GB2388368A

GB2388368A - Production of tartaric acid

Info

Publication number: GB2388368A
Application number: GB0210421A
Authority: GB
Inventors: Andrei Miasnikov; Thomas Amos Jacobsen
Original assignee: Danisco AS
Current assignee: International N&H Denmark ApS
Priority date: 2002-05-07
Filing date: 2002-05-07
Publication date: 2003-11-12
Also published as: GB0210421D0

Abstract

Method to produce tartaric acid comprises oxidation of 5-ketoaldonic acids or their salts in the presence of a nobel metal catalyst. The process may use catalysts based upon ruthenium, osmium, rhodium, palladium, iridium or platinum and may be supported.

Description

METHOD TO PRODUCE TARTARIC ACID

FIELD OF THE INVENTION

t0001] The invention relates to a method of producing tartaric acid and, more particularly, to a method to produce tartaric acid by oxidation of 5 5 ketoaldonic acids. Some of the disadvantages associated with the above method are low yield, slow process and toxic catalyst residues.

BACKGROUND OF THE INVENTION

2] Tartaric acid is a useful food ingredient. It is also used in a number of other industries and as a raw material for the synthesis of various 10 products. Currently, almost all tartaric acid on the market is produced by the traditional technology from cream of tartar (potassium hydrogen tartrate, a by-

product of the wine industry). However, this method is limited by the availability of raw material and production is subject to large yearly variations. Therefore, alter-native methods for producing tartaric acid are of substantial interest.

15 [0003] One known method for manufacturing tartaric acid is based on the use of maleic anhydride as the raw material. EP 0 911 392 A1 de scribes a method, wherein maleic anhydride is chemically converted to epoxy succinic acid followed by stereospecific hydrolysis of the epoxy- fing by a spe cific enzyme. However, maleic anKydride is a relatively expensive raw material 20 and methods based on conversion of carbohydrates into tartaric acid would be much more attractive.

10004] US 1,425,605 describes a method of producing tartaric acid from glucose or other carbohydrates in the presence of metal oxide catalysts, in particular, vanadate oxide. Another method for direct conversion of crbohy Z5 crates into tartaric acid is disclosed in US patent 2,257,284. Here, the oxida tion is carried out in nitric acid. Again, metal salts, particularly the vanadates are suggested as catalysts.

5] All the above-mentioned processes generated large number of byproducts and, consequently, tartaric acid yields remained low. Therefore, 30 most subsequent studies on production of tartaric acid by oxidation of carbo hydrate-related compounds focused on oxidising 5-ketogluconic acid rather than glucose or other neutral carbohydrates. 5-Ketogluconic acid is glucose derivative that can be produced by fermentation. One early method for produc ing tartaric acid from 5-ketogluconic acid is described in US patent 2,191,021' 35 wherein the 5-ketogluconic acid is oxidated into tartaric acid in nitric acid in the

presence of vanadate. Oxidation of 5-ketogluconic acids into tartaric acid in nitric acid has also been described in US patent 2,417230.

l0006l Isbell and Holt developed methods for conversion of 5 ketogluconate into tartaric acid in alkaline solution (Journal of Research of the 5 National Bureau of Standards, 35, 433438 (1945)). WO 96/15095 discloses a method of producing tartaric acid from 5- ketogluconate, wherein vanadate catalyst is used at alkaline conditions, with a particular emphasis on the use of carbonate buffers. This process overcomes one problem common to the earlier methods - low tartaric acid yield. However, two major problems remain. Firstly, 10 the process is very slow. It takes eight days to complete the oxidation. Sec ondly, and most importantly, the use of vanadate as the soluble catalyst in this process leads to significant risks related to its human toxicity. It also presents an environmental hazard and the need to remove vanadate after the oxidation step would cause a significant increase in production cost of tartaric acid.

15 [0007] The use of noble metal catalysts for the oxidation of sugars is well documented in the art. For example, oxidation of glucose to gluconic and saccharin acids has been the subject of many studies and inventions (Carbohydrate Research, 59 63-72 (1977); Journal of Catalysis 67, 1 -13 (1983); EP 0151 498). Oxidation of other mono- and oligosaccharides to the 20 corresponding sugar acids is also known (Patent Application DE 195 42 278, US Patent 5977350, Carbohydrate Research, 204, 121-129 (1990)).

8] Another type of reaction cataiysed by noble metal catalysts is the oxidation of the secondary alcohol group of a sugar molecule to a ketone For example gluconic acid can be oxidised to 2-ketogluconic acid (Carbohy 25 d rate Research 153, 227-235 (1986); European Patent 0 151 498) and fruc tose to 5-ketofructose (Carbohydrate Research 304, 155-164 (1997)). How ever, to the Applicants knowledge prior art does not teach how to use noble

metal-catalysed reaction to achieve C-C bond scission in carbohydrates in a highly specific manner and with high yield of products.

30 BRIEF DESCRIPTION OF THE INVENTION

9] An object of the present invention is thus to provide a method so as to alleviate the above disadvantages. The object of the invention is achieved by a method' which is characterized by what is stated in the inde pendent claim. The preferred embodiments of the invention are disclosed in 35 the dependent claims.

0] The invention is based on the unexpected realization that noble metal catalysts can selectively oxidise 5-ketogluconic acids into tartaric acid with high yield. This is the first example of using noble metal catalysis for carrying out a highly specific reaction of carbohydrate oxidation wherein car-

5 bon-carbon bond is split selectively.

1] It is an advantage of the method of the invention that the re-

moval of catalyst may be easily accomplished by filtration and no highly toxic component will be present in the reaction mixture. After removal of the catalyst, the tartaric acid may be recovered from the reaction mixture by many methods 10 well known in the art.

DETAILED DESCRIPTION OF THE INVENTION

2] The invention is directed to a method to produce tartaric acid by oxidation of 5-ketoaldonic acids or salts thereof in the presence of noble metal catalyst. Catalysts based on essentially any noble meta. such as ruthe 15 nium, osmium, rhodium, palladium, iridium or platinum can be used for practis-

ing current invention. Most preferable are the catalysts based on platinum and palladium. [0013] The catalysts may be used in many forms well known in the art. One preferred form of the cata yst is free metal in powdered form (e.g. so 20 called platinum black). Alternatively the catalyst can be supported on other ma-

terials such as activated carbon, alumina, silica, barium carbonate etc. For the present invention most preferable carriers are activated carbon and silica and carbon being more preferred.

4] The catalysts may additionally be modified by methods well ' I' I 'L 1 _ 1 _ _ I _ _ _

z Known In one err. hor example, noDIe metal catalysis mOulTleu wl''rl It'LlU tJI l-'I:j muth can be used in implementing current invention.

5] The reaction is preferably carried out in water solution. How ever, many other solvents, for example organic alcohols or ethers may be used. The use of various solvent mixtures and mixtures of various solvents 30 with water is also considered to be within the scope of this invention.

6] The reaction may be carried out in wide pH range 0 - 14.

However, preferable pH range is 5 - 11 and the most preferable range is 7 10. The pH may be maintained with various suitable buffers or by autotitration.

Examples of suitable buffers are: phosphate, pyrophosphate, carbonate, and 35 sulphate. Carbonate is the preferred buffer.

( [0017] The preferred reaction temperature is within 0 - 100 C range, 10 - 70 C being more preferred and 15 - 45 C being the most pre ferred temperature range.

l0018l According to the present invention, the concentration of sub 5 strafe (5-ketoaldonic acid) may be varied within a large range. Preferably, the concentration is within from 50 mM to saturated, more preferably above 200 mM. 5-ketogluconates of various cations can be used. Na+ and K+ salts are the most preferable. The use of K+ salt offers an additional advantage of sim plifying subsequent separation of tartaric acid from the reaction mixture (be 10 cause of low solubility of potassium hydrogen tartrate).

9] One preferable oxidising agent for practicing present inven tion is air. Of course, purified oxygen or air enriched with oxygen may also be used. The level of oxygen in reaction mixture may be controlled by the amount of air introduced into the reactor and the intensity of stirring. The reaction is 15 preferably carried out at atmospheric pressure. However, the pressure in the reactor may also be raised above atmospheric in order to enhance the reaction rate or reduced in order to control the reaction rate. In addition to molecular oxygen (02) various other sources of oxidising agents such as hydrogen per oxide may be used. One way to practice current invention is to use electro 20 chemical oxidation in combination with noble metal catalysis.

0] One preferred embodiment of the invention is the oxidation of 5ketogluconic acids to L(+)tartaric acid. However, a man skilled in the art would recognise that noble metal catalysts are known to lack any stereoselec tivity. Therefore, 5-keto-D-gluconic (5-keto-L-idonic) and 5keto-D-galactonic 25 (5-keto-L-altronic) acids could be used to produce L(+) tartaric acid; 5-keto-D altronic (5-keto-L-gaiactonic) and 5-keto-Didonic (5-keto-L-gluconic) acids for production of D(-)-tartaric acid. Mesotartaric acid can be obtained from either D- or L-forms of 5ketoallonic, 5-ketogulonic, 5-ketomannonic and 5-ketotalonic acids. 30 [0021] After the tartaric acid is produced according to the method of the invention the catalyst can be easily removed due to its insolubility. Separa tion of insoluble materials from liquid suspensions is a common task in chemi cal engineering and a man skilled in the art would know many suitable tech niques. For example, various forms of filtration, centrifugation or sedimentation 35 are suitable. Most suitable catalyst separation method is filtration. Preferred filters are sintered metal filters and so called candle filters. Flow-through cen

trifugation is an especially suitable centrifugation technique.

[00221 The tartaric acid may be recovered from the reaction mixture by many methods. Chromatographic methods such as ion-exchange, adsorp tion, exclusion chromatography and chromatographic separation methods 5 based on ionic coordination/chelation are ail suitable for separation of tartaric acid from the reaction mixtures of the current invention. In addition to chroma tographic separation techniques, many other methods known to the man skilled in the art are suitable: nano-filtration, precipitation in the form of poorly soluble salts (potassium semi- tartrate being particularly suitable). Both tartaric 10 acid and many of its salts crystalline easily which, of course, may be used for the separation and purification of tartaric acid obtained by the methods of this invention. Example 1

t0023] 0.5 ml of a solution containing potassium 5-ketogluconate 15 (0.5 M), 20 mg of platinum on carbon (5%) and 4.5 ml sodium carbonate buffer (0.5 M, pH 9.55) was mixed in a 25 ml Erlenmeyer flask. The flask was equipped with a loose silicon rubber stopper. The mixture was agitated using magnetic stirrer (50 mint') at room temperature (ZINC). Samples of 300 ml were taken every day and analysed by HPLC. The products were separated o 20 a Polyspher) OA HY column (RT 300-6.5, Merck KGaA, Germany) at 23 C, using 10 mM HCIO4 as the mobile phase at a flow rate of 0.5 milmin. Tartaric acid and 5-ketogluconic acid were measured with a UVdetector. After a period of 5 days the molar yield of tartaric acid exceeded 80%. In a control reaction without platinum catalyst, tartaric acid was formed in about 15% yield.

25 10024j Figure, illusti-ats the time coo, se Of tartaric acid Formation from 5-ketogluconic acid under conditions of Example 1. The concentrations of tartaric and 5-ketogluconic acid are expressed as molar percentage of the ini tial 5-ketogluconate concentrations. Control reaction was carried out under identical conditions except that a platinum catalyst was omitted.

30 Example 2

5] The reaction was carried as described in Example 1 but 40 mg of platinum catalyst was used rather than 20 mg. The yield of tartaric acid has been similar to that in the example 1 (about 80%) however, it was reached after only two days of incubation.

Example 3

l0026l The reaction was carried out under condition identical to those described in Example 1 except that palladium on carbon (5 %) was used instead of platinum. After 5 days of incubation tartaric acid was produced in 55 5 % yield.

Example 4

7] The reaction was carried out under condition identical to those described in Example 1 except that iridium on carbon (5 %) was used instead of platinum. After 5 days of incubation the yield of tartaric acid reached 1 0 85%.

Example 5

[0028J Oxidation was carried out in the same manner as in Example 1 but using 5% rhodium on carbon as catalyst. The yield of tartaric acid was 80%. 15 Example 6

9] A solution of 5-ketogluconic acid according to the example 1 is prepared. Using noble metal anode (e.g. platinum sponge, Fluka, 81100) electric current is passed through the solution, when tartaric acid is formed by anodic oxidation of 5-ketogluconate.

20 Example 7

0] The reaction was carried out under conditions identical to those described in Example 1 except BiONO3 (1.0 mg) was added to the reac-

tion mixture containing either platinum or palladium catalysts. After 5 days of reaction tartaric acid was produced in 61% (using Pt/C) or 56 % (using Pd/C) 25 yield.

10031] It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples de-

30 scribed above but may vary within the scope of the claims.

Claims

1. A method to produce tartaric acid by oxidation of 5-ketoaldonic acids or salts thereof in the presence of noble metal catalyst.

2. The method according to claim 1, wherein the noble metal cata 5 Iyst is selected from ruthenium, osmium, rhodium, palladium, irridium and platinum, preferably from palladium and platinum.

3. A method according to claim 1 or 2, wherein the noble metal cata-

lyst is a supported catalyst.

4 A method according to any of the preceding claims, wherein the 10 oxidation is carried out in a solvent.

5. The method according to claim 4, wherein the solvent is selected from water, alcohol and ethen

6. A method according to any of the preceding claims, wherein the oxidation is carried out in pH range from 5 to 11, preferably from

7 to 10.

15 7. The method according to claim 6, wherein the pH is maintained at the desired level by using buffer or autotitration.

8. The method according to claim 7, wherein the buffer is selected from phosphate, pyrophosphate, carbonate and sulphate.

9. A method according to any of the preceding claims, wherein air is 20 used as oxidation agent.

10. A method according to any of the preceding claims, wherein 5-

ketogluconic acid or a salt thereof is oxidized.

11. A method according to claim any of the preceding claims, wherein the oxidation is carried out by using a noble metal anode and electric 25 current is passed through the reaction solution.

12. A method according to claim any of the preceding claims, wherein L() tartaric acid is produced.

13. A method of producing tartaric acid substantially as described herein with reference to any of Examples 1-7.