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Silica Membrane (silica + membrane)
Selected AbstractsFabrication and Characterization of Nanoporous Carbon/Silica Membranes,ADVANCED MATERIALS, Issue 4 2005B. Park Nanoporous carbon/silica (C/SiO2) membranes (see Figure) with high permeabilities and high gas selectivities are prepared by the controlled pyrolysis of polyimide/silica (PI/SiO2) composites obtained from polymerization of alkoxysilanes in situ via a sol,gel reaction. The silica content and the nature of the silica network incorporated in the carbon matrix can be used to tune the gas permeation and separation properties of the final C/SiO2 membranes. [source] Microporous Niobia,Silica Membrane with Very Low CO2 PermeabilityCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 5 2008Vittorio Boffa Dr. Abstract A sol,gel-derived microporous ceramic membrane with an exceptionally low permeability for CO2 from gaseous streams was developed and characterized. The sols were prepared from a mixture of niobium and silicon alkoxide precursors by acid-catalyzed synthesis. Microporous films were formed by coating asymmetric ,-alumina disks with the polymeric sol (Si/Nb=3:1), followed by calcination at 500,°C. The membrane consists of a 150-nm-thick layer with a Si/Nb atomic ratio of about 1.5. The single-gas permeance of small gas molecules such as H2, CH4, N2, and SF6 decreases steadily with kinetic diameter. Hydrogen, helium, and carbon dioxide follow an activated transport mechanism through the membrane. The permeance of CO2 in this membrane is much lower than that in pure silica, and its behavior deviates strongly from the general trend observed with the other gases. This is attributed to a relatively strong interaction between CO2 and adsorption sites in the niobia,silica membrane. [source] Performance under thermal and hydrothermal condition of amorphous silica membrane prepared by chemical vapor depositionAICHE JOURNAL, Issue 8 2009Kazuki Akamatsu First page of article [source] Hydrogen separation of methyltriethoxysilane templating silica membraneAICHE JOURNAL, Issue 12 2007Jong-Ho Moon Abstract Hydrogen separation on microporous methyltriethoxysilane-templating silica composite/,-alumina membranes (below MTES membrane) was studied using three binary gas mixtures: H2/N2, H2/CO2, and H2/CH4. The characteristics of unsteady and steady-state permeation/separation on the MTES membrane were compared to each other. Although permeation flux in the H2/N2 mixture was comparatively low, H2 selectivity was high (H2/N2 SF , 30,60). On the contrary, the H2/CO2 mixture showed high permeation flux but low H2 selectivity (H2/CO2 SF , 1.5,6.5). The H2/CH4 mixture showed a large difference between permselectivity (28,48) and separation factor (10,22). Results from this study revealed that it was difficult to predict the separation factor using the one-component permeation ratio (permselectivity) over the experimental range tested. These separation characteristics could be primarily ascribed to the molecular size and structure of each gas, which likely contributed to steric hindrance or molecular sieving within the membrane pore. In addition, the adsorption affinity of each molecule on the membrane surface acted as a key factor in separation performance because it significantly influenced surface diffusion. The generalized Maxwell-Stefan model incorporating the dust gas model, and the Langmuir model could successfully predict the transient and steady-state permeation/separation. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Ceramic membranes for ammonia recoveryAICHE JOURNAL, Issue 6 2006Olivier Camus Abstract An extensive screening program has been performed to find a suitable membrane configuration and operating conditions for the effective recovery of ammonia from the syngas loop. All the experiments have been performed at steady state. MFI zeolite membranes in tubular and multi-channel fiber configurations have been tested along with tubular silica membranes. At 80°C, a high ammonia permeance (2.1 × 10,7 mol.m,2.s,1.Pa,1), and a selectivity of about 10 were found with the tubular zeolite membrane, whereas for the silica membrane an even higher ammonia permeance was measured (7.6 x 10,7 mol.m,2.s,1.Pa,1) with a selectivity of about 7. For both silica and zeolite membranes, the selectivity was found to increase with increasing temperature up to 80°C. This is a combined effect of weaker adsorption of ammonia and increased diffusion at higher temperature. The results have been modeled using both the well-mixed reactor and the log mean pressure difference approaches. To overcome their limitations in addressing changes in feed concentration along the membrane surface, a segmental model has been used to obtain suitable operating conditions and membrane areas required for an industrial application. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] SiO2 Entrapment of Animal Cells: Liver-Specific Metabolic Activities in Silica-Overlaid HepatocytesARTIFICIAL ORGANS, Issue 8 2002Maurizio Muraca Abstract: Rat hepatocytes in a collagen-gel sandwich configuration were exposed to silicon alkoxides in a gas phase, yielding a 0.05 to 0.15 ,m porous silica layer on the gel surface. Cell viability was unaffected by the procedure. After 24 h, bilirubin conjugation, ammonia removal, urea synthesis, and diazepam metabolism were unaffected by the procedure. However, both the ammonia removal rate and diazepam metabolism were increased after 48 hr, whereas urea synthesis was unaffected. These data indicate that silica overlay allows efficient metabolic activity of collagen-gel entrapped hepatocytes. The fact that the KM of bilirubin conjugation was unaffected by the presence of the silica membrane suggests that the transport of albumin-bound substrates is not decreased. The enhancement in some metabolic activities found 48 h after the entrapment procedure may be the result of favorable changes in the hepatocyte microenvironment. These characteristics might be useful for the development of organotypical bioartificial liver devices. [source] Microporous Niobia,Silica Membrane with Very Low CO2 PermeabilityCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 5 2008Vittorio Boffa Dr. Abstract A sol,gel-derived microporous ceramic membrane with an exceptionally low permeability for CO2 from gaseous streams was developed and characterized. The sols were prepared from a mixture of niobium and silicon alkoxide precursors by acid-catalyzed synthesis. Microporous films were formed by coating asymmetric ,-alumina disks with the polymeric sol (Si/Nb=3:1), followed by calcination at 500,°C. The membrane consists of a 150-nm-thick layer with a Si/Nb atomic ratio of about 1.5. The single-gas permeance of small gas molecules such as H2, CH4, N2, and SF6 decreases steadily with kinetic diameter. Hydrogen, helium, and carbon dioxide follow an activated transport mechanism through the membrane. The permeance of CO2 in this membrane is much lower than that in pure silica, and its behavior deviates strongly from the general trend observed with the other gases. This is attributed to a relatively strong interaction between CO2 and adsorption sites in the niobia,silica membrane. [source] Characteristics of ammonia permeation through porous silica membranesAICHE JOURNAL, Issue 5 2010Masakoto Kanezashi Abstract A sol,gel method was applied for the preparation of silica membranes with different average pore sizes. Ammonia (NH3) permeation/separation characteristics of the silica membranes were examined in a wide temperature range (50,400°C) by measurement of both single and binary component separation. The order of gas permeance through the silica membranes, which was independent of membrane average pore size, was as follows: He > H2 > NH3 > N2. These results suggest that, for permeation through silica membranes, the molecular size of NH3 is larger than that of H2, despite previous reports that the kinetic diameter of NH3 is smaller than that of H2. At high temperatures, there was no effect of NH3 adsorption on H2 permeation characteristics, and silica membranes were highly stable in NH3 at 400°C (i.e., gas permeance remained unchanged). On the other hand, at 50°C NH3 molecules adsorbed on the silica improved NH3 -permselectivity by blocking permeation of H2 molecules without decreasing NH3 permeance. The maximal NH3/H2 permeance ratio obtained during binary component separation was ,30 with an NH3 permeance of ,10,7 mol m,2 s,1 Pa,1 at an H2 permeation activation energy of ,6 kJ mol,1. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Ceramic membranes for ammonia recoveryAICHE JOURNAL, Issue 6 2006Olivier Camus Abstract An extensive screening program has been performed to find a suitable membrane configuration and operating conditions for the effective recovery of ammonia from the syngas loop. All the experiments have been performed at steady state. MFI zeolite membranes in tubular and multi-channel fiber configurations have been tested along with tubular silica membranes. At 80°C, a high ammonia permeance (2.1 × 10,7 mol.m,2.s,1.Pa,1), and a selectivity of about 10 were found with the tubular zeolite membrane, whereas for the silica membrane an even higher ammonia permeance was measured (7.6 x 10,7 mol.m,2.s,1.Pa,1) with a selectivity of about 7. For both silica and zeolite membranes, the selectivity was found to increase with increasing temperature up to 80°C. This is a combined effect of weaker adsorption of ammonia and increased diffusion at higher temperature. The results have been modeled using both the well-mixed reactor and the log mean pressure difference approaches. To overcome their limitations in addressing changes in feed concentration along the membrane surface, a segmental model has been used to obtain suitable operating conditions and membrane areas required for an industrial application. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Scale-up of molecular sieve silica membranes for reformate purificationAICHE JOURNAL, Issue 10 2004M. Duke First page of article [source] Membrane reactor modelling, validation and simulation for the WGS reaction using metal doped silica membranesASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010S. Battersby Abstract In this work, a Matlab Simulink© model was developed to analyse and predict the performance of a metal doped silica membrane reactor for H2 production via both the high and low temperature water gas shift reaction. An activated transport model for mixed gas separation with combined reaction was developed to model the effects within a membrane reactor unit. The membrane reactor was modelled as a number of perfectly mixed compartments containing a catalyst bed and a gas selective membrane. The combined model provided a good fit to experimentally measured results for higher conversions up to equilibrium, which is generally the case for industrial applications. Simulation results showed that H2 separation and H2 recovery improved with pressure, due to the H2 concentration driving force across the membrane. For a single stage membrane reactor unit, a maximum conversion of 93% could be achieved with a H2 recovery rate of 95%. In addition, the membrane reactor efficiency increased at higher temperatures and lower H2O:CO feed ratios, allowing for CO conversion improvements by the membrane reactor. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||