Experimental study on the oxidation of model gases-propylene, N-butane, acetylene at ambient temperature by non-thermal plasma and photocatalyst

Two features to facilitate chemical reactions at low temperature, non-thermal plasma and the weak dependency of photocatalyst on temperature, have been exploited by many researchers to effectively decompose hydrocarbon emissions emitted until the light-off of a three-way catalyst in spark ignition engines. To develop a realizable emissions reduction reactor, as part of such effort, this study investigates for the three model gases, propylene, n-butane and acetylene: 1) the conversion efficiency of the emissions reduction reactor, which utilizes the effect of dissociation, ionization-by-collision of the non-thermal plasma and the photocatalytic effect of TiO₂, and 2) the concentrations of the products such as acetaldehyde, acetic acid, polymerized hydrocarbons and NO₂. The operating parameters to obtain the plasma energy density ranging from 7.8 to 908 J/L were varied. When it comes to the plasma system, propylene, chemically the most active, showed the highest conversion efficiency in proportion to the energy density applied to the plasma system. The other two model gases showed relatively low but substantial conversion efficiency for the energy density above 190 J/L. Among photo-catalytic candidates, TiO₂ supported on alumina processed by sol-gel technique was found to be most effective. The resulting conversion efficiency of Total HC reached up to 71% for the reference condition of 2117ppmC1 at 302 J/L