Cooperative effects of zeolite mesoporosity and defect sites on the amount and location of coke formation and its consequence in deactivation

Lee, Kyung-Ho; Lee, Songhyun; Jun, Young-Sun; Choi, Minkee

doi:10.1016/j.jcat.2017.01.018

Cited by 120 publications

(69 citation statements)

References 65 publications

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“…The accumulation of coke in mesopores is likely related to the quality of the crystals. The increased number of silanols and Lewis acid sites on ZB and ZNS are prone to trap desorbed products [51][52][53] as confirmed by the disappearance of silanol groups on spent catalysts (Figure 26 S22). Taking a coke density of 1.1 g cm -3 , the volume of coke in the micropores corresponds to the loss of micropore volume measured by nitrogen adsorption (Figure 8).…”

Section: Methodsmentioning

confidence: 91%

Preparation of Single-Crystal “House-of-Cards”-like ZSM-5 and Their Performance in Ethanol-to-Hydrocarbon Conversion

et al. 2019

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The present study reports the unbiased chemical etching of micron-sized ZSM-5 crystals with an NH4F solution resulting in house-of-cards-like single crystals containing large rectangular cavities surrounded by thin (15 -30 nm), flat and highly crystalline walls. The formation of such house-of-cards-like architecture is a result of the preferential extraction of mis-oriented nanocrystalline domains followed by the uniform dissolution of the remaining part of the crystal.The characteristic features of NH4F-treated zeolites are the retention of framework composition (Si/Al) and Brønsted acidity, high crystallinity, a moderate increase in external surface area and increased accessibility to their active sites. Such a combination produces zeolitic catalysts with superior performances (activity, stability and coke resistance) in the ethanol-to-hydrocarbons conversion. The physicochemical properties of this newly engineered zeolite are compared with a hierarchical zeolite obtained by caustic leaching and zeolite nano-sheets synthesized with a bifunctional template, a di-quaternary ammonium-type surfactant.

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Section: Methodsmentioning

confidence: 91%

Preparation of Single-Crystal “House-of-Cards”-like ZSM-5 and Their Performance in Ethanol-to-Hydrocarbon Conversion

et al. 2019

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“…[30,31] During the aromatization process, the larger molecules mainly occupy the acid sites and thereby block the micropores, this results in coke formation and subsequently catalyst deactivation. [32] Hence, it is important to compare the carbon deposition of spent catalysts over parent, Pt, and Pt-M modified ZSM-5. The results of coke content analysis of spent catalysts are shown in Table 3.…”

Section: Catalyst Evaluationmentioning

confidence: 99%

Light Paraffinic Naphtha to BTX Aromatics over Metal‐Modified Pt/ZSM‐5

et al. 2020

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We investigated the conversion of light paraffinic naphtha (C5-C6) into BTX (benzene, toluene, and xylenes) aromatics using 1.0 wt % Pt-M/ZSM-5 (modifier M = 1 wt% Zn, 2 wt % of Fe, La, Ga) prepared using wet-impregnation method. The effects of Pt and modifier on light naphtha conversion, yield and aromatic selectivity (benzene, toluene, xylene, C9 + aromatics) were studied in fixed-bed flow reactor in atmospheric pressure, at 550°C, and WHSV 1.0 h À 1. Catalytic efficiency of modified Pt or Pt-M ZSM-5 catalysts has been equated to conventional ZSM-5 [Si/Al 2 = 30] catalyst. While the yield of total aromatics was slightly increased over Pt/ZSM-5 comparison to parent ZSM-5 from 32 wt % to 37 wt %, the value for in situ formed mesoporous Pt-Ga/ZSM-5 was significantly improved reaching 60 wt %. The higher selectivity to aromatics is attributed to the induced mesoporous volumes and dehydrogenation activity of Ga species. These species associated with Pt were effective in the conversion of light naphtha to olefins, which later converted into aromatics by secondary reactions: cracking, isomerization and dimerization. The Pt-Ga/ZSM-5 showed good stability toward the selective production of aromatics at a low toluene/benzene ratio ∼ 0.5 due to Pt component.

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“…Numerous studies have been reported to synthesize hierarchical structured zeolites [11][12][13][14][15][16] , though these morphologies lead to lower crystallinity and more framework defects [17,18] . Framework defects are prone to coke formation, as several studies have demonstrated a direct correlation between coke formation and silanol defects [19][20][21][22][23][24] .…”

Section: Introductionmentioning

confidence: 99%

Fluoride-mediated nano-sized high-silica ZSM-5 as an ultrastable catalyst for methanol conversion to propylene

Guo

Dai

et al. 2018

Journal of Energy Chemistry

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Cooperative effects of zeolite mesoporosity and defect sites on the amount and location of coke formation and its consequence in deactivation

Cited by 120 publications

References 65 publications

Preparation of Single-Crystal “House-of-Cards”-like ZSM-5 and Their Performance in Ethanol-to-Hydrocarbon Conversion

Preparation of Single-Crystal “House-of-Cards”-like ZSM-5 and Their Performance in Ethanol-to-Hydrocarbon Conversion

Light Paraffinic Naphtha to BTX Aromatics over Metal‐Modified Pt/ZSM‐5

Fluoride-mediated nano-sized high-silica ZSM-5 as an ultrastable catalyst for methanol conversion to propylene

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