Selective catalytic reduction of NOx by H2 over Na modified Pd/TiO2 catalyst

The effect of alkali metal Na on Pd/TiO2 catalyst for the selective catalytic reduction of NOx by H2 (H2-SCR) has been investigated. Compared with Pd/TiO2 and Na/TiO2, Pd–Na/TiO2 catalyst exhibited much higher catalytic activity and wider activity temperature window. Characterization results showed that more Pd0 and surface chemisorbed oxygen (Oα) existed on Pd0.5Na0.5/Ti than Pd/TiO2. In-situ DRIFTS results showed that more NOx adsorbed and activated on Pd0.5Na0.5/Ti, and these species are reactive. Meanwhile, NH3 species adsorbed on Lewis acid sites was generated by the reaction between NOx and H2, which then reduce NOx by the NH3-SCR route. As a consequence, the reduction of NOx over Pd–Na/TiO2 was significantly improved. Our study provides new insight for developing highly H2-SCR catalyst for the removal of NOx.