Removal of benzene by non-thermal plasma catalysis over manganese oxides through a facile synthesis method.

Three manganese oxide catalysts (MnO) were synthesized via a simple method, and then they were introduced into the non-thermal plasma (NTP) system for benzene removal. The XRD and EXAFS results showed the MnO were mainly in the MnO phase, and from the analysis of N adsorption/desorption isotherms, we knew the MnO calcined at 250 °C (Mn250) had the largest surface area of 274.5 m g. Besides, Mn250 also exerted higher benzene adsorption capacity (0.430 mmol g) according to CH-TPD. O-TPD indicated that Mn250 showed better oxygen mobility than Mn300. Moreover, by analyzing XPS results, it revealed that Mn250 exhibited rich abundant of surface adsorbed oxygen species (O) and moderate ratio of Mn/Mn, and the reducibility temperature was also the lowest among all the MnO catalysts drawn by H-TPR profiles. As a result, Mn250 combined with NTP could remove 96.9% of benzene at a low input power of 3 W (benzene concentration 200 ppm, and GHSV 60,000 mL g h), performing the best catalytic activity among the three catalysts and plasma only. Furthermore, the "NTP + Mn250" system also produced the highest CO concentration and lowest CO concentration in downstream, and the residual O after catalytic reaction was also the lowest, that is to say, the synergistic effect between NTP and Mn250 was more effective than other catalysts in benzene removal. Graphical abstract.