Microporous molecular separation membrane with high hydrothermal stability
View Patent ↗A hydrothermally stable, microporous organic-inorganic hybrid membrane based on silica, having an mean pore diameter of between 0.2 and 1.5 nm, is characterised in that between 5 and 40 mole % of the Si—O—Si bonds have been replaced by moieties having the one of the formulas: Si—{[C m H( n-1 )X]—Si—} q , Si—[C m H( n-2 )X 2 ]—Si or Si—C m H n —Si{(C m H n )—Si—} y in which m=1-8, n=2m, 2m−2, 2m−4, 2m−6 or 2m−8; provided that n≧2, X=H or (CH 2 ) p Si, p=0 or 1, and q=1, 2, 3 or 4. The membrane can be produced by acid-catalysed hydrolysis of suitable bis-silane precursors such as bis(trialkoxysily)alkanes, preferably in the presence of monoorganyl-silane precursors such as trialkoxy-alkylsilanes.
1. A microporous organic-inorganic hybrid membrane based on silica, supported by a mesoporous layer, the microporous membrane having an average pore size of less than 1.5 nm, and in which between a portion of the Si—O—Si bonds have been replaced by moieties having the following formula:
Si—C m H n —Si [I]
in a molar ratio represented by the following formulae:
Si 0.9-1.0 M 0.0-0.1 O 1.45-1.55 A 1 0.0-0.1 A 2 0.45-0.50 [A]
or
Si 0.9-1.0 M 0.0-0.1 O 1.45-1.55 A 1 0.30-0.36 A 2 0.30-0.35 [B]
in which:
A 1 is a monovalent organic moiety of the formula C r H s+1 bound to a silicon atom,
A 2 is a divalent organic moiety of the formula C m H n bound to two silicon atoms,
m=1-8,
n=2m, 2m−2, 2m−4, 2m−6, or 2m−8, provided that n≧2,
r=1−10,
s=2r, 2r−2, 2r−4 or 2r−6, provided that s≧2,
M is a metal selected from yttrium, lanthanum, titanium, zirconium, hafnium, aluminum, gallium, germanium and tin.
2. The membrane according to claim 1 , in which A 1 is methyl.
3. The membrane according to claim 1 , in which m=1-3 and n=2m, or m=6 and n=4 or 10.
4. The membrane according to claim 1 , which has an average pore diameter between 0.2 and 1.2 nm.
5. The membrane according to claim 1 , which shows a stable separation performance in the dehydration of butanol at 150° C.
6. The membrane according to claim 1 , which has a thickness of between 20 nm and 2 μm.
7. The membrane according to claim 1 , in which the mesoporous layer has been deposited on a macroporous carrier.
8. A method for separating molecules from each other and/or from organic molecules, comprising subjecting the molecules to be separated to a membrane according to claim 1 .
9. The method of claim 8 , in which the molecules arc hydrogen, nitrogen, ammonia, or water, or a combination thereof.
10. The method of claim 8 , in which the organic molecules are alkanes, alkanols, ethers, ketones, or a combination thereof.
11. The membrane according to claim 1 , in which m=2.
12. A process of producing a microporous organic-inorganic hybrid membrane, the process comprising:
(a) forming a membrane membrane having an average pore size of less than 1.5 nm, and in which a portion of the Si—O—Si bonds have been replaced by moieties having the following formula:
Si—C m H n —Si [I]
in a molar ratio is represented by the following formula:
Si 0.9-1.0 M 0.0-0.1 O 1.45-1.55 A 1 0.0-0.1 A 2 0.45-0.50 [A]
or
Si 0.9-1.0 M 0.0-0.1 O 1.45-1.55 A 1 0.30-0.36 A 2 0.30-0.35 [B]
in which:
A 1 is a movement organic moiety of the formula C r H s=1 bound to a silicon atom,
A 2 is a divalent organic moiety of the formula C m H n bound to two silicon atoms,
m=1-8,
n=2m, 2m−2, 2m−4, 2m−6, or 2m−8, provided that n≧2, and
r=1−10,
s=2r, 2r=2, 2r=4 or 2r=6, provided that s≧2,
M is a metal selected from yttrium, lanthanum, titanium, zirconium, hafnium, aluminum , gallium, germanium and tin, and
(b) supporting the membrane by a mesoporous layer.
13. The process according to claim 12 , in which the hydrolysis is carried out using at least 0.8 water molecules per alkoxide group of said silicon and metal alkoxides.
14. The process according to claim 12 , in which the hydrolysing is carried out in the absence of a surfactant
15. A microporous organic-inorganic hybrid membrane based on silica supported by a mesoporous layer, the microporous membrane having an average pore size of less than 1.5 nm, and in which between 5 and 24 mole % of the Si—O—Si bonds have been replaced by moieties having one of following formulas:
in which:
m=1-8,
n=2m, 2m−2, 2m−4, 2m−6, or 2m−8, provided that n≧2, and
p=0, 1, 2 or 3.
16. A microporous organic-inorganic hybrid membrane based on silica, supported by a mesoporous layer, the microporous membrane having an average pore size of less than 1.5 nm, and in which between 23 and 40% of the Si-O-Si bonds have been replaced by moieties having the following formula:
Si—C m H n—Si [I]
wherein
m=1−8, and
n=2m, 2m−2, 2m−4, 2m−6, or 2m−8, provided than n≧2.