Catalytic ozonation of toluene over amorphous Cu-Mn bimetallic oxide: Influencing factors, degradation mechanism and pathways

Herein, amorphous catalysts were employed to investigate the catalytic ozonation system, revealing the degradation mechanism and influencing factors (O-3 concentration, temperature, and humidity) for toluene catalytic ozonation. Cu0.2MnOx exhibited the highest toluene oxidized and excellent stability (similar to 85% at 60 h) based on the suitable value of O-ads/O-lat and potent synergy between Cu with Mn. To explore the effect of factors, the change of fresh and post-reaction samples was compared as revealed in the relevant characterization results (SEM, XRD, BET, XPS, TGA), DRIFTS and GC-MS identified the intermediates and byproducts. The results show that appropriate temperature (100 degrees C) and O-3 concentration (2100 ppm) can effectively enhance the number of reactive oxygen species. Although H2O can increase the production of .OH to promote degradation, it is easier to quench the active sites on the surface of amorphous catalysts. During the reaction, the main role of Cu in Cu-Mn bimetallic oxides is adsorption of toluene and O-3, formation of benzoic acid, and oxidation of short-chain products. As for the adjacent Mn, it works on the cleavage of O-O in O-3 and the ring-opening of benzene. Then, the mainly catalytic ozonation pathway of toluene was proposed and followed the order: toluene, benzoic acid, benzene, maleic anhydride, short-chain carbon species, CO2, and H2O.

Automated summary

In this study, amorphous catalysts were used to investigate the catalytic ozonation system for toluene, revealing the degradation mechanism and influencing factors. The Cu0.2MnOx catalyst showed the highest toluene oxidation rate and excellent stability. Suitable temperature and O-3 concentration effectively enhanced the number of reactive oxygen species. The catalytic ozonation pathway of toluene mainly involved benzoic acid, benzene, maleic anhydride, short-chain carbon species, CO2, and H2O.