Method for producing methionine

Abstract

The invention concerns a preparation of a compound of formula I,

[Chem 1]

CH.sub.3XCH.sub.2CH.sub.2C(NH.sub.2)COOH  (I) where X represents S or Se, by catalytic conversion of a compound of formula II

[Chem 2]

CH.sub.3XCH.sub.2CH.sub.2C(Y)CN  (II) where X represents S or Se and Y represents NH.sub.2 or OH, when Y represents NH.sub.2, the conversion being carried out in the presence of water and of at least one catalyst comprising at least alumina, titanium dioxide or a mixture thereof, and when Y represents OH, the conversion being carried out in the presence of water, of at least one catalyst comprising at least alumina, titanium dioxide, zirconia or a mixture thereof, and NH.sub.3 or an ammonium salt.

Claims

1. A method for preparing a compound of formula I,
[Chem 1]
CH.sub.3XCH.sub.2CH.sub.2C(NH.sub.2)COOH  (I) where X represents S or Se, by catalytic conversion of a compound of formula II
[Chem 2]
CH.sub.3XCH.sub.2CH.sub.2C(Y)CN  (II) where X represents S or Se and Y represents NH.sub.2 or OH, wherein, when Y represents NH.sub.2, the conversion is carried out in the presence of water and at least one catalyst comprising at least alumina, titanium dioxide or a mixture thereof, and when Y represents OH, the conversion is carried out in the presence of water, of at least one catalyst comprising at least alumina, titanium dioxide, zirconia or a mixture thereof, and NH.sub.3 or an ammonium salt.

2. The method according to claim 1, wherein it involves the compound of formula II in which Y represents OH and said conversion is carried out in the presence of water, of at least one catalyst comprising or consisting of at least alumina, titanium dioxide, zirconia or a mixture thereof, and NH.sub.3 or an ammonium salt.

3. The method according to claim 1, wherein said catalyst is doped with one or more of the elements and compounds selected from alkali metals, alkaline earth metals, lanthanum and any compound of the aforementioned elements, and at least one amongst K, Cs, Sr, Ba.

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

5. The method according to claim 1, wherein the catalyst is in a mass concentration comprised between 0.1% and 200% with respect to the mass of the compound (II).

6. The method according to claim 1, wherein the compound of formula (II) with Y represents NH 2 is in aqueous solution in a concentration ranging from 0.01 M to 10 M.

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

8. The method according to claim 1, wherein, before the conversion, the compound of formula (II) with Y representing NH.sub.2 is placed in the presence of ammonia.

9. The method according to claim 1, wherein the compound of formula (II) with Y representing OH, is placed in the presence of an ammonium salt selected from (NH.sub.4)H.sub.2PO.sub.4, (NH.sub.4).sub.2HPO.sub.4, (NH.sub.4).sub.3PO.sub.4, (NH.sub.4)HSO.sub.4, (NH.sub.4).sub.2SO.sub.4, (NH.sub.4)HCO.sub.3 or (NH.sub.4).sub.2CO.sub.3.

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

Description

EXAMPLES

[0035] The disclosure and its advantages are illustrated in the examples below.

Example 1: Preparation of Methionine from AMTBN in the Presence of TiO.SUB.2., According to the Disclosure

[0036] The hydrolysis reaction of AMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00001##

[0037] 65 g of AMTBN are introduced with 1000 ml of H.sub.2O into a 1 liter screw-top vial. The solution is stirred at room temperature with a flow of nitrogen (5 ml/min), the solution is injected into a tubular reactor heated to 100° 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 reaction is monitored over 48 hours by proton NMR.

[0038] The conversion of AMTBN is greater than 90%, the yield of methionine is on average 74% with an average selectivity of 81% and the yield of dinitrile is on average 11% with an average selectivity of 12%.

Example 2: Preparation of Methionine from AMTBN in the Presence of TiO.SUB.2 .and Ammonia, According to the Disclosure—Influence of the Specific Surface Area of TiO.SUB.2

[0039] The hydrolysis reaction of AMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00002##

[0040] 2.1 of TiO.sub.2 (in the form of anatase) with a BET of 90 m.sup.2/g

[0041] 0.4 g of TiO.sub.2 (in the form of anatase) (90 m.sup.2/g), then 0.1 g of AMTBN (98%) have been introduced with 2 ml of a solution of ammonia at 28 weight %. The solution has been heated at 90° C. for 10 minutes after which the solution has been filtered and analyzed by proton NMR.

[0042] The yield of methionine is 93%, that of AMTBM is 1% and that of dinitrile is 6%.

[0043] 2.2 of TiO.sub.2 (in the form of anatase) with a BET of 275 m.sup.2/g

[0044] 0.4 g of TiO.sub.2 (in the form of anatase) (275 m.sup.2/g), then 0.1 g of AMTBN (98%) have been introduced with 2 ml of a solution of ammonia at 28 weight %. The solution has been heated at 90° C. for 10 minutes after which the solution has been filtered and analyzed by proton NMR.

[0045] The yield of methionine is 95%, that of AMTBM is 1% and that of dinitrile is 4%.

[0046] A TiO.sub.2 catalyst having a BET of at least 90% should be preferred.

Example 3: Preparation of Methionine from AMTBN, in the Presence of Doped Titanium Dioxide and Ammonia, According to the Disclosure

[0047] This example covers the use of TiO.sub.2 doped with cesium and strontium, respectively. The doping has been performed by a method of impregnating TiO.sub.2 with cesium hydroxide or strontium hydroxide, with a content of 4 weight % of cesium and strontium (non-metallic).

[0048] A solution of AMTBN at 0.8 mol/L is brought into contact with 5 g of either one of the doped catalysts for 10 minutes at a temperature of 100° C.

[0049] The results are presented in table 1 below.

TABLE-US-00001 TABLE 1 AMTBN Selectivity Selectivity Selectivity Selectivity Doping conversion for Met for AMTBM for dinitrile for others Cs 95% 88%  0% 7% 5% Sr 96% 80% 13% 4% 3%

Example 4: Preparation of Methionine from AMTBN in the Presence of Titanium Dioxide and Ammonia According to a Continuous Method of the Disclosure

[0050] The hydrolysis reaction of AMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00003##

[0051] The catalyst is a titanium oxide having a specific surface area of 150 m.sup.2/g.

[0052] 5 g of this catalyst are placed in the reactor where a 0.1 mol/L aqueous solution of AMTBN is circulated with a flow rate of 0.2 ml/min, and an ammonia flow of 10 ml/min. The reaction temperature is 100° C. and the contact time is 6 minutes.

[0053] The results are presented in table 2 below.

TABLE-US-00002 TABLE 2 moni- Selectivity toring Conversion Selectivity Selectivity for Selectivity period of AMTBN for Met for AMTBM dinitrile for others 1 h 94% 88% 5% 3% 4% 4 h 96% 90% 2% 4% 4%

[0054] It is observed that the system is stable in conversion and in selectivity, with a high selectivity for methionine (90%), a very high conversion of AMTBN (96%) and a low selectivity for the other products. The yields of methionine and of AMTBM are respectively 86% and 2%.

Example 4: Preparation of Methionine from HMTBN, in the Presence of Titanium Dioxide and Di-Ammonium Hydrogen Phosphate, According to the Disclosure

[0055] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00004##

[0056] 13.1 g of HMTBN are introduced with 1000 ml of H.sub.2O into a 1 liter screw-top vial. 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 reaction is monitored by HPLC, the yield of methionine is 47%.

Example 5: Preparation of Methionine from HMTBN, in the Presence of Titanium Dioxide and of Ammonia, According to the Disclosure

[0057] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00005##

[0058] 13.1 g of HMTBN are introduced with 1000 ml of H.sub.2O in a 1 liter screw-top vial. The solution is stirred at room temperature with a flow of ammonia having a flow rate of 100 ml/min, the solution is injected into a tubular reactor heated to 90° C. with a flow rate of 0.1 ml/min (contact time 15 minutes) and containing 6 grams of TiO.sub.2 (anatase, 150 m.sup.2/g, Norpro, ST 61120). The reaction is monitored by HPLC, the yield of methionine is 80%.

Example 6: Preparation of Methionine in the Presence of Titanium Dioxide, from HMTBN but without a Source of Ammonia, According to the Prior Art

[0059] The hydrolysis reaction of HMTBN and the conditions under which it is carried out are described in the diagram below.

##STR00006##

[0060] 13.1 g of HMTBN are introduced with 1000 ml of H.sub.2O in 1 liter screw top vial. 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 reaction is monitored by HPLC, the yield of HMTBA is 1% and of methionine is 15%.

[0061] The comparison of the results of examples 4 to 5 according to the disclosure, with those obtained in a method carried out without ammonia or ammonium salt in example 6, demonstrates a considerable gain in the performance of the production of methionine in a method of disclosure. The same benefit is observed in the production of selenomethionine.