Synthesis and Structural Analysis of High-Silica ERI Zeolite with Spatially-Biased Al Distribution as a Promising NH3-SCR Catalyst

Jie Zhu; Koki Muraoka; Takeshi Ohnishi; Yutaka Yanaba; Masaru Ogura; Akira Nakayama; Toru Wakihara; Zhendong Liu; Tatsuya Okubo

doi:10.1002/advs.202307674

Synthesis and Structural Analysis of High-Silica ERI Zeolite with Spatially-Biased Al Distribution as a Promising NH₃-SCR Catalyst

Adv Sci (Weinh). 2024 Apr;11(14):e2307674. doi: 10.1002/advs.202307674. Epub 2024 Feb 2.

Authors

Jie Zhu¹, Koki Muraoka¹, Takeshi Ohnishi², Yutaka Yanaba², Masaru Ogura², Akira Nakayama¹, Toru Wakihara^{1

3}, Zhendong Liu^{1

3

4}, Tatsuya Okubo¹

Affiliations

¹ Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
² Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505, Japan.
³ Institute of Engineering Innovation, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-8656, Japan.
⁴ State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Haidian District, Beijing, 100084, China.

Abstract

Erionite (ERI) zeolite has recently attracted considerable attention for its application prospect in the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR), provided that the high-silica (Si/Al > 5.5) analog with improved hydrothermal stability can be facilely synthesized. In this work, ERI zeolites with different Si/Al ratios (4.6, 6.4, and 9.1) are synthesized through an ultrafast route, and in particular, a high-silica ERI zeolite with a Si/Al ratio of 9.1 is obtained by using faujasite (FAU) as a starting material. The solid-state ²⁹Si MAS NMR spectroscopic study in combination with a computational simulation allows for figuring out the atomic configurations of the Al species in the three ERI zeolites. It is revealed that the ERI zeolite with the highest Si/Al ratio (ERI-9.1, where the number indicates the Si/Al ratio) exhibits a biased Al occupancy at T1 site, which is possibly due to the presence of a higher fraction of the residual potassium cations in the can cages. In contrast, the Al siting in ERI-4.6 and ERI-6.4 proves to be relatively random.

Keywords: NH3‐SCR catalyst; NMR spectroscopy; density functional calculations; high‐silica ERI zeolite; spatially‐biased Al distribution.

Abstract

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