Modulation of b-axis thickness within MFI zeolite: Correlation with variation of product diffusion and coke distribution in the methanol-to-hydrocarbons conversion

Wang, Ning; Hou, Yilin; Sun, Wenjing; Cai, Dali; Chen, Zhaohui; Liu, Lingmei; Ge, Binghui; Hu, Ling; Qian, Weizhong; Wei, Fei

doi:10.1016/j.apcatb.2018.11.023

Cited by 84 publications

(60 citation statements)

References 51 publications

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“…The in situ XRD demonstrated that the crystallization process was a solid-state transformation through aS iF 6 2À intermediate. [18] Therefore, coke formation was retarded, and the catalytic lifetime of the catalyst was prolonged. Based on these results, ar eaction pathway was proposed, as illustrated in Scheme 1: the bulk zeolite crystals were first dissociated into smalls egments by NH 4 Fe tching.T hen, with the help of a template and NH 4 F, the segments recrystallizedo nt he silica substrate and formed sheet-like crystals.…”

Section: Resultsmentioning

confidence: 99%

“…Significantly,D S-HZSM-5 had am uch longerl ifetime;f or methanol conversionh igher than 90 %, the lifetimeo f DS-HZSM-5 was 610 hw hereas that of Conv-HZSM-5 was only 220 h. Specifically,o ur DS-HZSM-5 zeolite with sheet-like crystals had as hort b-axis length,w hich significantly improved the mass transfer by reducing the diffusionp ath. [18] Therefore, coke formation was retarded, and the catalytic lifetime of the catalyst was prolonged. Furthermore, the unique hollow-spherelike stacked morphology of DS-HZSM-5 endowed an abundant intercrystallite porosity,w hich increased the coke capacity and heat transfer and thus improved the stability of the catalyst.…”

Section: Resultsmentioning

confidence: 99%

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

Chen

et al. 2019

ChemSusChem

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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.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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

Chen

et al. 2019

ChemSusChem

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“…are small enough to diffuse randomly through the network of two intersecting channel systems without configuration limitations [15][16][17] . However, as the size of guest molecules further increasing, such as long chain hydrocarbons (C3, C4) or aromatic molecules, an anisotropic diffusion would occur, where the escape rates of the adsorbate in the intersecting pores of ZSM-5 zeolites are diverse in different channels segments (scheme 1b) 9,15,18,19 . Therefore, differentiating diffusivities in straight and sinusoidal channels for these anisotropic molecules over H-ZSM-5 zeolites are benefit to the understanding of activity, stability or product distribution in catalysis and the guidance of catalyst design with designated morphology.…”

Section: Schame 1 Amentioning

confidence: 99%

“…2 unexpectedly point out an obviously opposite result that enlarging the size along c-axis in H-ZSM-5 catalyst can result in a higher OCC catalytic activity and a better stability. It is well known that many factors in H-ZSM-5 crystal can influence the catalysis properties, such as acidities 26,29 , textural structures 27 and morphology [9][10][11][12] . On one hand, the influence of the textural structures and acid sites in our disquisitive catalysts can be excluded due to the similarity in these zeolites, as presented in Fig.…”

Section: Catalytic Behaviors Over H-zsm-5 Catalysts With Various Morpmentioning

confidence: 99%

Diffusion anisotropy descriptor revealing morphology effect of H-ZSM-5 zeolite for olefin catalytic cracking

Liu

Shi

Yang

et al. 2021

Preprint

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Zeolite morphology is vital in determining catalytic activity, selectivity and stability in zeolite catalysis, while quantitative description of morphology effect is great challenging but highly desirable. Herein, a descriptor to elucidate the morphology effect is proposed by revealing the diffusion anisotropy in straight and sinusoidal channels of H-ZSM-5 zeolite for olefin catalytic cracking. A series of H-ZSM-5 zeolites with similar nano-sheet morphology were precisely synthesized in which only the length in c-axis varies. It is unexpectedly demonstrated that the catalytic activity and stability can be obviously improved by employing samples with longer length in c-axis. Combining time-resolved in-situ FT-IR spectroscopy with molecular dynamic simulations, we revealed that the difference in catalytic performance can be attributed to the intracrystalline diffusive propensity in different channels. This work not only provides a clear descriptor revealing morphology effect, but also offers deep insight into design of highly effective zeolite catalysts for olefin catalytic cracking.

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“…Previous studies on zeolite ZSM-5 in the MTH reaction have concentrated on either designing materials/reactors for kinetic studies [11,16,20,22,[24][25] or gaining spatial insights by using advanced characterization techniques. [17,18,[26][27][28][29][30][31] However, none of these studies have been capable of disentangling the structure-reactivity relationships for specific zeolite-channel orientations under operando conditions.…”

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confidence: 99%

Disentangling Reaction Processes of Zeolites within Single‐Oriented Channels

Heijden

Stančiaková

et al. 2020

Angewandte Chemie

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Establishing structure–reactivity relationships for specific channel orientations of zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, a well‐defined model system was developed to build structure–reactivity relationships for specific zeolite‐channel orientations during various catalytic reaction processes, for example, the methanol‐ and ethanol‐to‐hydrocarbons (MTH and ETH) process as well as oligomerization reactions. The entrapped and effluent hydrocarbons from single‐oriented zeolite ZSM‐5 channels during the MTH process were monitored by using operando UV/Vis diffuse reflectance spectroscopy (DRS) and on‐line mass spectrometry (MS), respectively. The results reveal that the straight channels favor the formation of internal coke, promoting the aromatic cycle. Furthermore, the sinusoidal channels produce aromatics, (e.g., toluene) that further grow into larger polyaromatics (e.g., graphitic coke) leading to deactivation of the zeolites. This underscores the importance of careful engineering of materials to suppress coke formation and tune product distribution by rational control of the location of zeolite acid sites and crystallographic orientations.

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Modulation of b-axis thickness within MFI zeolite: Correlation with variation of product diffusion and coke distribution in the methanol-to-hydrocarbons conversion

Cited by 84 publications

References 51 publications

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

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

Diffusion anisotropy descriptor revealing morphology effect of H-ZSM-5 zeolite for olefin catalytic cracking

Disentangling Reaction Processes of Zeolites within Single‐Oriented Channels

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