Contributions of photocatalytic/catalytic activities of TiO2 and γ-Al2O3 in nonthermal plasma on oxidation of acetaldehyde and CO

The effects of photocatalysis and thermocatalysis in surface discharge type plasma reactors combined with TiO2- and Al2O3-based catalysts were analyzed. The photocatalytic decomposition of acetaldehyde was not observed although the TiO2 absorbed the UV light (300 < λ < 380 nm) emitted from N2 plasma. The intensity of UV emission from plasma decreased with increasing O2 concentration. In atmospheric air, the photocatalytic decomposition rate by UV light of plasma is lower than 0.2% of the decomposition rate by the plasma itself. The coating of γ-Al2O3 on the inside wall of plasma reactor improved the oxidation rate for CO by a factor of 3.5, while TiO2 improved by only a factor of 1.8, compared with the bare plasma reactor. The high activity of Al2O3 seems to be due to the active oxygen species produced by the O3 decomposition.

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