Enhancement of SCR activity and SO2 resistance on VOx/TiO2 catalyst by addition of molybdenum

• SO2 resistance improved through inhibition of SO2 and VO reaction.
• Increase of SO2 resistance is associated with reduction in SO2 adsorption.
• SO2 resistance is enhanced for high Mo6+/Mo5+ ratio in VOx/MoOx/TiO2.

VOx/TiO2 is widely used for the selective catalytic reduction (SCR) of NOx with NH3. In the case of using VOx/WOx/TiO2 as a commercial catalyst, these combinations represent appropriate SCR activity. However, they are insufficient to enhance the SO2 resistance. Accordingly, SCR activity and the SO2 resistance evaluated with the addition of promoters such as W and Mo into VOx/TiO2. The properties of the catalysts were studied using physio-chemical analyses, including BET surface area, X-ray diffraction (XRD), Raman spectroscopy, SO2 temperature programmed desorption (SO2-TPD), X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTs). V/3Mo/TiO2-hepta (molybdenum precursor using hepta-molybdate: (NH4)6Mo7O24) prepared by the addition of Mo as the promoter of VOx/TiO2 demonstrated excellent SO2 resistance. The increase of SO2 resistance was found to be due to reduce of SO2 absorption because the inhibiting the reaction of SO2 and VO by the addition of Mo. In addition, SO2 resistance was found to be improved as the amount of SO2 adsorption was reduced. The Mo promoter was confirmed to show enhanced SO2 resistance when the Mo6+/Mo5+ ratio was high.

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