title: Microwave-assisted partial hydrogenation of citral by using ionic liquid-coated porous glass catalysts.
abstract: The microwave-assisted hydrogenation of citral (3,7-dimethylocta-2,6-dienal) to citronellal with molecular hydrogen as the reducing agent was investigated. Several polar and non-polar solvents were screened and imidazolium-based ionic liquids were applied as modifiers for the palladium-containing porous glass catalysts (Pd/TP). The best results were obtained with N-ethyl-N'-methylimidazolium dicyanamide, N-ethyl-N'-methylimidazolium acetate, or N-ethyl-N'-methylimidazolium trifluoroacetate, which were used to prepare supported catalysts with an ionic liquid layer (SCILL) on Pd/TP by wet-impregnation. The influence of pressure and temperature when using these ionic liquid-containing catalysts, as well as their long-term stabilities, were examined. Working with microwave-assisted heating, high yields of citronellal were achieved under mild conditions within short reaction times. Catalyst characterization was carried out by means of BET measurements, X-ray photoelectron spectroscopy (XPS) and thermo-gravimetric analyses. The influences of the ionic liquid layer were derived from experiments carried out before and after the reactions.
authors.affiliation: Institute for Technical Chemistry and Environmental Chemistry (ITUC), Friedrich Schiller University Jena, Jena, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gallert
authors.forename: Martin
authors.initials: M
authors.lastname: Hahn
authors.forename: Martin
authors.initials: M
authors.lastname: Sellin
authors.forename: Christine
authors.initials: C
authors.lastname: Schmöger
authors.forename: Achim
authors.initials: A
authors.lastname: Stolle
authors.forename: Bernd
authors.initials: B
authors.lastname: Ondruschka
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Keller
authors.forename: Klaus D
authors.initials: KD
authors.lastname: Jandt
mesh_terms: D000080462:Acyclic Monoterpenes; D000447:Aldehydes / Q000737:chemistry; D002384:Catalysis; D005898:Glass / Q000737:chemistry*; D006865:Hydrogenation; D052578:Ionic Liquids / Q000737:chemistry*; D008872:Microwaves; D039821:Monoterpenes / Q000737:chemistry*; D016062:Porosity; D011312:Pressure; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D000080462:Acyclic Monoterpenes; D000447:Aldehydes; D052578:Ionic Liquids; D039821:Monoterpenes; C108217:citronellal; C007076:citral