Continuous catalytic aerobic oxidation of o‑chlorotoluene to o-chlorobenzoic acid under slug flow conditions

Abstract

A continuous-flow process was developed for the aerobic oxidation of o-chlorotoluene (OCT) to o-chlorobenzoic acid (OCBA) with pure oxygen. Acetic acid as cosolvent and CoBr₂/MnBr₂ as catalyst, with a small amount of acetaldehyde as the radical initiator to make the reaction rapidly stimulates. Through the regulation of gas–liquid mixing, slug flow obtains similar mass transfer coefficient of annular flow and the reactor volume was further reduced. The reaction parameters were easily controlled by take the advantages of continuous-flow reactor. Under the optimal reaction conditions, the isolated yield of OCBA reached up to 94%. Compared with the traditional batch process, shorter residence time, higher product yield and operation safety are achieved by adapting simple continuous-flow system.