A Bottom‐Up Strategy for the Synthesis of Highly Siliceous Faujasite‐Type Zeolite

Abstract

High‐silica zeolite Y is a desired catalytic material for oil refining and the petrochemical industry. However, its direct synthesis remains a symbolic challenge in the field of zeolite synthesis, with a limited improvement of the framework SiO2/Al2O3 ratio (SAR) from ≈5 to 9 over the past 60 years. Here, the synthesis of highly siliceous zeolite Y with tunable SAR up to 15.6 through a cooperative strategy is reported, which involves the use of FAU nuclei, a bulky organic structure‐directing agent (OSDA), and a gel system with low alkalinity (named NOA‐co strategy). A series of quaternary alkylammonium ions is discovered as effective OSDAs based on the NOA‐co strategy, and the relevant crystallization mechanism is elucidated. Moreover, the high‐silica products are demonstrated to have greatly improved (hydro)thermal stability, high concentration of strong acid sites, and uniform acid distribution, which lead to superior catalytic performance in the cracking of bulky hydrocarbons. It is anticipated that this synthetic strategy will benefit the synthesis and development of zeolitic catalysts in a wide range of reaction processes.

Titanosilicate zeolite precursors for highly efficient oxidation reactions

“…The OSDA used in the zeolite synthesis system not only provides shape commensurate with the cages and channels in zeolites but also is in charge of the nucleus formation and the crystal growth process; the lower the charge density of the OSDA, the higher the requirement for nucleation. 43,44 A series of commercialized and low charge density home-made quaternary ammonium cations have been employed to obtain amorphous titanosilicate zeolites, which are characterized by specic porosities, open structures, and abundant octahedrally coordinated Ti species. The obtained amorphous titanosilicate zeolite catalysts show enhanced catalytic performance in the oxidative desulfurization of dibenzothiophene (DBT) and the epoxidation of cyclohexene, with respect to the nal zeolite structures.…”

Tracking the crystallization behavior of high-silica FAU during AEI-type zeolite synthesis using acid treated FAU-type zeolite

“…Thus, the peak was assumed to be a superposition of Q 4 (1Al) and Q 3 (0Al)(1OH), based on a previous report. 16 In addition, only a peak derived from tetrahedral Al was observed in the 27 Al MAS NMR spectrum (Fig. 2d), indicating that there are no extra-framework Al species in the resultant high-silica FAU.…”

Selective valorization of lignin to phenol by direct transformation of C sp2 –C sp3 and C–O bonds

“…The reaction did not occur without a catalyst (entry 2). It is well-known that the HY 3 zeolite has its physique of Al-rich framework (31). However, most of the acid sites, especially the strong acid sites, are embedded deeply within the microporous framework that is difficult for the reactants to access and the reaction cannot occur (entry 3 of Table 1 for HY 3 ).…”