Resarch On Selectivly Catalytic Reduction Of NO With Oxygenated Hydrocarbons Over Perovskite-typed Oxides

Rare-earth Perovskite-typed mixed oxides with its excellent redox properties, diversity, good thermal stability and low cost is considered to be the ideal vehicle exhaust catalytic purifying material. Most of the traditional synthetic methods undergoing high-temperature calcination, resulting in larger particles, are not conducive to the improvement of the catalytic activity. In this paper, using citric acid complexation auto-combustion method combined with the high-energy ball milling, in order to obtain a high surface area, high catalytic activity of perovskite. The influence of three milling additives ammonium chloride (NH4Cl), zinc oxide (ZnO), sodium chloride (NaCl) and milling time on the catalytic properties of LaFeO3was inverstigated. The properties and the catalytic activity were studied using of characterization methods XRD, BET, H2-TPR, NO+O2and C3H6-TPD and activity evaluation device. The results showed that NH4Cl as additives got the best-performing LaFeO3, while milling time had marginal effect on the catalyst activity.A series of perovskite LaBO3(B=Mn, Cr, Fe, Co, Ni) was synthesized using this method to screen the catalyst applied to C3H6-SCR, LaFeO3showed the best catalytic performance. Cu2+doping of B site can improve the catalyst activity at low temperatures, improve the selectivity of N2, inhibition of the by-products of NH3, LaFe0.8Cu0.2O3was recognized as the best catalyst for C3H6-SCR of deNOx.The advantages of oxygenated hydrocarbons as reducing agents caused widespread attentions, many researchers have done lots of work about Cu-ZSM-5, Ag/Al2O3and γ-Al2O3. On the selected optimal catalyst LaFe0.8Cu0.2O3of this paper, different reducing agents including CO, NH3, hydrocarbons, oxygenated hydrocarbons were investigated for the selectivly catalytic reduction of NO. The results showed that, alkane, NH3as reducing agents had no advantage, CO, alcohols with terminal-OH group exhibited good catalytic activity, tert-butanol as isomers of butanol showed poor activity. Methanol which almost had no activity in the catalyst of Ag/Al2O3showed good activity in LaFe0.8Cu0.2O3, In-situ DRIFTS investigation was further carried out to explore the catalytic mechanism, the type and amount of adsorbed species of NO and methanol on the catalyst surface are the key factors of the catalytic activity.