Oxidation of 3,7‐dichloro‐8‐(chloromethyl)quinolone to quinclorac by oxygen

Abstract

AbstractBACKGROUNDQuinclorac (3,7‐dichloro‐8‐quinolinecarboxylic acid) is commercially produced from the partial oxidation of 3,7‐dichloro‐8‐(chloromethyl)quinolone by nitric acid in 98% sulfuric acid. Such technology suffers from some shortcomings, such as the discharge of NOx and wastewater, and the formation of nitro compounds. Oxygen is a clean, cheap oxidant. The key to realizing the production of quinclorac by oxidizing 3,7‐dichloro‐8‐(chloromethyl)quinolone with oxygen is the development of an efficient catalyst.RESULTSThe transformation of 3,7‐dichloro‐8‐(chloromethyl)quinolone to quinclorac oxidized by O2 molecule in acetic acid solution can be accomplished under a homogeneous catalyst system composed of H3PMo12O40/Ce/Co/Br. Experiments show that the optimal catalytic system consists of 0.209 (wt)% phosphomolybdic acid, 0.022 (wt)% Ce(III), 0.027 (wt)% Co(II) and 0.0161 (wt)% Br−.CONCLUSIONTemperature is an important parameter affecting reaction rate. The influence of oxygen concentration in the gas phase on quinclorac yield and 3,7‐dichloro‐8‐(chloromethyl)quinolone conversion is great. The activation energy of this catalytic reaction is 57.6 kJ mol−1. The reaction orders for oxygen and 3,7‐dichloro‐8‐(chloromethyl)quinolone are 0.26 and 0.93, respectively. © 2022 Society of Chemical Industry (SCI).