Sulfonated Aromatic Compounds

Abstract

The present invention relates to novel lignin-derived compounds and compositions comprising the same and their use as redox flow battery electrolytes. The invention further provides a method for preparing said compounds and compositions as well as a redox flow battery comprising said compounds and compositions. Additionally, an assembly for carrying out the inventive method is provided.

Claims

1. A sulfonated low molecular weight aromatic compound, wherein said compound is characterized by Formula (X), (XI), (XII), (XIII), (XIV) or (XV): ##STR00053## wherein each R.sup.1, R.sup.2, R.sup.3 or R.sup.4 is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, halogen, amine, amino, amide, nitro, oxo, carbonyl, phosphoryl, phosphonyl, cyanide and sulfonyl (SO.sub.3H), provided that at least one of R.sup.1-R.sup.4 is SO.sub.3H; ##STR00054## wherein each R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 or R.sup.6 is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, halogen, amine, amino, amide, nitro, oxo, carbonyl, phosphoryl, phosphonyl, cyanide and sulfonyl (SO.sub.3H), provided that at least one of R.sup.1-R.sup.6 is SO.sub.3H; ##STR00055## wherein each R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 or R.sup.8 is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, halogen, amine, amino, amide, nitro, oxo, carbonyl, phosphoryl, phosphonyl, cyanide and sulfonyl (SO.sub.3H), provided that at least one of R.sup.1-R.sup.8 is SO.sub.3H, preferably selected from a sulfonated compound according to Table 1, 2 or 3.

2. The sulfonated low molecular weight aromatic compound according to claim 1, wherein said compound is characterized by Formula (X) or (XI) and wherein R.sup.1 and R.sup.4 are independently selected from H or SO.sub.3H, R.sup.2 is selected from H, OH, and C.sub.1-C.sub.6 alkoxy, preferably methoxy, or SO.sub.3H, R.sup.3 is selected from H, OH and C.sub.1-C.sub.6 alkoxy, preferably methoxy.

3. The sulfonated low molecular weight aromatic compound according to claim 1 or 2, wherein the compound is characterized by one of the following: a) R.sup.4 is SO.sub.3H; b) R.sup.4 is SO.sub.3H, R.sup.3 is methoxy; c) R.sup.4 is SO.sub.3H, R.sup.2 and R.sup.3 are methoxy; d) R.sup.1 and R.sup.4 are SO.sub.3H; e) R.sup.1 and R.sup.4 are SO.sub.3H, R.sup.3 is methoxy; f) R.sup.1 and R.sup.4 are SO.sub.3H, R.sup.2 and R.sup.3 are methoxy; or g) R.sup.2 and R.sup.4 are SO.sub.3H, and R.sup.3 is methoxy, wherein each of the other of R.sup.1-R.sup.4 is OH or H, preferably H.

4. The sulfonated low molecular weight aromatic compound according to claim 1, wherein said compound is characterized by Formula (XII) or (XIII), wherein R.sup.1 and R.sup.2 are independently selected from H, OH and C.sub.1-C.sub.6 alkoxy, preferably methoxy, and R.sup.3-R.sup.6 are independently selected from H and SO.sub.3H.

5. The sulfonated low molecular weight aromatic compound according to claim 1, wherein said compound is characterized by Formula (XIV) or (XV) and wherein R.sup.1, R.sup.2 and R.sup.4 are independently selected from H, OH and C.sub.1-C.sub.6 alkoxy, preferably methoxy, and R.sup.3, R.sup.5-R.sup.8 are independently selected from H and SO.sub.3H.

6. The sulfonated low molecular weight aromatic compound according to claim 1 or 5, wherein the compound is characterized by one of the following: a) R.sup.1 is SO.sub.3H; b) R.sup.2 is SO.sub.3H; R.sup.1, R.sup.3 and R.sup.4 are preferably OH; c) R.sup.6 is SO.sub.3H; R.sup.1 and R.sup.4 or R.sup.1, R.sup.2 and R.sup.4 are preferably OH; d) R.sup.2 and R.sup.6 are SO.sub.3H; R.sup.1 and R.sup.4 or R.sup.1, R.sup.3 and R.sup.4 are preferably OH; e) R.sup.3 and R.sup.6 are SO.sub.3H; R.sup.1, R.sup.2 and R.sup.4 are preferably OH; f) R.sup.2 and R.sup.7 are SO.sub.3H; or g) R.sup.1 and R.sup.4 are SO.sub.3H; wherein each of the other of R.sup.1-R.sup.8 is/are C.sub.1-C.sub.6 alkoxy or H, preferably H.

7. A composition comprising at least two sulfonated low molecular weight aromatic compounds according to any one of claims 1 to 6, preferably at least two distinct low molecular weight aromatic compounds with at least one compound being in the oxidized state according to Formula (X), (XII) or (XIV), and/or at least corresponding compound being in the reduced state according to Formula (XI), (XIII) or (XV).

8. The composition according to claim 7, wherein said at least two sulfonated low molecular weight aromatic compounds are characterized by the following: (a) at least one compound according to Formula (X) and (XI), preferably as defined in claim 2 or 3, preferably at least one compound of Formula (X) (oxidized state) and at least one corresponding compound of Formula (XI) (reduced state); (b) at least one compound according to Formula (XII) and (XIII), preferably as defined in claim 4, preferably at least one compound of Formula (XII) (oxidized state) and at least one corresponding compound of Formula (XIII) (reduced state); and/or (c) at least one compound according to Formula (XIV) and (XV), optionally as defined in claim 5 or 6, preferably at least one compound of Formula (XIV) (oxidized state) and at least one corresponding compound of Formula (XV) (reduced state).

9. The composition according to claim 8, said composition comprising (a) at least two compounds according to Formula (X) and (XI), wherein said at least two compounds are distinctly sulfonated and/or substituted, preferably at least two distinct compounds being in the oxidized state according to Formula (X) and at least two corresponding distinct compounds according to Formula (XI) in the respective reduced state; (b) at least two compounds according to Formula (XII) or (XIII), wherein said at least two compounds are distinctly sulfonated and/or substituted, preferably at least two distinct compounds being in the oxidized state according to Formula (XII) and at least two corresponding distinct compounds according to Formula (XIII) in the respective reduced state; and/or (c) at least two compounds according to Formula (XIV) or (XV), wherein said at least two compounds are distinctly sulfonated and/or substituted, preferably at least two distinct compounds being in the oxidized state according to Formula (XIV) and at least two corresponding distinct compounds according to Formula (XV) in the respective reduced state.

10. The composition according to claim 9, wherein each of said at least two compounds comprises at least two SO.sub.3H groups, preferably two SO.sub.3H groups.

11. A method for preparing a sulfonated low molecular weight aromatic compound or a composition comprising or (essentially) consisting of the same, preferably according to any one of claims 1 to 10, comprising the steps of (1) providing a starting material; (2) optionally subjecting said starting material to a process suitable to obtain at least one low molecular weight precursor compound; (3) isolating and optionally modifying at least one low molecular weight precursor compound; thereby obtaining at least one low molecular weight aromatic precursor compound; (4) subjecting said at least one low molecular weight precursor compound to a sulfonation reaction, wherein one or more SO.sub.3H groups are introduced into said at least one precursor compound; thereby obtaining at least one sulfonated low molecular weight aromatic compound or a composition comprising the same or (essentially) consisting thereof; wherein said starting material is preferably selected from lignocellulosic material, crude oil, coal or pure organic substances.

12. The method according to claim 11, wherein said starting material is lignocellulosic material and said method comprises the followings steps: (1) subjecting lignocellulosic material to a pulping process; thereby obtaining modified lignin-derived components; (2) isolating said modified lignin-derived components; (3) subjecting said modified lignin-derived components to a chemical decomposition step; thereby obtaining at least one low molecular weight precursor compound; (4) isolating and optionally modifying at least one low molecular weight precursor compound; thereby obtaining at least one low molecular weight aromatic precursor compound; (5) subjecting said at least one low molecular weight aromatic precursor compound to a sulfonation reaction, wherein one or more SO.sub.3H groups are introduced into said at least one precursor compound; thereby obtaining at least one sulfonated low molecular weight aromatic compound or a composition comprising the same or (essentially) consisting thereof.

13. The method according to claim 12, wherein step (1) comprises the sub-steps of: (1.1) providing a lignocellulosic material; (1.2) subjecting said lignocellulosic material to (a) a Kraft process or (b) a sulfite process; (1.3) optionally separated the pulp from the process stream obtainable from the pulping process in sub-step (1.2).

14. The method according to claim 12 or 13, wherein step (3) comprises: (a) oxidative cracking (cracking and oxidizing) of the modified lignin-derived components in the presence of a heterogeneous or homogeneous catalyst comprising a metal ion or a metalloid component; or (b) reductive cracking (cracking and reducing) of the modified lignin-derived components in the presence of a heterogeneous or homogeneous catalyst comprising a metal ion or metalloid component; or (c) subjecting the modified lignin-derived components to electro-oxidation in alkaline or acidic solution.

15. The method according to of any one of claims 12 to 14, wherein the at least one precursor compound comprises one or two aromatic ring(s), preferably two non-annulated aromatic rings.

16. The method of according to claim 15, wherein the at least one precursor compound comprises two aromatic rings, wherein said two aromatic rings are linked by a linker moiety, preferably an aliphatic linker, or by a bond.

17. The method according to any one of claim 15 or 16, wherein the at least one precursor compound comprises two aromatic rings which form a biphenylic moiety.

18. The method according to any one of claims 15 to 17, wherein the one or two aromatic ring(s) is/are carbocyclic.

19. The method according to any one of claims 15 to 18, wherein the aromatic ring(s) is/are substituted in at least one, preferably two positions by a functional group, wherein at least one of these functional groups is preferably alkoxy or hydroxyl.

20. The method according to any one of claims 15 to 19, wherein the at least one precursor compound is characterized by Formula (Ia): ##STR00056## wherein each of R.sup.1-R.sup.5 is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, oxo or carbonyl, wherein at least one of R.sup.1, R.sup.3 or R.sup.5 is hydroxy or linear or branched, optionally substituted, C.sub.1-6 alkoxy; and R.sup.6 is selected from the group consisting of hydrogen, hydroxy, linear or branched, optionally substituted, C.sub.1-6 carboxyl, linear or branched C.sub.1-6 aldehyde, and linear or branched, optionally substituted, C.sub.1-6 alcohol; or by Formula (Ib): ##STR00057## wherein each of R.sup.1-R.sup.9 is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.6 aldehyde, ester, oxo or carbonyl, wherein R.sup.5 is preferably hydroxy or linear or branched, optionally substituted, C.sub.1 6 alkoxy; and R.sup.10 is selected from the group consisting of hydrogen, hydroxy, linear or branched, optionally substituted, C.sub.1-6carboxyl, linear or branched, optionally substituted, C.sub.1-6 aldehyde, and linear or branched C.sub.1-6 alcohol.

21. The method according to claim 20, wherein the at least one precursor compound is selected from the group consisting of phenolic derivatives of biphenyl, benzylalcohol, benzaldehydes and benzoic acid, preferably derivatives of p-hydroxy benzylalcohol, p-hydroxy benzaldehydes and p-hydroxy benzoic acid, or more preferably vanillin, guaiacol, eugenol, syringol, phenol, syringaldehyde, and/or a derivative of any of the above, and/or a combination of the above.

22. The method according to any one of claims 12 to 21, wherein step (4) comprises the sub-steps of (4.1) isolating said precursor compound; and optionally (4.2) subjecting said precursor compound to an annulation reaction; and/or (4.3) subjecting said precursor compound to an oxidation reaction.

23. The method according to claim 22, wherein the at least one precursor compound comprises one aromatic ring and is further processed in a sub-step (4.2), wherein said precursor compound comprising one aromatic ring is subjected to an annulation reaction, preferably a Diels-Alder reaction or a Friedel Crafts acylation, wherein the annulation reaction product is a low molecular weight aromatic bi- or tricyclic annulated aromatic compound, wherein said compound is characterized by Formula (II), (III) or (IV) ##STR00058## wherein each of R.sup.2, R.sup.3, R.sup.5-R.sup.8 of Formula (II) is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, oxo or carbonyl, wherein preferably at least one of R.sup.2, R.sup.3, R.sup.5-R.sup.8 is hydroxy or C.sub.1-3 alkoxy, and R.sup.1 and R.sup.4 of Formula (II) is/are selected from the group consisting of hydrogen, hydroxy, linear or branched, optionally substituted, C.sub.1-6 carboxyl, linear or branched, optionally substituted, C.sub.1-6 aldehyde, and linear or branched, optionally substituted, C.sub.1-6 alcohol, each of R.sup.1-R.sup.10 of Formula (III) is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, oxo or carbonyl, wherein preferably at least one of R.sup.2, R.sup.5, R.sup.6 and R.sup.8 is hydroxy or C.sub.1-3 alkoxy, wherein preferably R.sup.1, R.sup.4, R.sup.9 and R.sup.10 of Formula (III) is/are selected from the group consisting of hydrogen, hydroxy, linear or branched, optionally substituted, C.sub.1-6 carboxyl, linear or branched, optionally substituted, C.sub.1-6 aldehyde, and linear or branched, optionally substituted, C.sub.1-6 alcohol, each of R.sup.2, R.sup.3 and R.sup.1-R.sup.10 of Formula (IV) is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, oxo or carbonyl, wherein preferably at least one of R.sup.2, R.sup.3 and R.sup.1-R.sup.10 is hydroxy or C.sub.1-3 alkoxy, and R.sup.1, R.sup.4, R.sup.5 and R.sup.6 of Formula (IV) is selected from the group consisting of hydrogen, hydroxy, linear or branched, optionally substituted C.sub.1-6 carboxyl, linear or branched, optionally substituted, C.sub.1-6 aldehyde, and linear or branched, optionally substituted, C.sub.1-6 alcohol.

24. The method according to any one of claim 22 or 23, wherein the at least one monocyclic or (optionally annulated) bi- or tricyclic precursor compound obtained from any one of sub-steps (4.1) or (4.2) is further modified in a sub-step (4.3) by oxidizing said at least precursor compound in the presence of (i) an oxidizing agent selected from the group consisting of H.sub.2O.sub.2, O.sub.2 and air, and (ii) a homogeneous or heterogeneous catalyst, preferably comprising a metal ion or a metalloid component.

25. The method according to claim 24, wherein the at least one oxidized monocyclic precursor compound obtained from any one of sub-steps (4.1) or (4.3) comprises at least one hydroquinone compound, characterized by Formula (Va): ##STR00059## wherein each of R.sup.1-R.sup.5 is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, oxo or carbonyl, and wherein preferably one of R.sup.1, R.sup.3 and R.sup.5 is hydroxy; or by formula (Vb), ##STR00060## wherein each of R.sup.1-R.sup.9 is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, oxo or carbonyl, and wherein R.sup.5 is preferably hydroxy; and/or at least one quinone compound characterized by any of Formulae (VIa) to (VIb): ##STR00061## wherein each of R.sup.1-R.sup.2 and R.sup.4-R.sup.5 is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, oxo or carbonyl; or ##STR00062## wherein each of R.sup.2-R.sup.5 is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, oxo or carbonyl; or ##STR00063## wherein each of R.sup.1-R.sup.4 is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, oxo or carbonyl; or ##STR00064## wherein each of R.sup.1-R.sup.4 and R.sup.6-R.sup.9 is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, oxo or carbonyl.

26. The method according to claim 24 or 25, wherein the at least one oxidized (optionally annulated) bi- or tricyclic precursor compound obtained from any one of sub-steps (4.1)-(4.3) comprises at least one quinone and/or hydroquinone compound characterized by any of Formula (VII), (VIII) and/or (IX): ##STR00065## wherein each of R.sup.1-R.sup.8 with regard to Formula (VII) and/or each of R.sup.1-R.sup.10 with regard to Formula (VIII) and (IX) is independently selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, oxo or carbonyl; wherein at least one of R.sup.8 and R.sup.5 or R.sup.1 and R.sup.4 of Formula (VII) are hydroxy or oxo, or at least one of R.sup.9 and R.sup.6, R.sup.10 and R.sup.5, or R.sup.1 and R.sup.4 of Formula (VIII) are hydroxy or oxo, or at least one of R.sup.10 and R.sup.7 or R.sup.1 and R.sup.4 of Formula (IX) are hydroxy or oxo.

27. The method according to any one of claims 12 to 26, wherein step (4) further comprises a purification sub-step (4.4) to separate the at least one precursor compound, preferably a quinone or hydroquinone compound, from residual compounds by an extraction method, preferably by solid phase extraction or fluid-fluid phase extraction.

28. The method according to any one claims 12 to 27, wherein the at least one precursor compound, preferably a quinone or hydroquinone compound, is further subjected to a derivatization step (4.5), wherein one or more hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, halogen, amine, amino, amide, nitro, oxo, carbonyl, phosphoryl, phosphonyl or cyanide groups are introduced into a compound according to any of Formulae (I) to (IX) at a position of the aryl structure other than those characterized by an oxo or hydroxyl group, wherein said group(s) is/are directly bound to the aryl structure or bound via an alkyl linker to the aryl structure, preferably via a methyl linker.

29. The method according to any one of claims 12 to 28, wherein step (5) comprises introducing one or more SO.sub.3H-groups into a compound according to any of Formulae (I) to (IX) at a position of the aryl structure other than those characterized by an oxo or hydroxyl group, wherein said group(s) is/are directly bound to the aryl structure or bound via an alkyl linker to the aryl structure, preferably via a methyl linker.

30. The method according to any one of claims 12 to 29, wherein the at least one sulfonated low molecular weight aromatic compound, preferably a quinone or hydroquinone compound, is further subjected to a derivatization step (6), wherein one or more groups selected from hydrogen, hydroxy, carboxy, linear or branched, optionally substituted, C.sub.1-6 alkyl, linear or branched, optionally substituted, C.sub.1-6 alkenyl, linear or branched, optionally substituted, C.sub.1-6 alcohol, linear or branched, optionally substituted, C.sub.1-6 aminoalkyl, linear or branched, optionally substituted, C.sub.1-6 carboxyalkyl, linear or branched, optionally substituted, C.sub.1-6 alkoxy, linear or branched, optionally substituted, C.sub.1-6 aldehyde, ester, halogen, amine, amino, amide, nitro, oxo, carbonyl, phosphoryl, phosphonyl or cyanide groups are introduced into said compound, preferably at a position of the aryl structure other than those characterized by an oxo or hydroxyl or sulfonyl group, wherein said group(s) is/are directly bound to the aryl structure or bound via an alkyl linker to the aryl structure, preferably via a methyl linker.

31. The method according to any one of claims 12 to 30, further comprising a step (7) of isolating said at least one sulfonated (and optionally further derivatized) low molecular weight aromatic compound or a composition comprising or (essentially) consisting of the same.

32. The method according to any one claims 12 to 31, further comprising after step (5), (6) or (7) a step (8) of providing said one sulfonated (optionally further derivatized) low molecular weight aromatic compound or a composition comprising the same or (essentially) consisting thereof as a redox flow battery electrolyte.

33. A sulfonated (and optionally further derivatized) low molecular weight aromatic compound or a composition comprising or (essentially) consisting of the same, obtainable by a method according to any one of claims 11 to 32.

34. The sulfonated (and optionally further derivatized) low molecular weight aromatic compound or composition according to claim 33, wherein said compound is characterized by any one of Formulae (X)-(XV) as defined in any one of claims 1 to 6, and/or said composition comprises or (essentially) consists of compounds characterized by any one of Formulae (X)-(XV) as defined in any one of claims 1 to 6.

35. A redox flow battery electrolyte solution comprising the sulfonated (and optionally further derivatized) low molecular weight aromatic compound or composition according to any one of claims 1 to 10 or 33 or 34 dissolved or suspended in a suitable solvent, said solvent preferably being selected from water.

36. Use of a sulfonated (and optionally further derivatized) low molecular weight aromatic compound or a composition according to any one of claims 1 to 10 or 33 or 34 as a redox flow battery electrolyte.

37. A redox flow battery comprising the sulfonated and optionally further derivatized low molecular weight aromatic compound or the composition according to any one of claims 1 to 10 or 33 or 34 or the electrolyte solution according to claim 35.

38. The redox flow battery according to claim 37, wherein said redox flow battery comprises a first (optionally aqueous) electrolyte solution comprising a first (redox active) electrolyte; a first electrode in contact with said first (optionally aqueous) electrolyte solution; a second (optionally aqueous) electrolyte solution comprising a second (redox active) electrolyte; a second electrode in contact with said second (optionally aqueous) electrolyte solution; wherein one or both of the first and second (redox active) electrolytes comprise at least one sulfonated (and optionally further derivatized) low molecular weight aromatic compound as defined in any one of the preceding claims (preferably at least one sulfonated (and optionally further derivatized) (hydro-)quinone) or a composition comprising or (essentially) consisting of the same as defined in any one of the preceding claims.

Description

DESCRIPTION OF THE FIGURES

[0522] FIGS. 1 and 2 show steps (5) (sulfonation) and following steps of an exemplary method according to the invention.

EXAMPLES

[0523] The examples shown in the following are merely illustrative and shall describe the present invention in a further way. These examples shall not be construed to limit the present invention thereto. The following preparations and examples are given to enable those skilled in the art to more clearly understand and to practice the present invention. The present invention, however, is not limited in scope by the exemplified embodiments, which are intended as illustrations of single aspects of the invention only, and methods, which are functionally equivalent are within the scope of the invention. Indeed, various modifications of the invention in addition to those described herein will become readily apparent to those skilled in the art from the foregoing description, accompanying figures and the examples below. All such modifications fall within the scope of the appended claims.

Example 1: Preparation of Low Molecular Weight Aromatic Lignin-Derived Compounds by Cracking and Reduction by a Nickel Catalyst

[0524] Reductive cracking of a modified lignin-derived component according to step (E.2) of the inventive method may for example be carried out by means of a catalyst comprising nickel, e.g. supported on activated carbon (Ni/C). The catalysts are typically prepared by an incipient-wetness impregnation method and further treated by a carbothermal reduction method known in the art.

[0525] Herein, nickel nitrate(II) hexahydrate [Ni(NO.sub.3).sub.2 6H2O] is used and optionally added into water in a beaker known in the art. The solution is then stirred, e.g. for at least 30 min, to prepare an impregnation stock solution. Activated carbon having a water absorption capacity of typically above 1.8 mL g.sup.1 is added into the solution and the beaker may then covered by a culture dish to keep the sample wet for a prescribed time, preferably more than 12 h, more preferably 24 h. The sample is then dried at a temperature above 80 C., e.g. 120 C. overnight. The actual reduction is carried out in a container such as a preferably horizontal furnace in a flow of inert gas such as N.sub.2. The flow is, e.g., 10 mL min.sup.1 or more, preferably 30 mL min.sup.1 or more. The reduction temperature preferably reaches at least 400 C., preferably 450 C., e.g. over set time period such as at least 30 min, preferably at least 60 min. The temperature for conducting the reduction is maintained at 450 C. for at least 1 h, more preferably for at least 2 h. The Ni/l SBA-15 catalysts are reduced at 550 C. for 2 h. The Ni/Al.sub.2O.sub.3 catalyst is reduced at 700 C. for 2 h. The metal loading for each nickel- and copper-based catalyst is 10% (w/w) relative to the support. Herein, birch sawdust serves as lignocellulosic material and is treated with the ethanol-benzene mixture (v/v ratio 1:2) for 12 h. The treated birch sawdust, solvent (m/v 1:20), and catalyst (w/w 20:1) are placed in an autoclave reactor. The reactor is sealed and purged with Ar 4 to 6 times to expel air. Then, the reducing reaction is conducted at 200 C. at a stirring speed of at least 300 rpm, preferably 500 rpm. When the desired reaction time (usually 2 to 10 h) is reached, the reactor is cooled to ambient temperature before sampling.

[0526] Typically, the reaction generates 4-propylguaiacol and 4-propylsyringol as major products, together with minor alkene-substituted 4-propylguaiacol and 4-propylsyringol, as determined by standard gas chromatography. The compounds are isolated according to step (F), preferably by extraction.

Example 2: Preparation of Monomeric Aromatic Lignin-Derived Molecules from Lignosulfonate of a Sulfite Process by Electrooxidation

[0527] Lignosulfonate is provided by step (D) according to the present invention. Thereof, a 1 M aqueous NaOH solution is prepared, comprising 1% (W/W) lignosulfonate. Said solution is subjected to an electrooxidation according to step (E.3). Therein, the solution is employed as anolyte. A 1 M aqueous solution is employed as katalyte. A flow cell with a flow rate of 250 ml/min is used.

[0528] Electrolysis is allowed to take place galvanostatically for 8 h applying current of 1 mA/cm.sup.2. A typical resulting voltage is 1.4 V. The voltage curve typically is asymptotic and the solution changes preferably color from brown to dark brown.

[0529] Samples of the solution are taken every hour over a time span of 8 h and subsequently examined photometrically. Thereof, an absorption profile typical for ortho-benzoquinone is determined. Hence, a lower molecular weight aromatic lignin-derived compound, quinone compound, is prepared by said method.

[0530] Said compound is then isolated according to step (F) of the present invention. Therefore, said compound is extracted by dichloromethane and subsequently subjected to cycles of charging and discharging processes in a flow cell. The voltage curve shows that the compound is redox active, which may be reversibly electrolyzed.

Example 3: Preparation of an Annulated Quinone Compound by a Friedel-Crafts Acylation

[0531] Vanillin as a low molecular weight aromatic lignin-derived compound is provided by step (F) according to the present invention. Said compound is further annulated according to step (G) and oxidized according to step (H) according to the present invention in five steps as follows:

(i) Synthesis of 4-(benzyloxy)-3-methoxybenzaldehyde (2)

[0532] ##STR00039##

[0533] Vanillin (1) (1.0 eq.) and benzyl chloride (1.2 eq.) are dissolved in N,N-dimethylformamide and potassium iodine (0.5 mol %) is added. Afterwards potassium carbonate is added and the reaction is stirred above 60 C., preferably between 60 to 120 C. for at least 1 h, preferably 1 to 8 h. After completion of the reaction, the solution is diluted with distilled water and extracted with an appropriate solvent. The organic phase is washed with brine and the product is then isolated from the organic phase.

(ii) Synthesis of 4-(benzyloxy)-3-methoxybenzoic acid (3)

[0534] ##STR00040##

[0535] A mixture of 1,2-dimethoxyethane and potassium hydroxide (5 to 20 eq.) is purged with oxygen and the calculated amount of isolated product 2 (1.0 eq.) is added. After the absorption of oxygen ceases, the mixture is diluted with distilled water and neutral organic products are extracted with an appropriate solvent. The aqueous layer is acidified and the acidic organic products are extracted with an appropriate solvent. Product 3 is isolated from the organic layer.

(iii) Synthesis of 4-(benzyloxy)-3-methoxybenzoyl chloride (4)

[0536] ##STR00041##

[0537] Isolated product 3 (1.0 eq.) is dissolved in thionyl chloride (5-20 eq.) and the mixture is stirred at 60 to 120 C. for 1 to 8 h. After completion of the reaction excess thionyl chloride is evaporated to yield desired acyl chloride 4.

(iv) Synthesis of Anthraquinones (5-7)

[0538] ##STR00042##

[0539] Aluminiumtrichloride (0.1 eq.) is added to the crude acyl chloride 4 and the mixture is stirred for 30 to 300 min at 20 to 60 C. After completion of the reaction the mixture is carefully quenched with bicarb solution. The product is extracted with an appropriate solvent and the organic layer is washed with brine. The product is then isolated from the organic phase.

(v) Synthesis of 2,6-dihydroxy-3,7-dimethoxyanthracene-9,10-dione 8 and 2,6-dihydroxy-1,7-dimethoxyanthracene-9,10-dione 9

[0540] ##STR00043##

[0541] Anthraquinone 5 or 6 are dissolved in ethyl acetate, methanol or ethanol and palladium on charcoal (1 to 30 weight %) is added. The mixture is stirred at room temperature under hydrogen atmosphere (1-10 bar). The catalyst is filtered off and the product (9) is isolated from the mixture.

[0542] The product is then characterized by spectrographic means, and provided as redox active compound according to the present invention.

Example 4: Derivatization of (Hydro-)Quinones

Example 4.1 Reduction of Dimethoxy Benzoquinone

[0543] ##STR00044##

[0544] 23.2 g of sodium dithionite (0.134 mol, 1.32 eq.) was added to the suspension of 17.0 g (0.101 mol, 1.0 eq.) 2,6-dimethoxycyclohexa-2,5-diene-1,4-dione in 100 mL H.sub.2O. After 2 h stirring at room temperature the precipitate was filtered off and dried in the air to give 15.85 g (0.093 mol, 92% yield) of 2,6-dimethoxybenzene-1,4-diol as a white solid.

Example 4.2: Oxidation of Methoxy Benzohydroquinone

[0545] ##STR00045##

[0546] 1.4 g of catalyst Cu/AlO(OH) was added to a solution of 8.2 g (0.059 mol) 2-methoxy-1,4-dihydroxybenzene in 250 mL ethyl acetate, and the reaction mixture was stirred at room temperature for 147 h under an O.sub.2 atmosphere. After the conversion determined by HPLC reached 99%, the reaction mixture was filtered, and the recovered catalyst was washed with ethyl acetate (100 mL3). The filtrate was collected and solvent was removed in vacuo to give 7.66 g (0.055 mol, 95% yield) of 2-methoxycyclohexa-2,5-diene-1,4-dione as a yellow-brownish solid.

Example 4.3: Acetylation of Methoxy Benzohydroquinone

[0547] 8.24 g (0.059 mol, 1.0 eq.) of 2-methoxybenzene-1,4-diol was weighed into a 250 mL reaction flask equipped with a reflux condenser. 60 mL of dichloroethane and 15 mL (0.159 mol, 2.7 eq.) of acetic anhydride were added. 12 mL (0.096 mol, 1.63 eq.) of boron trifluoride ether solution was then slowly added at room temperature with stirring. The reaction mixture was heated to 90 C. for 20 hours. The mixture was cooled to 60 C., 30 mL H.sub.2O was added followed by 10 mL HCl (6 M). The resulting mixture was heated to 100 C. for 30 min, cooled down and extracted with ethyl acetate (150 mL3). The combined extracts were washed sequentially with H.sub.2O (100 mL), saturated sodium bicarbonate (100 mL) and H2O (100 mL) and then dried with anhydrous sodium sulfate. The solvent was removed in vacuo to give a brown solid residue, which was washed with methanol to give 7.49 g (0.041 mol, 70% yield) of 1-(2,5-dihydroxy-4-methoxyphenyl)ethan-1-one as a beige solid.

Example 4.4 Addition of Isonicotinic Acid to Benzoquinone

[0548] 2.16 g (0.02 mol, 1.0 eq.) of p-benzoquinone was suspended in 6.4 mL of acetic acid. 2.46 g (0.02 mol, 1.0 eq.) of nicotinic acid was added and the mixture was stirred for 2 h at rt. The resulting dark mixture was diluted with 3 mL of water and treated with 6.6 mL of HCl (6 M). On cooling, solid precipitated which was filtered off and dried overnight at 60 C. to give 3.13 g (0.012 mol, 59% yield) of 3-carboxy-1-(2,5-dihydroxyphenyl)pyridin-1-ium chloride as an yellow solid.

Example 4.5 Sulfonation of Anthraquinone

[0549] ##STR00046##

[0550] A solution of anthraquinone was heated (180 C.) in a solution of 20%-40% SO.sub.3 in concentrated sulfuric acid (oleum), resulting in a mixture of sulfonated anthraquinones. The crude mixture was poured onto ice and partially neutralized with calcium hydroxide. Subsequently, the mixture was filtrated and concentrated to yield the final product.

Example 4.6: Sulfonation of Hydroquinone (1,4-Dihydroxybenzene)

[0551] ##STR00047##

[0552] A solution of hydroquinone was heated (80 C.) in a solution of 20%-40% SO.sub.3 in concentrated sulfuric acid (oleum), resulting in a mixture of sulfonated hydroquinones. The crude mixture was poured onto ice and partially neutralized with calcium hydroxide. Subsequently, the mixture was filtrated and concentrated to yield the final product.

Example 4.7: Sulfonation of 1,4-Dihydroxy-2,6-dimethoxybenzene

[0553] A solution of hydroquinone was heated (80 C.) in a solution of 20%-35% SO.sub.3 in concentrated

##STR00048##

[0554] sulfuric acid (oleum), resulting in a mixture of sulfonated 1,4-dihydroxy-2,6-dimethoxybenzenes.

[0555] The crude mixture was poured onto ice and partially neutralized with calcium hydroxide.

[0556] Subsequently, the mixture was filtrated and concentrated to yield the final product.

Example 4.8: Sulfonation of 2-Methoxyhydroquinone

[0557] ##STR00049##

[0558] A solution of 2-methoxyhydroquinone was heated (80 C.) in a solution of 20%-40% SO.sub.3 in concentrated sulfuric acid (oleum), resulting in a mixture of sulfonated 2-methoxyhydroquinones. The crude mixture was poured onto ice and partially neutralized with calcium hydroxide. Subsequently, the mixture was filtrated and concentrated to yield the final product.

Example 5: Model Compounds from the Modification Reaction of Benzoquinones Paired with Sulfonated Anthraquinone in an Organic Redox Flow Battery

[0559] Table 4 shows three examples for pairings that were used in a fully organic redox flow battery that were achieved by the modification of quinones. Example A shows a pairing of a sulfonated benzohydroquinone that was achieved by a double substitution reaction with sulfur trioxide and a sulfonated anthraquinone that was also achieved by a double substitution reaction with sulfur trioxide. Example B shows a glycin substituted mono methoxy benzohydroquinone that was achieved by the nucleophilic attack of an glycin to the methoxy benzoquinone paired with the sulfonated anthraquinone. In example C a isonicotinic acid substituted benzohydroquinone is paired with the same anthraquinone. The isonicotinic acid was introduced by nucleophilic attack as well.

TABLE-US-00004 TABLE 4 Pairings for modified products in a fully organic redox flow battery [00050] A [00051] B [00052] C