Study of reaction mechanism based on further promotion of low temperature degradation of toluene using nano-CeO2/Co3O4 under microwave radiation for cleaner production in spraying processing

Highlights: • A novel synthesis of Nano-CeO₂@Co₃O₄ from complexation and impregnation was tried. • Activities were remarkably promoted by applying of nano-materials and microwave. • Kinetic studies on catalytic oxidation under microwave radiation were presented. • Microwave absorption properties were first provided for evaluation of activities. • A possible mechanism on catalytic oxidation under microwave radiation was showed. -- Abstract: Cleaner production in spraying processing was presented by advanced low temperature oxidation technology using combined methods of microwave radiation and nano-composites. Activities of samples for oxidation of toluene were estimated and the result exhibited that application of microwave radiation and nano-materials greatly promoted activities of catalysts. Moreover, the doping of Ce further enhanced catalytic activities. Samples of 5% Ce-Co showed optimal activity with conversion rate of 70% and CO₂ selection of 96% at 120 ℃ and 210 ℃, respectively. The lowest E_a (33.45 kJ/mol) was obtained calculating from kinetics process under microwave radiation using 5% Ce-Co indicating that the degradation of toluene might proceed more readily. Microwave absorption properties were first used tentatively to study the effect of "hot spots" induced by microwave radiation on catalytic oxidation of VOCs. Further, physicochemical properties of samples were also showed by XRD, SEM and XPS profiles to study oxidation activities of toluene. The maximum difference of toluene oxidation between no water and in water using 5% Ce-Co at 210 ℃ was only 3.06% manifesting that effects of moisture on activities were weak under microwave radiation. A possible degradation track using microwave heating was presented by the analysis of reaction byproducts using the GC–MS.