A Hybrid Reactor System Comprised of Non-Thermal Plasma and Mn/Natural Zeolite for the Removal of Acetaldehyde from Food Waste

Synthesis and Application of Zeolite Catalysts

Zeolites play a central role in many industrial and chemical engineering processes involving solid catalysts, which have attracted a great deal of attention from chemists, chemical engineers, and materials scientists due to their fascinating features [...]

Recent advances in volatile organic compounds abatement by catalysis and catalytic hybrid processes: A critical review

Air pollution, particularly for toxic and harmful compounds to humans and the environment, has aroused increasing public concerns. Among air pollutants, volatile organic compounds (VOCs) are the main sources of air pollution. Many attempts have been made to control VOCs using catalysts, plasma, photolysis, and adsorption. Among them, oxidative catalysis by noble metals or transition metal oxides is considered one of the most feasible and effective methods to control VOCs. This paper reviews the experimental achievements on the abatement of VOCs using noble metals, transition metals and modified metal oxide catalysts. Although the catalytic degradation of VOCs appears to be feasible, there are unavoidable problems when only catalysis treatments are applied to the field. Therefore, catalysts including hybrid processes are developed to improve the removal efficiency of VOCs. This review addresses new hybrid treatments to remove VOCs using catalysts, including hybrid treatment combined with plasma, photolysis, and adsorption. The mechanism of the oxidation of VOCs by catalysts is explained by adsorption-desorption principles, such as the Langmuir-Hinshelwood, Eley-Rideal, and Mars-van-Krevelen mechanisms. A π-backbonding interaction between unsaturated compounds and transition metals is introduced to better understand the mechanism of VOC removals. Finally, several factors affecting the catalytic activities, such as support, component ratio, preparation method, metal loading, and deactivation factor, are discussed.

Removal of toluene using ozone at room temperature over mesoporous Mn/Al2O3 catalysts

The catalytic oxidation of toluene with ozone at room temperature was carried out over hierarchically ordered mesoporous catalysts (CeO₂ (meso), Mn₂O₃ (meso), ZrO₂ (meso), and γ-Al₂O₃ (meso)) and Al₂O₃ with various textural properties and phases (γ-Al₂O₃ (meso), γ-Al₂O₃ (13 nm), and α-Al₂O₃) to examine the effects of the nature of the catalyst on the catalytic activity. The catalysts were characterized by N₂-physisorption measurements, powder X-ray diffraction, temperature programmed reduction, X-ray photoelectron spectroscopy and scanning transmission electron microscopy with energy dispersive spectroscopy. Among the ordered mesoporous catalysts, γ-Al₂O₃ (meso) had the highest toluene removal efficiency because of its highest surface area and pore volume, which in turn was selected for further investigation. Manganese (Mn) was introduced to various Al₂O₃ to improve the toluene removal efficiency. Comparing the Mn-loaded catalysts supported on various Al₂O₃ with different crystalline phases or pore structures, Mn/γ-Al₂O₃ (meso), had the highest catalytic activity as well as the highest CO₂/CO ratio. The higher activity was attributed to the larger surface area, weaker interaction between Mn and Al₂O₃, and larger portion of Mn₂O₃ phase. The increase in ozone concentration led to an improvement in the carbon balance but this enhancement was insufficient due to the deposition of by-products on the catalyst. After long term tests at room temperature, the reaction intermediates and carbonaceous deposits of the used catalysts were identified.