Catalytic reduction of nitric oxide with methane over the perovskite-type catalysts

摘要

A catalyst with the highest activity is selected from four series of perovskites for reducing NO with CH4 as a reducing agent. The influencing factors on catalytic activities are also closely examined by characterizing the perovskites by NO-TPD, CH4-TPR, and by investigating the effect of reactant concentrations. Experimental results indicate that the LaMnO3 catalyst has the highest activity. Also, substituting La with Sr decreases the activity in all four series catalysts. The result of NO-TPD experiment reveals that the NO adsorption is an influencing factor in this catalytic reduction reaction. The strongly adsorbed NO on the surface inhibits the reduction of the catalyst by CH4 and forces this reaction to take place at a higher temperature. The CH4-TPR reveals that the lattice oxygen delivery and CO2 desorption from catalyst are two other factors affecting the activity. The ease of lattice oxygen delivery and CO2 desorption will benefit the reduction of the catalyst by CH4 and hence produce more oxygen vacancies for the catalyst to react with NO. Basing on the above explanation and the results of the investigation on the effect of reactant concentrations, we propose that the reduction by CH4 is the first step in this NO + CH4 reaction and the CO2 desorption is the rate-determining step at a higher temperature range. [References: 29]