Insights into the Effect of the Adsorption Preference of Additives on the Anisotropic Growth of ZSM‐5 Zeolite

Abstract

Zeolite morphology plays a crucial role in affecting catalytic performance, while is persistently challenging to tailor through crystal anisotropic growth. It has been recognized that specific additives can be introduced into the synthesis of zeolites to achieve anisotropic growth, however their role and the underlying mechanism are not well understood. Herein, the effect of eight specific additives on the anisotropic growth of the ZSM-5 zeolite is unveiled within the framework of crystallization engineering. Either an inhibition effect or a promotion effect is revealed for each additive according to the crystallization kinetics. The adsorp-tion preference of typical additives on different surfaces was demonstrated by total internal reflection fluorescence microscopy (TIRFM) and transmission X-ray microscopy (TXM) together with 3D reconstruction. The calculated adsorption energy difference between MFI [100]/[101] and [010] surfaces was proposed as a key descriptor to estimate the possible morphology induced by additive. ZSM-5 zeolites varying from sphere-like, plate-like to noodle-like morphology could be synthesized by employing specific additives with increasing adsorption strength difference on distinct surfaces.

Anisotropic ZSM-5 nanorod assemblies: facile synthesis, epitaxial growth, and strikingly enhanced stability in benzene alkylation

“…In previous studies, some researchers have reported that when the additives were introduced into the starting gel, they would interact with exposed silicon hydroxyl groups (Si-OH) on the specific crystal facets and tailor the anisotropic growth of zeolites. [33][34][35]44,45 Therefore, it can be inferred that CTA + may preferentially interact with the Si-OH groups on the [010] and [100] surfaces of zeolites, suppressing the crystal growth along the a-axis and b-axis to achieve the nanorod's c-axis oriented growth. Based on the above detailed discussion, it may be thought that the formation of bundle-like ZSM-5 nanorod assemblies goes through "crystallization and oriented growth by particle attachment", which is different from the classical seedinduced process (crystallization and growth by layer-by-layer).…”

Coke Formation over Zeolite Catalysts in Light Alkanes Aromatization and Anti-Carbon-Deposition Strategies and Perspectives: A Review

“…(a) Structure directing agent (SDA): The method of adding a SDA into aluminosilicate gel to synthesize mesoporous structure in situ is flexible and easy to operate, with little damage to the pore structure, and the diffusion of reactants or products can be specifically facilitated . Moreover, the use of a multifunctional SDA can also save raw materials.…”

Nonionic polymer and amino acid-assisted synthesis of ZSM-5 nanocrystals and their catalytic application in the alkylation of 2-methylnaphthalene

“…To date, a variety of organic small compounds such as alcohols, lactams, ketones, and amino acids have been utilized as assisted additives or growth modifiers for the syntheses of various zeolites with specific morphology and porosity, including nanocrystal, lamellar, core–shell, hierarchical architecture and so on. 16–21 In particular, some common amino acids and their derivatives like arginine, carnitine and lysine have shown great advantages in modulating the shape and particle size of various zeolite crystals. 20–23 For instance, Rimer and his co-workers reported that the addition of amino acid arginine could help the formation of silicalite-1 ( MFI type) crystals with longer dimensions in the main direction of internal diffusion, possibly related to the fact that the growth modifier has the ability to impede nanoparticle addition.…”