Process for oxidatively carbonylating toluene to toluic acid, at least 50 mol % of the toluic acid being the p-isomer, said process comprising contacting and reacting, at 110.degree.-250.degree. C., at a pressure of at least 500 psi (3.45 MPa), toluene, carbon monoxide, oxygen and the catalyst ingredients consisting essentially of (a) a compound of rhodium or iridium; (b) a sulfur oxy-acid or a Group Ia or IIa metal salt of a sulfur oxy-acid; (c) a sulfur oxy-acid or sulfur oxy-acid mixture having a Hammett acidity value (--H.sub.o) of greater than 7.0; and (d) a cupric salt of a sulfur oxy-acid; said catalyst ingredients containing 0.3-30 mol % of (a) and 70-99.7 mol % of (b+c+d), with the molar ratios (b/a) and (c/a) each being at least 2 and the molar ratio (d/a) being at least 0.5, and recovering toluic acid.
This invention relates generally to the oxidative carbonylation of toluene, catalyzed by rhodium or iridium complexes in the presence of an oxidant and under mild conditions, whereby toluic acid is produced with para-selectivity up to 98%.
