SIMULTANEOUS RECOVERY OF ORGANIC COMPOUNDS AND EXTRACTANTS

Abstract

The invention relates to a method for recovering an organic compound from a feed stream comprising the steps ofextracting the organic compound into an organic solvent, thereby obtaining a mixture of the solvent and the organic compound; andsimultaneously crystallizing the solvent and the organic compound by cooling the mixture; and - separating the solid organic solvent and solid organic compound.

Claims

1. Method for recovering an organic compound from a liquid feed stream comprising the steps of: a liquid-liquid extraction, wherein the organic compound is extracted from the feed stream into an organic solvent, thereby obtaining an extract, which is a mixture of the organic solvent and the organic compound; simultaneously crystallizing the solvent and the organic compound by cooling said mixture; and a solid-solid separation step to separate the solid solvent and solid organic compound.

2. Method according to claim 1, wherein the solid solvent and solid organic compound are separated based on their difference in density or size.

3. Method according to claim 1, wherein the solid solvent and solid organic compound are separated by gravity settling, flotation, hydrocylones or centrifugation.

4. Method according to claim 1, wherein the solvent and the organic compound are simultaneously crystallized by cooling the mixture to a temperature equal to or lower than the eutectic temperature of the mixture.

5. Method according to claim 1, wherein the organic compound has a melting point in the range of 50-+250.

6. Method according to claim 1, wherein the organic compound is selected from the group consisting of carboxylic acids alcohols and cyclic esters.

7. Method according to claim 1, wherein the organic compound is selected from the group consisting of 1,4 butanediol, succinic acid, formic acid, malic acid, 2,5-furan dicarboxylic acid, 3 hydroxypropionic acid, aspartic acid, glucaric acid, glutamic acid, itaconic acid, levulinic acid, 3-hydroxybutyrolactone, glycerol, sorbitol, xylitol and arabitol.

8. Method according to claim 1, wherein the organic solvent has a melting point in the range of +10 to +100 C.

9. Method according to claim 1, wherein the organic solvent is selected from the group consisting of trialkylphosphine oxides, dialkylsulfoxides, aliphatic hydrocarbons, aromatic hydrocarbons, alcohols, carboxylic acids and esters.

10. Method according to claim 1, wherein the organic solvent is a trialkylphosphine oxide or dialkylsulfoxide.

11. Method according to claim 1, wherein the organic solvent is selected from tri-n-octylphosphine oxide (TOPO), dimethylsulfoxide (DMSO), dibutylsulfoxide (DBSO), p-xylene, 1-octanol, acetic acid, t-butyl alcohol and dioxane.

12. Method according to claim 1, wherein the mixture has a eutectic temperature in the range of 20 to +80 C.

13. Method according to claim 1, wherein the stream is a fermentation stream.

14. Method according to claim 1, wherein the method further comprises the step of fermenting a carbon source to obtain the organic compound.

15. Method according to claim 1, wherein the liquid feed stream is an aqueous stream.

16. Method according to claim 1, wherein the organic compound is 1,4 butanediol or itaconic acid; and wherein the organic solvent is tri-n-octylphosphine oxide.

17. Mixture comprising at least 1 wt. % crystals of a first organic compound, at least 1 wt. % crystals of a second organic compound different than the first compound and at least 25 wt. % of the first or second organic compound in liquid form, based on the total weight of the mixture.

18. Mixture obtainable by the simultaneous crystallization step as defined in claim 1.

19. Mixture according to claim 17, wherein the combined amount of crystals of the first and second organic compound is 10-50 wt. %, based on the total weight of the mixture.

20. Mixture according to claim 17, wherein the first compound is 1,4 butanediol or itaconic acid; and wherein the second compound is tri-n-octylphosphine oxide.

21. Method according to claim 5, wherein the organic compound has a melting point in the range of 10 to +200 C.

22. Method according to claim 5, wherein the organic compound has a melting point in the range of 0 to +100 C.

Description

EXAMPLE 1

Simultaneous Crystallization of BDO and TOPO

[0055] A mixture of 1,4 butanediol (BDO) an tri-n-octyl phosphine oxide (TOPO) was gradually cooled to a temperature below 16 C. (i.e. below the eutectic temperature of the mixture), which induced crystallization in the mixture.

[0056] A sample of the mixture comprising crystals was taken and analyzed under a microscope. Two types of crystals were observed: the first had a needle-like shape, the other had a snow like structure.

[0057] The temperature of the sample was then increased above the eutectic temperature and the snow like crystals melted, while the needle-like crystals remained.

[0058] The crystals were removed from the mixture and their melting temperature was measured to be 55 C., which corresponds to the melting point of TOPO.

[0059] The mixture was then seeded with end crystals of BDO to initiate crystallization. The resulting crystals were again analyzed under the microscope. The crystals had a shape of elongated tubes, which was different than the needle-like shape observed for the TOPO crystals. Therefore, it was concluded that these crystals must be BDO crystals.

[0060] The experiment shows the proof of concept for eutectic freeze crystallization of a TOPO-BDO mixture.

EXAMPLE 2

Simultaneous Crystallization of IA in H.SUB.2.O and TOPO

[0061] This example illustrates the energy efficiency of using organic solvents in eutectic freeze crystallization compared to the solvent being water.

[0062] The binary phase diagram of Itaconic Acid/Water was determined both experimentally and theoretically:

[0063] 1. Theory: The melting points were calculated using the Van't Hoff equation under standard conditions.

[0064] 2. Experimental (Crystal16 method): Liquid mixtures of water and itaconic acid with varying amounts of itaconic acid (1-15 wt. %) were prepared. The crystallization points of the different mixtures were experimentally determined by cooling a 1 mL sample of each of the mixtures in a parallel crystallizer (Crystal16, Technobis Group). The melting point was the highest temperature at which solid material started to form.

[0065] 3. Experimental: Two similar experiment as described in 2 were conducted with 100 mL samples of mixtures comprising 20 wt. % IA and 10 wt. % IA respectively, using a 100 mL crystallizer set-up. The difference between this method and the Crystal16 method illustrates the effect of scaling.

[0066] The results of determining the IA crystallization point using the above three methods are shown in Table 1.

TABLE-US-00001 TABLE 1 Crystallization Point of IA/water mixture Crystallization Temperature ( C.) IA/Water content Theory (1) Experimental (2) Experimental (3) 20 wt. % IA 48 47.85 15 wt. % IA 40 38 10 wt. % IA 28 28 29.28 3 wt. % IA 4 1 1 wt. % IA 0.5 1

[0067] The calculated and experimental values were roughly the same. Further, scaling of the experiment did not seem to have a large effect on the crystallization point. The data on the crystallization point of IA was combined with experimental data of the crystallization point of water in the mixture. From these combined data, the binary phase diagram was plotted, which is shown in FIG. 3. The eutectic point can be found at the intersection of the two lines. The eutectic point was calculated to be 2.4 wt. % itaconic acid at 05 C.

[0068] The above experiment was repeated for mixtures of itaconic acid and tri-n-octyl phosphine oxide (TOPO). The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Crystallization Point of IA/TOPO mixture Crystallization Temperature ( C.) IA/TOPO content Theory (1) Experimental (2) 1 wt. % IA 53 48.9 2.4 wt. % IA 64 54.3 3.8 wt. % IA 81 52.6 5.3 wt. % IA 88 51.4 7 wt. % IA 98 49.6 8.5 wt. % IA 103 46.5 10 wt. % IA 107 42.0 12 wt. % IA 115 36.0 13.3 wt. % IA 117 27.0 14 wt. % IA 118 23.1 15 wt. % IA 120 25.0 16.7 wt. % IA 129 98.0

[0069] An important difference between calculated and experimental data was observed. FIG. 4 shows the binary phase diagram of IA/TOPO with both the theoretical data (upper left line) and the experimental data (line with minimum of about 18 C.). Based on the experimental data, it can be concluded that crystallization of the mixture may already start at 14.2 wt % itaconic acid at around 21 C.

[0070] This Example shows that using TOPO instead of water increases the eutectic temperature from 0.5 C. to 21 C. in a IA/TOPO mixture. The eutectic temperature of TOPO near room temperature makes it an excellent solvent for energy efficient eutectic freeze crystallization as conducted in the method of the invention.

EXAMPLE 3

Separation of IA and TOPO Crystals

[0071] A mixture of itaconic acid (IA) and tri-n-octyl phosphine oxide

[0072] (TOPO) was prepared. The IA content in the mixture was chosen close to the eutectic point of 14.2 wt. %, as determined in Example 2. A vial was filled with this mixture. The temperature of the mixture was brought below 21 C. and the formation of crystals was analyzed. After crystallization, the crystals of IA were found at the bottom, while crystals of TOPO were found at the top of the vial. A photograph was taken of the vial, which is shown in FIG. 5.

[0073] It can be concluded from this experiment that TOPO crystals have a lower density than IA crystals and that the difference in density is sufficient to cause an effective separation of the two crystal types. This will make it easy to separate the two crystal layers without having to consume much energy.

EXAMPLE 4

Simultaneous Crystallization of BDO and TOPO

[0074] The experiments described in Example 2 were repeated for mixtures of 1,4 butanediol and tri-n-octyl phosphine oxide (TOPO). The results are shown in Table 3.

TABLE-US-00003 TABLE 3 Crystallization Point of BDO/TOPO mixture Crystallization Temperature ( C.) BDO/Water content Theory (1) Experimental (2) Experimental (3) 2 wt. % BDO 53 53.1 10 wt. % BDO 48 43.1 42.2 19 wt. % BDO 37.5 31.8 33 25 wt. % BDO 40 25.9 25 40 wt. % BDO 33 16.3 16 59 wt. % BDO 25 18.6 65 wt. % BDO 22 20.0 75 wt. % BDO 17 19.7 85 wt. % BDO 18 20.2 90 wt. % BDO 18.5 21.0

[0075] The binary phase diagram of TOPO-1,4-butanediol, is given in FIG. 6, where the curved middle line corresponds to the experimental results.

[0076] The data shown in FIG. 6 shows that the experimental results do not correspond to the calculated values. Based on the experimental results, it can be concluded that crystallization of the mixture starts at 16 C. at 40 wt % TOPO-1,4-butanediol.concentration. The theoretical values indicated that the eutectic point would be at 16.4 C. at 74.5 wt % composition.

[0077] Furthermore, the theoretical binary phase diagram of a 1,4-butanediol/water mixture was calculated. The eutectic point was determined at 28.4 C. at 64.3 wt. % BDO. Cooling to a temperature far below zero to achieve simultaneous crystallization will give rise to high energy costs. Therefore, the calculated value gives a good indication of the energy savings that can be obtained by using TOPO instead of water as the solvent.

[0078] This Example shows that the eutectic temperature of BDO/TOPO mixtures are is at 16 C., i.e. close to room temperature. The eutectic temperature of TOPO near room temperature makes it an excellent solvent for energy efficient eutectic freeze crystallization as conducted in the method of the invention.

EXAMPLE 5

Liquid-Liquid Extraction

[0079] Experiments were conducted to conduct liquid-liquid extraction from water into TOPO. TOPO was not miscible with water. The inventors found that TOPO could easily extract organic compounds such as BDO or IA from a water phase.