Evaluation and fabrication of pore‐size‐tuned silica membranes with tetraethoxydimethyl disiloxane for gas separation

Lee, Hye Ryeon; Kanezashi, Masakoto; Shimomura, Yoshihiro; Yoshioka, Tomohisa; Tsuru, Toshinori

doi:10.1002/aic.12501

Cited by 128 publications

(117 citation statements)

References 37 publications

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“…From the results, dp was numerically fitted using Eq. (36) to be 0.34 nm, which is comparable to that of a sol-gel silica membrane from TEOS 11), 19) . Although the method can be used for the data obtained here, and gives a reasonable estimate of the pore diameter, if there were pores.…”

Section: P M M Imentioning

confidence: 48%

“…Very recently, the group of Tsuru proposed a novel method for the determination of pore size which they call a normalized Knudsen-based permeance (NKP) derived from the GT model 19) . The NKP, f, is the ratio of the permeance of a target component to that predicted from a reference component (He) based on the Knudsen diffusion mechanism (Eq.…”

Section: Permeation In the Silica Layermentioning

confidence: 99%

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Review on Mechanisms of Gas Permeation through Inorganic Membranes

Oyama

Yamada

Sugawara

et al. 2011

J. Jpn. Petrol. Inst.

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The major mechanisms of gas permeation through solid membranes are described and the applicable equations describing the permeance are presented. The mechanisms depend on the relative size of the permeating molecules and the diameter of the pores. As pore size decreases the operable mechanisms are Hagen-Pouiselle flow, Knudsen diffusion, surface diffusion, gas-translation, and finally solid-state diffusion. The Hagen-Pouiselle mechanism involves flow through large pores, while the Knudsen mechanism involves collision of molecules with the walls of pores of intermediate size. Surface diffusion deals with movement of molecules trapped in the potential field of the walls of pores of relatively small size, while gas-translation involves molecules that can escape the field, but are constrained by the small pores. Finally, solid-state transport comprises dissolution and transport by diffusion within the solid. These mechanisms are illustrated for hydrogen permeance with the use of two membranes, an alumina membrane with intermediate sized pores and a silica on alumina membrane of dense structure. KeywordsPermeation mechanism, Inorganic membrane, Silica membrane, Solid-state diffusion, Glassy membranes mechanism, Hydrogen However, oftentimes the actual selectivity can deviate strongly from that defined above because of interactions between the species with each other or with the walls of the membranes. For example, the preferred adsorption or absorption of one species in the pores of a membrane can block the passage of other species. Thus, single-gas selectivities should be taken as a limiting case approximation.A fundamental expression for transport in membranes is derived from Fick's First Law, which relates the flux of species i to the concentration gradient. The gradient in turn can be related to the concentration in the inlet, cio and outlet, ciL, of a membrane of thickness L:The diffusivity in Fick's first law is the ordinary molecular diffusivity, Di(c) [m 2 ・s-1 ], which may have a concentration dependence. In the case of membranes an effective diffusivity, De,i is used, where the porosity ε and tortuosity τ of the membrane are included. The tortuosity is a factor that accounts for the increased length of a pore by the presence of twists and turns. For example, if a single straight pore is replaced by one having a single 90° turn, the tortuosity would be 2 or 1.4. In an early treatment the relative diameters of the diffusing molecules, dm, and pores, dP, was taken into account through a restrictive factor KrFor many membranes dm/dp is small, so Kr is unity. There have been many proposed mechanisms with a variety of materials based on various interaction and diffusion processes. These mechanisms are in broad terms distinguished by the ratio of pore diameter dp to kinetic diameter dm of the gas molecule. As the pore diameter becomes smaller, that is with increasing value of dm/dp, the interactions between the molecule and the surface become larger in proportion to the ratio of the area of the surface potential fi...

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Section: P M M Imentioning

confidence: 48%

Section: Permeation In the Silica Layermentioning

confidence: 99%

Review on Mechanisms of Gas Permeation through Inorganic Membranes

Oyama

Yamada

Sugawara

et al. 2011

J. Jpn. Petrol. Inst.

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“…The organic groups are incorporated in the silica network on a molecular level, and this makes them more stable than analogous pure organics, but they cannot withstand the same temperatures as fully inorganic silica. For example, the methyl groups in methylated silica are reported stable up to 450-550°C under inert atmosphere [19,[37][38][39][40] and up to 350-400°C in the presence of oxygen [38,40]. Placing organic groups in bridged configuration improves their thermal stability; methylene groups are reported stable up to 650°C under inert atmosphere [41].…”

Section: Thermal and Hydrothermal Stabilitymentioning

confidence: 99%

Structure–property tuning in hydrothermally stable sol–gel-processed hybrid organosilica molecular sieving membranes

Elshof

Dral

2015

J Sol-Gel Sci Technol

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Supported microporous organosilica membranes made from bridged silsesquioxane precursors by an acid-catalyzed sol-gel process have demonstrated a remarkable hydrothermal stability in pervaporation and gas separation processes, making them the first generation of ceramic molecular sieving membranes with sufficient performance under industrially relevant conditions. The commercial availability of various a,x-bis(trialkoxysilyl)alkane and 1,4-bis(trialkoxysilyl)benzene precursors facilitates the tailoring of membrane properties like pore size and surface chemistry via the choice of precursor(s) and process variables. Here, we describe the engineering of sols for making supported microporous thin films, discuss the thermal and hydrothermal stability of microporous organosilicas and give a short overview of the developments and applications of these membranes in liquid and gas separation processes since their first report in 2008.Graphical Abstract

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“…Here, ρ is the moving probability in a 3-dimensional space including the effective pore cross-sectional area, πd e 2 /4, and the activation energy for diffusion (Shelekhin et al, 1995;Lee et al, 2011).…”

Section: Condensable Vapor Permeation Modelmentioning

confidence: 99%

“…In order to design a porous inorganic membrane unit and to determine the optimized operating conditions for such separation processes, an understanding of the transport mechanisms of molecules within micropores is indispensable. The gas permeation mechanisms for microporous inorganic membranes with pores less than 1.0 nm in diameter have been extensively investigated in experimental and theoretical manners by many groups using zeolite, sol-gel derived, or CVD-modified glass membranes (Xiao and Wei, 1992;De Lange et al, 1995;Shelekhin et al, 1995;Burggraaf, 1999;Yoshioka et al, 2001aYoshioka et al, , 2013Lee et al, 2011). Gas permeation and separation mechanisms through a micropore are normally classified into Knudsen diffusion, surface diffusion, multilayer diffusion, capillary condensation, and molecular sieving (Uhlhorn et al, 1992;Gilron and Soffer, 2002).…”

Section: Introductionmentioning

confidence: 99%

Micropore Filling Phase Permeation of a Condensable Vapor in Silica Membranes: A Molecular Dynamics Study

Yoshioka

Nagasawa

Kanezashi

et al. 2013

J. Chem. Eng. Japan

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Molecular dynamics simulation was used to investigate the permeation properties of a virtual condensable vapor through micropores. A permeation model was proposed to simulate the movement of condensable vapor through a micropore. The model is called "micropore lling phase permeation (MFP)," and the e ect of feed gas pressure, pore size and pore size distributions on the vapor permeation properties was examined through model calculations. The observed permeance of ethane-like LJ particles at 260 K, a temperature below the critical temperature of real ethane, decreased stepwise at a speci c pressure as the mean pressure was increased for micropores sized 0.8 and 1.1 nm in diameter. Analysis of the adsorption isotherm in the pores and vapor permeation simulations revealed the formation of a high-density liquid-like phase in micropores as the MFP caused a decrease in the mobility of permeating molecules. The model calculations based on the MFP showed qualitative agreement with the simulation results.

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Evaluation and fabrication of pore‐size‐tuned silica membranes with tetraethoxydimethyl disiloxane for gas separation

Cited by 128 publications

References 37 publications

Review on Mechanisms of Gas Permeation through Inorganic Membranes

Review on Mechanisms of Gas Permeation through Inorganic Membranes

Structure–property tuning in hydrothermally stable sol–gel-processed hybrid organosilica molecular sieving membranes

Micropore Filling Phase Permeation of a Condensable Vapor in Silica Membranes: A Molecular Dynamics Study

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