The influence of molar ratios of Ce/Zr on the selective catalytic reduction of NOx with NH3 over Fe2O3-WO3/CexZrl-xO2 （0 〈 x 〈 1） monolith catalyst

A series of CexZrl_xO2 （0 ≤ x ≤ 1） with dif- ferent molar ratios of Ce/Zr were syhthesized via coprecip- itation method, and Fe2O3-WO3/CexZrl-xO2 monolithic catalysts were prepared, for selective catalytic reduction of nitrogen oxides by ammonia （NH3-SCR）. The structural properties and redox behavior of the catalysts were com- prehensively characterized by N2 physisorption, X-ray diffraction （XRD）, X-ray photoelectron spectra （XPS）, H2-temperature programmed reduction （H2-TPR） and activity measurement for NH3-SCR. The results showed that the NH3-SCR activities of the catalysts were gradually enhanced by increasing the molar ratios of Ce/Zr, especially the low- temperature catalytic activity and the reaction temperature window. Fe2O3-WO3/Ceo.68Zro.3202 monolithic catalyst presented the best NH3-SCR activity among the investigated catalysts, more than 90 % NOx could be removed in the temperature range of 247-454 ℃ on the catalyst under the gas hourly space velocities of 30,000 h- 1. And it always held more than 99 % N2 selectivity and less than 20 ppm （1 ppm =10-6 L/L ） N20 generation concentration between 200 and 500 ℃, the catalyst also displayed its strong resistance of H20 and SO2. Good textural and structural properties, more surface Fe, Ce and active oxygen were together contributed to the excellent NH3-SCR performance of Fe2O3-WO3/ Ce0.68Zr0.32O2 catalyst.