The Oxidation of Toluene by Cobalt–Copper–Bromide System. A Side-chain Acetoxylation

Abstract

The liquid-phase oxidation of toluene catalyzed by the cobalt(II) ion and the bromide ion in the presence of the copper(II) ion has been studied. Benzyl acetate was obtained in a good yield (50–70%) with mixed catalysts of metal acetates and sodium bromide in acetic acid at 100–150 °C, accompanied by small amounts of benzaldehyde and benzoic acid. The product distribution was greatly dependent on the NaBr concentration, which can be explained in terms of the high oxidizing ability of the copper(II) ion coordinated by the bromide ion. A synergistic effect was found on the yield of benzyl acetate upon the addition of copper(II) acetate with a high NaBr concentration, the maximum yield being obtained at the Co:Cu:NaBr ratio of 1:1:5–10. A change in the oxygen partial pressure also varied the product distribution, suggesting that the competitive reaction of the copper(II) ion with the oxygen molecule for the benzyl radical was simultaneously taking place at a diffusion-controlled rate. Benzyl acetate was considered to result from the oxidation of the benzyl radical by cop-per(II) bromide and the subsequent solvolysis by acetic acid. The addition of acetic anhydride had a negative effect on the formation of benzyl acetate.

Liquid Phase Oxidation of Xylenes: Effects of Water Concentration and Alkali Metals

“…Korea has the highest TPA capacity, 4,540,000 tons/year. 1 TPA, the raw material of polyester, is usually produced commercially by liquid phase oxidation of p-xylene (pX) with air, using a catalyst combination of cobalt, manganese and bromide ions in acetic acid at around 170-210 o C. 2,3 Detailed studies on the kinetics [4][5][6][7][8][9][10] and mechanism 4,5,[11][12][13][14][15][16][17] of the liquid phase oxidation of alkylaromatics to aromatic carboxylic acids have been conducted. It has also been attempted to replace the acetic acid solvent with water 18,19 and to eliminate the corrosive bromine component 20,21 and to utilize carbon dioxide as a co-oxidant.…”