Production of NMSBA from the oxidation of NMST in the homogeneous Co/Mn/Br/H3PMoxW12−xO40 catalytic system

Abstract 2‐nitro‐4‐methylsulphonylbenzoic acid (NMSBA) is an important intermediate for the preparation of the highly effective herbicide mesotrione. NMSBA is produced from the oxidation of 2‐nitro‐4‐ methylsulphonyltoluene (NMST) by nitric acid commercially, which suffers from the serious problems of low yield and heavy pollution. In this paper, a homogeneous system consisting of Co/Mn/Br/ · H 3 PMo x W 12− x O 40 has been applied to catalyze the production of NMSBA by oxidizing NMST with oxygen in acetic acid. The experiments indicate that the best value of x in the phosphomolybdenum tungsten heteropoly acid is 3. The optimum composition of this catalyst system is 1163 ppm H 3 Pmo 3 W 9 O 40 · 12.17H 2 O, 247.5 ppm Co, 453.5 ppm Mn, and 1075 ppm Br. Such a catalytic system is able to achieve a NMST conversion of 94.93% and a NMSBA selectivity of 99.84%. H 3 PMo 3 W 9 O 40 exceeds both H 3 PMo 12 O 40 and H 3 PW 12 O 40 as a catalyst in the production of NMSBA from the oxidation of NMST by oxygen.