Synthesis of EU-1/ZSM-48 Co-Crystalline Zeolites from High-Silica EU-1 Seeds: Tailoring Phase Proportions and Promoting Long Crystalline-Phase Stability

Unconventional seed-assisted strategy for Al-rich hierarchical ZSM-48 zeolite

Inferior diffusion capacity and insufficient acid density hinder the practical application of ZSM-48 zeolite. Finding a simple and practical strategy to simultaneously address these two defects remains a challenge. In response to this dilemma, we developed an unconventional seed-assisted synthesis strategy for Al-rich hierarchical ZSM-48 zeolite. This approach allows for achieving a broader range of silica to alumina ratio and accelerates the entire crystallization process through the selection of unconventional seeds. The synergy between the seed and organic template was demonstrated to play a pivotal role in facilitating nucleation. Direct evidence from 1H-29Si CP MAS NMR, TG, and IR results demonstrates that hexamethonium ions (HM2+) electrostatically adsorb at the defect sites on the seed, thereby promoting nucleation sites formation. Smaller seed crystals undergo more etching during the induction period, resulting in additional defects and enhanced nucleation ability. The obtained catalyst exhibits a diffusion time constant (Deff/L2) nine times that of conventional ZSM-48 zeolite when using p-xylene as a probe molecule. In m-xylene isomerization reaction, Al-rich hierarchical ZSM-48 demonstrates excellent stability along with higher selectivity and yield for p-xylene compared to typical ZSM-5 catalysts. Remarkably, long-term testing of 1000 h yields over 22.5 % of p-xylene, indicating the potential of this catalyst as an alternative for xylene isomerization reaction. This work not only advances the practical application process of ZSM-48 catalyst but also provides valuable insights for optimizing other zeolites.

Synthesis ZSM-48 Zeolites and Their Catalytic Performance: A Review

ZSM-48 is first discovered as an impurity phase in the synthesis of ZSM-39. ZSM-48 has a framework based on the ferrierite sheet with noninterpenetrating linear 10-ring channels which the dimensions...

Fabrication of a core–shell MFI@TON material and its enhanced catalytic performance for toluene alkylation

Core–shell MFI@TON composites were designed and synthesized as a highly shape-selective catalyst for toluene alkylation by passivating the nonselective acid sites and tuning the diffusion behavior.

Computational screening of structure directing agents for the synthesis of zeolites. A simplified model

Zeolite micropores become more energetically stable by the occlusion of organic structure directing agents (templates). This energetic stabilisation, if approximated by van der Waals zeo-template interactions, can be calculated in a fast way by using modern computing techniques incorporating big data handling algorithms for massive screening. A software suite is presented which calculates an arbitrarily large 2-D matrix (template×zeolite) giving the zeo-template van der Waals interaction energy corresponding to the minimum energy conformation assuming one template molecule in a pure silica zeolite unit cell. With the goal of simplicity, the software only needs two coordinate input files of template and zeolite unit cell. Though a number of approximations have been considered, the software allows to compare, for a given template, which competing zeolite phases may become more stabilised. Applied to zeolite hypothetical databases, it may be of help to suggest templates for their synthesis.