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Membranes (Basel) ; 11(12)2021 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-34940427


Thin pure-silica chabazite (Si-CHA) membranes have been synthesized by using a secondary growth method on a porous silica substrate. A CO2 permeance of 2.62 × 10-6 mol m-2 s-1 Pa-1 with a CO2/CH4 permeance ratio of 62 was obtained through a Si-CHA membrane crystallized for 8 h using a parent gel of H2O/SiO2 ratio of 4.6. The CO2 permeance through the Si-CHA membrane on a porous silica substrate was twice as high as that through the membrane synthesized on a porous alumina substrate, which displayed a similar zeolite layer thickness.

Membranes (Basel) ; 9(7)2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31319501


Hydrophobic pure-silica *BEA-type zeolite membranes with large pores were prepared on tubular silica supports by hydrothermal synthesis using a secondary growth method and were applied to the separation of alcohol/water mixtures by pervaporation (PV), an alternative energy-efficient process for production of biofuels. Amorphous pure-silica tubular silica supports, free of Al atoms, were used for preparing the membranes. In this study, the effects of the synthesis conditions, such as the H2O/SiO2 and NH4F/SiO2 ratios in the synthetic gel, on the membrane formation process and separation performance were systematically investigated. The successfully prepared dense and continuous membranes exhibited alcohol selectivity and high flux for the separation of ethanol/water and butanol/water mixtures. The pure-silica *BEA membranes obtained under optimal conditions (0.08SiO2:0.5TEAOH:0.7NH4F:8H2O) showed high PV performance with a separation factor of 229 and a flux of 0.62 kg·m-2·h-1 for a 1 wt % n-butanol/water mixture at 318 K. This result was attributed to the hydrophobicity and large pore size of the pure-silica *BEA membrane. This was the first successful synthesis of hydrophobic large-pore zeolite membranes on tubular supports with alcohol selectivity, and the obtained results could provide new insights into the research on hydrophobic membranes with high permeability.

Membranes (Basel) ; 9(4)2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-30939830


Silicalite-1 membranes with high pervaporation performance were prepared successfully on a silica-particle-coated tubular silica support using a gel-free steam-assisted conversion (SAC) method. The effects of the silica-particle layer formed on the top surface of the silica support and the physical properties of the silica particles themselves on the membrane-formation process were investigated. The silica particles coated served as the additional silica source for growing the silicalite-1 seed crystal layer into the silicalite-1 membrane. As a result, it was possible to form a dense and continuous membrane even under gel-free conditions. Furthermore, it was found that the properties of the silica particles, such as their primary particle diameter, had a determining effect on their solubility during the steam treatment, that is, on the supply rate of the silica source. The silicalite-1 membrane obtained using the spherical-silica-particle-coated support had an approximately 9-µm-thick separation layer and showed very high pervaporation performance, exhibiting a separation factor of 105 and a flux of 3.72 kg m-2 h-1 for a 10 wt % ethanol/water mixture at 323 K. Thus, the gel-free SAC method can be used with a silica support coated with silica particles to readily prepare high-performance membranes without producing any chemical waste.

Chem Commun (Camb) ; 51(13): 2551-4, 2015 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-25566848


A new concept was proposed to control the pore size in a novel silica membrane. The tuning of the pore sizes in triethoxysilane (TRIES)-derived membranes was successfully conducted via an in situ reaction between NH3 and Si-H groups at high temperatures. The formation of Si-NH2 and/or Si-NH groups in the silica structure enhanced the hydrogen selectivity.