Selective Oxidation of Linear Alkanes by a Schiff Base Ligand [1,4-bis(Salicylidene Amino)-Phenylene] Vanadium (VO2+) Complex Bonded on Modified Silica Gel Support1

Abstract

A Schiff base complex from vanadium (VO2+) has been successfully immobilized by chemical reaction on an isocyanate modified silica gel support. This catalyst proves to be an active heterogeneous catalyst for the selective oxidation of n-pentane and n-hexane in the presence of molecular oxygen at moderate temperatures (150°C) and pressures (∼20 atm). The products were identified by GC/MS analysis, and the product distribution was found to be entirely different from that reported in the literature. The oxygenated compounds formed from n-pentane are mostly mesaconic acid (COOH(CH3)C=CHCOOH) while those from n-hexane are alcohols (2-methyl-2,4-pentanediol, 1-hexanol, and 1,6-hexanediol), ketones (2-hexanone), and acids. As analyzed by thermogravimetric analysis, the catalyst was seen to be stable up to 393°C and the atomic absorption study shows a negligible leaching of the catalyst.