Improved performance of silica membranes for gas separation

Microporous Niobia–Silica Membrane with Very Low CO2 Permeability

“…Table 1 lists the activation energies calculated from Figure 5, together with some data on pure and metal-oxide-doped silica membranes that have been reported elsewhere. [20][21][22][23][24][25][26] The values measured in the present study are close to those reported by Nair et al, who found activation energies for helium permeance of 23 kJ mol À1 in silica. [21] Asaeda and co-workers reported an increase in apparent activation energy of H 2 permeance from 3.4 to 44 kJ mol À1 when the Zr dopant loading in silica was increased from 10 mol % to 90 mol %.…”

“…As a reference, a thin film of silica was prepared following the same protocol using a standard polymeric silica sol. [20] The ATR measurements were performed at room temperature on a Bruker Tensor 27 equipped with a MCT detector in a dedicated measuring cell, which is described elsewhere. [33] The total volume of the cell was 120 mL.…”

“…The literature values in Table 1 indicate either positive activation energies for CO 2 permeance [22,23] or slightly negative values. [20] Apart from data in a study in which activation energies of À9.2 to À11.2 kJ mol À1 were measured, [24] none of the reported values is close to (À14.2 AE 0.6) kJ mol À1 as measured on the NS membrane. Figure 6 compares the H 2 /CO 2 and CH 4 /CO 2 ideal permselectivities of the NS membrane at different temperatures with that of the support.…”

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

“…Predetermined water and nitric acid solutions were added drop-wise to the TEOS/ethanol mixture placed in an ice bath to prevent partial hydrolysis as recommended by de Vos and Verweij [13]. After the addition was completed, the reaction mixture was heated to 60 • C for 3 h under constant stirring in a glove box.…”

“…After the addition was completed, the reaction mixture was heated to 60 • C for 3 h under constant stirring in a glove box. The standard silica sol molar TEOS:HNO 3 :H 2 O:EtOH ratio was 1:0.085:6.4:3.8 [13,14].…”