Selective catalytic reduction

About: Selective catalytic reduction is a research topic. Over the lifetime, 10502 publications have been published within this topic receiving 226291 citations.

NOx-Reduction in Diesel Exhaust Gas with Urea and Selective Catalytic Reduction

Abstract: High values of NOx reduction may be obtained with urea as a reducing agent and a standard SCR catalyst based on TiO2-WO3-V2O5. The process was carefully investigated for possible secondary emissions and it could be shown that urea-SCR does not lead to relevant emissions of nitrogen dioxide, nitrous oxide, hydrogen cyanide and isocyanic acid. Further investigations using a HPLC method have also proved that addition compounds of higher molecular mass than urea (and urea itself) are not emitted in appreciable amounts as long as the process is properly managed, i.e., as long as the emission of ammonia is kept low. The limiting secondary emission is ammonia slip, the major problem when ammonia is used directly as a reducing agent.

Selective catalytic reduction of nitrogen oxides by combining a non-thermal plasma and a V2O5-WO3/TiO2 catalyst

Abstract: The selective catalytic reduction (SCR) of nitrogen oxides (NOx) by a combination of dielectric barrier discharge plasma and a monolithic V2O5-WO3/TiO2 catalyst using ammonia as a reducing agent was studied in synthetic gas mixtures at temperatures between 100 and 250°C. The mixtures were similar to diesel exhaust gases. For gas mixtures (NOx,0=NH3,0=500 ppm) in which 95% of the nitrogen oxides were in the form of NO, the removal of NOx below 140°C without plasma treatment was negligible. Treating the gas mixture with dielectric barrier discharges before the catalytic conversion, about 70% of the NOx was reduced at temperatures as low as 100°C. By plasma treatment 170 ppm of the NO was converted, 110 ppm by oxidation to NO2 and 60 ppm by reduction with products of NH3. Due to the coexistence of NO and NO2 on the catalyst, the selective catalytic reduction was enhanced. Similar effects were observed for the selective catalytic reduction in gas mixtures containing equal amounts of NO and NO2 without plasma treatment. Relative reaction rates for different NOx-reducing reactions over the catalyst are evaluated using a macroscopic model.