Insight into the role of Si/Al of MCM-41 zeolite in non-thermal plasma-assisted catalytic oxidation of toluene over bimetal Nb-Mn supported on MCM-41

This study explored how the Si/Al ratio in Nb-Mn/MCM-41 catalysts affect toluene degradation via plasma catalysis. Adjusting the Si/Al ratio altered catalyst acidity and redox properties, decreasing the Si/Al ratio led to increased acidity, higher Mn 3+ /Mn 4+ ratio and greater O ads /O lat ratio as indicated by NH 3 -TPD, XPS, and O 2 -TPD analysis. Lower Si/Al (Nb-Mn/M(25)) boosted toluene removal efficiency to 98.2% under dry conditions due to increased oxygen vacancies and acidity. Moderate humidity enhanced conversion, but higher humidity levels proved detrimental, especially for low Si/Al catalysts. At a humidity level of 3.11 vol%, the toluene removal efficiency of Nb-Mn/M(25) exhibited a reduction of 15.3%, while Nb-Mn/M(200) with higher Si/Al ratio decreased only by 3%. Hydrophobic, higher Si/Al catalysts showed better resistance to humidity's negative impact. These findings offered insights into designing efficient catalysts for VOC removal by optimized Si/Al ratio and managing humidity.