TY - JOUR
T1 - Selective side-chain oxidation of alkyl aromatic compounds catalyzed by cerium modified silver catalysts
AU - Beier, Matthias Josef
AU - Schimmoeller, Bjoern
AU - Hansen, Thomas Willum
AU - Andersen, Jens Enevold Thaulov
AU - Pratsinis, Sotiris E.
AU - Grunwaldt, Jan-Dierk
PY - 2010
Y1 - 2010
N2 - Silver supported on silica effectively catalyzes the aerobic side-chain oxidation of alkyl aromatic compounds
under solvent-free conditions. Toluene, p-xylene, ethylbenzene and cumene were investigated as
model substrates. Typically, the reaction was performed at ambient pressure; only for toluene an elevated
pressure was required. Carboxylic acids, such as benzoic acid or p-toluic acid, additionally increased the
reaction rate while CeO2 could act both as a promoter and an inhibitor depending on the substrate and
the reaction conditions. Silver catalysts were prepared both by standard impregnation and flame spray
pyrolysis. Addition of a Ce precursor to the FSP catalyst resulted in significantly smaller silver particles.
Ce-doped FSP catalysts in general exhibited a superior catalytic performance with TONs up to 2000
except for cumene oxidation that appeared to proceed mainly by homogeneous catalysis. In addition,
flame-made catalysts were more stable against silver leaching compared to the impregnated catalysts.
The structure of the silver catalysts was studied in detail both by X-ray absorption spectroscopy and
transmission electron microscopy suggesting metallic silver to be required for catalytic activity. Catalytic
studies point to a radical mechanism which differs depending on the type of substrate.
AB - Silver supported on silica effectively catalyzes the aerobic side-chain oxidation of alkyl aromatic compounds
under solvent-free conditions. Toluene, p-xylene, ethylbenzene and cumene were investigated as
model substrates. Typically, the reaction was performed at ambient pressure; only for toluene an elevated
pressure was required. Carboxylic acids, such as benzoic acid or p-toluic acid, additionally increased the
reaction rate while CeO2 could act both as a promoter and an inhibitor depending on the substrate and
the reaction conditions. Silver catalysts were prepared both by standard impregnation and flame spray
pyrolysis. Addition of a Ce precursor to the FSP catalyst resulted in significantly smaller silver particles.
Ce-doped FSP catalysts in general exhibited a superior catalytic performance with TONs up to 2000
except for cumene oxidation that appeared to proceed mainly by homogeneous catalysis. In addition,
flame-made catalysts were more stable against silver leaching compared to the impregnated catalysts.
The structure of the silver catalysts was studied in detail both by X-ray absorption spectroscopy and
transmission electron microscopy suggesting metallic silver to be required for catalytic activity. Catalytic
studies point to a radical mechanism which differs depending on the type of substrate.
KW - Silver catalysis
KW - Homogeneous vs. heterogeneous catalysis
KW - Flame spray pyrolysis
KW - p-Xylene
KW - Selective aerobic oxidation
U2 - 10.1016/j.molcata.2010.08.001
DO - 10.1016/j.molcata.2010.08.001
M3 - Journal article
SN - 1381-1169
VL - 331
SP - 40
EP - 49
JO - Journal of Molecular Catalysis A: Chemical
JF - Journal of Molecular Catalysis A: Chemical
ER -