Contributions of photocatalytic/catalytic activities of TiO 2 and γ-Al 2O 3 in nonthermal plasma on oxidation of acetaldehyde and CO

Abstract

The effects of photocatalysis and thermocatalysis in surface discharge type plasma reactors combined with TiO 2- and Al 2O 3-based catalysts were analyzed. The photocatalytic decomposition of acetaldehyde was not observed although the TiO 2 absorbed the UV light (300 < λ < 380 nm) emitted from N 2 plasma. The intensity of UV emission from plasma decreased with increasing O 2 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-Al 2O 3 on the inside wall of plasma reactor improved the oxidation rate for CO by a factor of 3.5, while TiO 2 improved by only a factor of 1.8, compared with the bare plasma reactor. The high activity of Al 2O 3 seems to be due to the active oxygen species produced by the O 3 decomposition.