The present invention provides a non-hazardous, improved continuous oxidation process for the preparation of substituted benzoic acid of formula (I) by using continuous process reactor system with improved process controls. (I) wherein: R 1 is H, F, Cl, Br, I, NO2, amine, or C1-C5 alkyl; R2 is H, F, Cl, Br, I, NO2, amine, or C1-C5 alkyl; and R3 is H, F, Cl, Br, I, NO2, amine, C1-C5 alkyl;