The Cah <sub> 2 </ Sub> Mn-zsm-5 Catalyst Modified C, <sub> 2 </ Sub> H-<sub> 4 </ Sub> Select Restore No Activity

The removal of nitrogen oxides is a serious environmental problem need to be solved. Recently, the selective catalytic reduction of nitrogen oxides with hydrocarbons is considered to be one of the most potential method to remove nitrogen oxides after the NH₃-SCR process and the three way catalysts. The literature reported more about the zeolite catalysts which was prepared by the ion-exchanged or the impregnation method. Moreover, as the pure zeolite catalysts have some defects, they also have been modified by the addition of co-ion or the promoter.On the basis of laboratory's early work, we mixed the CaH₂ with M-ZSM-5 (M=Cu, Mn,Ni,Ag,Co,Fe)which was prepared by impregnation , the CaH₂ was used as promoter and the ethylene was used as reducing agent. The influence of the addition of CaH₂ was investigated on the selective catalytic reduction of NO with ethylene. It was found that the CaH₂ made the NO conversion on Mn-ZSM-5 much higher than the other catalysts. The effect of the pretreated temperature , GHSV, the proportion of CaH₂ , the concentration of C₂H₄ and O₂ was investigated over Mn-ZSM-5/CaH₂, the stability of Mn-ZSM-5/10%CaH₂ was also investigated. It showed that the activity of Mn-ZSM-5/10%CaH₂ which was pretreated at 400 ℃ was high even at the GHSV=24000 h^-1. The Mn-ZSM-5/10%CaH₂ also had the good stability.The XRD suggested that the calcium not only responsed with the silicon and oxygen in the zeolite, But also responsed with the activated manganese and produced the new compound, eg Ca₃SiO₅, Ca₂Mn₃O₈ and the compound composed of Ca, Mn, Si, O. The TG showed the temperature range of the new compound creation. The TPD showed that the addition of CaH₂ changed the distribution of the acid sites and increased the activity of Mn-ZSM-5/10%CaH₂ in high temperature.