Process for the catalytic production of an analogue of methionine

Abstract

A method for preparing 2-hydroxy-4-methylthiobutyric acid (HMTBA) or 2-hydroxy-4-methylselenobutyric acid (HMSeBA) by catalytic conversion of 2-hydroxy-4-methylthiobutyronitrile or 2-hydroxy-4-methylselenobutyronitrile, respectively, where said conversion is carried out in the presence of water and at least one weak acid and one catalyst comprising at least one of alumina, titanium dioxide and zirconia.

Claims

1. A method for preparing 2-hydroxy-4-methylthiobutyric acid (HMTBA) or 2-hydroxy-4-methylselenobutyric acid (HMSeBA) by catalytic conversion of 2-hydroxy-4-methylthiobutyronitrile or 2-hydroxy-4-methylselenobutyronitrile, respectively, wherein said conversion is carried out in the presence of water and at least one weak acid and one catalyst comprising at least one of alumina, titanium dioxide and zirconia.

2. The method according to claim 1, wherein said weak acid is selected from formic acid, acetic acid, propionic acid, linear or branched butanoic acid, pentanoic acid, carbonic acid, phosphoric acid, dihydrogen phosphate acid, glycolic acid, thioacetic acid, cyanoacetic acid, lactic acid, pyruvic acid and oxalic acid.

3. The method according to claim 1, wherein the weak acid is in at least one molar equivalent relative to the hydroxy-nitrile, or even in excess, wherein the molar ratio of the weak acid to 2-hydroxy-4-methylthiobutyronitrile or 2-hydroxy-4-methylselenobutyronitrile, ranges from 0.001 to 50.

4. The method according to claim 1, wherein the catalyst is in a mass concentration of 0.1% to 200% relative to the mass of HMTBN.

5. The method according to claim 1, wherein 2-hydroxy-4-methylthiobutyronitrile or 2-hydroxy-4-methylselenobutyronitrile is in aqueous solution in a concentration ranging from 0.01 M to 10 M.

6. The method according to claim 1, wherein said catalyst has a BET specific surface area of at least 10 m.sup.2/g.

7. The method according to claim 1, wherein said catalyst is doped with one or more compounds selected from sulfates, phosphates, borates, tungstates, heteropolyacids responding to one of the formulas H.sub.nXM.sub.12O.sub.40 and H.sub.nX.sub.2M.sub.18O.sub.62 in which n is an integer not exceeding 10, X represents Si, Ge, P or As and M represents Mo or W, such as phosphomolybdic acid of formula H.sub.6P.sub.2Mo.sub.18O.sub.62, as well as any other doping compound providing acidity to the catalyst.

8. The method according to claim 1, wherein the conversion is carried out at a temperature ranging from 20 C. to 200 C.

9. The method according to claim 1, wherein it is carried out continuously.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The disclosure and its advantages over the prior art are illustrated in the examples below, in support of the following figures:

[0030] FIG. 1 shows the conversion of HMTBN, the selectivity to HMTBA, the selectivity to methionine and the selectivity to HMTBM, as a function of time, of a reaction according to a method of the disclosure under the conditions described in Example 1.

[0031] FIG. 2 shows the conversion of HMTBN, the selectivity to HMTBA, the selectivity to methionine and the selectivity to HMTBM, as a function of time, of a reaction according to a method of the disclosure under the conditions described in Example 2.

EXAMPLES

[0032] In the experimental part which follows:

[0033] Examples 1-6 illustrate various variations of a method of the disclosure;

[0034] Examples 7 and 8 illustrate a technique for doping a catalyst to obtain a doped catalyst which can be used in a method of the disclosure, according to a variant such as that which is the subject of Example 6;

[0035] Example 9 illustrates a step of separating the hydroxy acid salt into the hydroxy acid; and

[0036] Examples 10 to 15 illustrate methods outside the disclosure, by way of comparison.

Example 1: Preparation of HMTBA in the Presence of Titanium Dioxide and Acetic Acid, According to the Disclosure

[0037] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00001##

[0038] In a 1 liter screw cap bottle, 14.0 g of HMTBN with 2000 ml of H.sub.2O and 60 mg of acetic acid are introduced. The solution is stirred at room temperature with a flow of nitrogen and injected into a tubular reactor heated to 120 C. with a flow rate of 0.05 ml/min (contact time 24 minutes) and containing 60 grams of TiO.sub.2 (anatase, 150 m.sup.2/g, Norpro, ST 61120).

[0039] The reaction is followed by HPLC. The yield of HMTBA is 88%.

Example 2: Preparation of HMTBA in the Presence of Titanium Dioxide and Acetic Acid, According to the Disclosure

[0040] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00002##

[0041] In a 1 liter screw cap bottle, 13.1 g of HMTBN with 990 ml of H.sub.2O and 10 ml of acetic acid are introduced. The solution is stirred at room temperature with a flow of nitrogen, the solution is injected into a tubular reactor heated to 160 C. with a flow rate of 0.1 ml/min (contact time 10 minutes) and containing 4 grams of TiO.sub.2 (anatase, 150 m.sup.2/g, Norpro, ST 61120). The HMTBA salt obtained is converted into HMTBA by stripping ammonia according to a technique illustrated in Example 9.

[0042] The reaction is followed by HPLC: the conversion of HMTBN, the selectivity to HMTBA, the selectivity to methionine and the selectivity to HMTBM, as a function of time are represented in [FIG. 1].

[0043] The yield of HMTBA is 95% and 5% of methionine.

Example 3: Preparation of HMTBA in the Presence of Titanium Dioxide and Acetic Acid, According to the Disclosure

[0044] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00003##

[0045] In a 1 liter screw cap bottle, 13.1 g of HMTBN with 800 ml of H.sub.2O and 200 ml of acetic acid were introduced. The solution is stirred at room temperature with a flow of nitrogen, the solution is injected into a tubular reactor heated to 160 C. with a flow rate of 0.1 ml/min (contact time 10 minutes). The reactor contains 4 grams of TiO.sub.2 (anatase, 150 m.sup.2/g, Norpro, ST 61120). The HMTBA salt obtained is converted into HMTBA by stripping ammonia according to a technique illustrated in Example 9.

[0046] The reaction is followed by HPLC: the conversion of HMTBN, the selectivity to HMTBA, the selectivity to methionine and the selectivity to HMTBM, as a function of time are represented in [FIG. 2].

[0047] The yield of HMTBA is 89% and 11% of methionine.

Example 4: Preparation of HMTBA in the Presence of Titanium Dioxide and Formic Acid, According to the Disclosure

[0048] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00004##

[0049] In a 1 liter screw cap bottle, 13.1 g of HMTBN with 990 ml of H.sub.2O and 10 ml of formic acid were introduced. The solution is stirred at room temperature with a flow of nitrogen, the solution is injected into a tubular reactor heated to 160 C. with a flow rate of 0.1 ml/min (contact time 10 minutes). The reactor contains 4 grams of TiO.sub.2 (anatase, 150 m.sup.2/g, Norpro, ST 61120).

[0050] The reaction is followed after 2 hours by HPLC.

[0051] The obtained HMTBA salt is converted into HMTBA by stripping ammonia according to a technique illustrated in Example 9.

[0052] The yield of HMTBA is 90% and 10% of methionine.

Example 5: Preparation of HMTBA in the Presence of an Alumina Doped with Sulfate and Acetic Acid, According to the Disclosure

[0053] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00005##

[0054] In a 1 liter screw cap bottle, 13.1 g of HMTBN with 800 ml of H.sub.2O and 200 ml of acetic acid were introduced. The solution is stirred at room temperature with a flow of nitrogen, the solution is injected into a tubular reactor heated to 160 C. with a flow rate of 0.1 ml/min (contact time 10 minutes). The reactor contains 4 grams of Al.sub.2O.sub.3 (gamma, 300 m.sup.2/g, IFPEN, 33006 GFSA 401, alumina doped with 10% by weight of sulfate function).

[0055] The reaction is followed after 2 hours by HPLC.

[0056] The obtained HMTBA salt is converted into HMTBA by stripping ammonia according to a technique illustrated in Example 9.

[0057] The yield of HMTBA is 96% and 4% of methionine.

Example 6: Preparation of HMTBA in the Presence of Zirconia and Acetic Acid, According to the Disclosure

[0058] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00006##

[0059] In a 1 liter screw cap bottle, 13.1 g of HMTBN with 800 ml of H.sub.2O and 200 ml of acetic acid were introduced. The solution is stirred at room temperature with a flow of nitrogen, the solution is injected into a tubular reactor heated to 160 C. with a flow rate of 0.1 ml/min (contact time 10 minutes). The reactor contains 6 grams of ZrO.sub.2 (monoclinic, 100 m.sup.2/g, Norpro, XZ 16075).

[0060] The reaction is followed after 2 hours by HPLC.

[0061] The obtained HMTBA salt is converted into HMTBA by stripping ammonia according to a technique illustrated in Example 9.

[0062] The yield of HMTBA is 74% and 16% of methionine.

Example 7: Preparation of TiO.SUB.2 .Doped with 10% by Weight of Sulfate (SO.SUB.4.) with Sulfuric Acid

[0063] In a 1 liter flask, 20 g of TiO.sub.2 (anatase, 150 m.sup.2/g, Norpro, ST 61120) powder with 500 mL of water and 2.04 g of sulfuric acid are introduced. The solution is stirred for 2 hours at room temperature, then the water is evaporated. The obtained powder is then dried at 200 C. for 3 hours and then it is calcined at 700 C. in air for 2 hours.

[0064] An elemental analysis was carried out to measure the sulfur, an amount of sulfur of 3.4% by mass of catalyst is observed, which corresponds to an amount of sulfate of 10% by mass.

Example 8: Preparation of TiO.SUB.2 .Doped with 10% by Weight of Sulfate (SO.SUB.4.) with Ammonium Sulfate

[0065] In a 1 liter flask, 20 g of powder TiO.sub.2 (anatase, 150 m.sup.2/g, Norpro, ST 61120) with 500 mL of water and 2.78 g of ammonium sulphate are introduced. The solution is stirred for 2 hours at room temperature, then the water is evaporated. The obtained powder is then dried at 200 C. for 3 hours and then it is calcined at 700 C. in air for 2 hours. An elemental analysis was carried out to measure the sulfur, an amount of sulfur of 3.2% by mass of catalyst is observed, which corresponds to an amount of sulfate of 9.8% by mass.

Example 9: Conversion of the Ammonium Salt of HMTBA to HMTBA

[0066] The HMTBA ammonium salt solution obtained according to the disclosure is concentrated in organics to an organics content of 87% by weight. The temperature of the medium changes from 100 to 130 C. (atmospheric pressure). After this concentration step, the conversion to HMTBA amounts is 21% (mol). Then, a steam stripping phase is carried out. The stripping water is introduced in liquid form. The organic content is kept constant at 87% by weight. The temperature is stationary between 115 and 121 C. The stripping rate is between 3.8 and 4.3 ml/min. After 200 minutes under these conditions, a conversion to HMTBA of 47% is obtained. A further stripping step is carried out to result in HMTBA in yields of around 100%.

Example 10: Preparation of HMTBA in the Presence of Acetic Acid, not Forming Part of the Disclosure

[0067] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00007##

[0068] In a 20 ml screw cap bottle, 0.131 g of HMTBN with 8 ml of H.sub.2O and 2 ml of acetic acid were introduced. The solution is stirred at 160 C. for ten minutes.

[0069] The solution is analyzed by HPLC, no reaction is observed.

Example 11: Preparation of HMTBA in the Presence of Formic Acid, not Forming Part of the Disclosure

[0070] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00008##

[0071] In a 20 ml screw cap bottle, 0.131 g of HMTBN with 9 ml of H.sub.2O and 1 ml of acetic acid were introduced. The solution is stirred at 160 C. for ten minutes.

[0072] The solution is analyzed by HPLC, no reaction is observed.

Example 12: Preparation of HMTBA in the Presence of Titanium Dioxide, According to the Prior Art

[0073] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00009##

[0074] In a 1 liter screw cap bottle, 13.1 g of HMTBN with 1000 ml of H.sub.2O were introduced. The solution is stirred at room temperature with a flow of nitrogen, the solution is injected into a tubular reactor heated to 160 C. with a flow rate of 0.1 ml/min (contact time 10 minutes) and containing 4 grams of TiO.sub.2 (anatase, 150 m.sup.2/g, Norpro, ST 61120).

[0075] The reaction is followed by HPLC, the yield of HMTBA is 1% and 15% of methionine.

Example 13: Preparation of HMTBA in the Presence of a Gamma Phase Alumina, According to the Prior Art

[0076] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00010##

[0077] In a 10 ml screw cap bottle, 0.4 g of -Al.sub.2O.sub.3 (300 m.sup.2/g), then 0.1 g of HMTBN (97%) with 1 ml of water were introduced. The solution was heated at 90 C. for 60 minutes after which the solution was filtered and analyzed by proton NMR.

[0078] No conversion of HMTBN is observed

Example 14: Preparation of HMTBA in the Presence of a Gamma Phase Alumina, According to the Prior Art

[0079] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00011##

[0080] In a 20 ml screw cap bottle, 0.4 g of -Al.sub.2O.sub.3 (300 m.sup.2/g), then 1.1 g of HMTBN (97%) with 10 ml of water were introduced. The solution was heated at 90 C. for 18 hours after which the solution was filtered and analyzed by proton NMR.

[0081] A yield of HMTBM of 30% and of HMTBA of 6% is observed.

Example 15: Preparation of HMTBA in the Presence of TiO.SUB.2 .Anatase, According to the Prior Art

[0082] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00012##

[0083] In a 10 ml screw cap bottle, 1 g of TiO.sub.2 (as anatase) (90 m.sup.2/g), then 1.1 g of HMTBN (97%) with 1 ml of water were introduced. The solution was heated at 90 C. for 96 hours after which the solution was filtered and analyzed by proton NMR.

[0084] No traces of HMTBM or HMTBA are observed.

[0085] The comparison of the results of Examples 1 to 6 according to the disclosure, with those obtained in a method carried out without a catalyst (Examples 10 and 11) or without weak acid (Examples 12 to 15) demonstrates a considerable gain in the performance of the production of a hydroxy acid in a method of the disclosure, which is moreover unexpected.