Method and a system for producing glycolic acid and/or glycolate

Abstract

A method and a system for producing glycolic acid and/or glycolate from sustainable resources. A method for catalytic production of glycolic acid and/or glycolate including the step of: oxidation of a starting material including between 0.1-100 wt/wt % glycolaldehyde at a temperature of between −10° C. and 100° C. with an oxidant in the presence of a metal-based catalyst including a catalytically active metal, which is selected from the group of palladium and platinum; or mixtures thereof.

Claims

1. A method for catalytic production of glycolic acid comprising the steps of: obtaining a C.sub.1-C.sub.3 oxygenate mixture, wherein the C.sub.1-C.sub.3 oxygenate mixture originates from thermal fragmentation of at least one carbohydrate, wherein the C.sub.1-C.sub.3 oxygenate mixture comprises 10 wt % to 95 wt % of glycolaldehyde, 0.1 wt % to 60 wt % of formaldehyde, and 0.1 wt % to 80 wt % pyruvaldehyde and oxidizing the C.sub.1-C.sub.3 oxygenate mixture at a temperature of between −10° C. and 100° C. with an oxidant in the presence of a metal-based catalyst comprising a catalytically active metal, which is selected from the group consisting of palladium, platinum, and mixtures thereof.

2. The method according to claim 1, wherein the C.sub.1-C.sub.3 oxygenate mixture further comprises at least one of the following: acetol in an amount of 0.1-80 wt/wt %, and/or glyoxal in an amount of 0.1-80 wt/wt %.

3. The method according to claim 1, wherein the C.sub.1-C.sub.3 oxygenate mixture further comprises a solvent selected from the group consisting of water, methanol, ethanol, and mixtures thereof.

4. The method according to claim 1, wherein the metal-based catalyst comprises one or more further catalytically active metals, and at least 50 wt/wt % of the catalytically active metals of the metal based catalyst is selected from the group consisting of palladium, platinum, and mixtures thereof.

5. The method according to claim 1, wherein the metal-based catalyst further comprises catalytically active gold.

6. The method according to claim 1, wherein the metal-based catalyst does not comprise catalytically active gold.

7. The method according to claim 1, wherein the metal-based catalyst comprises platinum dispersed on a support of active carbon.

8. The method according to claim 1, wherein the oxidation is performed at a temperature between −10° C. and 100° C.

9. The method according to claim 1, wherein the oxidant is selected from the group consisting of oxygen, hydrogen peroxide, and mixtures thereof.

10. The method according to claim 1, wherein the oxidant is oxygen and the oxidation is performed at a O.sub.2 partial pressure between 0.1-40 bar.

11. The method according to claim 1, wherein the at least one carbohydrate is a mono- and/or di-saccharide(s).

12. The method according to claim 1, wherein the oxidation step is followed by isolation, and optionally further purification, of glycolic acid.

13. The method according to claim 12, wherein the isolation is performed by precipitating glycolic acid.

14. The method according to claim 12, wherein glycolic acid is isolated in the form of a salt via precipitation.

15. The method according to claim 14, wherein the precipitation is performed by reacting glycolic acid with a base to form glycolate.

16. The method according to claim 11, wherein the mono- and/or di-saccharide(s) is selected from the group consisting of sucrose, lactose, xylose, arabinose, ribose, mannose, tagatose, galactose, glucose, fructose, and mixtures thereof.

17. The method according to claim 1, wherein glycolic acid is produced in yields ranging from 30-90%.

18. The method according to claim 1, wherein the C.sub.1-C.sub.3 oxygenate mixture further comprises acetol.

19. The method according to claim 1, wherein the C.sub.1-C.sub.3 oxygenate mixture further comprises glyoxal.

Description

EXAMPLES

Example 1

(1) The oxidation of glycolaldehyde was performed over a platinum catalyst using air as oxidant at atmospheric pressure. The experimental procedure was as follows: Glycolaldehyde dimer (100 mg) was dissolved in water (15.0 g, starting material) and the catalyst (50 mg), 5 wt/wt % Pt/C (Sigma-Aldrich), was added. The slurry was stirred using a magnetic stir bar, and heated to the desired oxidation reaction temperature in an oil bath. A gas line was submerged in the slurry and air was bubbled through the slurry at a rate of 0.2-0.5 NI/min. The reaction flask was fitted with a reflux condenser, cooled to 2° C., to minimize evaporation of water. After the desired reaction time, solids were removed from the oxidation reaction product by filtration and the reaction liquid was analyzed by HPLC. At a reaction temperature of 40° C., a yield of 76 mol % of glycolic acid was obtained after 3.5 hr. At a reaction temperature of 30° C., the reaction was allowed to proceed for 23.5 hr, at which point a yield of >99 mol % was obtained. No glycolaldehyde molecules or by-products were observed in either case, likely due to the complete oxidation of any by-products formed.

Example 2

(2) The oxidation of a C.sub.1-C.sub.3 oxygenate mixture as starting material was also investigated. The mixture was prepared by the following procedure: A fluidized bed with an inner diameter of 41 mm was loaded with 50 ml of 150-250 μm glass beads. The bed was fluidized with nitrogen and heated to 510° C. A feedstock of a 20 wt/wt % aqueous solution of glucose was injected into the fluid bed at a rate of 2 g/min. The feedstock was injected using a two fluid nozzle to deliver the feedstock as a fine mist into the bed. The superficial gas velocity in the reactor at reaction conditions was approx. 40 cm/s. The gas stream leaving the reactor was immediately cooled to 1° C. using a surface condenser to separate the liquid product from the permanent gasses, and the liquid C.sub.1-C.sub.3 oxygenate mixture product collected.

(3) Before the oxidation reaction step was performed, the C.sub.1-C.sub.3 oxygenate mixture was concentrated by removing part of the water solvent on a rotary evaporator, and purified by thin film evaporation to remove non-volatile components. The concentration of the C.sub.1-C.sub.3 oxygenate mixture (starting material) was adjusted to 3.5 wt/wt % glycolaldehyde by adding water. 200 mg of catalyst was added to 10 g of the oxygenate solution. The reaction was otherwise performed using the same procedure as described above for glycolaldehyde, except the oxidation was carried out at a temperature of 30° C. A yield of 79 mol % of glycolic acid (from glycolaldehyde) and 73 mol % pyruvic acid (from pyruvaldehyde and acetol) was obtained. The only other product observed in the oxidation reaction product was trace amounts of oxalic acid.

(4) As the fragmentation has been demonstrated to give up to 66 mol % yield of glycolaldehyde from glucose, this would correspond to an overall yield of 52 mol % glycolic acid from glucose (on a carbon basis).

EMBODIMENTS

(5) The present invention is further defined by the following embodiments:

Embodiment 1

(6) A method for catalytic production of glycolic acid and/or glycolate comprising the step of: oxidation of a starting material comprising between 0.1-100 wt/wt % glycolaldehyde at a temperature of between −10° C. and 100° C. with an oxidant in the presence of a metal-based catalyst comprising a catalytically active metal, which is selected from the group consisting of palladium and platinum; or mixtures thereof.

Embodiment 2

(7) The method according to embodiment 1 further comprising a step of subjecting at least one carbohydrate to thermal fragmentation so as to provide a C.sub.1-C.sub.3 oxygenate mixture comprising between 0.1-100, such as 0.1-80 wt/wt % glycolaldehyde, and using the C.sub.1-C.sub.3 oxygenate mixture comprising glycolaldehyde as the starting material in the oxidation step.

Embodiment 3

(8) The method according to any one of embodiments 1-2, wherein the starting material comprises at least one of the following: pyruvaldehyde in an amount of 0.1-80 wt/wt %, acetol in an amount of 0.1-80 wt/wt %, formaldehyde in an amount of 0.1-80 wt/wt %, and/or glyoxal in an amount of 0.1-80 wt/wt %.

Embodiment 4

(9) The method according to any one of embodiments 1-3, wherein the starting material comprises pyruvaldehyde in an amount of 0.1-60 wt/wt %, such as in an amount of 0.1-40 wt/wt %, such as in an amount of 0.1-30 wt/wt %.

Embodiment 5

(10) The method according to any one of embodiments 1-4, wherein the starting material comprises acetol in an amount of 0.1-40 wt/wt %, such as in an amount of 0.1-20 wt/wt %, such as in an amount of 0.1-10 wt/wt %.

Embodiment 6

(11) The method according to any one of embodiments 1-5, wherein the starting material comprises glyoxal in an amount of 0.1-40 wt/wt %, such as in an amount of 0.1-20 wt/wt %, such as in an amount of 0.1-10 wt/wt %.

Embodiment 7

(12) The method according to any one of embodiments 1-6, wherein the starting material comprises formaldehyde in an amount of 0.1-60 wt/wt %, such as in an amount of 0.1-40 wt/wt %, such as in an amount of 0.1-20 wt/wt %.

Embodiment 8

(13) The method according to any one of embodiments 1-7, wherein the starting material comprises from 0.1-95 wt/wt %, such as from 0.1-80 wt/wt %, 10-80 wt/wt % or 20-60 wt/wt % glycolaldehyde.

Embodiment 9

(14) The method according to any one of embodiments 1-8, wherein the starting material further comprises a solvent selected from the group consisting of water, methanol and ethanol; or mixtures thereof.

Embodiment 10

(15) The method according to embodiment 9, wherein the solvent is water.

Embodiment 11

(16) The method according to any one of embodiments 1-10, wherein the metal-based catalyst comprises one or more further catalytically active metals, and at least 50 wt/wt %, such as at least 60 wt/wt %, such as at least 70 wt/wt %, such as at least 80 wt/wt %, such as at least 90 wt/wt %, such as at least 95 wt/wt % of the catalytically active metals of the metal based catalyst is selected from the group consisting of palladium and platinum; or mixtures thereof.

Embodiment 12

(17) The method according to any one of embodiments 1-11, wherein the metal-based catalyst further comprises catalytically active gold.

Embodiment 13

(18) The method according to any one of embodiments 1-12, wherein the metal-based catalyst does not comprise catalytically active gold.

Embodiment 14

(19) The method according to any one of embodiments 1-13, wherein the metal-based catalyst further comprises one or more other catalytically active metal(s).

Embodiment 15

(20) The method according to any one of embodiments 1-14, wherein the metal-based catalyst comprises a support on which the catalytically active metal is dispersed.

Embodiment 16

(21) The method according to any one of embodiments 1-15, wherein the metal-based catalyst is a heterogeneous catalyst.

Embodiment 17

(22) The method according to any one of embodiments 1-16, wherein the support is selected from the group consisting of active carbon, alumina such as alpha alumina, silicon carbide, silica, titania, and zirconia; or mixtures thereof.

Embodiment 18

(23) The method according to any one of embodiments 1-17, wherein the metal-based catalyst comprises platinum dispersed on a support of active carbon.

Embodiment 19

(24) The method according to any one of embodiments 1-18, wherein the metal-based catalyst is present in an amount of between 0.0001 to 1 and 0.1 to 1 (catalytically active metal to glycolaldehyde mass ratio (w/w)).

Embodiment 20

(25) The method according to any one of embodiments 1-19, wherein the method is conducted as a continuous method and the starting material is fed to the oxidation at a rate of 0.4-400 g(glycolaldehyde)/(g(catalytically active metal)hr).

Embodiment 21

(26) The method according to any one of embodiments 1-20, wherein the oxidation is performed at a temperature between −10° C. and 100° C., such as between −5° C. and 80° C., such as between 0° C. and 70° C., such as between 5° C. and 70° C., such as between 10° C. and 60° C., such as between 15° C. and 50° C., such as between 20° C. and 40° C.

Embodiment 22

(27) The method according to any one of embodiments 1-21, wherein the oxidant is selected from the group consisting of oxygen and hydrogen peroxide; or mixtures thereof.

Embodiment 23

(28) The method according to any one of embodiments 1-22, wherein the oxidant is supplied in the form of atmospheric air.

Embodiment 24

(29) The method according to any one of embodiments 1-23, wherein the amount of oxidant is between 1 to 1 and 10,000 to 1 (oxidant to substrate, molar ratio).

Embodiment 25

(30) The method according to any one of embodiments 1-24, wherein the oxidant is oxygen and the oxidation is performed at a O.sub.2 partial pressure between 0.1-40 bar, such as between 0.15-1 bar.

Embodiment 26

(31) The method according to any one of embodiments 2-25, wherein the carbohydrate is supplied in the form of an aqueous solution containing at least 20 wt. % mono- and/or disaccharide.

Embodiment 27

(32) The method according to any one of embodiments 2-26, wherein the mono- and/or di-saccharide(s) is selected from the group consisting of sucrose, lactose, xylose, arabinose, ribose, mannose, tagatose, galactose, glucose and fructose; or mixtures thereof.

Embodiment 28

(33) The method according to embodiment 27, wherein the monosaccharide(s) is selected from the group consisting of glucose, galactose, tagatose, mannose, fructose, xylose, arabinose, ribose; or mixtures thereof.

Embodiment 29

(34) The method according to any one of embodiments 1-28, wherein the oxidation step is followed by isolation, and optionally further purification, of glycolic acid.

Embodiment 30

(35) The method according to any one of embodiments 1-29, wherein the isolation is performed by precipitating glycolic acid.

Embodiment 31

(36) The method according to any one of embodiments 1-30, wherein glycolic acid is precipitated in the form of a salt.

Embodiment 32

(37) The method according to any one of embodiments 1-31, wherein the precipitation is performed by reacting glycolic acid with a base to form glycolate.

Embodiment 33

(38) The method according to any one of embodiments 1-32, wherein the oxidation step is performed in the presence of a base.

Embodiment 34

(39) The method according to any one of embodiments 1-33, wherein the oxidation step is followed by the addition of a base.

Embodiment 35

(40) The method according to any one of embodiments 32-34, wherein the base is selected from the group consisting of LiOH, NaOH, KOH, Ca(OH).sub.2, Mg(OH).sub.2, Ba(OH).sub.2, and CaCO.sub.3; or mixtures thereof.

Embodiment 36

(41) A system for continuously performing the method according to any one of embodiments 1-35, said system comprising an oxidation unit, such as a trickle bed reactor, having an inlet and an outlet and a catalyst as defined in any one of above embodiments, and a thermolytic fragmentation unit having an inlet and outlet, wherein the inlet of said oxidation unit is fluidly connected to the outlet of said thermolytic fragmentation unit.

Embodiment 37

(42) The system according to embodiment 36 further having an additional O.sub.2 inlet in the oxidation unit.

Embodiment 38

(43) A glycolic acid and/or glycolate obtainable or obtained by the method according to any one of embodiments 1-35.