Insight into the promotional effect of NO2 on toluene oxidation over MnCe/HZSM-5 catalyst

A thorough probe into the activation mechanism of NO2 on toluene oxidation during co-removal of toluene in NH3-SCR unit is imperative but still lacking. This study unraveled the promotional effects of NO2 on toluene conversion, CO2 selectivity and catalytic stability over a MnCe/HZSM-5 catalyst. 1000 ppm NO2 was sufficient for complete oxidation of 50 ppm toluene into CO2 at 280 ? in the absence of O-2 (C7H8 + 18NO(2) & RARR; 7CO(2) + 4H(2)O + 18NO). NO2 had stronger oxidizing ability than O-2, while O-2 re-oxidized NO to NO2, resulting in a synergistic contribution to toluene conversion. NO2 participated in toluene oxidation producing predominant NO and negligible organic N-byproducts. The N in NO2 scarcely took part in the organic synthesis process. NO2 gave one of its O easily to provide additional O-sur and improved mobility and activity of O-lat, hence speeding up the re-oxidation of reduced metal sites. The activation of NO2 on toluene oxidation predominantly followed Mars-van Krevelen mechanism. The Langmuir-Hinshelwood mechanism also existed but was less important.

Automated summary

This study reveals the promotional effects of NO2 on toluene oxidation, including improved toluene conversion, CO2 selectivity, and catalytic stability. NO2 exhibits stronger oxidizing ability and synergistic contribution with O2. NO2 mainly produces NO during toluene oxidation, while the nitrogen in NO2 is barely involved in the organic synthesis process.