Synthesis and Structural Analysis of High‐Silica ERI Zeolite with Spatially‐Biased Al Distribution as a Promising NH<sub>3</sub>‐SCR Catalyst
Jie Zhu, Koki Muraoka, Takeshi Ohnishi, Yutaka Yanaba, Masaru Ogura, Akira Nakayama, Toru Wakihara, Zhendong Liu, Tatsuya Okubo
Abstract
Abstract Erionite (ERI) zeolite has recently attracted considerable attention for its application prospect in the selective catalytic reduction of NO x with NH 3 (NH 3 ‐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 29 Si 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.