Preparation of particulate/polymeric sol–gel derived microporous silica membranes and determination of their gas permeation properties

Abstract

a b s t r a c tMonodisperse silica sols with well-defined spherical particles ranging in size from 5 to 310 nm were prepared through Stober process. Both particulate and polymeric sol-gel routes were employed for the preparation of stable silica sols. The use of polymeric species in combination with particulate silica spheres may allow the design of predefined membrane pore structures with high thermal stability by cubic/random/close packing of monodisperse spherical particles incorporated into the polymeric network. The size and volume content of spheres were varied in order to modify the consolidation behaviour of 2-structural silica membranes which would enhance the thermal stability. The low shrinkage level for sphere loaded 2-structural systems compared to the pure polymeric counterparts might be explained by the decrease in the structural free energy of the polymeric/particulate 2-structural system. The thermal stability of the microporous membranes may thus be improved by incorporating particulates into the polymeric network through the formation of a lower extent of thermally induced microcrack formation. The N 2 permeation through 90 nm silica sphere added silica membranes remained constant when they were heat treated in the 250-400 • C range indicating the stability of the pore network.

Interlayer-free microporous cobalt oxide silica membranes via silica seeding sol–gel technique

“…The H2 hysteresis implies an "ink-bottle" pore type [29] where the pore size and pore shape are ill-defined. This mesoporous structure is associated with the base catalyzed sol in the Stӧber process using ammonia which often produces mesoporous silica structures [30,31]. There is also a substantial amount of adsorption at low relative pressure range (o 0.1), thus confirming the presence of micropores.…”

Modeling study of silica membrane performance for hydrogen separation

“…[1] To feed a fuel cell, the hydrogen stream needs purification, mainly because carbon monoxide poisons the anodic catalyst of the fuel cell and its concentration must be lower than 10 ppm. As H 2 is often generated at high temperatures by natural gas and alcohols reforming or coal gasification, [3,4] separation of H 2 attracts energy penalties because of the required cool down of high temperature streams to meet the operating requirements of polymeric membranes. As H 2 is often generated at high temperatures by natural gas and alcohols reforming or coal gasification, [3,4] separation of H 2 attracts energy penalties because of the required cool down of high temperature streams to meet the operating requirements of polymeric membranes.…”

“…[2] Conventional gas separation technologies using organic membranes require low temperature operation, owing to the poor thermal stability and anti-oxidation properties of polymers. As H 2 is often generated at high temperatures by natural gas and alcohols reforming or coal gasification, [3,4] separation of H 2 attracts energy penalties because of the required cool down of high temperature streams to meet the operating requirements of polymeric membranes. Inorganic membranes derived from ceramics, silica or metal alloys and zeolites can be employed at high temperature gas separation owning to their thermal stability and good resistance to chemical attack.…”

Nanocomposite membranes consisting of poly(vinyl chloride) graft copolymer and surface-modified silica nanoparticles

“…[1][2][3] Recently, organic-inorganic hybrid membranes containing inorganic fillers have been extensively studied for gas separation, because the addition of such fillers can effectively modulate perm-selective properties. [4][5][6][7][8][9][10][11] Initial attempts have explored the addition of micron-sized porous zeolite particles to take advantage of the size selective properties of well-defined zeolite pores. However, zeolite-containing hybrid membranes commonly exhibit poor selectivities due to the formation of defects at the polymer/zeolite interface resulting from poor adhesion and inadequate particle dispersion.…”

“…12 Hybrid membranes containing nonporous inorganic silica fillers have attracted wide interest. These hybrid membranes are prepared by the direct addition of fumed silica, 4,5 using a sol-gel method, [6][7][8][9] or in situ polymerization. 10,11 For certain glassy amorphous polymers such as poly(4-methyl-2-pentyne), physical dispersion of nanoparticles enhances both membrane permeability and selectivity simultaneously.…”