Morphology‐Controlled Synthesis of H‐type MFI Zeolites with Unique Stacked Structures through a One‐Pot Solvent‐Free Strategy

Abstract

H‐type aluminosilicate zeolites are extensively used as solid‐acid catalysts and support materials in industrial catalysis. However, the conventional synthesis methods involving hydrothermal syntheses and ion‐exchange processes suffer from severe water pollution and toxic gas emissions. Herein, H‐type MFI zeolite catalysts with a unique stacked structure were directly synthesized in the presence of NH4F and with the help of zeolite confinement through a solvent‐free route without further ion‐exchange procedures. A range of ex situ and in situ characterization procedures were used to provide evidence of the simultaneous use of pre‐made ZSM‐5 and NH4F as a confined Al source and mineralizer, respectively. The confined zeolite framework of ZSM‐5 prevented the formation of AlFx species between NH4F and Al atoms, ensuring that the prepared samples had desirable acidic properties. Moreover, the resulting morphology could be controlled by using different silica substrates. The obtained H‐type MFI zeolites showed excellent catalytic performance in methanol‐to‐gasoline reactions owing to their unique structure and directly exposed acidic sites. The developed one‐pot strategy provides an alternative method for the facile synthesis of H‐type zeolites with defined morphology.

Seed- and solvent-free synthesis of ZSM-5 with tuneable Si/Al ratios for biomass hydrogenation

“…However, the role of anionic Fspecies in the formation of the crystal from this amorphous phase remains elusive. 18 The work herein, reports on a novel solvent-free and seed-free methodology, that can be used to synthesize MFI zeolites using only two reagents; SiO2 and C12H28NF. It was also established that through combination of these two precursors with NaAlO2, the method could be used to synthesize ZSM-5 materials with Si/Al ratios ranging from 18 to infinity.…”

State of the Art and Perspectives of Hierarchical Zeolites: Practical Overview of Synthesis Methods and Use in Catalysis

“…Reproduced with permission. [185] Copyright 2019, Wiley-VCH. synthesis method to generate hierarchical ZSM-5 with specifically nanocrystals on the surface of an intact ZSM-5 zeolite.…”

“…The catalyst was tested with success in the MTG reaction. [ 185 ] Hollow ZSM‐5 can also be obtained by adjustment of the hydrothermal synthesis. This can be done in a one‐pot hydrothermal synthesis with a high concentration of SDA, and occurs through a dissolution–recrystallization process.…”

A Brief Review on Solvent-Free Synthesis of Zeolites

“…Wu et al [51] synthesized a hollow zeolite shell assembled by ZSM-5 with a short baxis by the solvent-free method. SiO 2 spheres were used as silica source, with prefabricated ZSM-5 and NH 4 F as Al source and mineralizer, respectively.…”