Synergistic effect of V2O5-WO3/TiO2 and H-ZSM-5 catalysts prepared by physical mixing on the selective catalytic reduction of NOx with NH3

There are more application areas where catalysts need a high activity for the selective catalytic reduction (SCR) of either NO or NO2 with NH3. V2O5-WO3/TiO2 is a conventional catalyst with high activity for the SCR of NO, while its catalytic performance is significantly low for the SCR of NO2. In this work, a physical mixture of V2O5- WO3/TiO2 catalyst and H-ZSM-5 zeolite (V2O5-WO3/TiO2 + H-ZSM-5; PM) was prepared for the SCR of NOx with NH3. The PM catalyst exhibited similar deNOx efficiency to the V2O5-WO3/TiO2 catalyst in the NH3-SCR of NO. However, in the case of the NH3-SCR of NO2, the PM catalyst showed higher catalytic activities than the V2O5- WO3/TiO2 catalyst, attributed to a higher amount of NO2 and N2O4 adsorption. Also, the PM catalyst produced much less N2O than the H-ZSM-5 catalyst because of less NH4NO3 formed, which is an intermediate of N2O formation. Moreover, the PM catalyst exhibited higher SO2 tolerance than the V2O5-WO3/TiO2 catalyst due to the migration of ammonium bisulfate to the zeolite domain. This study demonstrates the desirable characteristics of PM catalyst, such as high deNOx efficiency, low N2O production, and high SO2 resistance, which are of practical importance to apply for the SCR of either NO or NO2.