Promotion effect of tungsten on the activity of Pt/HZSM-5 for H2-SCR

• The H2-SCR activity of Pt/HZSM-5 with low Pt loading was significantly improved by W.
• It was found that W is favorable for Pt presenting its metallic state in the catalyst.
• It is proposed that W inhibits the unfavorable nitrate species formation on Pt.
• It is proposed that W accelerates the dissociation of NO on Pt surface.

Pt/HZSM-5 modified by W was studied in the selective catalytic reduction of NOx by hydrogen (H2-SCR). A maximum NOx conversion of 91.1% with N2 selectivity of 74.2% was achieved over 0.1 wt.%Pt–1 wt.%W/HZSM-5 at 110 °C for the feed gas mixture 910 ppm NO, 90 ppm NO2, 5000 ppm H2, 10% O2 in N2 at gas hourly space velocity 36,000 h−1. It was found that the interaction between Pt and W is favorable for Pt presenting metallic state in the catalyst. Due to the strong interaction, the dissociation of NO and H2 on Pt was significantly accelerated and the formation of unfavorable nitrate species was effectively suppressed. As a consequence, the H2-SCR activity and N2 selectivity were greatly promoted by W doping the Pt/HZSM-5 catalysts.

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