Hydrierungen mit Silber: Hochaktiver und chemoselektiver Ag‐In/SiO₂‐ Katalysator für die Direktsynthese von Allylalkohol aus Acrolein

Selective Hydrogenation of Citral in an Organic Solvent, in a Ionic Liquid, and in Substance

“…The results of X-ray powder diffraction (XRD) reveal that during catalyst reduction at T red = 603 K under H 2 both an expansion of the Ag lattice due to the formation of an Ag-In substitutional solid solution and the formation of a silver-indium alloy (2h = 39.8 fi Ag 3 In) was induced. Probably, these special structural characteristics of the Ag-In/SiO 2 catalyst are only one condition, though tunable by catalyst preparation and catalyst pretreatment, for an active and selective catalyst for the production of allylic alcohols, as shown by its applicability for the selective hydrogenation of acrolein in the gas and liquid phase [24] as well as for the selective hydrogenation of citral in the liquid phase. However, due to the lack of possibilities for in situ characterization in liquid-phase reactions (exception: in situ EXAFS/XANES and ATR-IR spectroscopy [27]), the structural particularities do not allow conclusions to be drawn on active sites under liquid-phase reaction conditions.…”

“…Physicochemical characterization of the catalyst [24], amongst others by transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX), showed that there are small bimetallic particles in the range of d = (5.0 -1.5) nm. The results of X-ray powder diffraction (XRD) reveal that during catalyst reduction at T red = 603 K under H 2 both an expansion of the Ag lattice due to the formation of an Ag-In substitutional solid solution and the formation of a silver-indium alloy (2h = 39.8 fi Ag 3 In) was induced.…”

“…, d pore = 12 nm), as described in [24]. The Rh-Sn/SiO 2 catalyst was prepared via controlled surface reaction (CSR method) of Sn(n-C 4 H 9 ) 4 (Merck) with supported (SiO 2 , Aerosil 200, Degussa) rhodium and subsequent temperature-programmed reduction in the range of 323 to 623 K in a hydrogen atmosphere [25].…”

“…Recently, it could be shown that promotion of Ag/SiO 2 with indium allows the chemoselective synthesis of allyl alcohol (maximum selectivity = 75 %, yield = 70 %) by selective hydrogenation of acrolein with molecular hydrogen with high and even technically attractive space-time yields [24]. Aside from Ag-In catalysts, also gold-indium catalysts are suitable for the preferential hydrogenation of the C=O group.…”

Selektivhydrierung von Citral in organischem Lösungsmittel, in ionischer Flüssigkeit und in Substanz

“…In jüngster Zeit konnte gezeigt werden, dass Promotieren von Ag/SiO 2 mit Indium die chemoselektive Synthese von Allylalkohol (maximale Selektivität = 75 %, Ausbeute = 70 %) durch Selektivhydrierung von Acrolein mit molekularem Wasserstoff mit hohen, auch technisch attraktiven Raum-Zeit-Ausbeuten ermöglicht [24]. Neben Ag-In-Katalysatoren eignen sich auch Gold-Indium-Katalysatoren für die bevorzugte Hydrierung der C=O-Gruppe.…”