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Title:
PROCESS FOR THE OXIDATION OF SORBOSE
Document Type and Number:
WIPO Patent Application WO/2013/010811
Kind Code:
A1
Abstract:
The present invention relates to a process for the oxidation of sorbose using a specific catalyst, as well as to the catalyst as such.

Inventors:
BONRATH WERNER (CH)
GRUENEWALD ELENA (DE)
KARGE REINHARD (CH)
MEDLOCK JONATHAN (CH)
PRUESSE ULF (DE)
VORLOP KLAUS (DE)
Application Number:
PCT/EP2012/063205
Publication Date:
January 24, 2013
Filing Date:
July 06, 2012
Export Citation:
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Assignee:
DSM IP ASSETS BV (NL)
BONRATH WERNER (CH)
GRUENEWALD ELENA (DE)
KARGE REINHARD (CH)
MEDLOCK JONATHAN (CH)
PRUESSE ULF (DE)
VORLOP KLAUS (DE)
International Classes:
B01J23/52; C07C51/235; C07C59/215
Domestic Patent References:
WO2005003072A12005-01-13
WO2008148549A22008-12-11
Foreign References:
US4599446A1986-07-08
Other References:
None
Attorney, Agent or Firm:
KURT, Manfred (Wurmisweg 576241/636, Kaiseraugst, CH)
Download PDF:
Claims:
Claims

1. A process for the oxidation of sorbose, wherein a catalyst comprising

0.1 to 30 wt.-%, based on the total weight of the catalyst, of a bimetallic mixture of:

20 to 80 wt.-%, based on the total weight of the metal content of the catalyst, of Au, and

20 to 80 wt.-%, based on the total weight of the metal content of the catalyst, of Pt, and

70 to 99.9 wt.-%, based in the total weight of the catalyst, of a support material, is used and

wherein the oxidation is carried out at a pH of≥7.

2. Process according to claim 1 , wherein the process is carried out at a pH of ≥ 7 and < 10.

3. A process according to claim 1 and 2, wherein the catalyst comprises 0.5 to 20 wt.-%, based in the total weight of the catalyst, of the bimetallic mixture.

4. A process according to any of the preceding claims, wherein the catalyst comprises 40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Au.

5. A process according to any of the preceding claims, wherein the catalyst comprises 40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Pt.

6. A process according to any of the preceding claims, wherein the support material of the catalytic system is a inorganic oxide, an inorganic carbonate or an inorganic sulphate, preferably Al203, Ce02, Zr02, Ti02, Mn02, Zn02, Sn02, La02, Y203 and BaS04.

7. A process according to any of the preceding claims, wherein the concentration of the starting material (sorbose) is 50 to 300 mmol Γ1, preferably 100 to 250 mmol 1.

8. A catalyst comprising

0.5 to 20 wt.-%, based on the total weight of the catalyst, of a bimetallic mixture of

40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Au, and

40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Pt, and

80 to 99.5 wt.-%, based in the total weight of the catalyst, of a support material chosen from the group consisting of Al203, Ce02, Zr02, Ti02, Mn02, Zn02, Sn02, La02, Y203 and BaS04.

9. A catalyst according to claim comprising

0.5 to 8 wt.-%, based on the total weight of the catalyst, of a bimetallic mixture of

50 wt.-%, based on the total weight of the metal content of the catalyst, of Au, and

50 wt.-%, based on the total weight of the metal content of the catalyst, of Pt, and

92 to 99.5 wt.-%, based in the total weight of the catalyst, of a support material which is Ce02.

Description:
PROCESS FOR THE OXIDATION OF SORBOSE

The present invention relates to a process for the oxidation of sorbose using a specific catalyst, as well as to the catalyst as such.

Sorbose is a ketose belonging to the group of sugars known as monosaccharides. The commercial production of vitamin C (ascorbic acid) often starts from with sorbose. L- Sorbose is the configuration of the naturally-occurring sugar.

Vitamin C (L-ascorbic acid or L-ascorbate) is an essential nutrient for humans and certain other animal species. In living organisms ascorbate acts as an antioxidant by protecting the organism against oxidative stress. It is also a cofactor in at least eight enzymatic reactions including several collagen synthesis reactions that cause the most severe symptoms of scurvy when they are dysfunctional. In animals these reactions are especially important in wound-healing and in preventing bleeding from capillaries.

In industrial synthesis Vitamin C is produced from glucose by two main routes.

The Reichstein process, developed in the 1930s, uses a single pre-fermentation followed by a purely chemical route.

The modern two-step fermentation process, originally developed in China in the 1960s, uses additional fermentation to replace part of the later chemical stages. Both processes yield approximately 60 % vitamin C from the glucose feed.

The reaction steps are as follows:

Due to the importance of Vitamin C and the industrial scale of production thereof, there is always room for improvements of this above mentioned reaction.

The present invention relates to an improvement of reaction step Nr. 3 (oxidation of the sorbose to gulonic acid).

It was found that a specific catalyst significantly improves the conversion and the selectivity of this reaction.

The catalyst which was found comprises

0.1 to 30 weight-% (wt.-%), based on the total weight of the catalyst, of a bimetallic mixture and 70 to 99.9 wt.-%, based in the total weight of the catalyst, of a support material.

The bimetallic mixture of this catalyst comprises

20 to 80 wt.-%, based on the total weight of the metal content of the catalyst, of Au and 20 to 80 wt.-%, based on the total weight of the metal content of the catalyst, of Pt.

Therefore the present invention relates to a process for the oxidation of sorbose, wherein a catalyst comprising

0.1 to 30 wt.-%, based on the total weight of the catalyst, of a bimetallic mixture of

20 to 80 wt.-%, based on the total weight of the metal content of the catalyst, of Au, and

20 to 80 wt.-%, based on the total weight of the metal content of the catalyst, of Pt, and

70 to 99.9 wt.-%, based in the total weight of the catalyst, of a support material, is used, and wherein the oxidation is carried out at a pH of≥7.

All percentages always add up to 100.

Preferably the process is carried out at a pH of≥7 and <10. A preferred embodiment of the present invention relates to a process, wherein the catalyst comprises 0.5 to 20 wt.-%, based in the total weight of the catalyst, of the bimetallic mixture.

A more preferred embodiment of the present invention relates to a process, wherein the catalyst comprises 0.5 to 10 wt.-%, based in the total weight of the catalyst, of the bimetallic mixture.

An especially preferred embodiment of the present invention relates to a process, wherein the catalyst comprises 0.5 to 8 wt.-%, based in the total weight of the catalyst, of the bimetallic mixture.

A preferred embodiment of the present invention relates to a process, wherein the catalyst comprises 40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Au, most preferably 50 wt.-%.

A preferred embodiment of the present invention relates to a process, wherein the catalyst comprises 40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Pt, most preferably 50 wt.-%.

The support material of the catalytic system is an inorganic oxide, an inorganic carbonate or an inorganic sulphate as well as mixtures thereof. Preferably the support material is chosen from the group consisting of Al 2 0 3 , Ce0 2 , Zr0 2 , Ti0 2 , Mn0 2 , Zn0 2 , Sn0 2 , La0 2 , Y 2 0 3 and BaS0 . More preferably, the support material is Al 2 0 3 and Ce0 2 , most preferably the support material is Ce0 2 .

The oxidation process is carried out at elevated temperature, preferably between 40 °C and 80 °C, more preferably between 50 °C and 70 °C. The oxidizing agent used in a process according to present invention is air, 0 2 or H 2 0 2 . The preferred oxidizing agent is 0 2 . The process according to present invention is usually carried at a partial O2 pressure of 0.2 to 8 bar, preferably below 1 bar. The amount of the bimetallic mixture (of the catalyst) used in the process according to present invention can be up to 10 wt.-%, based on the total weight of the starting material, preferably less than 5 wt.-%. The process according to the present invention is carried out in water or an aqueous solution.

A preferred embodiment of the present invention relates to a process, wherein the concentration of the starting material (sorbose) is 50 to 300 mmolT 1 , preferably 100 to 250 mmol Γ 1 .

Preferably, sorbose is L-sorbose.

A preferred embodiment of the present invention relates to a process (A) for the oxidation of sorbose, wherein a catalyst comprising

0.5 to 20 wt.-%, based on the total weight of the catalyst, of a bimetallic mixture of

40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Au, and

40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Pt, and

80 to 99.5 wt.-%, based in the total weight of the catalyst, of a support material chosen from the group consisting of Al 2 0 3 , Ce0 2 , Zr0 2 , Ti0 2 , Mn0 2 , Zn0 2 , Sn0 2 , La0 2 , Y 2 0 3 and BaS0 4 , is used and

wherein the oxidation is carried out at a pH of≥7 and <10.

Another preferred embodiment of the present invention relates to a process (Α'), which is the process (A) carried out at a temperature of between 40 °C and 80 °C, preferably between 50 °C and 70 °C and wherein the oxidizing agent is air, 0 2 or H 2 0 2 , preferably 0 2 , and wherein the process is carried out in water or an aqueous solution, and wherein the concentration of the starting material (sorbose) is 50 to 300 mmolT 1 , preferably 100 to 250 mmoi r 1 . A more preferred embodiment of the present invention relates to a process (B) for the oxidation of sorbose, wherein a catalyst comprising

0.5 to 10 wt.-%, based on the total weight of the catalyst, of a bimetallic mixture of

40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Au, and

40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Pt, and

90 to 99.5 wt.-%, based in the total weight of the catalyst, of a support material chosen from the group consisting of Al 2 0 3 and Ce0 2 , is used and

wherein the oxidation is carried out at a pH of≥ 7 and < 10.

Another preferred embodiment of the present invention relates to a process (Β'), which is the process (B) carried out at a temperature of between 40 °C and 80 °C, preferably between 50 °C and 70 °C and wherein the oxidizing agent is air, O2 or H2O2, preferably O2, and wherein the process is carried out in water or an aqueous solution, and wherein the concentration of the starting material (sorbose) is 50 to 300 mmol 1 , preferably 100 to 250 mmol I "1 .

An especially preferred embodiment of the present invention relates to a process (C) for the oxidation of sorbose, preferably L-sorbose, wherein a catalyst comprising

0.5 to 8 wt.-%, based on the total weight of the catalyst, of a bimetallic mixture of

50 wt.-%, based on the total weight of the metal content of the catalyst, of Au, and 50 wt.-%, based on the total weight of the metal content of the catalyst, of Pt, and 92 to 99.5 wt.-%, based in the total weight of the catalyst, of a support material which is Ce0 2 , is used and

wherein the oxidation is carried out at a pH of≥7 and <10.

Another preferred embodiment of the present invention relates to a process (C), which is the process (C) carried out at a temperature of between 40 °C and 80 °C, preferably between 50 °C and 70 °C and wherein the oxidizing agent is air, 0 2 or H 2 0 2 , preferably O2, and wherein the process is carried out in water or an aqueous solution, and wherein the concentration of the starting material (sorbose) is 50 to 300 mmolT 1 , preferably 100 to 250 mmol Γ 1 .

The catalyst used in the process according to the present invention can be prepared by any known process, for example by the wet impregnation method (Wl) or the incipient wetness method.

Furthermore the present invention also relates to a new catalyst comprising

0.5 to 20 wt.-%, based on the total weight of the catalyst, of a bimetallic mixture of

40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of

Au, and

40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Pt, and

80 to 99.5 wt.-%, based in the total weight of the catalyst, of a support material chosen from the group consisting of Al 2 0 3 , Ce0 2 , Zr0 2 , Ti0 2 , Mn0 2 , Zn0 2 , Sn0 2 , La0 2 , Y 2 0 3 and BaS0 4 .

A preferred catalyst comprises

0.5 to 10 wt.-%, based on the total weight of the catalyst, of a bimetallic mixture of

40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Au, and

40 to 60 wt.-%, based on the total weight of the metal content of the catalyst, of Pt, and

90 to 99.5 wt.-%, based in the total weight of the catalyst, of a support material chosen from the group consisting of ΑΙ 2 Οβ and Ce0 2 . A more preferred catalyst comprises

0.5 to 8 wt.-%, based on the total weight of the catalyst, of a bimetallic mixture of

50 wt.-%, based on the total weight of the metal content of the catalyst, of Au, and 50 wt.-%, based on the total weight of the metal content of the catalyst, of Pt, and

92 to 99.5 wt.-%, based in the total weight of the catalyst, of a support material which is

Ce0 2 .

The following examples serve to illustrate the invention. All parts are related to weight and the temperature is given in degree Celsius, if not otherwise stated.

Examples

Catalyst preparation

General remarks

5 groups of catalysts have been prepared. To show the inventiveness of the process according to the present invention comparative examples have been made.

Example 1: 1 % Au/Pt on AI 2 O 3 support prepared by incipient wetness impregnation

For the preparation of 4 g 1 % Au Pt 50:50 (1 % w/w total metal loading of gold and platinum at a molar ratio of 50:50) / AI2O3 catalyst via the incipient wetness method (IW), 0.04 g hydrogen tetrachloroaurate(lll) hydrate (50 % Au, Chempur) and 0.05 g dihydro- gen hexachloroplatinate(IV) hydrate (40 % Pt, Chempur) were dissolved in 2 ml deion- ised water. This solution was added dropwise to 3.96 g alumina support Puralox KR-90 (Sasol) while mixing intensively in an agate mortar. The resulting precursor was dried overnight at 70 °C and then reduced for 2 hours at 250 °C in hydrogen stream (5 % v/v H 2 in N 2 ). 1 % Au, 1 % Pt and 1 % Au Pt catalysts with varying metal ratios were prepared analogously using an appropriate amount of hydrogen tetrachloroaurate(lll) hydrate for the monometallic gold catalysts, dihydrogen hexachloroplatinate(IV) hydrate for the monometallic platinum catalysts or a mixture of the two components.

The following catalyst have been prepared:

Table 1a: Examples (inventive examples)

Table 1 b: Examples (comparative examples)

Example 2: 1 % Au/Pt on AI 2 O 3 support prepared by wet impregnation

For the preparation of 10 g 1 % Au Pt 50:50 (1 % w/w total metal loading of gold and platinum at a molar ratio of 50:50) / Al 2 0 3 catalyst via the wet impregnation method (Wl), 9.9 g alumina support (Puralox KR-90, Sasol) were dispersed in 175 ml deionised water at room temperature. 10 ml hydrogen tetrachloroaurate(lll) hydrate solution (5 g Au 1 , HAuCI 4 hydrate from Chempur) and 25 ml dihydrogen hexachloroplatinate(IV) hydrate solution (2 g Pt 1 , H 2 PtCl 6 hydrate from Chempur) were mixed and added at once to the vigorously stirred suspension. After 45 min, 0.3 g sodium borohydride (96 % NaBH 4 , Sigma-Aldrich) were solved in 5 ml water and added to the suspension. When gas for- mation was completed, the catalyst was filtered, washed with warm (50 - 60°C) water and dried overnight at 70°C.

1 % Au, 1 % Pt and 1 % Au Pt catalysts with varying metal ratios were prepared analogously.

The following catalyst have been prepared

Table 2a: Examples (inventive examples)

Table 2b: Examples (comparative examples)

Example 3: 5 % Au/Pt on Al 2 0 3 support prepared by wet impregnation

For the preparation of 1 g 5 % Au Pt 50:50 (5 % w/w total metal loading of gold and platinum at a molar ratio of 50:50) / Al 2 0 3 catalyst via the wet impregnation method (Wl), 0.95 g alumina support (Puralox KR-90, Sasol) were dispersed in 85 ml deionised water at room temperature. 5 ml hydrogen tetrachloroaurate(lll) hydrate solution (5 g Au 1 , HAuCI 4 hydrate from Chempur) and 6.25 ml dihydrogen hexachloroplatinate(IV) hydrate solution (4 g Pt 1 , H 2 PtCl6 hydrate from Chempur) were mixed and added at once to the vigorously stirred suspension. After 45 min, 0.13 g sodium borohydride (96 % NaBH 4 , Sigma-Aldrich) were solved in 5 ml water and added to the suspension. When gas for- mation was completed, the catalyst was filtered, washed with warm (50 to 60 °C) water and dried overnight at 70 °C.

5 % Au, 5 % Pt and 5 % Au Pt catalysts with varying metal ratios were prepared analogously.

Table 3a: Examples (inventive examples)

Table 3b: Examples (comparative examples)

Example Au:Pt molar ratio

3g 100:0

3h 90:10

3i 10:90

3k 0:100

Example 4: 5 % Au/Pt on Ce0 2 support prepared by wet impregnation

For the preparation of 1 g 5 % Au Pt 50:50 (5 % w/w total metal loading of gold and platinum at a molar ratio of 50:50) / Ce02 catalyst via the wet impregnation method (Wl), 0.95 g ceria support (Chempur) were dispersed in 85 ml deionised water at 80 °C. 3 ml sodium hydroxide solution (0.2 mol 1 ) were added to the vigorously stirred suspension. 10 minutes after the addition of sodium hydroxide 5 ml hydrogen tetrachloroaurate(lll) hydrate solution (5 g Au 1 , HAuCI 4 hydrate from Chempur) and 6.25 ml dihydrogen hexachloroplatinate(IV) hydrate solution (4 g Pt 1 , H 2 PtCl6 hydrate from Chempur) were mixed and added at once to the stirred suspension. After 20 min, 0.13 g sodium boro- hydride (96 % NaBH 4 , Sigma-Aldrich) were solved in 5 ml water and added to the suspension. When gas formation was completed, the catalyst was filtered, washed with warm (50 °C to 60°C) water and dried overnight at 70 °C.

5 % Au, 5 % Pt and 5 % Au Pt catalysts with varying metal ratios were prepared analogously.

Table 4a: Examples (inventive examples)

Table 4b: Examples (comparative examples)

Example Au:Pt molar ratio

4g 100:0

4h 0:100 Example 5: 5 % Au/Pt 50:50 on Ce0 2 support prepared by wet impregnation

For the preparation of 1 g 5 % Au Pt 50:50 (5 % w/w total metal loading of gold and platinum at a molar ratio of 50:50) / Ce02 catalyst via the wet impregnation method (Wl), 0.95 g ceria support (Chempur) were dispersed in 85 ml deionised water at 80 °C. 5 ml hydrogen tetrachloroaurate(lll) hydrate solution (5 g Au 1 , HAuCI 4 hydrate from Chempur) and 6.25 ml dihydrogen hexachloroplatinate(IV) hydrate solution (4 g Pt 1 , H 2 PtCl6 hydrate from Chempur) were mixed and added at once to the vigorously stirred suspension. After 45 min, 0.44 g sodium citrate dihydrate (Merck) dissolved in 5 ml water were added and 5 minutes after the addition of sodium citrate 0.04 g sodium borohydride (96 % NaBH 4 , Sigma-Aldrich) were solved in 5 ml water and added to the suspension. When gas formation was completed, the catalyst was filtered, washed with warm (50 to 60 °C) water and dried overnight at 70 °C.

Oxidation process examples

Example 6: Oxidation of L-sorbose

L-sorbose oxidation was carried out at 50 °C in a thermostatted glass reactor with a volume of 150 ml in reaction batches of 100 ml. The pH value of the reaction suspension was kept constant at a value of 8 by addition of sodium hydroxide solution (1 molT 1 ) using a TitroLine alpha plus titration unit (Schott) equipped with a SL 80-120 pH electrode (Schott). Oxygen was bubbled through the suspension with a flow rate of 500 ml-min "1 at atmospheric pressure. The suspension was stirred with a magnetic stirrer at 1000 rpm. The initial L-sorbose concentration was 100 mmol 1 and the concentration of the bimetallic mixture (gold and platinum) was 0.4 g noble metal per liter. The results for the various catalysts are summarized in the following tables. Table 6a: Oxidation of L-sorbose using the catalysts of Example 1 (inventive examples)

Catalyst Time for 70 % L-sorbose conSelectivity at 70 % L-sorbose conversion [min] version [%]

1 a 104 17

1 b 172 25

1 c 102 25

Table 6b: Oxidation of L-sorbose using the catalysts of Example 1 (comparative examples)

Catalyst Time for 70 % L-sorbose conSelectivity at 70 % L-sorbose conversion [min] version [%]

1 d > 400 —

1 e about 235 13

1f > 400 —

i g > 400 —

Table 6c: Oxidation of L-sorbose using the catalysts of Example 2 (inventive examples)

Catalyst Time for 70 % L-sorbose conSelectivity at 70 % L-sorbose conversion [min] version [%]

2a 78 26

2b 68 30

2c 94 33

Table 6d: Oxidation of L-sorbose using the catalysts of Example 2 (comparative examples)

Catalyst Time for 70 % L-sorbose conSelectivity at 70 % L-sorbose conversion [min] version [%]

2d >400 —

2e 133 34

2f 375 37 Table 6e: Oxidation of L-sorbose using the catalysts of Example 3 (inventive examples)

Catalyst Time for 70 % L-sorbose conSelectivity at 70 % L-sorbose conversion [min] version [%]

3a 269 47

3b 142 40

3c 158 43

3d 173 46

3e 108 50

3f 80 41

Table 6f: Oxidation of L-sorbose using the catalysts of Example 3 (comparative examples)

Catalyst Time for 70 % L-sorbose conSelectivity at 70 % L-sorbose conversion [min] version [%]

3g >400 —

3h >400 —

3i >400 —

3k >400 —

Table 6g: Oxidation of L-sorbose using the catalysts of Example 4 (inventive examples)

Catalyst Time for 70 % L-sorbose conSelectivity at 70 % L-sorbose conversion [min] version [%]

4a >400 —

4b about 430 51

4c 142 51

4d 156 50

4e 144 50

4f 344 56 Table 6h: Oxidation of L-sorbose using the catalysts of Example 4 (comparative examples)

It can be seen from these experiments that the process according to the present invention shows a significant improvement of the reaction step.

The following example 7 shows the influence of the O2 partial pressure. The example was carried out in analogy of Example 6 with the exception that the pressure was varied. The catalyst of Example 5 was used.

Example 7: Oxidation of L-sorbose under different oxygen partial pressures

Lower oxygen pressures were adjusted using air and air / nitrogen mixtures under atmospheric pressure and a gas flow rate of 500 ml-min "1 .

Oxygen partial pressures of more than 1 bar were adjusted using pure oxygen under higher pressures. In such cases, the reactions were carried out at 50 °C in a thermostat- ted stainless steel reactor with a total volume of 500 ml (350 ml reaction batch). The top of the reactor was equipped with a thermocouple (Pt100 4-wire temperature probe, Greisinger electronic), a gas inlet and a gas outlet port (both with needle valves), a sampling port with a dip tube and a needle valve, all of them made of stainless steel, a pressure sensor (GMSD, Greisinger electronic), a pressure-resistant gel-filled pH electrode (SL 80-120 pH electrode, Schott), a dosage port for NaOH supply and a stirrer.

The pH of the reaction suspension was kept constant at a desired value of 8 by addition of sodium hydroxide solution (2 mol 1 ) using a Pro-Minent-Dulcometer PHD titration unit (ProMinent) equipped with a backpressure/overflow valve DHV-S-DL (ProMinent). NaOH consumption was controlled by a Kern PLS-4000-2 balance (Kern & Sohn GmbH). Oxygen was fed into the reactor through the gas inlet port; its pressure was adjusted by a pressure reducer and controlled by a digital pressure-meter (GMH 31 10, Greisinger electronic). The temperature in the reactor was controlled by a GMH 3710 precision thermometer (Greisinger electronic). Stirring was achieved by a home-made gas entrainment impeller with a teflon gas outlet part fixed at a stainless steel tube connected to a permanent magnetic clutch. It was actuated by a laboratory stirrer (IKA RW 16 basic, IKA Labortechnik) with a stirring rate adjusted to a value of 1000 rpm. The initial L-sorbose concentration was 100 mmol 1 and the concentration of the catalytically active metals (gold and platinum) was 0.4 g noble metal per liter.

Table 7: Oxidation of L-sorbose using the catalyst of Example 5 at various pressures

Catalyst 0 2 partial pressure [bar] Selectivity at 70 % L-sorbose conversion [%]

5 0.1 63

5 0.2 59

5 1 54

5 3 45

5 5 44

5 8 34