Membranes for dewatering acid mixtures

1. A supported membrane suitable for dewatering acidic mixtures, comprising a microporous separating layer and a macroporous ceramic support, wherein the microporous separating layer comprises a bridged organosilica directly applied on the macroporous ceramic support, in the absence of an intermediate mesoporous or finer layer, the bridged organosilica comprising divalent C 1 -C 9 organic groups and/or trivalent C 1 -C 9 organic groups directly bound to the silicon atoms of the organosilica.

2. The membrane according to claim 1 , wherein the organosilica has the formula Si (1-x) M x A 1 i A 2 j A 3 k O 1.25-1.85 , wherein:

M is one or more metal(s);

A 1 is a monovalent C 1 -C 9 hydrocarbyl or fluorohydrocarbyl group;

A 2 is a divalent organic group having the formula —C m H n ;

A 3 is a trivalent organic group having the formula—C m H (n-1) <;

i=0-0.67;

j=0-0.75;

k=0-0.33,

0.5<i+2j+3k<1.1; and 2j+3k>0.3;

m=1-9 and n=2(m−p) and 0≤p<m, wherein the values m, n and p may be different between formulas A 1 and A 2 ;

x=0-0.2.

3. The membrane according to claim 2 , wherein one or more of the following values apply:

A 1 is a monovalent C 1 -C 9 hydrocarbyl group;

i=0-0.33;

j=0.25-0.5;

k=0-0.1,

m=1-6;

x=0-0.1.

4. The membrane according to claim 3 , wherein one or more of the following values apply:

A 1 is a monovalent C 1 -C 4 hydrocarbyl group;

i=0-0.2;

j=0.35-0.5;

m=1-6;

x=0-0.1.

5. The membrane according to claim 4 , wherein one or both more of the following values apply:

j=0.45-0.5;

m=1 or 2.

6. The membrane according to claim 2 , wherein A 1 has the formula C q H r F s , wherein q=1-4, and r+s=2(q−t)+1 and 0≤t<q.

7. The membrane according to claim 1 , wherein the macroporous support comprises a alumina.

8. The membrane according to claim 1 , which has a stable water/acetic acid separation factor in the presence of 90% acetic acid in water at 100° C. of at least 100 for at least 120 days.

9. A process for producing a membrane of claim 1 , wherein the membrane is suitable for dewatering acidic mixtures, comprising one or more cycles of (a) directly applying a bridged organosilica on a macroporous support in and (b) drying the support with the applied organosilica, until the membrane is essentially microporous, the bridged organosilica comprising divalent C 1 -C 9 organic groups and/or trivalent C 1 -C 9 organic groups directly bound to the silicon atoms of the organosilica.

10. The process according to claim 9 , wherein the cycle of applying and drying of the organosilica is performed 2-4 times.

11. The process according to claim 9 , further comprising (c) calcining the dried support with applied membrane.

12. The process according to claim 9 , wherein the bridged organosilica is applied by hydrolysis of a precursor having the formula (RO) 3 Si—C m H n —Si(OR) 3 and/or (RO) 3 Si C m H (n−1) [Si(OR) 3 ] 2 wherein R is C 1 -C 4 -alkoxy, m=1-9 and n=2(m−p) and 0≤p<m.

13. The process according to claim 9 , wherein the bridged organosilica further comprises monovalent groups of formula C q H r F s , wherein q=1-4, and r+s=2(q−t)+1 and 0 ≤t<q, wherein the process comprises co-hydrolysis of a precursor having the formula (RO) 3 Si-C q H r F s , wherein R is C 1 -C 4 -alkoxy.

14. The process according to claim 9 , wherein the macroporous support comprises α-alumina.

15. A process for dewatering an aqueous acidic mixture, comprising contacting a feed mixture containing at least water and an acid with a membrane according to claim 1 to obtain a permeate and a retentate, and recovering the retentate.

16. The process according to claim 15 , wherein the feed mixture comprises 20-95 wt% of acid and 5-50 wt.% of water, and the retentate comprises less than 3% water.

17. The process according to claim 16 , wherein the retentate comprises less than 1% water.

18. The process according to claim 15 , wherein the acid comprises a carboxylic acid.

19. The process according to claim 15 , wherein the acidic mixture results from the production of the acid.

20. The process according to claim 15 , wherein the mixture results from an esterification process.

21. The process according to claim 19 , wherein the mixture comprises between 20 and 80 wt.% of an alcohol and/or an ester of the acid and alcohol.

22. The process according to claim 15 , wherein the mixture results from an acetalisation process.

23. The process according to claim 15 , wherein the acidic mixture is a recycle stream in the production of another compound.

24. The process according to claim 15 , wherein said contacting is performed at a temperature between 90 and 150 ° C.