Selective Catalytic Reduction Of No_x By H₂ Over Pt/SiO₂@TiO₂?ZrO₂? Catalyst

The selective catalytic reduction of NO,(H2-SCR)by hydrogen has attracted more and more attention.Pt and Pd based catalysts are active in the H2-SCR of NO,.In the present study,the performance of Pt/SiO2@TiO2(ZrO2)catalyst on H2-SCR has been investigated.In view of the fact that the activity of Pt/SiO2@TiO2 is significantly higher than that of Pt/TiO2.The coating amount of TiO2(Ti/Si=1:3.5,1:5,1:7.5,1:10)is systematically studied in this study.And it was found that the optimumn Ti/Si molar ratio is 1:5,over which catalyst the NOx conversion was over 80%at 75-200?.and the N2 selectivity is also increased by 30%compared with that of Pt/SiO2.The XRD,XPS and IR spectra of CO adsorption showed that the interaction between Pt-Ti leads to increased content of Pt1 on the catalyst surface and improved dispersion of Pt.In situ IR analysis showed that the coating of Ti increased the content of Bronsted acid on the surface of SiO2,which contributes to the generation of NH4+,thus promoting the generation of N2.On the basis of the study of Pt/SiO2@TiO2,the effect of the coating amount of ZrO2(Zr/Si=1:5,1:10,1:15)on the catalytic activity of Pt/SiO2@ZrO2 was also studied.The results showed that the catalyst with Zr/Si=1:10 showed the highest activity and the N2 selectivity is also significantly increased.The XRD,XPS,IR spectra of CO adsorption showed that amorphous ZrO2 is present on SiO2,and the electron transfer between Si and Zr was beneficial to enhancing the oxidation and redox property of the catalyst.In addition,the interaction between Pt and Zr enhanced the Pt0 content and its dispersion on the surface of the support,thus improving the activity and selectivity of the catalyst.The addition of Zr enhanced the surface acidity and NO+O2 adsorption ability of the catalyst,which promotes the activation of the reactants.As a result,the N2 selectivity of the catalyst is increased.