The effect of zirconia additive on the activity and structure stability of V2O5/WO3-TiO2 ammonia SCR catalysts

The NH3-SCR activities of zirconia containing V2O5/WO3-TiO2 catalysts have been studied before and after aging treatment. On fresh catalysts, the addition of zirconia increases high temperature activity and N2 selectivity but decreases low temperature activity. Interestingly, zirconia prominently enhances the NH3-SCR activities of aged catalysts, with 10 wt% ZrO2 containing catalyst exhibits the highest NO conversions and N2 selectivity in the temperature range of 150–550 °C. The catalysts were characterized by XRD, SEM, XPS, DRIFTS and NH3-TPD. SCR kinetic studies were also conducted to understand the mechanistic features of the zirconia modified catalysts. The main results show that the addition of zirconia inhibits the shrinking of catalyst surface area and the growth of TiO2 crystallite size, and therefore improves the thermal stability of V2O5/WO3-TiO2 catalysts. These advantages of zirconia additive can essentially benefit the catalysts performance with high temperature durability.

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► ZrO2 improves thermal stability and activity of aged V2O5/WO3-TiO2 SCR catalyst.
► This durability results from diffusion barriers by ZrO2 and ZrxTi1−xO2 formation.
► Increased surface acid strength by ZrO2 contributes to high temperature SCR activity.
► Kinetic study shows ZrO2 does not change reaction mechanism of V2O5/WO3-TiO2 catalyst.