Kinetic study on the reaction routes in the oxidation of K/A oil by nitric acid with microreactors

A continuous-flow microreactor system was applied to evaluate the detailed kinetics of the reaction routes involved in the oxidation of K/A oil by nitric acid, which is essential to obtain an in-depth comprehension of complex reaction mechanisms, having important guiding significance for the two-stage temperature control strategy. 6-hydroxyimino-6-nitrohexanoic acid (AMNA) was identified as a major intermediate and its presence was confirmed through UPLC-MS and ¹H NMR characterizations. A multi-step reaction kinetic model was developed, revealing good prediction with the experimental results. Finally, the model was applied to investigate the effects of operating parameters on the reaction routes distribution and reaction rate. The simulation results showed that high temperature and nitric acid concentration contributed to high selectivity of adipic acid through promoting the AMNA route, and greatly reduced the required reaction time, indicating that the accurate control over the conditions in this rapid and strongly exothermic process was of paramount importance.