Abstract

Aerobic Oxidation of Aldehydes: Lessons Learned and to be Learned using Continuous Flow Microreactor

Alain Favre-Reguillon, Associate Professor, University of Lyon

The liquid phase oxidation of aldehydes by ground state dioxygen (3O2) into the corresponding carboxylic acid (aldehyde autoxidation) is a slow spontaneous process that could be easily observed when looking at an aldehyde bottle stored for a rather long time in a close chemical storage cabinet. This process has been first described by Wöhler and Liebig (1832) and since then, the rate of aldehyde autoxidation has been claimed to be increased by numerous catalysts. However, we have shown that aldehyde autoxidation is highly dependent of the presence of inhibitors and due to low transfer rate of O2 in the liquid phase, the chemical performances of aerobic oxidation (productivity and selectivity) can be falsified by oxygen starvation in the liquid phase. One way this issue can be addressed is to operate at higher oxygen pressure but since aldehyde oxidation is a strongly exothermic process (?rH = -287 kJ/mol) and proceeds via highly reactive free radical species, the combination of fuel, oxidant and energy raise safety concerns in classical batch reactors. In order to reach the chemical regime and improve the productivity, continuous flow microreactors will be used and new operating conditions and improved productivity will be presented.