Recently, various promoters for commercial selective catalytic reduction (SCR) catalysts are used to improve DeNOx activity at low temperature. We aimed at finding the optimum condition to prepare V2O5/TiO2 catalyst by changing promoters (W, Ce, Zr and Mn), not only for improving SCR reactivity, but also for reducing N2O formation at high temperature. In addition, we changed the order of impregnation between promoter and vanadium precursors on TiO2 support and observed its effect on activity and N2O selectivity. We utilized various analytical techniques, such as N2 adsorption-desorption, X-ray Diffraction (XRD), Raman spectroscopy, UV-visible Diffuse Reflectance Spectroscopy (UV-vis DRS) and Temperature Programmed Reduction with hydrogen (H2-TPR) to investigate the physicochemical properties of V2O5/TiO2 catalysts. It was found that W and Ce added V2O5/TiO2 catalysts showed the most active DeNOx properties at low temperature. Additionally, the difference in impregnation order affected the SCR activity. The superiority of low temperature activity of the vanadium firstly added catalysts (W or Ce/V/TiO2) is attributed to the formation of more polymerized V2O5 on the sample.
Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.
W and Ce are known to be a good promoters to improve selective catalytic reduction (SCR) activity for V2O5/TiO2catalysts. This work aimed at finding the optimum ratio and loading of promoters (W and Ce) on V2O5/TiO2catalyst in order to improve SCR reactivity in low temperature region and to minimize N2O formation in high temperature region. In addition, we changed the order of impregnation between W and Ce precursors on V2O5/TiO2catalyst during the preparation and observed its effect on SCR activity and N2selectivity. We utilized various analytical techniques, such as N2adsorption-desorption, X-ray diffraction (XRD), and temperature-programmed reduction with hydrogen (H2TPR) to investigate the physicochemical properties of catalysts. It was found that W- and Ce-overloaded V2O5/TiO2catalyst such as W/Ce/V/TiO2(15 : 15 : 1 wt%) showed the most remarkable DeNOxproperties over the wide temperature region. Additionally, this catalyst significantly suppressed N2O formation during SCR reaction, especially in high temperature region (350–400°C). Based on the characterization results, it was found that such superior activity originated from the improved reducibility and morphology of W and Ce species on V2O5/TiO2catalyst when they are incorporated together at high loading.
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