Nanosized microporous crystals: emerging applications

Mintova, Svetlana; Jaber, Maguy; Valtchev, Valentin

doi:10.1039/c5cs00210a

Cited by 325 publications

(211 citation statements)

References 253 publications

(299 reference statements)

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“…Molecular transport throughout the zeolite structure and, consequently, the effectiveness factor, can be improved by minimizing the mean diffusion length in individual crystals. This can be achieved by using crystals with a nanometric size, for example zeolite nanosheets or by facilitating the access to internal sites via the formation of mesopores throughout the whole crystal . Zeolites combining arrays of connected meso and micropores, also named “hierarchical zeolites” have shown better catalytic performance than bulk crystals in reactions involving large molecules .…”

Section: Methodsmentioning

confidence: 99%

Demonstration of Improved Effectiveness Factor of Catalysts Based on Hollow Single Crystal Zeolites

et al. 2018

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Pt/NaY zeolites with bulk and hollow morphologies have been used as model catalysts in the hydrogenation of cyclohexene as model reaction. In contrast to most hierarchical zeolites, the presence of a single internal cavity modifies only the mean diffusion length, without changing the external surface area and the crystal size. Differences in catalytic activities have been attributed to a shorter diffusion length in hollow crystals. The volume fraction of zeolite used in bulk crystals (ca. 0.63–0.70) matches well with the shell thickness in hollow crystals, leading to an efficiency factor value for the latter close to 1.

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Section: Methodsmentioning

confidence: 99%

Demonstration of Improved Effectiveness Factor of Catalysts Based on Hollow Single Crystal Zeolites

et al. 2018

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“…It is critical and difficult to control the zeolite nucleation kinetics to obtain a desired nanosized colloidal zeolite . To date, only a few types of zeolites have been prepared successfully with nanosized dimensions and stabilized in colloidal suspensions …”

Section: Introductionmentioning

confidence: 99%

A Topotactic Synthetic Methodology for the Synthesis of Nanosized MFI Zeolites with Hierarchical Structures

Wang

et al. 2018

Chemistry A European J

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Much effort has been invested in the designed synthesis of zeolites with nanosized and hierarchical structures in recent decades, on account of increasing demands in practical applications, especially catalysis. Herein, a new topotactic synthetic strategy is demonstrated to synthesize nanosized and hierarchical zeolites in a one-step procedure. By using silica spheres as the adjustable amorphous precursors and tetrapropylammonium hydroxide as a structure-directing agent, effortless control of both size and porosity can be achieved in this system with no extra templates. With a simple hydrothermal process, hierarchical zeolite spheres can be modified with acid cites (Al species incorporated in the framework). Benefitting from its mesoporosity, palladium nanoparticles are incorporated into the nanosized hierarchical zeolite, which makes the materials suitable for use in a cascade catalysis reaction of benzimidazole derivatives, including independent acid catalysis and hydrogenation sites. The nanocomposites show exceptional activity and stability in catalysis and recycling reaction. This strategy can be developed into other versatile and practicable scaffolds for advanced zeolite catalytic nanoreactor systems.

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“…As nano-sized ZSM-5 zeolites with shorter diffusion length favored the adsorption and desorption of reactants in the micropores compared with the micro-sized zeolite, the catalytic cracking activity increased with the decrease of crystal size [15,[98][99][100]. Tago et al [101] studied the catalytic performance of ZSM-5 zeolite with macro-size (2300 nm) and nano-size (90 nm) in naphthene cracking.…”

Section: Nano-sized Zsm-5 Zeolitementioning

confidence: 99%

Strategies to Enhance the Catalytic Performance of ZSM-5 Zeolite in Hydrocarbon Cracking: A Review

2017

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ZSM-5 zeolite is widely used in catalytic cracking of hydrocarbon, but the conventional ZSM-5 zeolite deactivates quickly due to its simple microporous and long diffusion pathway. Many studies have been done to overcome these disadvantages recently. In this review, four main approaches for enhancing the catalytic performance, namely synthesis of ZSM-5 zeolite with special morphology, hierarchical ZSM-5 zeolite, nano-sized ZSM-5 zeolite and optimization of acid properties, are discussed. ZSM-5 with special morphology such as hollow, composite and nanosheet structure can effectively increase the diffusion efficiency and accessibility of acid sites, giving high catalytic activity. The accessibility of acid sites and diffusion efficiency can also be enhanced by introducing additional mesopores or macropores. By decreasing the crystal size to nanoscale, the diffusion length can be shortened. The catalytic activity increases and the amount of carbon deposition decreases with the decrease of crystal size. By regulating the acid properties of ZSM-5 with element or compound modification, the overreaction of reactants and formation of carbon deposition could be suppressed, thus enhancing the catalytic activity and light alkene selectivity. Besides, some future needs and perspectives of ZSM-5 with excellent cracking activity are addressed for researchers' consideration.

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Nanosized microporous crystals: emerging applications

Cited by 325 publications

References 253 publications

Demonstration of Improved Effectiveness Factor of Catalysts Based on Hollow Single Crystal Zeolites

Demonstration of Improved Effectiveness Factor of Catalysts Based on Hollow Single Crystal Zeolites

A Topotactic Synthetic Methodology for the Synthesis of Nanosized MFI Zeolites with Hierarchical Structures

Strategies to Enhance the Catalytic Performance of ZSM-5 Zeolite in Hydrocarbon Cracking: A Review

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