A new approach to silver-catalysed aerobic oxidation of octadecanol: Probing catalysts utilising a flat, two-dimensional silicon-based model support system

Aerobic oxidation of a thin film of octadecanol at 105 degrees C and ambient pressures to its corresponding carbonyl derivatives (a mixture of aldehyde and carboxylic acid) was for the first time performed over a flat-model (i.e. two-dimensional), silicon wafer-supported metallic silver catalyst. The experimental set-up was extraordinary simple. An open-to-the-atmosphere glass beaker was used as reactor. Just enough octadecanol was placed on the silicon-supported catalytic surface to cover it with a thin film when melted. Reaction progress was monitored by ATR-FTIR analyses to identify the appearance of octadecanal and octadecanoic acid carbonyl stretching peaks at 1730 and 1710 cm(-1) respectively. The successful demonstration of this simple approach in studying catalysed small-molecule condensed organic reactions opens a new avenue towards simplified catalytic mechanistic studies of such processes. The catalyst was prepared by spin coating silver nitrate on a flat silicon wafer with (100) surface orientation, pretreated to have 4-5 silanol (-Si-OH) groups per nm(2). Reduction by hydrogen at 350 degrees C afforded metallic silver particles on the two-dimensional support at a nominal surface concentration of ca. 21-23 silver atoms/nm(2). XPS differentiation between the catalyst precursor, AgNO3. and the metallic silver catalytic surface required use of the Auger MNN kinetic energies. TEM studies of the active catalyst showed no serious aggregation of metallic Ag particles occurred during reduction. (C) 2012 Elsevier B.V. All rights reserved.