Plasma catalytic hybrid processes: gas discharge initiation and plasma activation of catalytic processes

Abstract

Catalytic reactions of a gas mixture can efficiently be induced by pre-treatment using a gas discharge plasma or by combined treatment in a plasma catalytic hybrid reactor. The effects of plasma treatment can be excitation of molecules, formation of short lived radicals, formation of long lived intermediate species, emission of UV-radiation, or simply gas heating. By dielectric barrier discharge (DBD) pre-treatment of Diesel engine exhaust selective catalytic reduction (SCR) of nitric oxides on a V 2O 5-WO 3/TiO 2-catalyst could be induced at temperatures as low as 100 °C. Due to the low specific plasma input energy density ε sp of about 10 J/l gas heating does not play a role. Plasma catalytic methane steam reforming using a Ni-catalyst was performed in a dielectric packed bed reactor at temperatures down to 200 °C. Since for reforming ε sp values exceed 1 kJ/l both non-thermal plasma effects and gas heating contribute to the plasma catalytic hybrid process. A review focusing on the plasma-chemical kinetics is given.