Diffusivities in the binary components system within MFI-type zeolite crystals

Masuda, Toshio; Fujikata, Yoshihiro; Ikeda, Hideo; Hashimoto, Kenji

doi:10.1016/s1387-1811(00)00151-7

Cited by 26 publications

(23 citation statements)

References 18 publications

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“…While the acid sites in H-ZSM-5 slow down n-hexane diffusivity considerably, this effect is largely absent when 2-methylpentane is present in the micropores. Our observations are confirmed by a recent experimental study of diffusion in silicalite of binary mixtures of alkanes (n-heptane, n-octane) and aromatics (ortho-and [55]. These authors found that a component with a low diffusion coefficient can considerably slow down diffusion of a faster one by selective blocking of the zeolite intersections [65].…”

Section: Fig 13supporting

confidence: 89%

“…The decrease in diffusion rates for these components is probably caused by the decrease of the probability for the molecule to jump to a free neighboring adsorption site. A sharp drop in the diffusivity was indeed observed by Masuda et al [55], who studied binary diffusion of n-heptane and n-octane in silicalite. These alkanes do not have any preference for a particular adsorption site.…”

Section: Self-diffusivity Of 2-methylpentane/n-hexanesupporting

confidence: 57%

“…11 Self-diffusivities of mixture components in silicalite as a function of the 2-methylpentane fraction in the gas phase (left) and as a function of the 2-methylpentane loading (total hydrocarbon pressure 6.6 kPa, 433 K) component studies [53] and indicating that the mobility of the slower component is not noticeably affected by the presence of a fast one [54][55][56]. A peculiar observation is found in the dependence of the n-hexane self-diffusivity on the 2-methylpentane fraction.…”

Section: Self-diffusivity Of 2-methylpentane/n-hexanementioning

confidence: 99%

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Positron Emission Profiling: a Study of Hydrocarbon Diffusivity in MFI Zeolites

Hensen

Jong

Santen

2007

Adsorption and Diffusion

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Section: Fig 13supporting

confidence: 89%

Section: Self-diffusivity Of 2-methylpentane/n-hexanesupporting

confidence: 57%

Section: Self-diffusivity Of 2-methylpentane/n-hexanementioning

confidence: 99%

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Positron Emission Profiling: a Study of Hydrocarbon Diffusivity in MFI Zeolites

Hensen

Jong

Santen

2007

Adsorption and Diffusion

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“…4,10,36 In all these systems, it was found that the diffusivity of the slow component is essentially unaffected by the presence of the fast component. The diffusive behavior can be understood on the basis of a simple jump diffusion model, in which diffusion is thought of as a sequence of activated jumps from one site to another, as was already demonstrated by Masuda et al 10 Such a jump can only be successful if the site to which the molecule jumps is empty. Although the jump frequency itself does not depend on the composition of the mixture, the number of successful jumps will.…”

Section: B Binary Adsorption: Results and Comparison With Cbmc Simulmentioning

confidence: 97%

Adsorption and Diffusion of n-Hexane/2-Methylpentane Mixtures in Zeolite Silicalite: Experiments and Modeling

et al. 2001

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With the tracer-exchange positron emission profiling (TEX-PEP) technique, the reexchange process of radioactively labeled molecules with a steady-state feed stream can be measured inside a zeolite-packed bed reactor. When the experimental tracer-exchange curves are modeled, values for the micropore diffusion and adsorption constant can be obtained. As one can choose which component to label, this technique is ideally suited for studying multicomponent diffusion. In the present study, this technique has been used to measure the diffusive and adsorptive properties of an n-hexane/2-methylpentane mixture in zeolite silicalite. The measurements were performed at different ratios of n-hexane and 2-methylpentane in the gas phase at a constant total hydrocarbon pressure of 6.6 kPa and a temperature of 433 K. A slight preference for the adsorption of n-hexane was found because it is entropically more favorable to adsorb these molecules as they have no preferential siting in the zeolite pores. The diffusivity of the slowly moving 2-methylpentane is not strongly affected by the presence of the fast moving n-hexane. The mobility of the linear alkane however strongly decreases with increasing 2-methylpentane ratio and suddenly drops at a loading of approximately three 2-methylpentane molecules per unit cell. This is caused by the fact that the branched alkanes are preferentially sited in the intersections between the straight and zigzag channels of silicalite and therefore effectively block the zeolite pore network. These results show that the adsorptive properties of the components and the structure of the zeolite network play an important role in the behavior of multicomponent mixtures in zeolites.

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“…We have also reported the intracrystalline diffusivity of benzene, toluene, xylene isomers, and lighter hydrocarbons within MFI-type and Y-type zeolite in the gas phase by the constant volumetric method (Masuda et al, 1996(Masuda et al, , 2000(Masuda et al, , 2001Masuda, 2003aMasuda, , 2003bFujikata et al, 1998). There have been few reports, however, concerning direct experimental measurements of diffusivity under high-temperature and high-pressure conditions in the liquid phase.…”

Section: Introductionmentioning

confidence: 99%

Liquid-phase diffusivity of benzene within mesoporous materials measured by a laser Raman technique

Nakasaka

Tago

Yano

et al. 2010

Chemical Engineering Science

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The intracrystalline diffusivities of benzene within a series of porous materials in the liquid phase (cyclohexane was used as solvent) were measured by a constant volumetric method using Raman spectroscopy at a temperature range from 323 to 393 K.Silicalite-1, mono-dispersed mesoporous silica spheres (MMSS), Silica Gel, -Al 2 O 3 , and SiO 2 -Al 2 O 3 were used as adsorbents. The intracrystalline diffusivity was calculated by parameter fitting using theoretical equations and the experimental transient change of benzene concentrations with time in response to the adsorption. The intracrystalline diffusivities of benzene within mesoporous silicas were almost the same as that within the micropore of silicalite-1, though the pore diameters of silicalite-1 and mesoporous silicas were different from each other. It is considered that the pore walls as well as the solvent molecules of cyclohexane affect the diffusion of benzene molecules in the meso pore region.3

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Diffusivities in the binary components system within MFI-type zeolite crystals

Cited by 26 publications

References 18 publications

Positron Emission Profiling: a Study of Hydrocarbon Diffusivity in MFI Zeolites

Positron Emission Profiling: a Study of Hydrocarbon Diffusivity in MFI Zeolites

Adsorption and Diffusion of n-Hexane/2-Methylpentane Mixtures in Zeolite Silicalite: Experiments and Modeling

Liquid-phase diffusivity of benzene within mesoporous materials measured by a laser Raman technique

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