Hybrid H<sub>2</sub>-Selective Silica Membranes Prepared by Chemical Vapor Deposition

Gu, Yu; Vaezian, Bita; Khatib, Sheima J.; Oyama, S. Ted; Wang, Zhenxing; Achenie, Luke E.K.

doi:10.1080/01496395.2012.659788

Cited by 9 publications

(4 citation statements)

References 38 publications

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“…This explains why there are no Knudsen diffusion cells in all minimum acceptable grid models except for M2. From experimental results, the measured pore size varies from 0.50 to 0.85 nm, 33 which is much smaller than the appropriate pore size for Knudsen diffusion mechanism. This is possible evidence that Knudsen diffusion is not present in the membrane.…”

Section: ■ Results and Discussionmentioning

confidence: 96%

Mixed Mechanism Model for Permeation of Gases in Hybrid Inorganic–Organic Membranes

Wang

Achenie

Khatib

et al. 2013

Ind. Eng. Chem. Res.

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A general mixed mechanism model formulated within a grid framework is proposed. In particular, the framework is employed to account for the variability in the diffusion of carbon dioxide and methane in a certain class of inorganic−organic membranes. This variability is a basis for separation of gas mixtures into the various components. Various sizes of the cells within the grid are developed for a series of hybrid inorganic−organic membranes. Parameters in each model are estimated from the permeance results of both carbon dioxide and methane. Acceptable grid models are determined by comparing the estimated parameters of a surface diffusion mechanism with the values reported in the open literature. For each membrane, the model with the minimum number of grid cells is studied. The diffusion in the studied membranes is dominated by activated Knudsen at lower temperatures and limited by surface diffusion when the temperature is above a critical value. Activated Knudsen diffusion is the major mechanism that affects carbon dioxide/methane selectivity.

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Section: ■ Results and Discussionmentioning

confidence: 96%

Mixed Mechanism Model for Permeation of Gases in Hybrid Inorganic–Organic Membranes

Wang

Achenie

Khatib

et al. 2013

Ind. Eng. Chem. Res.

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“…To improve the hydrothermal stability of silica membranes, various silicon compounds with different functional groups were studied such as silanes containing organic functional groups (methyl [13,14,15,16], propyl [15], hexyl [17], phenyl [15,18,19,20], and vinyl [21,22]) attached directly to a single silicon atom, and alkoxy siloxanes bridged with ≡Si–R–Si≡ structures (e.g., bis(triethoxysilyl)ethane) [23,24,25,26]. However, there were few reports focused on the number of the functional groups in a silicon compound.…”

Section: Introductionmentioning

confidence: 99%

Gas Separation Silica Membranes Prepared by Chemical Vapor Deposition of Methyl-Substituted Silanes

et al. 2019

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The effect on the gas permeance properties and structural morphology of the presence of methyl functional groups in a silica membrane was studied. Membranes were synthesized via chemical vapor deposition (CVD) at 650 °C and atmospheric pressure using three silicon compounds with differing numbers of methyl- and methoxy-functional groups: tetramethyl orthosilicate (TMOS), methyltrimethoxysilane (MTMOS), and dimethyldimethoxysilane (DMDMOS). The residence time of the silica precursors in the CVD process was adjusted for each precursor and optimized in terms of gas permeance and ideal gas selectivity criteria. Final H2 permeances at 600 °C for the TMOS-, MTMOS-, and DMDMOS-derived membranes were respectively 1.7 × 10−7, 2.4 × 10−7, and 4.4 × 10−8 mol∙m−2∙s−1∙Pa−1 and H2/N2 selectivities were 990, 740, and 410. The presence of methyl groups in the membranes fabricated with the MTMOS and DMDMOS precursors was confirmed via Fourier-transform infrared (FTIR) spectroscopy. From FTIR analysis, an increasing methyl signal in the silica structure was correlated with both an improvement in the hydrothermal stability and an increase in the apparent activation energy for hydrogen permeation. In addition, the permeation mechanism for several gas species (He, H2, Ne, CO2, N2, and CH4) was determined by fitting the gas permeance temperature dependence to one of three models: solid state, gas-translational, or surface diffusion.

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“…There have been reports on the tailoring of the pore size of silica membranes by using the chemical structures of silica precursors via both the sol-gel route and CVD method. The precursors are various structured alkoxides: bridged alkoxides with ≡Si-R-Si≡ structure (e.g., bis(triethoxysilyl) ethane) [19,20], disiloxane alkoxides with ≡Si-O-Si≡ structure (e.g., hexamethyldisiloxane, hexaethoxy disiloxane, tetraethoxydimethyl disiloxane) [16,17,21], and silanes consisting of organic functional groups (methyl, propyl, hexyl, phenyl), which are directly attached to a single silicon atom [8,11,12,22,23]. For example, in our previous work, three series of silica membranes were prepared by the CVD method using tetramethoxysilane (TMOS), phenyltrimethoxysilane (PTMS), and diphenyldimethoxysilane (DPDMS, also called dimethoxydiphenylsilane (DMDPS) in the references [12,14,15]) as the silica precursors (the chemical structures of the precursors are provided in Figure 1) [12].…”

Section: Introductionmentioning

confidence: 99%

Development of hydrogen-selective triphenylmethoxysilane-derived silica membranes with tailored pore size by chemical vapor deposition

Zhang

Yamada

Saito

et al. 2016

Journal of Membrane Science

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Amorphous silica membranes were developed, based on an in silico molecular design, to exhibit excellent hydrogen-selective performance for separating hydrogen from mixtures containing larger organic molecules, such as methylcyclohexane and toluene. Triphenylmethoxysilane (TPMS) was synthesized and used as a novel precursor to prepare membranes by the counter-diffusion chemical vapor deposition method. Under the optimized bubbler temperature and counter-diffusion chemical vapor deposition reaction time, the fresh membranes showed high reproducibility and high hydrogen permeance in the order of 10 −6 mol m − 2 s − 1 Pa − 1 and high H2/SF6 ideal selectivity of over 12000 at 573 K. Moreover, the TPMS-derived membrane exhibited good stability after hydrogen regeneration, even after placement in a dehumidifier cabinet at room temperature for 90 days. Single gas permeation performance and normalized Knudsen-based permeance evaluation showed that the TPMS-derived membrane (three phenyl groups on the precursor) had a pore size of 0.486 nm, and exhibited looser structures with larger pore size than those of a diphenyldimethoxysilane (DPDMS)-derived membrane (two phenyl groups on the precursor). These results suggest that the pore size of silica membranes can be tailored with various structured silica precursors containing phenyl groups.

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Hybrid H₂-Selective Silica Membranes Prepared by Chemical Vapor Deposition

Cited by 9 publications

References 38 publications

Mixed Mechanism Model for Permeation of Gases in Hybrid Inorganic–Organic Membranes

Mixed Mechanism Model for Permeation of Gases in Hybrid Inorganic–Organic Membranes

Gas Separation Silica Membranes Prepared by Chemical Vapor Deposition of Methyl-Substituted Silanes

Development of hydrogen-selective triphenylmethoxysilane-derived silica membranes with tailored pore size by chemical vapor deposition

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Hybrid H2-Selective Silica Membranes Prepared by Chemical Vapor Deposition

Cited by 9 publications

References 38 publications

Mixed Mechanism Model for Permeation of Gases in Hybrid Inorganic–Organic Membranes

Mixed Mechanism Model for Permeation of Gases in Hybrid Inorganic–Organic Membranes

Gas Separation Silica Membranes Prepared by Chemical Vapor Deposition of Methyl-Substituted Silanes

Development of hydrogen-selective triphenylmethoxysilane-derived silica membranes with tailored pore size by chemical vapor deposition

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Hybrid H₂-Selective Silica Membranes Prepared by Chemical Vapor Deposition