The Role of Surface Reactions in De-NOx Processes in Corona Discharge-Catalyst (or Zeolite) Hybrid Systems

摘要

The objective of this work was to explain the efficient NO_X removal from simulated flue gas observed in the hybrid corona discharge-catalyst hybrid systems with either V_2O_5/TiO_2 catalyst or zeolite,both at room temperature.The simulated flue gas was a mixture of N_2 (80%):O_2 (5%):CO_2 (15%):NO (200 ppm).After analysing the results of several experiments on NO_X removal in the corona discharge-catalyst (or zeolite) systems,two different mechanisms of NO_X conversion in the hybrid systems are proposed.In the positive corona discharge-catalyst system,NO_X molecules are removed due to the activation of the catalyst surface by the corona discharge (TiO_2+epsilon (>=3.2 eV) -> hole~++e),which is followed by:(a) the catalyst surface driven formation of NH_2 radicals (which reduce NO_X into N_2 in gas phase) and H~+ (or NH_4~+) ions,(b) the oxidation of NO_X to surface-trapped NO_3~-.The NO_3~- ions trapped on the catalyst surface are precursors of the formation of NH_4NO_3 aerosols depositing on the catalyst surface.In the corona discharge-zeolite system,the conversion of NO_X into NH_4NO_3,N_2 and H_2O occurs due to the reactions involving zeolite-fixed NH_4~+ ions.