILP+IL‐SO₃H, b) S, c) Fe, and d) Ru.

Figure 3

Reaction profile for the hydrodeoxygenation of benzylideneacetone (1) using Fe₂₅Ru₇₅@SILP+IL‐SO₃H. Reaction conditions: Fe₂₅Ru₇₅@SILP+IL‐SO₃H (58 mg of catalyst containing 0.015 mmol total metal and 0.038 mmol (2.50 equiv.) IL‐SO₃H), substrate (0.38 mmol), mesitylene (0.5 mL), H₂ (50 bar), 150 °C. Conversion and product distribution were determined by GC using tetradecane as an internal standard.

Figure 4

Comparative rate studies for the hydrodeoxygenation of 1‐phenyl‐1‐butanone (2) and 4‐phenyl‐2‐butanone (1 a) using Fe₂₅Ru₇₅@SILP+IL‐SO₃H. Reaction conditions: Fe₂₅Ru₇₅@SILP+IL‐SO₃H (58 mg catalyst containing 0.015 mmol total metal and 0.038 mmol (2.50 equiv.) IL‐SO₃H), substrate (0.38 mmol), mesitylene (0.5 mL), H₂ (50 bar), 150 °C. Conversion was determined by GC using tetradecane as an internal standard.