Relating coke formation and characteristics to deactivation of ZSM-5 zeolite in methanol to gasoline conversion

Zhijian Wan, Gang Kevin Li, Chuanfu Wang, Hong Yang, Dongke Zhang

    Research output: Contribution to journalArticle

    20 Citations (Scopus)
    17 Downloads (Pure)

    Abstract

    Two ZSM-5 catalysts, differing only in their crystal size, viz, nanocrystal at ∼ 100 nm and microcrystal at 13 μm, respectively, were synthesised and tested in methanol to gasoline (MTG) conversion, with a focus on the formation and characteristics of coke deposits. Over time periods when methanol conversion decreased to 50%, herein termed as the service lifespan of the catalyst, the nanocrystal catalyst incurred 31.1 wt% coke deposition, while the microcrystal counterpart had 14.1 wt% coke. The nanocrystal catalyst showed a service lifespan almost seven times longer than the microcrystal catalyst. The difference in the catalytic service lifespans was examined in terms of the rate of formation of internal coke and structural properties of external coke, as determined using nitrogen physisorption, TGA and TEM. It was found that the internal coke was quickly formed in the microcrystal catalyst leading to rapid coverage of the active sites and blockage of the pores, resulting in fast deactivation. In contrast, coke formed preferentially on the external surface in the case of the nanocrystal catalyst. This external coke was of porous graphitic structures, and thus was not detrimental to the catalytic performance. The coke fouled nanocrystal catalyst was regenerated and the activity of the regenerated catalyst was evaluated under the same reaction conditions. An increase in catalytic service lifespan compared to the pristine nanocrystal catalyst was observed, due to the effect of decreased Al concentration on the catalytic performance.

    Original languageEnglish
    Pages (from-to)141-151
    Number of pages11
    JournalApplied Catalysis A: General
    Volume549
    DOIs
    Publication statusPublished - 5 Jan 2018

    Fingerprint

    Coke
    Gasoline
    Methanol
    Catalysts
    Nanocrystals
    Microcrystals
    ZSM-5 zeolite
    Physisorption
    Structural properties
    Catalyst activity
    Nitrogen
    Deposits
    Transmission electron microscopy
    Crystals

    Cite this

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    title = "Relating coke formation and characteristics to deactivation of ZSM-5 zeolite in methanol to gasoline conversion",
    abstract = "Two ZSM-5 catalysts, differing only in their crystal size, viz, nanocrystal at ∼ 100 nm and microcrystal at 13 μm, respectively, were synthesised and tested in methanol to gasoline (MTG) conversion, with a focus on the formation and characteristics of coke deposits. Over time periods when methanol conversion decreased to 50{\%}, herein termed as the service lifespan of the catalyst, the nanocrystal catalyst incurred 31.1 wt{\%} coke deposition, while the microcrystal counterpart had 14.1 wt{\%} coke. The nanocrystal catalyst showed a service lifespan almost seven times longer than the microcrystal catalyst. The difference in the catalytic service lifespans was examined in terms of the rate of formation of internal coke and structural properties of external coke, as determined using nitrogen physisorption, TGA and TEM. It was found that the internal coke was quickly formed in the microcrystal catalyst leading to rapid coverage of the active sites and blockage of the pores, resulting in fast deactivation. In contrast, coke formed preferentially on the external surface in the case of the nanocrystal catalyst. This external coke was of porous graphitic structures, and thus was not detrimental to the catalytic performance. The coke fouled nanocrystal catalyst was regenerated and the activity of the regenerated catalyst was evaluated under the same reaction conditions. An increase in catalytic service lifespan compared to the pristine nanocrystal catalyst was observed, due to the effect of decreased Al concentration on the catalytic performance.",
    keywords = "Catalyst coking, Deactivation, Methanol to gasoline, Percolation theory, ZSM-5 zeolite",
    author = "Zhijian Wan and Li, {Gang Kevin} and Chuanfu Wang and Hong Yang and Dongke Zhang",
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    Relating coke formation and characteristics to deactivation of ZSM-5 zeolite in methanol to gasoline conversion. / Wan, Zhijian; Li, Gang Kevin; Wang, Chuanfu; Yang, Hong; Zhang, Dongke.

    In: Applied Catalysis A: General, Vol. 549, 05.01.2018, p. 141-151.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Relating coke formation and characteristics to deactivation of ZSM-5 zeolite in methanol to gasoline conversion

    AU - Wan, Zhijian

    AU - Li, Gang Kevin

    AU - Wang, Chuanfu

    AU - Yang, Hong

    AU - Zhang, Dongke

    PY - 2018/1/5

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    AB - Two ZSM-5 catalysts, differing only in their crystal size, viz, nanocrystal at ∼ 100 nm and microcrystal at 13 μm, respectively, were synthesised and tested in methanol to gasoline (MTG) conversion, with a focus on the formation and characteristics of coke deposits. Over time periods when methanol conversion decreased to 50%, herein termed as the service lifespan of the catalyst, the nanocrystal catalyst incurred 31.1 wt% coke deposition, while the microcrystal counterpart had 14.1 wt% coke. The nanocrystal catalyst showed a service lifespan almost seven times longer than the microcrystal catalyst. The difference in the catalytic service lifespans was examined in terms of the rate of formation of internal coke and structural properties of external coke, as determined using nitrogen physisorption, TGA and TEM. It was found that the internal coke was quickly formed in the microcrystal catalyst leading to rapid coverage of the active sites and blockage of the pores, resulting in fast deactivation. In contrast, coke formed preferentially on the external surface in the case of the nanocrystal catalyst. This external coke was of porous graphitic structures, and thus was not detrimental to the catalytic performance. The coke fouled nanocrystal catalyst was regenerated and the activity of the regenerated catalyst was evaluated under the same reaction conditions. An increase in catalytic service lifespan compared to the pristine nanocrystal catalyst was observed, due to the effect of decreased Al concentration on the catalytic performance.

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    KW - Deactivation

    KW - Methanol to gasoline

    KW - Percolation theory

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