近日，吉林大学于吉红团队实现了低电荷密度有机结构导向剂直接合成高硅八面沸石。这一研究成果发表在2025年5月8日出版的《美国化学会志》上。

具有高SiO₂/Al₂O₃比（SAR）的超稳定Y（USY）沸石（八面沸石型，FAU）已广泛应用于流化催化裂化和加氢裂化过程。然而，它们的制备通常涉及劳动密集型的后处理，这不可避免地会引入缺陷、额外的框架物种和成分梯度。在此，研究组报告了直接合成FAU型沸石，其SAR高达21.28，创下历史新高，在异丙苯和直馏柴油的催化裂化中表现出优异的催化性能。这是通过使用高硅初始凝胶和种子，以及四甲基铵（TMA⁺）和四丁基铵（TBA⁺）阳离子的低电荷密度有机结构导向剂（OSDA）来实现的，同时尽量减少使用高电荷密度无机Na⁺阳离子。

综合核磁共振分析，包括二维（2D）异核相关（HETCOR）实验（¹H-¹³C、¹H-²⁷Al、¹H-²⁹Si）和基于同步辐射X射线衍射的Rietveld改进，表明（1）TMA⁺和TBA⁺在初始凝胶中优先与Si物种相互作用，而不是Al物种，促进Si掺入FAU结构的长程序；（2）TMA⁺阳离子被紧紧地限制在方钠石（sod）笼中，而TBA⁺阳离子占据了八面沸石（fau）超笼，采用折叠丁基链构型。 低电荷密度OSDA阳离子的包封，加上高电荷密度Na⁺阳离子的排除，产生了SAR为21.28的高硅Y沸石。合成的Y型沸石在异丙苯裂解中表现出改进的耐久性和增强的活性，对目标产物[液化石油气（LPG）和汽油]的选择性相当，同时与传统的USY型沸石相比，在直馏柴油催化裂化中结焦减少了28%。

附：英文原文

Title: Direct Synthesis of Highly Siliceous Faujasite-type Zeolite Enabled by Low Charge Density Organic Structure-directing Agents

Author: Zhenrui Mi, Shaojie Li, Wei Liu, Jia Wang, Donghao Deng, Pusheng Liu, Peng Tian, Chuang Liu, Wenfu Yan, Kake Zhu, Zhendong Wang, Zhongmin Liu, Jihong Yu

Issue&Volume: May 8, 2025

Abstract: Ultrastable Y (USY) zeolites (Faujasite-type, FAU) with high SiO2/Al2O3 ratios (SARs) have been widely applied in fluidized catalytic cracking and hydrocracking processes. However, their preparation typically involves labor-intensive post-treatments that inevitably introduce defects, extra-framework species, and compositional gradients. Herein, we report the direct synthesis of FAU-type zeolite with a record-high SAR up to 21.28, which shows superior catalytic performance in the catalytic cracking of cumene and straight-run diesel. This was achieved by using a highly siliceous initial gel and seed, together with low charge-density organic structure-directing agents (OSDAs) of tetramethylammonium (TMA+) and tetrabutylammonium (TBA+) cations, while minimizing the use of high charge-density inorganic Na+ cations. Comprehensive NMR analyses, including two-dimensional (2D) heteronuclear correlation (HETCOR) experiments (1H–13C, 1H–27Al, 1H–29Si), and synchrotron radiation X-ray diffraction-based Rietveld refinements, revealed that (1) TMA+ and TBA+ preferentially interact with Si species over Al species in the initial gel, promoting Si incorporation into the FAU structure’s long-range order; and (2) TMA+ cations were tightly confined within the sodalite (sod) cages, while TBA+ cations occupied the faujasite (fau) supercages, adopting folded butyl chain configurations. The encapsulation of low charge-density OSDA cations, coupled with the exclusion of high charge-density Na+ cations, resulted in a highly siliceous Y zeolite with a SAR of 21.28. The synthesized Y zeolite exhibited improved durability and enhanced activity in cumene cracking and comparable selectivity for the target products [liquefied petroleum gas (LPG) and gasoline] while reducing coke formation by 28% in straight-run diesel catalytic cracking compared to conventional USY zeolites.

DOI: 10.1021/jacs.4c18522

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c18522