Rapid fabrication of highly b-oriented zeolite MFI thin films using ammonium salts as crystallization-mediating agents

Lü, Xiaofei; Peng, Yong; Wang, Zhengbao; Yan, Yushan

doi:10.1039/c5cc02980e

Cited by 45 publications

(44 citation statements)

References 29 publications

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“…Thediffraction patterns of zeolite films with y = 0.085 or 0.13 (Supporting Information, Figure S7) show only the peaks from the (020), (040), (060), (080), and (0100) planes,w hich, together with the SEM images,c onfirm the formation of highly b-oriented MFI zeolite films. [13] Thet hickness of the MFI zeolite film produced for y = 0.085 is about 700 nm, as presented in Figure 1e.W ith y > 0.13, crystals cannot sufficiently grow to fill up the gaps between b-oriented seeds (Supporting Information, Figure S7f).…”

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confidence: 88%

“…[8a,12] However,n or eports were found on the templatefree synthesis of b-oriented MFI films.B yu sing synthesis solutions free from organic templates in the secondary growth method, it should be possible to avoid the crucial calcination step and thus minimize the risk of crack formation in the zeolite layer and save the cost of the expensive templating agent. Theo bjective of this work is to study the effect of compositional constraints in the secondary growth synthesis of b-oriented MFI zeolite films using an organic-free precursor.Inspired by Yansa nd Yoonsw ork, [9,13] we have synthesized b-oriented MFI seed monolayers by manually rubbing…”

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confidence: 99%

“…Inspired by Yansa nd Yoonsw ork, [9,13] we have synthesized b-oriented MFI seed monolayers by manually rubbing…”

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confidence: 99%

“…Previous reports [9,13,16] used ammonium salts as crystallization mediating agents.Some publications showed that twin growth of b-oriented MFI seed layers can be effectively suppressed by introducing ammonium salts as additives to the secondary growth solutions containing TPAOHo rT EAOH as the SDA. [9,13] Inspired by this finding,i nt his work we investigated the effect of ammonium sulfate addition to organic template free secondary growth solutions on the surface morphology of MFI zeolite layer. Secondary growth was conducted with solution of molar composition (1 SiO 2 :0.57 NaOH:137.5 H 2 O:0.0050 (Al 2 (SO 4 ) 3 ·18 H 2 O):y (NH 4 ) 2 SO 4 )f or which y was varied from 0.025 to 0.18.…”

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confidence: 99%

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Template‐Free Synthesis of Highly b‐Oriented MFI‐Type Zeolite Thin Films by Seeded Secondary Growth

et al. 2019

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Highly b-oriented, closely packed, MFI zeolitefilms are prepared on seeded stainless-steel plates using organic template-free,s econdary growth solutions,c ontaining aluminum sulfate as ac rystallization agent. The number of aoriented twin crystals is significantly reduced, and even eliminated, simply by restricting the pH value of the secondary growth solution to the narrowrange of 11.1-11.3. Values of pH can be adjusted through the controlled addition of (NH 4 ) 2 SO 4 or H 2 SO 4 to secondary growth solutions of the composition (1 SiO 2 :0.57 NaOH:137.5 H 2 O:0.0050 (Al 2 (SO 4 ) 3 ·18 H 2 O)) or by simply decreasing the molar composition of NaOH with no extra additives.MFI zeolite films are attractive for aw ide range of applications,i ncluding molecular sieve membranes,c atalytic membrane reactors,l ow-dielectric-constant materials,a nd corrosion-resistant coatings. [1] Both experimental data and simulation results [2] have suggested that the straight channel along the b-axis is the fastest diffusion pathway in MFI crystals and b-oriented zeolite films exhibit superior performance compared to randomly oriented ones. [3] At present, one of the most important applications of b-oriented MFI films is as membranes for separation of p-xylene from xylene isomers. [4] Therefore,s ynthesizing high-quality,b -oriented MFI zeolite films is of great interest from the viewpoint of both fundamental studies and practical applications.B-oriented MFI films have been grown on stainless-steel substrates through the accurate manipulation of synthesis solution composition [5] and kinetic parameters [6] for crystal nucleation and growth during in situ synthesis.Continuous boriented zeolite films and membranes were also successfully prepared on different supports with the secondary (seeded)growth method, taking advantage of ab-oriented zeolite seed layer deposited on the substrate prior to hydrothermal treatment. [7] Decoupling the nucleation and growth steps can significantly reduce the difficulty in manipulating the orientation of zeolite films,w hich in turn enhances the reproducibility and scalability of the zeolite layer synthesis.In the methods mentioned above for the synthesis of boriented MFI zeolite films,o rganic template (or structuredirecting agent, SDA) was necessary for the formation of zeolite crystals.T emplating agents are incorporated in zeolite pores during hydrothermal synthesis and acalcination step is necessary to follow the film/membrane synthesis process to remove the template and open the zeolite channels.D uring the calcination process,a na brupt shrinkage of the zeolite lattice,a nd differences in the thermal expansion characteristics of zeolite films and their supports yield substantial stresses that often result in microcracks in zeolite films. [8] These microcracks make zeolite films less effective in practical applications.Moreover,t he growth of a-oriented twin crystals is unavoidable when tetrapropylammonium hydroxide (TPAOH), the most common template,i su sed in the secondary growth method. [7...

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confidence: 88%

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confidence: 99%

“…Inspired by Yansa nd Yoonsw ork, [9,13] we have synthesized b-oriented MFI seed monolayers by manually rubbing…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Template‐Free Synthesis of Highly b‐Oriented MFI‐Type Zeolite Thin Films by Seeded Secondary Growth

et al. 2019

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“…Therefore, much attention has been attracted to prepare the MFI zeolite grown only along the b-axis to decrease the diffusion length. However, most of the related studies were to prepare the b-oriented MFI zeolite without aluminum atoms [59][60][61]. It is of great challenge to prepare b-oriented MFI zeolite containing aluminum atoms for catalytic reactions, for the difficulty on effectively controlling the growth orientation with the co-existence of silicon and aluminum atoms.…”

Section: B-oriented Mfi 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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Highly Oriented Growth of Catalytically Active Zeolite ZSM‐5 Films with a Broad Range of Si/Al Ratios

Schmidt

Ristanović

et al. 2017

Angewandte Chemie

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Highly b‐oriented zeolite ZSM‐5 films are critical for applications in catalysis and separations and may serve as models to study diffusion and catalytic properties in single zeolite channels. However, the introduction of catalytically active Al3+ usually disrupts the orientation of zeolite films. Herein, using structure‐directing agents with hydroxy groups, we demonstrate a new method to prepare highly b‐oriented zeolite ZSM‐5 films with a broad range of Si/Al ratios (Si/Al=45 to ∞). Fluorescence micro‐(spectro)scopy was used to monitor misoriented microstructures, which are invisible to X‐ray diffraction, and show Al3+ framework incorporation and illustrate the differences between misoriented and b‐oriented films. The methanol‐to‐hydrocarbons process was studied by operando UV/Vis diffuse reflectance micro‐spectroscopy with on‐line mass spectrometry, showing that the b‐oriented zeolite ZSM‐5 films are active and stable under realistic process conditions.

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Rapid fabrication of highly b-oriented zeolite MFI thin films using ammonium salts as crystallization-mediating agents

Cited by 45 publications

References 29 publications

Template‐Free Synthesis of Highly b‐Oriented MFI‐Type Zeolite Thin Films by Seeded Secondary Growth

Template‐Free Synthesis of Highly b‐Oriented MFI‐Type Zeolite Thin Films by Seeded Secondary Growth

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

Highly Oriented Growth of Catalytically Active Zeolite ZSM‐5 Films with a Broad Range of Si/Al Ratios

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