An investigation on N2O formation route over Pt/HY in H2-SCR

• N2 selectivity exhibits a “volcano” shape with the increase of O2 and NO2 concentration in H2-SCR over Pt/HY.
• N2O formation being influenced by O2 and NO2 at Pt-support interface is proposed to be different from that on Pt surface.
• The reduction of nitrous species by spillover H at the Pt-support interface mainly produces N2O.
• Two N2O formation routes on Pt surface and at the Pt-support interface are proposed.

Selective catalytic reduction of NOx by H2 (H2-SCR) was investigated in feed gas mixture of 1000 ppm NOx, 5000 ppm H2, 0–20% O2 in N2 with GHSV of 32,000 h−1 over Pt/HY catalyst. It was found that the N2 selectivity exhibits a “volcano” shape versus the concentration of O2 and NO2, and the change pattern of N2 selectivity were determined by both of them. It is suggested that the nitrous species at the Pt-support interface being taken part in the reaction in scale is determined by the amount of H(ad) migrated there by spillover, and the reduction of them mainly produces N2O. The suggestion is strongly supported by FTIR and the relationship that more nitrous species reduction at the Pt-support interface led to lower N2 selectivity in the H2-SCR, respectively. It is proposed that when the amount of H(ad) is insufficient for reducing the nitrous species to N2 on Pt surface, increasing O2 and NO2 in the feed gas must lead to the H(ad) further decreasing, and hence cause more N2O formation there. On the other hand, the H spillover due to overmany H(ad) on Pt surface must be suppressed by increasing O2 and NO2.

N2 and N2O formation routes on Pt surface and at Pt–HY interface.Figure optionsDownload as PowerPoint slide