SYNTHESIS OF LEVULINIC ACID BY HYDRATION OF FURFURYL ALCOHOL IN THE PRESENCE OF A HOMOGENEOUS ACID CATALYST AND OF A SOLVENT BASED ON ETHER AND/OR ACETALS

Abstract

The present invention relates to a process for synthesizing levulinic acid by hydration of furfuryl alcohol at a temperature of between 25 and 140 C. in the presence of a homogeneous acid catalyst and of an ether- and/or acetal-based solvent. The use of such a solvent makes it possible to obtain an equivalent or even better yield compared to those obtained with known solvents, while at the same time exhibiting high stability properties.

Claims

1. A process for synthesizing levulinic acid by hydration of furfuryl alcohol at a temperature of between 25 and 140 C. in the presence of a homogeneous acid catalyst and of an ether- and/or acetal-based solvent.

2. The process as claimed in claim 1, wherein the ether- and/or acetal-based solvent is chosen from the compounds corresponding to one or the other of the structures I and II, taken alone or as a mixture: ##STR00005## in which R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently chosen from: linear or branched aliphatic groups of 1 to 6 carbon atoms, optionally substituted by alkoxy groups, cyclic or polycyclic aliphatic groups of 5 to 12 carbon atoms, optionally substituted by alkoxy or alkyl groups, linear or branched olefinic groups of 1 to 6 carbon atoms, optionally substituted by alkoxy groups, 1 aromatic or polyaromatic groups of 6 to 12 carbon atoms, R.sub.1 and R.sub.2 may be bonded together by covalent bonds so as to form a ring, R.sub.3 and R.sub.4 may be bonded together by covalent bonds so as to form a ring, n is an integer between 1 and 6.

3. The process as claimed in claim 1, wherein the solvent is chosen from diethyl ether, diisopropyl ether, diisobutyl ether, dibutyl ether, diphenyl ether, 2-methoxy-2-methylpropane, 2-methoxy-2-methylbutane, 2,5-dihydrofuran, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2,3-dihydropyran, tetrahydropyran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, benzofuran, 2,2-dimethoxypropane, 2,2-di(2-ethylhexyloxy) propane, 2-methoxytetrahydrofuran and di(2-methoxyethyl) ether, taken alone or as a mixture.

4. The process as claimed in claim 1, wherein the homogeneous acid catalyst is chosen from a homogeneous, organic or inorganic Brnsted acid.

5. The process as claimed in claim 1, wherein the homogeneous acid catalyst is hydrochloric acid.

6. The process as claimed in claim 1, wherein water is present in an amount such that the water/furfuryl alcohol molar ratio is between 0.9 and 10.0 mol/mol.

7. The process as claimed in claim 1, wherein the solvent is present in an amount such that the solvent/furfuryl alcohol molar ratio is between 0.1 and 5 mol/mol.

8. The process as claimed in claim 1, wherein the homogeneous acid catalyst is present in an amount such that the acid/furfuryl alcohol molar ratio is between 0.01 and 1.0 mol/mol.

9. The process as claimed in claim 1, which is carried out at a temperature of between 60 and 110 C.

10. The process as claimed in one of the preceding claims, claim 1, which is carried out at a pressure of between 0.01 MPa and 1 MPa.

11. The process as claimed in claim 1, wherein the reaction effluent resulting from the synthesis is subjected to at least one separation step.

12. The process as claimed in claim 1, wherein the reaction effluent resulting from the synthesis is subjected to at least one thermal separation step.

13. The process as claimed in claim 1, wherein the reaction effluent resulting from the synthesis is subjected to at least one step of thermal separation in the presence of a flux having a boiling point greater than that of the levulinic acid.

14. The process as claimed in claim 13, wherein the flux has a boiling range of between 250 and 620 C. and is of petroleum origin and/or of vegetable origin and/or based on polymers or a mixture thereof.

15. The process as claimed in claim 13, wherein the flux is chosen from a petroleum cut chosen from a vacuum gas oil, a heavy oil obtained from a fluidized-bed catalytic cracking, a settling oil, an unconverted oil originating from a hydrocracker, or a polyethylene glycol having an average molar mass of greater than or equal to 600 g/mol.

Description

LIST OF THE FIGURES

[0137] The information regarding the elements referenced in FIG. 1 enables a better understanding of the invention, without said invention being limited to the particular embodiments illustrated in FIG. 1. The various embodiments presented can be used alone or in combination with one another, without limitation of combination.

[0138] FIG. 1 represents the diagram of a preferred embodiment of the process of the present invention, comprising: [0139] the synthesis of levulinic acid by hydration of furfuryl alcohol in the presence of a homogeneous acid catalyst in a continuously or batchwise operating reactor A in which furfuryl alcohol 1, water 2, hydrochloric acid 3 and the solvent 1,4-dioxane 4 are introduced and this mixture is heated in order to synthesize the levulinic acid.

[0140] The reaction effluent 5 is sent continuously or batchwise into a preliminary thermal separation section B which can be implemented by distillation or evaporation. The preliminary thermal separation step B makes it possible to separate a light fraction 6 containing the hydrochloric acid, the solvent and the unconverted water, which can be at least partly recycled into the reactor A (recycle not shown), and a heavy fraction (residue) 7 comprising the levulinic acid and the humins freed of light compounds. This composition is mixed with a flux 8 and then this mixture is sent into a thermal separation section C which can be implemented by distillation or evaporation and which makes it possible to obtain a light fraction containing the levulinic acid 9 and a heavy fraction 10 containing the humins and the flux.

EXAMPLES

[0141] The following examples are carried out according to the protocol below.

[0142] A flask with a capacity of 500 mL and equipped with a condenser is charged with 172 g of a solvent, 20 g of water (1.11 mol) and 20 g of an aqueous 37% by weight solution of hydrochloric acid (0.7 mol of water and 0.21 mol of HCl). The mixture is brought to a temperature of 80 C. under magnetic stirring. 132 g of furfuryl alcohol (1.35 mol) are then poured into the flask over a duration of addition of 6 h by means of a peristaltic pump. At the end of the addition, the mixture is left to react at the reaction pressure and temperature for a maturation phase of 15 minutes, before being cooled. The final mixture is taken for analysis and the concentrations by mass of solvent and of levulinic acid present are quantified by .sup.1H NMR spectroscopy calibrated by addition of a known amount of acetonitrile. The theoretical final concentrations by mass of levulinic acid and solvent are 45.4% and 50.0%, respectively.

[0143] Example 1 (not in accordance with the invention) uses methyl ethyl ketone (MEK) as solvent. The measured yield of levulinic acid is 82%, and the degradation rate of the solvent is 12%.

[0144] Example 2 (in accordance with the invention) uses 1,4-dioxane as solvent. The measured yield of levulinic acid is 87%, and the degradation rate of the solvent is 1%.

[0145] Example 3 (in accordance with the invention) uses 1,2-dimethoxyethane as solvent. The measured yield of levulinic acid is 82%, and the degradation rate of the solvent is 4%.

[0146] Thus, the examples presented here confirm that the use of a solvent of ether or acetal type makes it possible to obtain equivalent or even better yields compared to those obtained in ketones such as MEK, while at the same time significantly limiting the degradation of the solvent by maintaining the rate below a value of 5%.

TABLE-US-00001 TABLE 1 Final LA Final solvent concen- concen- tration tration Yield.sub.LA X.sub.sol Example Solvent (% wt) (% wt) (%) (%) 1 (not in MEK 37.4 44.1 82 12 accordance with the invention) 2 (in 1,4- 39.5 49.8 87 1 accordance dioxane with the invention) 3 (in 1,2- 37.4 48.0 82 4 accordance dimethoxy- with the ethane invention)