Roles of NOx on the formation and the removal of an intermediate of the NOx reduction by hydrocarbons on zeolite catalysts

Abstract

Temperature programmed oxidation (TPO) has been used to investigate the role of nitrogen oxide on the catalytic reduction of nitric oxide over zeolite catalyst. The result shows that propene produced the intermediates on HY, HM, HZSM-5, Cu- ZSM-5 less than toluene and the intermediates formed from toluene is “harder” than the intermediate formed from propene. The amount of carbon formed on catalyst were HM>Cu-ZSM-5>HY~H-ZSM-5, respectively. It can be suggested that the nature of the intermediates depend on type of hydrocarbon and type of catalyst. It was obvious that the effect of time greatly affected the amount of the intermediates. However, the greater accumulation was occurred on the selective catalytic reduction of nitrogen oxide over Cu-ZSM-5 by propene and toluene. Additionally, the oxidizing gas mixture of nitrogen oxide and oxygen in helium can remove effectively the intermediates on Cu-ZSM-5. By considering the formation and the removal of the intermediates on the zeolite catalysts, it was found that NO2 play a crucial role in forming and removing intermediates. NO2 affect the high amount of intermediates and the removal the intermediates at lower temperature.