AN ELECTROCHEMICAL METHOD FOR PREPARING AN AMINE AND/OR A NITRILE

Abstract

The present invention relates to an electrochemical method for converting an amino acid and/or its salts to an amine and/or a nitrile. The total yield and selectivity of amine and nitrile obtained by the method according to the present invention is higher than prior art when the reaction medium has a high concentration of amino acid and/or its salts at the beginning of the reaction.

Claims

1. An electrochemical method for converting an amino acid and/or its salts to an amine and/or a nitrile in the presence of a solvent and a compound generating a mediator in reduced form in the solvent, wherein the concentration of the amino acid and/or its salts in the solvent is equal to or greater than 0.15 mol/L.

2. The method according to claim 1, wherein the concentration of the amino acid and/or its salts in the solution is in the range of 0.15 mol/L to 2 mol/L.

3. The method according to claim 1, wherein the concentration of the compound generating a mediator in reduced form in the solution is in the range of 0.01 mol/L to 1 mol/L.

4. The method according to claim 1, wherein the compound generating a mediator in reduced form in the solvent is selected from the group consisting of alkali metal bromides, alkali metal chlorides, alkali metal iodides, ammonium bromide, iron salts, cerium salts, manganese salts, copper salts, cobalt salts and chromium salts.

5. The method according to claim 4, wherein the compound generating a mediator in reduced form in the solvent is sodium bromide or ammonium bromide.

6. The method according to claim 4, wherein the compound generating a mediator in reduced form in the solvent is an iron salt.

7. The method according to claim 1, wherein the amino acid is selected from the group consisting of lysine, cysteine, leucine, serine, tyrosine, arginine, histidine and isoleucine.

8. The method according to claim 1, wherein the salt of amino acid is selected from the group consisting of hydrochloride salt, hydrobromide salt and hydroiodide salt.

9. The method according to claim 1, wherein the conversion is carried out in a reactor comprising both an anode and a cathode and the distance between the anode and the cathode is in the range of 1 mm to 10 cm.

10. The method according to claim 1, wherein the anode and/or the cathode comprises a catalyst.

11. The method according to claim 1, wherein the catalyst of the anode is Pt and the catalyst of the cathode is Ni or Cu.

12. The method according to claim 2, wherein the concentration of the amino acid and/or its salts in the solution is in the range of 0.50 mol/L to 1.0 mol/L.

13. The method according to claim 3, wherein the concentration of the compound generating a mediator in reduced form in the solution is in the range of 0.05 mol/L to 0.2 mol/L.

14. The method according to claim 6, wherein the compound generating a mediator in reduced form in the solvent is iron (II) sulphate.

15. The method according to claim 9, wherein the conversion is carried out in a reactor comprising both an anode and a cathode and the distance between the anode and the cathode is in the range of 3 mm to 1 cm.

Description

EXPERIMENTAL PART

[0076] Materials [0077] Sodium bromide: CAS No 7647-15-6 from Sigma-Aldrich [0078] Iron(II) sulfate heptahydrate: CAS No 7782-63-0 from Sigma-Aldrich [0079] L-lysine monohydrochloride: CAS No 657-27-2 from Sigma-Aldrich [0080] Sulfuric acid: CAS No 7664-93-9 from Sinopharm

Example 1 (Comparative Example)

[0081] As batch reactor, a 10 ml glass vessel (diameter 2.5 cm) is used. A Pt coil (coil=0.5 cm high, 1 cm diameter, circumference=3.1 cm, surface area=1.6 cm.sup.2) serves as anode. As cathode a Ni foam is bent into cylindrical shape (Size=5.5 cm×5.5 cm—long enough to reach out of the reactor). It is bend in a cylindrical shape and wrapped around a cylindrical foam (diameter=2 cm). The cathode surface area=5.5 cm×0.5 cm (Pt coil height)=2.75 cm.sup.2. The Pt wire above the coil is insulated by a PTFE tube in order to prevent echem reactions at the wire and pierced through the spacer to keep the Pt electrode in place. The Ni cathode leaves a gap open to be able to see the Pt coil. The distance between both electrodes is 3 mm [0082] No reference electrode and no stirring are used. [0083] The reactor is filled with 6 ml of a solution of lysine monohydrochloride (0.14 M) and NaBr (0.19 M). The measured pH is around 6. [0084] Reaction parameters: The total experiment time: 7 h, current=41 mA (equals a current density of 15 mA/cm.sup.2 at anode). [0085] During reaction, samples are taken and analyzed by NMR. The results are summarized in Table 1.

Example 2(Bromide Mediator, 0.28 M Lysine Monohydrochloride, Ni Cathode)

[0086] As batch reactor, a 10 ml glass vessel (diameter 2.5 cm) is used. A Pt coil (coil=0.5 cm high, 1 cm diameter, circumference=3.1 cm, surface area=1.6 cm.sup.2) serves as anode. As cathode a Ni foam is bent into cylindrical shape (Size=5.5 cm×5.5 cm—long enough to reach out of the reactor). It is bend in a cylindrical shape and wrapped around a cylindrical foam (diameter=2 cm). The cathode surface area=5.5 cm×0.5 cm (Pt coil height)=2.75 cm.sup.2. The Pt wire above the coil is insulated by a PTFE tube in order to prevent echem reactions at the wire and pierced through the spacer to keep the Pt electrode in place. The Ni cathode leaves a gap open to be able to see the Pt coil. The distance between both electrodes is 3 mm [0087] No reference electrode and no stirring are used. [0088] The reactor is filled with 5 ml lysine monohydrochloride (0.28 M) and NaBr (0.14 M). The measured pH is around 6. [0089] Reaction parameters: The total experiment time: 14 h, current=41 mA (equals a current density of 15 mA/cm.sup.2 at anode). [0090] During reaction, samples are taken and analyzed by NMR. The results are summarized in Table 1.

Example 3 (Bromide Mediator, 1 M Lysine Monohydrochloride, Ni Cathode)

[0091] As batch reactor, a 10 ml glass vessel (diameter 2.5 cm) is used. A Pt coil (coil=0.5 cm high, 1 cm diameter, circumference=3.1 cm, surface area=1.6 cm.sup.2) serves as anode. As cathode a Ni foam is bent into cylindrical shape (Size=5.5 cm×5.5 cm—long enough to reach out of the reactor). It is bend in a cylindrical shape and wrapped around a cylindrical foam (diameter=2 cm). The cathode surface area=5.5 cm×0.5 cm (Pt coil height)=2.75 cm.sup.2. The Pt wire above the coil is insulated by a PTFE tube in order to prevent echem reactions at the wire and pierced through the spacer to keep the Pt electrode in place. The Ni cathode leaves a gap open to be able to see the Pt coil. The distance between both electrodes is 3 mm [0092] No reference electrode and no stirring are used. [0093] The reactor is filled with 5 ml lysine monohydrochloride (1 M) and NaBr (0.14 M). The measured pH is around 6. [0094] Reaction parameters: The total experiment time: 72 h, current=41 mA (current density=15 mA/cm.sup.2). [0095] During reaction, samples are taken and analyzed by NMR. The results are summarized in Table 1.

Example 4 (Bromide Mediator, 2 M Lysine Monohydrochloride (Saturated), Cu Cathode)

[0096] As batch reactor, a 10 ml glass vessel (diameter 2.5 cm) is used. A Pt coil (height=1.5 cm, diameter=1 cm, circumference=3.1 cm, surface area=4.7 cm.sup.2) serves as anode. As cathode a Cu foam is bent into cylindrical shape (Size=5.5 cm×5.5 cm—long enough to reach out of the reactor). It is bend in a cylindrical shape and wrapped around a cylindrical foam (diameter=2 cm). The cathode surface area=5.5 cm×0.5 cm (Pt coil height)=2.75 cm.sup.2. The Pt wire above the coil is insulated by a PTFE tube in order to prevent echem reactions at the wire and pierced through the spacer to keep the Pt electrode in place. The Cu cathode leaves a gap open to be able to see the Pt coil. The distance between both electrodes is 3 mm [0097] No reference electrode and no stirring are used. [0098] The reactor is filled with 8 ml lysine monohydrochloride (2 M) and NaBr (0.2 M). The measured pH is around 6. [0099] Reaction parameters: The total experiment time: 31 h, current=113 mA (15 mA/cm.sup.2). [0100] During reaction, samples are taken and analyzed by NMR. The results are summarized in Table 1.

Example 5 (Fe.SUP.3+./Fe.SUP.2+ Mediator, 1 M Lysine Monohydrochloride, Cu Cathode)

[0101] As batch reactor, a 20 ml glass reactor is used. A Pt cylindrical mesh (height=2 cm, diameter=1 cm, circumference=3.1 cm, surface area=6.3 cm.sup.2) serves as anode. As cathode a Cu foam is bent into cylindrical shape (thickness=2 cm, size=4 cm×8 cm—long enough to reach out of the reactor). It is bend in a cylindrical shape and wrapped around a cylindrical polymer foam (diameter=2 cm). The cathode surface area=4 cm×2 cm (Pt coil height)=8 cm.sup.2. The Pt wire above the coil is insulated by a PTFE tube in order to prevent electrochemical reactions at the wire and is pierced through the spacer to keep the Pt electrode in place. The Cu cathode leaves a gap open to be able to see the Pt electrode. [0102] No reference electrode and no stirring are used. The distance between both electrodes is 3 mm [0103] The reactor is filled with 10 ml reaction solution containing 1 M lysine monohydrochloride and 0.14 M ironsulfate heptahydrate. During the preparation of the 10 ml solution, the pH is adjusted to 1 with 1 M sulfuric acid. [0104] Reaction parameters: total reaction time is 96 h. Current=120 mA (equivalent to a current density of 15 mA/cm.sup.2 at the anode). [0105] During reaction, samples are taken and analyzed by NMR. The results are summarized in Table 1.

TABLE-US-00001 TABLE 1 Reactant Mediator APN + DAP + Conz Conz APN DAP APA Glutaronitrile other Glutaronitrile EX 1 0.14M 0.14 M 65% 18% 14% 3% 0% 86% NaBr EX 2 0.28M 0.14 M 72% 20% 5% 2% 1% 94% NaBr EX 3 1M 0.14 M 84% 14% 2% 1% 0% 98% NaBr EX 4 2M 0.2 M 42% 45% 0 8% 5% 95% NaBr EX 5 1M 0.14 M 62% 32% 1% 0% 5% 94% FeSO.sub.4 Conversion = 100%. Examples, 2 and 3 use of Ni cathode. Examples 4 and 5 use of Cu APN = 5-aminopentanitrile DAP = 1, 5-diaminopentane APA = aminopentanamide