PROCESS FOR THE ISOLATION OF LEVULINIC ACID

Abstract

A process for the isolation of levulinic acid including the following steps: a. performing acid catalyzed hydrolysis of a C6 carbohydrate-containing feedstock to obtain reaction product X, b. purifying of reaction product X to provide a composition 1, comprising at least 75 wt. % levulinic acid, at most 15 wt. % solvent and at most 10 wt. % impurities, based on the total weight of composition 1, c. feeding composition 1 to a melt crystallization cycle, d. repeating the melt crystallization cycle as many times as necessary to obtain as composition 2 a levulinic acid with a predetermined purity, and e. isolating the levulinic acid with a predetermined purity.

Claims

1. A process for the isolation of levulinic acid with a predetermined purity, comprising the following steps: a. performing acid catalyzed hydrolysis of a C6 carbohydrate-containing feedstock to obtain reaction product X, b. purifying of reaction product X to provide a composition 1, comprising at least 75 wt. % levulinic acid, at most 15 wt. % solvent and at most 10 wt. % impurities, based on the total weight of composition 1, c. feeding composition 1 to a melt crystallization cycle, d. repeating the melt crystallization cycle as many times as necessary to obtain as composition 2 levulinic acid with the predetermined purity, and e. isolating the levulinic acid with the predetermined purity.

2. The process according to claim 1, wherein the melt crystallization cycle comprises the following steps: i. Feeding composition 1 to a melt crystallizer, wherein composition 1 is cooled to the freezing point or below the freezing point of levulinic acid to crystallize the levulinic acid in composition 1, ii. Separating a liquid 1 from the crystallized levulinic acid, iii. Purify the crystals obtained according to step i, after separation of liquid 1, iv. Melting the crystals obtained according to step iii, after separation of liquid 1, to obtain a composition 2.

3. The process according to claim 1, wherein the melt crystallization cycle comprises the following steps: i. Feeding composition 1 to a melt crystallizer wherein composition 1 is cooled to at least one temperature Tc, wherein Tc ( C.)=1.23.(W1)(a value between 94.5 and 109.5) to crystallize the levulinic acid, wherein W1 is the weight % of levulinic acid in composition 1, ii. Draining a liquid 1, wherein liquid 1 is 30-80 wt. % of composition 1, based on the total weight of composition 1, iii. Treating the crystals obtained in step i, after draining liquid 1, at at least one temperature Tw ( C.)=1.23.(W1)(a value between 84.5 and 101.5) to partly melt the crystals and to obtain a liquid 2, wherein W1 is the weight % of levulinic acid in composition 1, iv. Draining liquid 2, wherein liquid 2 is 5-50 wt % of composition 1, based on the total weight of composition 1, v. Melting the crystals obtained according to step iii, after draining of liquid 2, at at least one temperature Tm ( C.)=1.23.(W1)(a value lower than 84.5) to obtain a composition 2, wherein W1 is the weight % of levulinic acid in composition 1.

4. The process according to claim 1, wherein the predetermined purity of levulinic acid in composition 2 is at least 98 wt. %, based on the total weight of composition 2.

5. The process according to claim 2, wherein the melt crystallizer is a static melt crystallizer.

6. The process according to claim 1, wherein the melt crystallization cycle is repeated 0-6 times.

7. The process according to claim 1, wherein the melt crystallization cycle is repeated 1-4 times.

8. The process according to claim 2, wherein the cooling in step i is performed for 5 minutes to 24 hours.

9. The process according to claim 3, wherein step iii is performed for 5 minutes to 2 hours.

10. An isolation section in a plant for the production of levulinic acid, comprising at least one melt crystallizer.

11. The isolation section according to claim 10, wherein the at least one melt crystallizer is a static melt crystallizer.

12. Use of melt crystallization for the isolation of a levulinic acid composition, comprising at least 98 wt. % levulinic acid, based on the total weight of the composition.

13. The process according to claim 3, wherein the predetermined purity of levulinic acid in composition 2 is at least 98 wt. %, based on the total weight of composition 2, and wherein the melt crystallizer is a static melt crystallizer.

14. The process according to claim 3, wherein the cooling in step i is performed for 5 minutes to 24 hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In FIGS. 1 and 2 a scheme of a plant according to one embodiment of the invention is shown.

DETAILED DESCRIPTION OF THE INVENTION

[0068] In the plant according to FIGS. 1 and 2 a continuous process for the production of levulinic acid can be performed.

[0069] According to FIG. 1 water, C6 carbohydrate-containing feedstock and an acid catalyst are mixed in a pretreatment reactor. The obtained mixture is fed to a reactor. The reaction mixture is brought to the desired temperature and pressure by steam. After the required reaction time the reaction mixture leaves the reactor and the pressure is reduced to atmospheric pressure in a flash tank. Steam is removed from the flash tank. Thereafter, the reaction mixture is neutralized by the addition of a base and a solid/liquid separation takes place to remove char. Solution 1 is obtained after solid/liquid separation.

[0070] In FIG. 2 the further purification of solution 1 is shown.

[0071] According to FIG. 2 solution 1 is fed to an isolation section formed by a series of three evaporation steps to obtain levulinic acid. During the first evaporation step solvent is removed and solution 2 is formed. Solution 2 is fed to the second evaporation step. During the second evaporation step formic acid and solvent are removed and solution 3 is formed. Solution 3 is fed to the third evaporation step. During the third evaporation step tar is removed and levulinic acid is obtained as the final product. This levulinic acid product is fed as composition 1 to a melt crystallization cycle comprising melt crystallizer 1 and melt crystallizer 2. In the melt crystallizer 1 the levulinic acid in composition 1 is crystallized and liquid 1.1 is drained. The crystals are objected to sweating and liquid 1.2 is obtained. After draining of liquid 1.2 the crystals are melted to obtain composition 2. Composition 2 is fed to melt crystallizer 2 for repeated melt crystallization. In the melt crystallizer 2 the levulinic acid in composition 2 is crystallized and liquid 2.1 is drained. The crystals are objected to sweating and liquid 2.2 is obtained. After draining of liquid 2.2 the crystals are melted to obtain a levulinic acid product with a predetermined purity.

[0072] The invention is further directed to the use of melt crystallization for the isolation of a levulinic acid composition, comprising at least 98 wt. % levulinic acid, based on the total weight of the composition.

[0073] Although the invention has been described in detail for purposes of illustration, it is understood that such detail is solely for that purpose and variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the claims.

[0074] It is further noted that the invention relates to all possible combinations of features described herein, preferred in particular are those combinations of features that are present in the claims.

[0075] It is further noted that the term comprising does not exclude the presence of other elements. However, it is also to be understood that a description on a product comprising certain components also discloses a product consisting of these components. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps.

[0076] The invention will now be explained by way of the following examples without however being limited thereto.

EXAMPLE 1

[0077] 1000 grams of 90.2 wt. % of a levulinic acid (LA) solution that was obtained from the overhead of an evaporator, was fed to a laboratory scale static melt crystallizer. The static melt crystallizer was a jacketed glass vessel (volume 5 l.) equipped with a stainless steel U-tube for cooling. The U-tube was submerged in the feed solution.

[0078] The first crystallization step was carried out at 10 C. for 6 hours. The temperature was determined in the levulinic acid solution. After the crystal growth phase, the liquid was drained from the crystals. The crystals, attached to the wall of the U-tube, were subjected to a sweating phase in order to remove the impurities. The sweating phase lasted for 3 hours at a temperature of 20 C. and the sweating liquid 1.2 was drained. The temperature of 20 C. was the temperature of the cooling medium.

[0079] After the sweating phase, the crystals were melted by bringing the temperature of the cooling medium in the U-tube to 40 C. The crystals melted from the U-tube surface. 358 grams of melted levulinic acid crystals were obtained with a purity of 96.1 wt. % LA and 2.7 wt. % of water.

[0080] The 358 grams melt from the first crystallization step was subjected to a second crystallization step, carried out at 15 C., also for 6 hours. The crystallization temperature was determined in the levulinic acid product. After draining the liquid 2.1 the crystals were subjected to sweating at 30 C for a period of 3 hours and the sweating liquid 2.2 was drained. The temperature during sweating was the temperature of the cooling medium. The crystals were melted to yield 104 grams of melted crystals could be retrieved with a purity of 99%, Moreover the melt was colorless. The combined drained liquids 2.1 and 2.2 were 254 g and had a purity of 94.9%.

[0081] The combined drained liquids 1.1 and 1.2 (642 grams) from the first crystallization step was subjected to a third crystallization step, performed at 10 C. for 16 hours. This liquid had an LA concentration of 86.8 wt. %. The temperature during crystallization was the temperature of the liquid. After the third crystallization step the not crystallized liquid 3.1 was drained. The crystals were subjected to sweating phase of 2 hours at 15 C., followed by 3 hours at 20 C. and the sweating liquid 3.2 was drained. The temperature during sweating was the temperature of the cooling medium. After melting the crystals a liquid of 284 g was obtained at a purity of 96% and 3% of water. The combined drained liquids 3.1 and 3.2 were 358 g with a levulinic acid purity of 79.5%.

EXAMPLE 2

[0082] 931 grams of a 97.5 wt. % solution of levulinic acid was obtained via fractional distillation and consequently from the overhead of an evaporator. The solution was fed to a laboratory scale static melt crystallizer. The static melt crystallizer was a jacketed glass vessel (volume 5 l.) equipped with a stainless steel U-tube for cooling. The U-tube was submerged in the feed solution.

[0083] The crystallization step was carried out at 20 C. for 4 hours. The temperature was determined in the levulinic acid solution. After the crystal growth phase, the liquid 1.1 was drained from the crystals. The crystals, attached to the wall of the U-tube, were subjected to a sweating phase in order to remove the impurities. The sweating phase lasted for 3 hours at a temperature of 30 C. and the sweating liquid 1.2 was drained. The sweating temperature of 30 C. was the temperature of the cooling medium.

[0084] After the sweating phase, the crystals were melted by bringing the temperature of the cooling medium in the U-tube to 40 C. The crystals melted from the U-tube surface. 230 grams of melted levulinic acid crystals were obtained with a purity of 99.8 wt. % LA and 0.2 wt. % of water. The combined drained liquids 1.1 and 1.2 (701 grams) from the crystallization step had a concentration of 96.7% of levulinic acid. By using one crystallization step a highly pure levulinic acid sample was obtained.

EXAMPLE 3

[0085] 45.36 kg of a 79.8 wt. % levulinic acid (LA) and 3.69 wt. % formic acid (FA) solution was obtained from the overhead of an evaporator, and was fed in 8 batches to a laboratory scale static melt crystallizer (Volume 5 l). The static melt crystallizer was a jacketed glass vessel equipped with a stainless steel U-tube for cooling. The U-tube was submerged in the feed solution.

[0086] The first crystallization step was carried out at 2 C. for 8 hours. The temperature was determined in the levulinic acid solution. After the crystal growth phase, the liquid 1.1 was drained from the crystals. The crystals, attached to the wall of the U-tube, were subjected to a sweating phase in order to remove the impurities. The sweating phase lasted for 3 hours at a temperature of 15 C. and the sweating liquid 1.2 was drained. The temperature of 15 C. was the temperature of the cooling medium.

[0087] After the sweating phase, the crystals were melted by bringing the temperature of the cooling medium in the U-tube to 35 C. The crystals melted from the U-tube surface. The collected melted crystals had a total weight of 11.3 kg with a purity of 90.3 wt. % LA and 1.3 wt. % of FA.

[0088] The combined sweat liquid 1.2 was 10.17 kg with 83 wt. % LA and FA concentration of 2 wt. %. The combined drained liquid 1.1 was 23.9 kg with a LA concentration of 73.5 wt. % and FA concentration of 5.5 wt. %.

[0089] The second crystallization step was carried out in 3 batches in the 5 l static lab crystallizer at 10 C. for 6 hours. The temperature was determined in the levulinic acid solution. After the crystal growth phase, the liquid 2.1 was drained from the crystals. The crystals, attached to the wall of the U-tube, were subjected to a sweating phase in order to remove the impurities. The sweating phase lasted for 3 hours at a temperature of 20 C. and the sweating liquid 2.2 was drained. The temperature of 20 C. was the temperature of the cooling medium.

[0090] After the sweating phase, the crystals were melted by bringing the temperature of the cooling medium in the U-tube to 40 C. The crystals melted from the U-tube surface. The collected melted crystals had a total weight of 3.96 kg with a purity of 93.8 wt. % LA and 0.5 wt. % of FA.

[0091] The combined sweat liquid 2.2 was 3.6 kg with 90.5 wt. % LA and FA concentration of 1.1 wt. %. The combined drained liquid 2.1 was 3.79 kg with a LA concentration of 86.5 wt. % and FA concentration of 2.3 wt. %.

[0092] The third crystallization step was carried out in 1 batch in the 5 l static lab crystallizer at 15 C. for 6 hours. The temperature was determined in the levulinic acid solution. After the crystal growth phase, the liquid 3.1 was drained from the crystals. The crystals, attached to the wall of the U-tube, were subjected to a sweating phase in order to remove the impurities. The sweating phase lasted for 3 hours at a temperature of 25 C. and the sweating liquid 3.2 was drained. The temperature of 25 C. was the temperature of the cooling medium.

[0093] After the sweating phase, the crystals were melted by bringing the temperature of the cooling medium in the U-tube to 40 C. The crystals melted from the U-tube surface. The melted crystals had a total weight of 1.12 kg with a purity of 99.3 wt. % LA and 0.04 wt. % of FA.

[0094] The sweat liquid 3.2 was 1.34 kg with 95.1 wt. % LA and FA concentration of 0.2 wt. %. The drained liquid 3.1 was 0.94 kg with a LA concentration of 85.4 wt. % and FA concentration of 1.8 wt. %.

[0095] After 3 crystallization steps a more than 99 wt. % pure levulinic acid sample was obtained from a 79 wt. % pure levulinic acid feedstock and the amount of formic acid in the sample was reduced from more than 3 wt. % to less than 0.1 wt. %.