Selective Aerobic Oxidation of Toluene in the Presence of Co2+ and Task-Specific Organic Salts, Including Ionic Liquids

This paper presents research on the catalytic activity of systems composed of transition-metal compounds and organic bromide salts, [X][Br] or [X][Br-3], in the oxidation of toluene and its derivatives with oxygen using acetic acid as a solvent. Salts containing imidazolium, tetraalkylammonium, bromoalkylammonium, phenylalkylammonium, or benzylalkylammonium cations in combination with Co2+ compounds were used. It was found that the [X][Br] and [X][Br-3] systems with Co2+ compounds enabled the oxidation of toluene and its derivatives to the corresponding carboxylic acids with high selectivities and reaction rates. Moreover, long-term corrosion studies on three selected stainless steels showed that the organic salts that contained nitrogen atoms had an inhibitory effect on the corrosion caused by the Br- ions present in the reaction system. For the first time, the possibility of replacing inorganic bromides, used on an industrial scale in the Amoco process, by organic bromide salts, including ionic liquids, with corrosion-inhibiting properties was demonstrated.