Proton conducting membrane
A reactor comprising a first zone comprising a dehydrogenation catalyst and a second zone separated from said first zone by a proton conducting membrane comprising a mixed metal oxide of formula (I) Ln a W b O 12−y wherein Ln is Y or an element numbered 57 to 71; the molar ratio of a:b is 4.8 to 6, preferably 5.3 to 6; and y is a number such that formula (I) is uncharged, e.g. y is 0≦y≦1.8.
1. A proton conducting membrane comprising a dehydrogenation catalyst and at least one mixed metal oxide of formula (II)
Ln a W b−c Mo c O 12−y (II)
wherein Ln is Y or an element numbered 57 to 71;
the molar ratio of a:b is 4.8 to 6; c is 0 to (0.5×b); and
y is a number such that formula (II) is uncharged.
2. A membrane as claimed in claim 1 wherein Ln is La.
3. A membrane as claimed in claim 1 wherein said dehydrogenation catalyst is a zeolite catalyst.
4. A membrane as claimed in claim 3 wherein said zeolite has the structure CHA or MFI.
5. A membrane as claimed in claim 4 wherein said zeolite is a ZSM-5, with a metal selected from Mo, W, Fe, V or Cr.
6. A membrane as claimed in claim 1 wherein said molar ratio of a:b is 5.3 to 6.
7. A membrane as claimed in claim 1 wherein y is 0≦y≦1.8.
8. A membrane as claimed in claim 1 wherein the mixed metal oxide has a conductivity of at least 1×10 −3 S/cm.
9. A membrane comprising a dehydrogenation catalyst and at least one mixed metal oxide, wherein said mixed metal oxide is of formula (I)
Ln a W b O 12−y (I)
wherein Ln is Y or an element numbered 57 to 71;
the molar ratio of a:b is 4.8 to 6; and
y is a number such that formula (I) is uncharged.
10. A membrane comprising a dehydrogenation catalyst and at least one mixed metal oxide, wherein the mixed metal oxide is of formula (III):
Ln x WO 12−y′ (III)
wherein Ln is Y or an element numbered 57 to 71 of the periodic table;
x is 4.8 to 6; and
y′ is 0≦y′≦1.8.
11. A supported proton conducting membrane comprising a porous support and a non porous proton conducting membrane thereon;
wherein said non porous proton conducting membrane comprises a mixed metal oxide of formula (II)
Ln a W b−c Mo c O 12−y (II)
wherein Ln is Y or an element numbered 57 to 71;
the molar ratio of a:b is 4.8 to 6; c is 0 to (0.5×b); and
y is a number such that formula (II) is uncharged; and wherein said support comprises a porous mixed metal oxide of formula (II)
Ln a W b−c Mo c O 12−y (II)
wherein Ln is Y or an element numbered 57 to 71;
the molar ratio of a:b is 4.8 to 6; c is 0 to (0.5×b); and
y is a number such that formula (II) is uncharged.
12. A supported proton conducting membrane as claimed in claim 11 wherein said non porous membrane is produced by spray pyrolysis and said porous support is produced by solid state reaction.
13. A supported proton conducting membrane as claimed in claim 11 wherein the particle size of the membrane is 100 to 800 nm in diameter and the particle size of the support is 1000-8000 nm in diameter.
14. A supported proton conducting membrane as claimed in claim 11 comprising a dehydrogenation catalyst on said proton conducting membrane so as to form the layered structure support-membrane-catalyst.
15. A reactor comprising a first zone comprising a dehydrogenation catalyst and a second zone separated from said first zone by a proton conducting membrane comprising a mixed metal oxide of formula (II)
Ln a W b−c Mo c O 12−y (II)
wherein Ln is Y or an element numbered 57 to 71;
the molar ratio of a:b is 4.8 to 6; c is 0 to (0.5×b); and
y is a number such that formula (II) is uncharged.
16. A process for the dehydrogenation of substance, comprising introducing said substance into the first zone of a reactor as claimed in claim 15 to thereby dehydrogenate said substance;
allowing hydrogen formed during said dehydrogenation to pass through said proton conducting membrane into said second zone;
introducing a purge gas into said second zone, preferably to react with the hydrogen; or
applying reduced pressure in said second zone to thus remove hydrogen from said second zone.
17. A process for the formation of a proton conducting membrane comprising a rare-earth tungstate having general formula (II)
Ln a W b−c Mo c O 12−y (II)
wherein Ln is Y or an element numbered 57 to 71;
the molar ratio of a:b is 4.8 to 6; c is 0 to (0.5×b); and
y is a number such that formula (II) is uncharged, comprising forming a solution of an organometallic compound of Ln and an organometallic compound of W ions and if present Mo ions in an organic solvent,
forming a membrane on a support by coating said support with said solution;
drying to remove said organic solvent; and
calcining to form said proton conducting membrane.
18. A process as claimed in claim 17 wherein the step of forming a membrane on a support is by dip coating or spray coating.