Alcohol‐Assisted Synthesis of Sheet‐Like ZSM‐5 Zeolites with Controllable Aspect Ratios

Abstract

Sheet‐like ZSM‐5 has been regarded as a promising material for catalytic applications due to its diffusion superiority. However, it still remains a challenge to obtain a desirable sheet‐like morphology because of the complex synthesis process of zeolites. Here, a facile strategy for synthesizing sheet‐like ZSM‐5 is developed by only adding ethanol as zeolite growth modifier in the synthesis gel. It is thought that ethanol might be preferentially absorbed on the {010} surface of zeolite crystals, interact with the exposed silicon hydroxyl groups on the crystal {010} facet, and suppress the growth of b axis, resulting in the sheet‐like shape. Through finely tunning synthesis parameters, sheet‐like ZSM‐5 crystals with thin b‐axis thickness of 90 nm and different aspect ratios could be obtained. Owing to its shorter diffusion path and optimized acidity, sheet‐like ZSM‐5 exhibits better catalytic performance than conventional ZSM‐5 in the alkylation of benzene with ethanol.

MFI nanosheets: a rising star in zeolite materials

“…Synthesis of ZSM-5 NSs with b-axis thickness greater than 50 nm using other mineralizing agents has been widely reported in the literature. 29,31 It is reasonable to believe that the thickness can be regulated by adding extremely small seeds or seed fragment solution in the fluorine-free synthetic system.…”

“…The main strategies available for direct preparation of b -axis-oriented MFI NSs include introducing zeolite growth modifiers to the synthesis solution, which are specifically adsorbed on the most energetically favorable surface (010) of the crystal and inhibit the attachment of incoming building units, thereby reducing the b -axis growth rate. Much encouraging progress has been achieved to directly synthesize the sheet-like MFI crystals by employing different types of additives, including alcohol, 28,29 tributylphosphine oxide, 30 and urea. 31,32 However, the above methods usually end up with crystals with relatively thick b -axis thickness (above 50 nm).…”

Morphology and Microstructural Optimization of Zeolite Crystals Utilizing Polymer Growth Modifiers for Enhanced Catalytic Application

“…Through the optimization of synthesis methods and parameters, these physicochemical properties could be modulated to a certain extent by adjusting the morphology and microstructural characteristics of the zeolite crystals, making them well fit for the requirement of a specific catalytic reaction [9][10][11][12][13][14]. Among the various modulation strategies, the introduction of so-called "zeolite growth modifiers" (ZGMs) has shown great advantages in precisely modulating of the morphology and microstructure of various zeolite crystals, with remarkable effects in terms of enhancing their catalytic activity, selectivity, and/or stability for a broad range of industrially important catalytic processes [10,[15][16][17][18][19][20].…”

c-Axis-oriented sheet-like Cu/AEI zeolite contributes to continuous direct oxidation of methane to methanol

“…35 and 36) and urea 15,17 have widely been employed to modify the crystal morphology of different types of zeolites. 22,37 Recently, we adopted the commercially available typical surfactant cetyltrimethylammonium bromide (CTAB) as a crystal growth inhibitor (CGI) to synthesize an AEI zeolite with sheet-like crystals in the c-axis orientation. 38 The acidic AEI zeolites were applied in the propene to butene reaction, and the sheet-like AEI zeolite exhibited a higher selectivity for iso-butene and a longer catalytic lifetime as compared to the cubic sample.…”

“…35 and 36) and urea 15,17 have widely been employed to modify the crystal morphology of different types of zeolites. 22,37…”