The byproducts of ammonia-selective catalytic reduction (NH3-SCR) process over MnFe/TiO 2 catalysts under the conditions of both with and without SO 2 poisoning were analyzed. In addition to the NH 3 -SCR reaction, the NH 3 oxidation and the NO oxidation reactions were also evaluated at temperatures of 100-300 C to clarify the reactions occurred during the SCR process. The results indicated that major byproducts for the NH 3 oxidation and NO oxidation tests were N 2 O and NO 2 , respectively, and their concentrations increased as the reaction temperature increased. For the NH 3 -SCR test without the presence of SO 2 , it revealed that N 2 O was majorly from the NH3-SCR reaction instead of from NH 3 oxidation reaction. The byproducts of N 2 O and NO 2 for the NH 3 -SCR reaction also increased after increasing the reaction temperature, which caused the decreasing of N 2 -selectivity and NO consumption. For the NH 3 -SCR test with SO 2 at 150 C, there were two decay stages during SO 2 poisoning. The ﬁrst decay was due to a certain amount of NH 3 preferably reacted with SO 2 instead of with NO or O 2 . Then the catalysts were accumulated with metal sulfates and ammonium salts, which caused the second decay of NO conversion. The efﬂuent N 2 O increased as poisoning time increased, which was majorly from oxidation of unreacted NH 3 . On the other hand, for the NH3-SCR test with SO 2 at 300 C, the NO conversion was not decreased after increasing the poisoning time, but the N 2 O byproduct concentration was high. However, the SO 2 led to the formation of metal sulfates, which might inhibit NO oxidation reactions and cause the concentration of N 2 O gradually decreased as well as the N 2 -selectivity increased.
- Low-temperature catalyst
- Nitrogen oxides
- Nitrous oxid
- SO poisoning
- Selective Catalytic Reduction (SCR)