Tuning the pore sizes of novel silica membranes for improved gas permeation properties via an in situ reaction between NH3 and Si–H groups

2015 ◽  
Vol 51 (13) ◽  
pp. 2551-2554 ◽  
Author(s):  
Masakoto Kanezashi ◽  
Rui Matsugasako ◽  
Hiromasa Tawarayama ◽  
Hiroki Nagasawa ◽  
Tomohisa Yoshioka ◽  
...  
Keyword(s):  
High Temperatures ◽  
Gas Permeation ◽  
Silica Membranes ◽  
Pore Sizes ◽  
In Situ Reaction ◽  
Permeation Properties

The tuning of pore sizes in triethoxysilane (TRIES)-derived membranes via an in situ reaction between NH3 and Si–H groups at high temperatures.

scholarly journals Colorless and Transparent Copolyimides and Their Nanocomposites: Thermo-Optical Properties, Morphologies, and Gas Permeabilities

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 585 ◽  
Author(s):  
Hyeon Shin ◽  
Young-Je Kwark ◽  
Jin-Hae Chang
Keyword(s):  
Optical Properties ◽  
Coefficient Of Thermal Expansion ◽  
Amic Acid ◽  
Gas Permeation ◽  
Molar Ratio ◽  
Molar Ratios ◽  
Thermal Imidization ◽  
Organically Modified ◽  
Permeation Properties

A series of linear aromatic copolyimides (Co-PIs) were synthesized by reacting 4,4′-biphthalic anhydride (BPA) with various molar contents of 2,2′-bis(trifluoromethyl)benzidine (TFB) and p-xylylenediamine (p-XDA) in N,N′-dimethylacetamide (DMAc). Co-PI films were fabricated by solution casting and thermal imidization with poly(amic acid) (PAA) on glass plates. The thermo-optical properties and gas permeabilities of Co-PI films composed of various molar ratios of p-XDA (0.2–1.0 relative to BPA) were investigated. Thermal properties were observed to deteriorate with increasing p-XDA concentration. However, oxygen-transmission rates (O2TRs) and optical transparencies improved with increasing p-XDA concentration. Co-PI hybrids with a 1:0.2:0.8 molar ratio of BPA:TFB:p-XDA and organically modified hectorite (STN) were prepared by the in situ intercalation method. The morphologies and the thermo-optical and gas permeation properties of the hybrids were examined as functions of STN loading (5–50 wt %). XRD and TEM revealed substantial increases in clay particle agglomeration in the Co-PI hybrid films as the clay loading was increased from 5 to 50 wt %. The coefficient of thermal expansion (CTE) and the O2TR of a Co-PI hybrid film were observed to improve with increasing STN concentration; however, its optical transparency decreased gradually with increasing STN concentration.

scholarly journals Estimation of Pore Size Distribution of Amorphous Silica-Based Membrane by the Activation Energies of Gas Permeation

Processes ◽  
2018 ◽  
Vol 6 (12) ◽  
pp. 239 ◽  
Author(s):  
Guozhao Ji ◽  
Xuechao Gao ◽  
Simon Smart ◽  
Suresh K. Bhatia ◽  
Geoff Wang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Pore Size Distribution ◽  
Apparent Activation Energy ◽  
Pore Size ◽  
Size Distribution ◽  
Cobalt Oxide ◽  
High Temperatures ◽  
Gas Permeation ◽  
Oscillator Model ◽  
Silica Membranes

Cobalt oxide silica membranes were prepared and tested to separate small molecular gases, such as He (dk = 2.6 Å) and H2 (dk = 2.89 Å), from other gases with larger kinetic diameters, such as CO2 (dk = 3.47 Å) and Ar (dk = 3.41 Å). In view of the amorphous nature of silica membranes, pore sizes are generally distributed in the ultra-microporous range. However, it is difficult to determine the pore size of silica derived membranes by conventional characterization methods, such as N2 physisorption-desorption or high-resolution electron microscopy. Therefore, this work endeavors to determine the pore size of the membranes based on transport phenomena and computer modelling. This was carried out by using the oscillator model and correlating with experimental results, such as gas permeance (i.e., normalized pressure flux), apparent activation energy for gas permeation. Based on the oscillator model, He and H2 can diffuse through constrictions narrower than their gas kinetic diameters at high temperatures, and this was possibly due to the high kinetic energy promoted by the increase in external temperature. It was interesting to observe changes in transport phenomena for the cobalt oxide doped membranes exposed to H2 at high temperatures up to 500 °C. This was attributed to the reduction of cobalt oxide, and this redox effect gave different apparent activation energy. The reduced membrane showed lower apparent activation energy and higher gas permeance than the oxidized membrane, due to the enlargement of pores. These results together with effective medium theory (EMT) suggest that the pore size distribution is changed and the peak of the distribution is slightly shifted to a larger value. Hence, this work showed for the first time that the oscillator model with EMT is a potential tool to determine the pore size of silica derived membranes from experimental gas permeation data.

Permeation properties of hydrogen and water vapor through porous silica membranes at high temperatures

AIChE Journal ◽  
2010 ◽  
Vol 57 (3) ◽  
pp. 618-629 ◽  
Author(s):  
Toshinori Tsuru ◽  
Ryousuke Igi ◽  
Masakoto Kanezashi ◽  
Tomohisa Yoshioka ◽  
Shinji Fujisaki ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Temperatures ◽  
Porous Silica ◽  
Silica Membranes ◽  
Permeation Properties
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