Insight into the promoting effect of support pretreatment with sulfate acid on selective catalytic reduction performance of CeO2/ZrO2 catalysts

Zhitao Han; Xiaodi Li; Xinxin Wang; Yu Gao; Shaolong Yang; Liguo Song; Jingming Dong; Xinxiang Pan

doi:10.1016/j.jcis.2021.10.191

Insight into the promoting effect of support pretreatment with sulfate acid on selective catalytic reduction performance of CeO₂/ZrO₂ catalysts

J Colloid Interface Sci. 2022 Feb 15;608(Pt 3):2718-2729. doi: 10.1016/j.jcis.2021.10.191. Epub 2021 Nov 5.

Authors

Zhitao Han¹, Xiaodi Li², Xinxin Wang³, Yu Gao³, Shaolong Yang⁴, Liguo Song³, Jingming Dong³, Xinxiang Pan⁵

Affiliations

¹ Marine Engineering College, Dalian Maritime University, Dalian 116026, China. Electronic address: hanzt@dlmu.edu.cn.
² School of Resources and Environmental Sciences, XinJiang University, Wulumuqi 830000, China.
³ Marine Engineering College, Dalian Maritime University, Dalian 116026, China.
⁴ School of Naval Architecture and Ocean Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
⁵ Marine Engineering College, Dalian Maritime University, Dalian 116026, China; School of Electronic and Information Technology, Guangdong Ocean University, Zhanjiang 524088, China.

PMID: 34785048
DOI: 10.1016/j.jcis.2021.10.191

Abstract

In this paper, sulfated ZrO₂ were synthesized via precipitation and impregnation method, and the promoting effects of support sulfation on selective catalytic reduction (SCR) performance of CeO₂/ZrO₂ catalysts were investigated. The results revealed that sulfated ZrO₂ could significantly enhance the SCR activity of CeO₂/ZrO₂ catalysts in a wide temperature range. Especially when S/Zr molar ratio was 0.1, CeO₂/ZrO₂-0.1S catalyst exhibited a large operating temperature window of 251 ∼ 500 °C and its N₂ selectivity was 100 % in the temperature range of 150 ∼ 500 °C. Moreover, CeO₂/ZrO₂-0.1S catalyst possessed a superior low-temperature activity over 0.1S-CeO₂/ZrO₂ catalyst. After exposing to 100 ppm SO₂ for 15 h, a high NO conversion efficiency of CeO₂/ZrO₂-0.1S catalyst (90.7 %) could still be reached. The characterization results indicated that ZrO₂ treated with a proper dosage of sulfate acid was beneficial to enlarge the specific surface area greatly. Sulfated ZrO₂ was also in favor of promoting the transformation of CeO₂ from crystalline state to highly-dispersed amorphous state, and inhibiting the transformation of ZrO₂ from tetragonal to monoclinic phase. It could also enhance the total surface acidity greatly with an increase in both Brønsted acid sites and Lewis acid sites, thus significantly improving NH₃ adsorption on catalyst surface. Besides, the promoting effect of support sulfation on SCR performance of CeO₂/ZrO₂ catalysts was also related with the enhanced redox property, higher Ce³⁺/(Ce³⁺+Ce⁴⁺) ratio and abundant surface chemisorbed labile oxygen. The in-situ DRIFTS results implied that nitrate species coordinated on the surface of CeO₂/ZrO₂-0.1S catalyst could participate in the Selective catalytic reduction with ammonia (NH₃-SCR) reactions at either medium or high temperature, suggesting that both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms might be followed in SCR reactions.

Keywords: CeO(2)/ZrO(2); Mechanism; Selective Catalytic Reduction; Sulfated ZrO(2); Surface Acidity; in-situ DRIFTS.

MeSH terms

Ammonia
Catalysis
Cerium*
Oxidation-Reduction
Sulfates*

Substances

Sulfates
Cerium
Ammonia