Sorption and activation of hydrocarbons by molecular sieves

Lercher, Johannes A.; Seshan, Kulathuiyer

doi:10.1016/s1359-0286(97)80106-4

Cited by 17 publications

(20 citation statements)

References 30 publications

(39 reference statements)

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“…504 At most catalytic reaction temperatures, the net effect of an increase in chain length is a decrease in Gibbs free energy of adsorption and therefore an increase in reactivity. 447,448,453 The degree of compensation between adsorption entropy and enthalpy is a clear function of the pore size, 191,194,448 so that the discrimination of zeolites between n-alkanes of various lengths depends on the pore topology. To the extent that the reactivity of n-alkanes as a function of chain length varies with zeolite topology, it issby definition 433 san example of (reactant) shape selectivity.…”

Section: Reactant Shape Selectivitymentioning

confidence: 99%

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Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

2008

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Section: Reactant Shape Selectivitymentioning

confidence: 99%

“…130 Working out how to exactly merge adsorption control into shape selectivity set off a flurry of continuing activities that has not come to an end yet. 191,247,248,[447][448][449][450][451][452][453] It seems to provide the keys to puzzles that have riddled the classical shape selectivity model right from its inception.…”

Section: Introductionmentioning

confidence: 99%

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

2008

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“…• Apply a specific isotherm, such as the Langmuir isotherm [47,[68][69][70][71][72][73][74][75][76][77].…”

Section: Thermodynamics Of Adsorptionmentioning

confidence: 99%

“…A fourth approach is based on extrapolating a specific isotherm to the Henry regime [47,[68][69][70][71][72][73][74][75][76][77], as exemplified by the popular Langmuir isotherm. It equates the reference loading, q 0 (mol/kg), with the saturation capacity, q sat (mol/kg), and uses a fixed reference pressure (typically p 0 = 101325 Pa) as standard state.…”

Section: Thermodynamics Of Adsorptionmentioning

confidence: 99%

Shape-selective n-alkane hydroconversion at exterior zeolite surfaces

Maesen

Krishna²,

Baten³

et al. 2008

Journal of Catalysis

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A critical review of the adsorption and catalysis of n-and methylalkanes demonstrates that the interior surface of TON-and MTT-type zeolites dominates both adsorption and catalysis, and that the contribution from the exterior surface is negligible. For both n-and methylalkane isomers, the experimental Henry constants at the interior TON-type zeolite surface are more than an order of magnitude greater than those at the exterior surface. Molecular simulations on exclusively interior TON-type silica surface reproduce the adsorption isotherms of n-and methylalkane isomers remarkably well and suggest that even an isomer as bulky as 2,3-dimethylpentane could have access to the interior TON-type zeolite surface. Only the reference state used in solution thermodynamics affords an equitable comparison between internal and external surface thermodynamics. It indicates that methylalkanes adsorb in a structured fashion at the exterior TON-type zeolite surface when the interior surface is inaccessible. But the entropic penalty for this organized exterior surface "pore mouth" or "key-lock" adsorption is high, so that methylalkanes prefer adsorption at the interior surface when it is accessible. We speculate that CHA-and ERI-type sieves exhibit exterior surface catalysis in long n-alkane conversion, but the database remains too small to allow investigation of the full potential of shape selectivity in exterior zeolite surface catalysis.

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“…Experimentally, the adsorption capacities of chloroanilines on montmorillonite and kaolinite sieves depend on the hydrophilicity and lipophilicity of adsorbates; that is, the extent of adsorption on hydrophobic adsorbents increases with lipophilicity of adsorbates (Angioi, et al, 2005;Polati, et al, 2006). Additionally, the effects of moisture competition and high temperature desorption, which reduce the VOC adsorption capacities of adsorbents, have been extensively investigated (Keener and Zhou, 1990;Chou and Chiou, 1997;Lercher and Seshan, 1997;Yun, et al, 1998;Gawryś et al, 2001;Bilgiç and Aşkin, 2003;Manjare and Ghoshal, 2006). Generally, various solvents (such as ketones and alcohols) are gathered together in an internal circulation cabinet.…”

Section: Introductionmentioning

confidence: 99%

Competition among Mixed Adsorbates Affecting the Adsorption of Gaseous Methyl Ethyl Ketone by Hydrophobic Molecular Sieve

Cheng

Tsai

2007

Aerosol Air Qual. Res.

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Internal circulation cabinets, equipped with adsorbents for emitted volatile organic compounds (VOCs), are extensively used to store organic solvents in Taiwanese university and hospital laboratories.This work evaluates how ketone and isopropanol (IPA) respectively influence the methyl ethyl ketone (MEK) adsorption capacity of a hydrophobic molecular sieve (MS) with a high Si/Al ratio of 1000, and concentration (C, ppm) are closely fitted using a Langmuir isotherm. Lower VOC concentration ratios less than 0.17 for mixing acetone and IPA respectively with MEK rarely affect the MEK adsorption by HiSiv 1000. However, the effect of competitive adsorption, which evidently reduces the adsorption capacity of MEK, is related to the higher mixture concentration ratio (> 0.80) of IPA to MEK. The experimental results show that the hydrophobicity characteristics of MEK, acetone and IPA were responsible for variation in adsorption capacity of hydrophobic molecular sieve. Working parameters of adsorbent materials in the internal circulation cabinet have been also provided for preventing breakthrough of VOC adsorption by the molecular sieve.

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Sorption and activation of hydrocarbons by molecular sieves

Cited by 17 publications

References 30 publications

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

Shape-selective n-alkane hydroconversion at exterior zeolite surfaces

Competition among Mixed Adsorbates Affecting the Adsorption of Gaseous Methyl Ethyl Ketone by Hydrophobic Molecular Sieve

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