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Water mediated oxygen activation in NH3 SCR reaction over Cu-SAPO-34 catalyst: a first principles study

Abstract

At low temperature, water can greatly improve the NH3 selective catalytic reduction (SCR) performance of Cu-SAPO-34 under standard reaction conditions. During the SCR process on Cu-CHA catalysts, oxygen (O2) activation over pairs of Cu(NH3)2+ complexes is a crucial step. The concertration of H2O in the reaction atmosphere may affect the local environement of Cu ions and subsquent oxygen activation. In this work, first-principles calculations are used to study the adsorption of NH3 on Cu sites and the detailed reaction paths of O2 activation with or without water in Cu-SAPO-34. NH3 adsorption is generally favored over H2O on Cu ions, yet at low temperature and with partial pressure of water vapor, H2O and NH3 molecules could co-adsorb on the same Cu site from the phase diagram analysis. During the O2 activation process, this kind of behavior will influence the formation of Cu(NH3)2+ complex and a new kind of Cu(NH3)(H2O)+ complex will form during the reduction process of Cu2+ ions. Compared with O2 activation over pairs of Cu(NH3)2+ complexes, Cu(NH3)2+-Cu(NH3)(H2O)+ complexes changes the torsion angle of Cu-O-O-Cu configuration and decrease the reaction energy barriers of O2 activation in Cu-SAPO-34. Our results shed light on the water mediated NH3 SCR reaction mechanism of Cu-SAPO-34 from the molecular level.

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Publication details

The article was received on 31 Dec 2018, accepted on 04 Feb 2019 and first published on 06 Feb 2019


Article type: Paper
DOI: 10.1039/C8CY02618A
Citation: Catal. Sci. Technol., 2019, Accepted Manuscript

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    Water mediated oxygen activation in NH3 SCR reaction over Cu-SAPO-34 catalyst: a first principles study

    L. Shi, J. Zhang, G. Shen, D. Fan, Y. Wen, Y. Zhao, R. Chen, M. Shen and B. Shan, Catal. Sci. Technol., 2019, Accepted Manuscript , DOI: 10.1039/C8CY02618A

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