Investigations on the reaction kinetics and the catalytic effect of Cu(II) and V(V) in the oxidation of cyclohexanol by nitric acid

In this paper, the reaction kinetics of the oxidation of cyclohexanol by nitric acid to adipic acid (AA) with and without using Cu(II) and V(V) as catalysts was studied in a continuous flow stirred tank reactor at conditions close to the industrial process. Rate equations of power law type and lumping of the reaction intermediates were applied to describe the reaction kinetics. The effect of the catalyst on the selectivity of products including the dicarboxylic acid and the unrecoverable N2 and N2O was investigated. Cu(II) or V(V) alone and the combination of them enhance the selectivity of AA by suppressing the formation of the by-product glutaric acid and succinic acid with Cu(II) being more effective than V(V), and the combination of Cu(II) and V(V) being more effective than Cu(II). In the presence of the catalysts, the consumption of HNO3 and the production of the unrecoverable nitrogen containing compounds per mole of AA are reduced. Based on the experimental results, the way for the catalysts to influence the reaction mechanism was proposed.