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. A method for forming an amine and/or a nitrile comprising: electrochemically converting an amino acid and/or its salts to an amine and/or a nitrile in a solvent, and transferring an electron from a compound thereby generating a mediator in reduced form in the solvent, wherein the amino acid and/or its salts in the solvent are present in a concentration that is equal to or greater than 0.15 mol/L and the compound is an iron salt.

2. The method according to claim 1, wherein the amino acid and/or its salts are present in a concentration ranging from 0.15 mol/L to 2 mol/L.

3. The method according to claim 2, wherein the amino acid and/or its salts are present in a concentration ranging from 0.50 mol/L to 1.0 mol/L.

4. The method according to claim 1, wherein the compound is present in a concentration ranging from 0.01 mol/L to 1 mol/L.

5. The method according to claim 4, wherein the compound is present in a concentration ranging from 0.05 mol/L to 0.2 mol/L.

6. 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.

7. 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.

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

9. The method according to claim 8, wherein the distance separating the anode and the cathode is in the range of 3 mm to 1 cm.

10. The method according to claim 8, wherein the reactor further comprises an anode catalyst and/or a cathode catalyst.

11. The method according to claim 10, wherein the anode catalyst is Pt and the cathode catalyst is Ni or Cu.

12. The method according to claim 1, wherein the iron salt is iron (II) sulphate.

Description

EXPERIMENTAL PART

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

Example 1 (Comparative Example)

(2) 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 cm5.5 cmlong 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 cm0.5 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 No reference electrode and no stirring are used. 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. Reaction parameters: The total experiment time: 7 h, current=41 mA (equals a current density of 15 mA/cm.sup.2 at anode). 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)

(3) 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 cm5.5 cmlong 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 cm0.5 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 No reference electrode and no stirring are used. The reactor is filled with 5 ml lysine monohydrochloride (0.28 M) and NaBr (0.14 M). The measured pH is around 6. Reaction parameters: The total experiment time: 14 h, current=41 mA (equals a current density of 15 mA/cm.sup.2 at anode). 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)

(4) 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 cm5.5 cmlong 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 cm0.5 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 No reference electrode and no stirring are used. The reactor is filled with 5 ml lysine monohydrochloride (1 M) and NaBr (0.14 M). The measured pH is around 6. Reaction parameters: The total experiment time: 72 h, current=41 mA (current density=15 mA/cm.sup.2). 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)

(5) 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 cm5.5 cmlong 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 cm0.5 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 No reference electrode and no stirring are used. The reactor is filled with 8 ml lysine monohydrochloride (2 M) and NaBr (0.2 M). The measured pH is around 6. Reaction parameters: The total experiment time: 31 h, current=113 mA (15 mA/cm.sup.2). 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)

(6) 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 cm8 cmlong 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 cm2 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. No reference electrode and no stirring are used. The distance between both electrodes is 3 mm 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. 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). During reaction, samples are taken and analyzed by NMR. The results are summarized in Table 1.

(7) 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