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XANES and DRIFTS study of sulfated Sb/V/Ce/TiO<sub>2</sub> catalysts for NH<sub>3</sub>-SCR
Kumar, Pullur Anil,Jeong, Young Eun,Gautam, Sanjeev,Ha, Heon Phil,Lee, Kyung Ju,Chae, Keun Hwa Elsevier 2015 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.275 No.-
<P><B>Abstract</B></P> <P>A study of structural and mechanistic investigation of the Sb/V/Ce/Ti catalysts sulfated at different temperatures was carried out by X-ray absorption near edge spectroscopy (XANES) and diffused reflectance infrared Fourier transformed spectroscopy (DRIFTS). The high temperature sulfated catalyst, especially Sb/V/Ce/Ti-S500 (sulfated at 500°C temperatures), exhibited superior NO<I> <SUB>x</SUB> </I> conversion at low temperatures (150–200°C) compared to Sb/V/Ce/Ti-S400 and Sb/V/Ce/Ti-S300 (sulfated at 400 and 300°C) catalysts. The Ce L<SUB>3</SUB> edge XANES spectra of Sb/V/Ce/Ti-S500 catalyst showed the formation of Ce(III) dominant sulfate species, resulting in the enhancement of Lewis and Brønsted acid strength. The formation of Ce(III) sulfate species on Sb/V/Ce/Ti-S500 catalyst was clearly indicated by Ce M<SUB>4,5</SUB> and S K edge XANES spectra peaks at 881.9eV attributed to Ce<SUP>3+</SUP> oxidation state and 2481eV assigned to S<SUP>6+</SUP> oxidation state of sulfate species. Furthermore, the in situ DRIFTS results revealed that the Lewis and Brønsted acid sites of Sb/V/Ce/Ti-S500 catalysts increased significantly, followed by Sb/V/Ce/Ti-S400 and Sb/V/Ce/Ti-S300. At 200°C, the reaction between the pre-adsorbed NH<SUB>3</SUB> species with NO+O<SUB>2</SUB> on sulfated catalysts exhibited the formation of mono-dentate, bi-dentate, bridging nitrates and NO<SUB>2</SUB> species. Meanwhile, the subsequent formation of NO<SUB>2</SUB> via NO oxidation was promoted on Sb/V/Ce/Ti-S400 and Sb/V/Ce/Ti-S500 catalysts, followed by surface interaction with adsorbed NH<SUB>3</SUB> to produce N<SUB>2</SUB> and H<SUB>2</SUB>O at low temperatures (<220°C).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sb/V/Ce/Ti catalysts sulfated at 500°C achieved superior NO<I> <SUB>x</SUB> </I> conversion ⩽220°C. </LI> <LI> XANES spectra of Sb/V/Ce/Ti catalysts sulfated at 500°C revealed the formation of more active Ce<SUP>3+</SUP> species. </LI> <LI> The formation of more abundant Lewis and Brønsted acid sites on Sb/V/Ce/Ti catalysts achieved by high temperature sulfation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( Pullur Anil Kumar ),하헌필 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
The Ceria based transition metal oxide catalysts for NOx reduction with NH<sub>3</sub> were synthesized by homogeneous precipitation by urea. All the catalysts showed high BET-surface area and better dispersion of transition metal oxide species. Surface acidity and reducibility of the prepared catalysts are crucial for a NOx reduction at wide temperatures (low to high). The catalysts were characterized by XRD, BET-surface area, NH<sub>3</sub>-TPD, H<sub>2</sub>-TPR, SEM and XPS. NOx conversion was evaluated at different temperatures in the presence of 3 vol% O<sub>2</sub>, H<sub>2</sub>O and SO<sub>2</sub>.
( Pullur Anil Kumar ),정영은,권동욱,이소민,김동호,김종식,하헌필 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
Herein, we discussed NOX reduction performance of Sb-V-CeO<sub>2</sub>/TiO<sub>2</sub> (SbVCT) catalysts subjected to hydrothermal aging, where 6 vol. % of H<sub>2</sub>O was fed to the SbVCT for 16 hours with variable temperatures of 550-750 °C. The fresh and aged SbVCT catalysts were characterized using XRD, TEM, Raman, N<sub>2</sub> physisorption, NH<sub>3</sub>-TPD, H<sub>2</sub>-TPR, and in situ NH<sub>3</sub>-DRIFT. The SbVCT catalysts aged at ≤ 600 °C showed better NOX conversions than the others aged at > 600 °C. This was because aging at ≤ 600 °C could help minimize the loss of surface redox/acid characters that were originally inherent to surface vanadyl and CeO<sub>2</sub> species for the SbVCT prior to aging process. In contrast, aging of the SbVCT at ≥ 650 °C led to the transformation of surface vanadyl and CeO<sub>2</sub> species into CeVO<sub>4</sub> and large CeO<sub>2</sub> aggregates. This in turn led to the loss of surface redox/acid characters indigenous to the SbVCT and reduced its NOX reduction performance.
Nd promoted Vanadia-Ceria catalysts for low temperature NH₃-SCR
최현,하헌필,( Pullur Anil Kumar ),정영은,( Danh Thi Huong ),이관영 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
Composite catalysts by doping Nd into vanadia-ceria are prepared to obtain further improved catalytic properties by homogeneous precipitation method using urea as a precipitation agent which exhibits high NOx conversion at 150-400C. The results showed that the Nd help to increase the activity of vanadia-ceria for NH₃- SCR, The SCR mechanism is investigated through various characterizations, such as XRD, BET-SA,XPS, NH₃- TPD, H₂- TPD and FE-SEM.