Electrolytic method to make alkali alcoholates using ceramic ion conducting solid membranes
View Patent ↗Disclosed are processes of making solutions of metal alcoholates in their corresponding alcohols using an electrolytic process. In one embodiment, sodium methylate in methanol is made from methanol and sodium hydroxide solution. The sodium hydroxide solution is placed in the anolyte compartment and the methanol is placed in the catholyte compartment, and the two compartments are separated by a ceramic membrane that selectively transports sodium under the influence of current. In preferred embodiments, the process is cost-effective and not environmentally harmful.
1. A method for producing alkali metal alcoholates, the method comprising:
feeding a catholyte solution comprising an alcohol corresponding to the alkali metal alcoholate desired to be produced into a catholyte compartment of an electrolytic cell;
feeding an anolyte solution comprising an aqueous solution of one or more alkali metal salts corresponding to the alkali metal alcoholate desired to be produced into an anolyte compartment of the cell; and
applying an electric voltage to the cell sufficient to electrolyze the one or more alkali metal salts,
wherein the anolyte compartment and the catholyte compartment are separated by a ceramic membrane comprising an alkali metal ion super ion conducting material that, upon application of electric potential to the cell, selectively transports alkali metal cations from the anolyte compartment to the catholyte compartment, and is substantially impermeable to water, wherein the ceramic membrane operates at a current density of at least about 100 mA/cm 2 ;
and
wherein the anolyte compartment is maintained at a temperature below about 80° C. during alkali metal salt electrolysis.
2. The method of claim 1 , wherein the catholyte solution comprises methanol or a solution of sodium methoxide in methanol.
3. The method of claim 1 , wherein the anolyte solution comprises an alkali metal salt selected from the group consisting of: sodium hydroxide, sodium chloride, sodium carbonate, sodium bicarbonate, sodium sulfate, sodium chlorate, sodium nitrate, sodium phosphate, sodium perchlorate, sodium nitrite, sodium nitrate, sodium phosphate, sodium hypochlorite, and sodium organic salts.
4. The method of claim 1 , wherein the anolyte solution comprises an alkali metal salt selected from the group consisting of: lithium hydroxide, lithium chloride, lithium carbonate, lithium bicarbonate, lithium sulfate, lithium chlorate, lithium nitrate, lithium phosphate, lithium perchlorate, lithium nitrite, and any combination thereof.
5. The method of claim 1 , wherein the anolyte solution comprises an alkali metal salt selected from the group consisting of: potassium hydroxide, potassium chloride, potassium carbonate, potassium bicarbonate, potassium sulfate, potassium chlorate, potassium nitrate, potassium phosphate, potassium perchlorate, potassium nitrite, and any combination thereof.
6. The method of claim 1 , wherein the electric potential (IR) drop across the ceramic membrane is less than about 1.0 volts.
7. The method of claim 1 , wherein the ceramic membrane selectively transports an alkali metal cation selected from the group consisting of: Na + , Li + , and K + .
8. The method of claim 1 , wherein the catholyte is continuously or intermittently fed into the catholyte compartment.
9. The method of claim 1 , wherein the anolyte is continuously or intermittently fed into the anolyte compartment.
10. The method of claim 1 , wherein the ceramic membrane comprises a NaSICON material.
11. The method of claim 1 , wherein the ceramic membrane comprises an alkali metal analog of a NaSICON material corresponding to the alkali metal cation to be transported.
12. The method of claim 1 , wherein the ceramic membrane comprises a material having the formula M 1 M 2 A(BO 4 ) 3 where M 1 and M 2 are independently chosen from Na, Li, and K; and A and B are independently selected from elements having a valence of 2+, 3+, 4+, or 5+.
13. The method of claim 1 wherein the membrane has a flat plate geometry in the form of thin sheets supported on porous ceramic substrates or thicker plates.
14. The method of claim 1 wherein the membrane has a tubular geometry in the form of thin sheets supported on porous ceramic substrates or thicker tubes.
15. The method of claim 1 wherein the membrane is coated with sodium ion conducting oxide materials.
16. The method of claim 1 , further comprising the step of purging the catholyte compartment with one or more inert or nonflammable gases during operation of the electrolytic cell.
17. The method of claim 1 wherein the ceramic membrane comprises a ceramic material having the formula NaM 2 (BO 4 ) 3 where M and B is selected from elements having a valence of 2+, 3+, 4+, or 5+.
18. The method of claim 1 wherein the ceramic membrane comprises a ceramic material having the formula Na 3 Zr 2 Si 2 PO 12 .
19. The method of claim 1 wherein the ceramic membrane comprises a ceramic material having the formula Na 5 RESi 4 O 12 where RE is Yttrium or a rare earth element.
20. The method of claim 1 , wherein alkali metal alcoholate solution formed in the catholyte compartment has a concentration of about 1% to about 32% by weight.
21. The method of claim 1 , wherein alkali metal alcoholate solution formed in the catholyte compartment has a concentration of about 6% to about 32% by weight.
22. The method of claim 1 , wherein alkali metal alcoholate solution formed in the catholyte compartment has a concentration of about 12% to about 28% by weight.
23. The method of claim 1 , wherein the ceramic membrane selectively transports an alkali metal cation selected from the group consisting of: Li + and K + .
24. The method of claim 1 , wherein the anolyte compartment is maintained at a temperature below about 65° C. during alkali metal salt electrolysis.
25. The method of claim 1 , wherein the anolyte compartment is maintained at a temperature below about 50° C. during alkali metal salt electrolysis.