Enhanced plasma mineralization of adsorbed toluene by optimization the hybrid support of Ag–Mn catalysts

Effect of zeolite acidity and structure on ozone oxidation of toluene using Ru-Mn loaded zeolites at ambient temperature

Five different Ru-Mn/zeolites were used to investigate their catalytic efficiencies for removing toluene (100 ppm) with ozone (1000 ppm) at room temperature. In general, most of metal oxide catalysts for removal of organic compounds need higher temperature than the ambient temperature, but Mn-based catalysts shows activity for prevalent organic pollutants even at room temperature with ozone. For the removal of toluene at room temperature without further heating, bimetallic Ru added Mn catalysts were applied in combination with different zeolite supports. The catalytic activity of the Ru-Mn catalysts strongly depended on the zeolite, of which the characteristics such as acidity and adsorption degree of toluene are dependent on the ratio of SiO₂/Al₂O₃. Among the five Ru-Mn catalysts used, Ru-Mn/HY (SiO₂/Al₂O₃ ratio: 80) and Ru-Mn/ZSM-5 (SiO₂/Al₂O₃ ratio: 80) had higher toluene and ozone removal efficiencies. The toluene removal efficiency of Ru-Mn/zeolites was proportional to the pore volume and surface area. In terms of ozone degradation, Ru-Mn/HY(80) and Ru-Mn/HZSM-5(80) had the highest removal efficiencies. Overall, the catalytic ozone oxidation of toluene using Ru-Mn/zeolites seemed to be affected by a combination of the acidic properties of zeolites, Mn³⁺/Mn⁴⁺ ratio, and concentration ratio of oxygen vacancies to oxygen lattices on the catalyst surface.

Catalytic ozonation of toluene using Mn-M bimetallic HZSM-5 (M: Fe, Cu, Ru, Ag) catalysts at room temperature

We investigated the catalytic efficiency of Mn-based bimetallic oxides in degrading toluene and ozone at room temperature. The room temperature-active bimetallic oxide catalysts were prepared by the addition of Fe, Cu, Ru, and Ag precursors to Mn/HZSM-5. We obtained H₂-temperature-programmed reduction (H₂-TPR) profiles, X-ray diffraction patterns, and X-ray photoelectron spectra to investigate the characteristics of the prepared catalysts. The catalytic efficiency of Mn-based bimetallic oxide catalysts in degrading toluene and ozone at room temperature was mostly improved by the addition of the secondary metals. The prepared bimetallic oxide catalysts, Cu-Mn/HZSM-5, Fe-Mn/HZSM-5, Ru-Mn/HZSM-5, and Ag-Mn/HZSM-5, enhanced efficiency for toluene removal compared to Mn/HZSM-5. The H₂-TPR profiles of the Mn-based bimetallic oxide catalysts showed stronger and broader adsorption-desorption bands at lower temperatures than the profile of Mn/HZSM-5. Additionally, the ratio of the surface defective oxygen over the lattice oxygen on the bimetallic oxide catalysts was higher than that of Mn-only catalysts; the ratio of Mn³⁺ over Mn⁴⁺ was higher for all bimetallic oxide catalysts, as well. Among the bimetallic oxide catalysts, Ru-Mn/HZSM-5 showed the highest efficiency for the removal of toluene to CO_x due to the synergetic effect of the oxidation state and reducible potential at room temperature.