Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Irregular influence of alkali metals on Cu-SAPO-34 catalyst for selective catalytic reduction of NO x with ammonia Guangpeng Yang a,b , Xuesen Du a, *, Jingyu Ran a, *, Xiangmin Wang a , Yanrong Chen a , Li Zhang a , Vladislav Rac c , Vesna Rakic c , John Crittenden b a Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, School of Energy and Power Engineering, Chongqing University, Chongqing, 400044, China b Brook Byers Institute for Sustainable Systems and School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, United States c Faculty of Agriculture, Department of Chemistry, University of Belgrade, Nemanjina 6, 11080, Zemun, Serbia GRAPHICAL ABSTRACT ARTICLE INFO Editor: Xiaohong Guan Keywords: Cu-SAPO-34 Alkali metal Migration Cu species ABSTRACT SCR activity of Cu-SAPO-34 catalyst was reduced by alkali metal ions. The alkali metals ions (Li + , Na + and K + ) have shown irregular influences on Cu-SAPO-34. The order of poisoning strengths under 400 °C was found to be: Na + >K + > Li + , which is not consistent with the basicities of their corresponding metals. Experimental re- sults and calculations showed that the alkali metal ions readily replace H + and Cu 2+ /Cu + ions. These exchanges result in the loss of Brønsted acid sites and migration of isolated Cu 2+ ions in Cu-SAPO-34, which decrease the NH 3 -SCR activity. Both the basicity and ion diameter will affect the exchanging behavior of an alkali ion. Na + and Li + ions will influence both H + and Cu 2+ /Cu + ions but K + ions only preferably replace the H + . We hypothesize that K + cannot enter into a small ring (6-membered ring) to replace a Cu 2+ /Cu + ion because of its large ion diameter. The displaced Cu 2+ /Cu + ions will transfer to adjacent unbonded Al site to form a CuAlO 2 species. 1. Introduction The selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) is an effective way to reduce the NO x emission from both mobile and point sources. The Cu-SAPO-34 catalyst used for removing NO x in mobile sources has drawn much attention, because of its high destruction ef- ficiency for NO x reduction over a wide temperature range and superior resistance to hydrothermal aging, compared with traditional V-based https://doi.org/10.1016/j.jhazmat.2019.122007 Received 24 September 2019; Received in revised form 7 December 2019; Accepted 30 December 2019 ⁎ Corresponding authors. E-mail addresses: gpyang@cqu.edu.cn (G. Yang), xuesendu@cqu.edu.cn (X. Du), ranjy@cqu.edu.cn (J. Ran). Journal of Hazardous Materials 387 (2020) 122007 Available online 31 December 2019 0304-3894/ © 2019 Elsevier B.V. All rights reserved. T