Investigation on the mechanism of diffusion in mesopore structured ZSM-5 and improved heavy oil conversion

Zhao, Liang; Shen, Baojian; Gao, Jinsen; Chen, Xu

doi:10.1016/j.jcat.2008.06.015

Cited by 142 publications

(73 citation statements)

References 24 publications

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“…In the research of Ogura et al, there was a higher catalytic cracking activity of cumene on meso-microporous ZSM-5 prepared by alkaline treatment than the parent microporous ZSM-5 [18]. In our previous works [19,20], it was also proved that alkalitreatment on ZSM-5 is an effective method to improve the propylene yield in heavy oil catalytic cracking.…”

Section: Introductionmentioning

confidence: 89%

Influence of combined alkaline treatment and Fe–Ti-loading modification on ZSM-5 zeolite and its catalytic performance in light olefin production

Hao

Shen

Wang

et al. 2012

Journal of Industrial and Engineering Chemistry

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Section: Introductionmentioning

confidence: 89%

Influence of combined alkaline treatment and Fe–Ti-loading modification on ZSM-5 zeolite and its catalytic performance in light olefin production

Hao

Shen

Wang

et al. 2012

Journal of Industrial and Engineering Chemistry

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“…Among which, introducing mesopores into the original structure of microporous zeolites is one of the most efficient methods [5][6][7]. Such mesostructured zeolite materials have not only the advantages of micropores, which ensure acidity and shape selectivity, but also the advantages of mesopores, which promote the adsorption of molecules [8][9][10] and diffusion rate for mass transfer within zeolites [8,[11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Adsorption and Diffusion of Xylene Isomers on Mesoporous Beta Zeolite

Song

et al. 2015

Catalysts

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Abstract:A systematic and detailed analysis of adsorption and diffusion properties of xylene isomers over Beta zeolites with different mesoporosity was conducted. Adsorption isotherms of xylene isomers over microporous and mesoporous Beta zeolites through gravimetric methods were applied to investigate the impact of mesopores inside Beta zeolites on the adsorption properties of xylene isomers in the pressure range of lower 20 mbar. It is seen that the adsorption isotherms of three xylene isomers over microporous and mesoporous Beta zeolites could be successfully described by the single-site Toth model and the dual-site Toth model, respectively. The enhanced adsorption capacities and decreased Henry's constants (KH) and the initial heats of adsorption (Qst) for the all xylene isomers are observed after the introduction of mesopores in the zeolites. For three xylene isomers, the order of Henry's constant is o-xylene > m-xylene > p-xylene, whereas the adsorption capacities of Beta zeolite samples for xylene isomers execute the following order of o-xylene > p-xylene > m-xylene, due to the comprehensive effects from the molecular configuration and electrostatic interaction. At the same time, the diffusion properties of xylene isomers in the mesoporous Beta zeolites were also studied through the desorption curves measured by the zero length column (ZLC) method at 333-373 K. It turned out that the effective diffusion time constant (Deff/R 2 ) is a growing trend with the increasing mesoporosity, whereas the tendency of the activation energy is just the reverse, indicating the contribution of mesopores to facilitate molecule diffusion by shortening diffusion paths and reducing diffusion resistances. Moreover, the diffusivities of three xylene isomers in all Beta zeolites follow an order of p-xylene > m-xylene > o-xylene OPEN ACCESSCatalysts 2015, 5 2099 as opposed to KH, conforming the significant effects of adsorbate-adsorbent interaction on the diffusion.

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“…Desilication has been proven to be effective method to introduce mesoporosity in different types of zeolite structures [5][6][7][8][9][10][11][12][13][14][15][16]. Till now the majority of desilication studies has been done with zeolites of medium Si/Al ratio where aluminium acts as the pore directing agent regulating the extent of the Si extraction.…”

Section: Introductionmentioning

confidence: 99%

Desilication of highly siliceous zeolite ZSM-5 with NaOH and NaOH/tetrabutylamine hydroxide

Sadowska

Góra‐Marek

Drozdek

et al. 2013

Microporous and Mesoporous Materials

131

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Elsevier Sadowska, K.; Góra-Marek, K.; Drozdek, M.; Kustrowski, P.; Datka, J.; Martínez-Triguero, J.; Rey Garcia, F. (2013). Desilication of highly siliceous zeolite ZSM-5 with NaOH and NaOH/tetrabutylamine hydroxide. ABSTRACTThe results of both chemical and XPS analysis pointed out that desilication of highly siliceous ZSM-5 of Si/Al = 164 was more effective in the surface zone than in the bulk, contrary to zeolite ZSM-5 of Si/Al = 31.6. According to the IR studies in parent zeolite the concentration of protonic sites was very close to the concentration of Al indicating that all Al atoms can form Si-OH-Al. The results of our quantitative IR studies strongly support the realumination thesis, i.e. some Al atoms extracted in basic solutions are subsequently reinserted forming new acidic hydroxyls. In desilicated zeolites all Al atoms were able to form protonic sites, however part of them dehydroxylated during the activation of zeolite producing Lewis acid sites according to the stoichiometry: one protonic site was transformed into one Lewis site. Low temperature nitrogen adsorption revealed that the treatment of highly siliceous zeolite with 0.2 M NaOH/TBAOH mixture produced mesopores of smaller diameter and narrower pore size distribution than in the case of zeolite of medium Si/Al ratio. This result can be explained by low concentration of Al which similarly as TBA + cations plays the role of pore directing agents (PDA). Contrary to TBA + , the presence of Al in desilication mixture, led to the formation of larger pores. Therefore, in highly siliceous zeolite TBA + played dominant role as PDA producing narrower pores. Highly siliceous zeolite with uniform distribution of relatively narrow pores may be useful catalyst or catalyst support. The influence of desilication temperature on porosity development was also investigated. The increase of desilication temperature from 338 K to 353 K resulted in both more extensive demetalation (more Si and Al is extracted) and the distinct increase of the volume and surface of mesopores. Both lower concentration of protonic sites and higher concentration of Lewis 2 sites confirmed partial zeolite destruction upon desilication at elevated temperature. The experiments of pivalonitrile sorption followed by IR spectroscopy showed a significant increase of accessibility of acid sites to bulky pivalonitrile molecules.

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Investigation on the mechanism of diffusion in mesopore structured ZSM-5 and improved heavy oil conversion

Cited by 142 publications

References 24 publications

Influence of combined alkaline treatment and Fe–Ti-loading modification on ZSM-5 zeolite and its catalytic performance in light olefin production

Influence of combined alkaline treatment and Fe–Ti-loading modification on ZSM-5 zeolite and its catalytic performance in light olefin production

Adsorption and Diffusion of Xylene Isomers on Mesoporous Beta Zeolite

Desilication of highly siliceous zeolite ZSM-5 with NaOH and NaOH/tetrabutylamine hydroxide

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