Toluene Degradation by Thermal Catalytic Oxidation over K-OMS-2 Catalysts

Abstract:

The goal of this research was to synthesize two different catalysts, namely K-OMS-2 and MnO_x. The K-OMS-2 was an octahedral manganese complex prepared by hydrothermal method, while manganese oxide (MnO_x) was directly synthesized by precipitation method. Both catalysts were employed to decompose toluene, an organic solvent that is widely used in industries. The catalysts were characterized by means of X-ray diffraction (XRD) and N₂-physorption. The surface areas of K-OMS-2 and MnO_x were 83.50 and 20.04 m²/g, respectively. The precipitation route gave XRD patterns of γ-Mn₂O₃ structure_, and a successful structure of an octahedral molecular sieve manganese oxide was obtained by the hydrothermal method. The toluene degradation was carried out in gas hourly space velocity (GHSV) range of 20,000-60,000 h^-1 with toluene concentration of 7,700 ppmv. The higher GHSV over K-OMS-2 gave the lower contact time consequently resulting in the lower %toluene degradation, whereas the best GHSV over γ-Mn₂O₃ was suitable at 40,000 h^-1. The complete oxidation temperature of toluene over K-OMS-2 occurred at 260 °C and was lower than the temperature by γ-Mn₂O₃ at 300 °C. The higher surface area of K-OMS-2 may not facilitate internal toluene diffusion to active K-OMS-2 sites because molecular toluene (5.6 Å) cannot migrate through its smaller pore diameter (4.6 Å); however, the fully oxidized K-OMS-2 can provide higher average oxidation state (AOS) and higher amount of lattice oxygen assisting toluene degradation compared to γ-Mn₂O₃. The full factorial design of experiment (DOE) exhibited a strong effect of temperature and catalyst types on toluene removal; in contrast gas hour space velocity (GHSV) exhibited no significant effect on %toluene removal even with increasing GHSV.

• Periodical: Advanced Materials Research (Volumes 931-932)
• Pages: 22-26
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.931-932.22
• Online since: May 2014
• Authors: Patiparn Boonruam, Sutasinee Neramittagapong*, Arthit Neramittagapong, Kitirote Wantala
• Keywords: Catalytic Oxidation, Full Factorial Design (FFD), Hydrothermal Method, K-OMS-2, Toluene

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