Method for producing alkali metal alcoholates in an electrolysis cell

1 . A process for producing a solution L 1 < 21 > of an alkali metal alkoxide XOR in an alcohol ROH, in an electrolysis cell E < 1 >, where X is an alkali metal cation and R is an alkyl radical having 1 to 4 carbon atoms, said process comprising the following steps:

(i) providing an alkali metal cation-conducting solid-state electrolyte ceramic, F′ < 19 >, having a surface O F′ < 190 >;

(ii) removing a portion of the alkali metal cation-conducting solid-state electrolyte ceramic F′ < 19 > by sputtering with noble gas cations N + < 30 >, which produces an alkali metal cation-conducting solid-state electrolyte ceramic F < 18 > having a surface O F < 180 > which differs from surface O F < 190 > in at least one subregion O FA < 183 >, wherein: the surface O F < 180 > comprises the surfaces O A/MK < 181 > and O KK < 182 >, and wherein O A/MK < 181 > and/or O KK < 182 > comprise at least a portion of O FA < 183 >;

(iii) arranging the alkali metal cation-conducting solid-state electrolyte ceramic F < 18 > in the electrolysis cell E < 1 >, wherein said electrolysis cell comprises at least one anode chamber K A < 11 >, at least one cathode chamber K K < 12 > and at least one interposed middle chamber K M < 13 >;

wherein the at least one anode chamber K A < 11 > comprises:

at least one inlet Z KA < 110 >;

at least one outlet A KA < 111 >;

and an interior I KA < 112 > with an anodic electrode E A < 113 >;

the at least one cathode chamber K K < 12 > comprises:

at least one inlet Z KK < 120 >;

at least one outlet A KK < 121 >;

and an interior I KK < 122 > with a cathodic electrode E K < 123 >;

and the at least one middle chamber K M < 13 > comprises:

at least one inlet Z KM < 130 >;

at least one outlet A KM < 131 >;

and an interior I KM < 132 >;

wherein I KA < 112 > and I KM < 132 > are divided from one another by a diffusion barrier D < 14 >, and A KM < 131 > is connected by a connection V AM < 15 > to the inlet Z KA < 110 >, such that liquid can be passed from I KM < 132 > into I KA < 112 > via the connection V AM < 15 >;

and I KK < 122 > and I KM < 132 > are divided from one another by a dividing wall W < 16 > comprising the alkali metal cation-conducting solid-state electrolyte ceramic F < 18 >, wherein F < 18 > makes direct contact with the interior I KK < 122 > via the surface O KK < 182 > and with the interior I KM < 132 > via the surface O A/MK < 181 >;

(iv-β) and wherein the following steps (β1), (β2), (β3) proceed simultaneously:

(β1) a solution L 2 < 22 > comprising the alcohol ROH is routed through I KK < 122 >, wherein when O KK < 182 > includes at least a portion of O FA < 183 >, and the solution L 2 < 22 > makes direct contact with the at least one subregion O FA < 183 >;

(β2) a neutral or alkaline, aqueous solution L 3 < 23 > of a salt S comprising X as cation is routed through I KM < 132 >, then via V AM < 15 > through I KA < 112 >, where, when O A/MK < 181 > includes at least a portion of O FA < 183 >, and the solution L 3<23 > makes direct contact with at least one subregion O FA < 183 >;

(β3) voltage is applied between E A < 113 > and E K < 123 >;

thereby providing solution L 1 < 21 > at the outlet A KK < 121 >, with a higher concentration of XOR than in L 2 < 22 > and providing aqueous solution L 4 < 24 > at the outlet A KA < 111 >, with a lower concentration of S than in L 3 < 23 >.

2 . The process of claim 1 , wherein: S MF′ <S MF ; and wherein S MF′ is the mass-based specific surface area SM of the alkali metal cation-conducting solid-state electrolyte ceramic F′ before performance of step (ii) and S MF is the mass-based specific surface area SM of the alkali metal cation-conducting solid-state electrolyte ceramic F after performance of step (ii).

3 . The process of claim 2 , wherein the quotient S MF /S MF′ ≥1.01.

4 . The process of claim 1 , wherein at least 1% of surface O A/MK < 181 > is formed by O FA < 183 > and/or at least 1% of surface O KK < 182 > is formed by O FA < 183 >.

5 . The process of claim 1 , wherein the alkali metal cation-conducting solid-state electrolyte ceramic F′< 19 > has a structure of the formula:

M I 1+2w+x−y+z M II w M III x Zr IV 2−w−x−y M V y (SiO 4 ) z (PO 4 ) 3−z

where M I is selected from Na + and Li + ;

M II is a divalent metal cation;

M III is a trivalent metal cation;

M V is a pentavalent metal cation;

the Roman indices I, II, III, IV, V indicate the oxidation numbers in which the respective metal cations exist;

wherein w, x, y, z are real numbers, and wherein 0≤x<2, 0≤y<2, 0≤w<2, 0≤z<3;

and wherein w, x, y, z are chosen such that 1+2w+x−y+z≥0 and 2−w−x−y≥0.

6 . The process of claim 1 , wherein X is selected from the group consisting of Li + , Na + , and K + .

7 . The process of claim 6 , wherein X=Na + .

8 . The process of claim 1 , wherein S is a halide, sulfate, sulfite, nitrate, hydrogencarbonate or carbonate of X.

9 . The process of claim 8 , wherein S is a chloride of X.

10 . The process of claim 1 , wherein R is selected from the group consisting of methyl and ethyl.

11 . The process of claim 10 , wherein R=methyl.

12 . The process of claim 1 , wherein the connection V AM < 15 > is formed within the electrolysis cell E < 1 >.

13 . The process of claim 1 , wherein the connection V AM < 15 > is formed outside the electrolysis cell E < 1 >.

14 . The process of claim 1 , wherein O A/MK < 181 > and O KK < 182 > comprise at least a portion of O FA < 183 >.

15 . The process of claim 14 , wherein at least 1% of the surface O A/MK < 181 > is formed by O FA < 183 > and at least 1% of the surface O KK < 182 > is formed by O FA < 183 >.

16 . The process of claim 4 , wherein the alkali metal cation-conducting solid-state electrolyte ceramic F′ < 19 > has a structure of the formula:

M I 1+2w+x−y+z M II w M III x Zr IV 2−w−x−y M V y (SiO 4 ) z (PO 4 ) 3−z

where M I is selected from Na + and Li + ;

M II is a divalent metal cation;

M III is a trivalent metal cation;

M V is a pentavalent metal cation;

the Roman indices I, II, III, IV, V indicate the oxidation numbers in which the respective metal cations exist;

wherein w, x, y, z are real numbers, where 0≤x<2,0≤y<2,0≤w<2,0≤z<3;

and wherein w, x, y, z are chosen such that 1+2w+x−y+z≥0 and 2−w−x−y≥0.

17 . The process of claim 16 , wherein X is selected from the group consisting of Li + , Na + , K + .

18 . The process of claim 17 , wherein X=Na + .

19 . The process of claim 17 , wherein S is a halide, sulfate, sulfite, nitrate, hydrogencarbonate or carbonate of X.

20 . The process of claim 19 , wherein S is a chloride of X and R is selected from the group consisting of methyl and ethyl.