Liquid phase oxidation of alkyl aromatics at low oxygen partial pressures

•Oxygen partial pressure threshold for PX oxidation kinetics.•Kinetic model of PX oxidation involving the influence of oxygen partial pressure.•Provide helpful insights into industrial PX oxidation process.

The liquid phase oxidation of p-xylene (PX) is generally assumed to be zeroth-order with respect to the gaseous reactant, i.e. oxygen in most of published literature. In this work, it was verified by both batch and continuous experiments at conditions of industrial interests that there exists a threshold for low oxygen partial pressure (OPP), which is between 17.1 and 22.8 kPa. The OPP is of substantial influence on the PX oxidation kinetics when the OPP reduces from 22.8 kPa. Based on the free radical chain reaction mechanism, the simplified PX oxidation kinetic model with eight parameters was developed and these parameters were estimated with narrow confidence intervals through the batch experiments. The reliability of this kinetic model was further validated through successful predictions of the continuous PX oxidation experiments. Hopefully the experimental results and the kinetic model may provide insights into industrial PX oxidation process.