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The mechanism of ammonium bisulfate formation and decomposition over V/WTi catalysts for NH3-selective catalytic reduction at various temperature

Abstract

In this work, the mechanism of ammonium bisulfate (ABS) formation and decomposition over V/WTi for NH3-selective catalytic reduction (SCR) at various temperature is deeply investigated. The bridged bidentate, chelating bidentate, and tridentate sulfates bound to TiO2 are formed as dominant intermediates at 200, 250 and 300 ˚C, respectively. These sulfates react with affinitive ammonium species to form ammonium (bi)sulfate species along with the coverage on active sites and embedding VOSO4 intermediates, which results in inferior intrinsic NH3-SCR conversion rate at 200 ˚C and 250 ˚C, respectively. At 300 ˚C, trace amounts of ABS on TiO2 present no influence on NH3-SCR performance. The electrons deviating toward sulfates through the bond between ABS and metal oxides (WO3 and TiO2) weaken the stability of ABS and lower its decomposition temperature, while the vanadia species play an opposite role due to sulfur species existing in an electron saturation state with the formation of VOSO4 intermediate. The presence of NO+O2 could break the bonds inside ABS and react with the ammonium species originated from ABS, which pulls NH3 out of ABS formation equilibrium and accelerates its decomposition and competitively inhibits its formation. Correspondingly, the faster NH3-SCR conversion rate and higher N2 selectivity improve the ABS poisoning resistance of V/WTi catalyst at low temperature.

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Publication details

The article was received on 11 Apr 2017, accepted on 05 May 2017 and first published on 05 May 2017


Article type: Paper
DOI: 10.1039/C7CP02324C
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    The mechanism of ammonium bisulfate formation and decomposition over V/WTi catalysts for NH3-selective catalytic reduction at various temperature

    C. Li, M. Shen, T. Yu, J. wang, J. Wang and Y. Zhai, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP02324C

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