EP2616452A1

EP2616452A1 - Process for producing dioxolane

Info

Publication number: EP2616452A1
Application number: EP11754391.8A
Authority: EP
Inventors: Sergio Mastroianni
Original assignee: Rhodia Operations SAS
Current assignee: Rhodia Operations SAS
Priority date: 2010-09-15
Filing date: 2011-09-07
Publication date: 2013-07-24
Also published as: FR2964658A1; BR112013005871A2; WO2012034905A1; CN103097372A; US20130178638A1; FR2964658B1

Abstract

The present invention relates to a process for producing dioxolane from crude glycerol obtained from raw materials such as the crude glycerol obtained during the production of biodiesel or glycerol obtained during the conversion of fats or oils. The invention in particular aims to dissolve the glycerol in an organic solvent and to form an insoluble phase comprising the salts included in the crude glycerol, and then to react the glycerol obtained with an aldehyde or a ketone.

Description

PROCESS FOR PRODUCING DIOXOLANE

The present invention relates to a process for producing dioxolane from crude glycerol obtained from raw materials such as crude glycerol obtained during the manufacture of biodiesel or glycerol obtained during transformation of fats or oils. The invention aims in particular to dissolve glycerol in an organic solvent and form an insoluble phase comprising the salts included in the crude glycerol; and then reacting the obtained glycerol with an aldehyde or a ketone.

PRIOR ART

It is well known to manufacture a dioxolane from glycerol and a ketone or an aldehyde. This reaction is especially mentioned in the following publications: R.J. Fessenden & J. F. Fessenden, Organic Chemistry, Second Edition, Page 524, 1982 and T. W. Greene, Protective Groups in Organic Chemistry, John Wiley & Sons, 1981. It is however more difficult to manufacture a dioxolane using crude glycerol. Glycerol, 1,2,3-propanetriol, is present in combination form in vegetable and animal oils and fats. It is especially present in the form of triglycerides combined with fatty acids such as stearic, oleic, palmitic and lauric acids. The most common industrial process for obtaining glycerol from vegetable and animal oils and fats involves saponification reactions, high pressure hydrolysis and transesterification with alcohols, such as ethanol or methanol.

Glycerol is also a by-product of biodiesel which is generally obtained by the transesterification of glycerides with short chain alcohols, for example methanol or ethanol. The transesterification reaction is catalyzed by an acid or a base, depending on the characteristics of the oils and / or greases used. After the transesterification reaction, the resulting esters are separated from excess reactants, catalyst and by-products by a two-step process. First, the glycerol is separated by decantation or centrifugation, then the soaps, the catalyst and alcohol residues are removed by washing with water and bubbling or using magnesium silicate with filtration. The significant production of biodiesel as an alternative to fossil sources is accompanied by a high production of crude glycerol obtained as a by-product.

Depending on the manufacturing processes, the crude glycerol obtained includes impurities such as glycerides and salts that involve many complex processing steps before it can be used to make dioxolane.

It is thus sought the development of a simple and industrial process for manufacturing dioxolane from crude glycerol which is inexpensive and under usual conditions of temperature and pressure; to obtain high purity dioxolane that would be suitable for a number of applications.

INVENTION

It has now been demonstrated that it is possible to produce dioxolane from crude glycerol by a process that is simple to implement, effective and that, moreover, does not alter glycerol or its color. This process consists in adding to the crude glycerol an amount of organic solvent which will dissolve the glycerol and thus form an insoluble phase consisting of a heterogeneous mixture of salts and some organic compounds. This insoluble phase will then be separated from the liquid medium and the purified glycerol can be used for the manufacture of dioxolane. This process allows excellent purification and separation of glycerol regardless of the type of crude glycerol used. In particular, a purity greater than 95% of glycerol containing very small amounts of residual salts is obtained; and the solvent used can be perfectly recycled. The dioxolane obtained has a purity quite equivalent with a dioxolane conventionally manufactured from pure glycerol.

The present invention thus relates to a process for the manufacture of dioxolane comprising at least the following stages:

(a) in the presence of crude glycerol and of at least one organic solvent comprising from 1 to 10 carbon atoms and comprising at least one ketone, aldehyde, alcohol, acetal and / or ketal function, so as to form a liquid phase comprising glycerol dissolved in the solvent (s) and also forming an insoluble phase;

(b) separating the insoluble phase and the liquid phase;

(c) optionally separating the solvent and glycerol from the liquid phase;

(d) adding to the liquid phase or glycerol (if step (c)) a catalyst, and optionally a ketone or an aldehyde, to form a dioxolane by catalyzed reaction between glycerol and the ketone or aldehyde; and

(e) recovery of dioxonale.

The insoluble phase is generally a heterogeneous dispersed phase in the majority phase and may be related to a precipitate.

The process of the invention can be carried out continuously or discontinuously. The steps mentioned can be performed successively and one after the other or not. Each of the steps of the process can be carried out continuously or discontinuously.

The crude glycerol is preferably obtained from renewable raw materials, in particular the crude glycerol is obtained during the manufacture of biodiesel or obtained during the transformation of fats or oils, particularly animal or vegetable fats or oils. The crude glycerol is generally obtained by saponification reaction, transesterification and / or hydrolysis of animal or vegetable fats or oils. The crude glycerol generally comprises from 5 to 95% by weight of glycerol, in particular from 40 to 90% by weight of glycerol. Crude glycerol also includes inorganic salts, glycerides, water and other organic compounds.

The crude glycerol may optionally be treated for the process of the invention, in particular for example by adjusting the pH, filtration or distillation. It is thus possible to filter the crude glycerol to remove insoluble organic material and / or distill it generally at temperatures between 100 and 120 ° C at atmospheric pressure to remove water and volatile compounds. Part or all of the water contained in the crude glycerol can also be evaporated before glycerol is dissolved in the solvent.

Step a) of the process according to the invention aims at dissolving the glycerol in the organic solvent and forming an insoluble phase comprising the salts of the crude glycerol.

One or more solvents can be used. The solvent according to the invention may in particular be a ketone, an alcohol, an aldehyde, an acetal and / or a ketal. Acetals are obtained by nucleophilic addition of an alcohol to an aldehyde in an acidic medium, followed by removal of water. The ketals are obtained by the same type of reaction performed on ketones.

The ketones preferentially used are acetone, cyclohexanone, methyl cyclohexanone, cyclopentanone, methyl cyclopentanone and methyl isobutyl ketone (MIBK). The preferred aldehydes are formaldehyde, acetaldehyde and furfuraldehyde. The alcohols preferentially used are ethanol, methanol and isopropanol. The ketals and acetals are preferably dioxonales such as 2,2-dimethyl-1,3-dioxolane 4 methanol (solketal) for example.

Particularly preferred is a mixture of organic solvents, such as a mixture of alcohol and ketone, particularly a mixture of acetone and ethanol. In step a), no catalyst capable of catalyzing a reaction between the glycerol and the organic solvent or solvents of the medium, especially an esterification catalyst, will be used. Step a) can last between 2 minutes and 1 hour. It can be carried out at a temperature of between 10 and 100 ° C., in particular between 20 and 50 ° C. The pH during this step can be between 6 and 12, preferably between 7 and 12.

The mass ratio between the crude glycerol and the solvent (crude glycerol / solvent) is in particular a function of the solubility of the glycerol in said solvent, and for example preferably between 1/1 and 1/50.

Step b) aims at the separation of the precipitate obtained in step a) from the liquid phase comprising the solvent and the dissolved glycerol. In particular, filtration, decantation or centrifugation can be carried out.

Step c) is optionally aimed at separating the solvent and glycerol which is dissolved in the solvent. In particular, evaporation or distillation can be carried out for this purpose.

In step c) it is also possible to separate the water contained in the crude glycerol.

The evaporation will include the passing of the organic solvent (s) in the gaseous state so as to recover the glycerol in the liquid state.

To carry out the distillation, one or more distillation columns can be used. In particular, the different compounds can be distilled on the same distillation column by varying the temperature, and possibly the pressure; for example proceed to the distillation of the organic solvent, then an increase in the temperature to distill the glycerol. We usually use temperatures between 60 and 190 ° C, and pressures between 2 and 1000 m bar.

This step c) may in particular be used to purify the glycerol and to rid the medium of an organic solvent which may be involved in the catalyzed reaction forming dioxolane of step d).

Step d) is intended to form dioxolane by reacting the glycerol with an aldehyde or a ketone in the presence of a catalyst. This reaction can be carried out in the liquid phase comprising glycerol or else with glycerol freed from the organic solvent or solvents if a step c) has been carried out. It should be noted that a ketone or an aldehyde may be added, in particular if a step c) has been carried out and as a function of the solvent or solvents used in step a).

The ketones preferentially used are acetone, cyclohexanone, methyl cyclohexanone, cyclopentanone, methyl cyclopentanone and methyl isobutyl ketone. The preferred aldehydes are formaldehyde, acetaldehyde and furfuraldehyde. It is particularly possible to use according to the invention one or more ketones and / or aldehydes to react with glycerol in the reaction medium.

Depending on the method used, it is possible to use various proportions of glycerol and ketone or aldehyde in the reaction medium. For example, in a batch, a molar ratio of 1 to 5 of ketone or aldehyde relative to glycerol may be used. In a continuous process, it is possible, for example, to use glycerol in a loop and add small proportions of ketone or aldehyde; in particular from 5 to 20 mol%. The dioxolane formed generally corresponds to the following general formula (I):

in which R and R 1 represent, independently of one another, a hydrogen atom or an alkyl chain comprising from 1 to 10 carbon atoms, especially from 1 to 5 carbon atoms, such as in particular methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl and isopentyl. In the case of a reaction with an aldehyde, one of the groups R or R 1 is a hydrogen atom. In the case of a reaction with a ketone, the groups R and R 1 do not represent a hydrogen atom.

The dioxolane formation reaction is generally conducted at a temperature between 0 and 150 ° C, preferably between 20 and 80 ° C.

This reaction can be carried out for 30 minutes to 8 hours, usually between 1 and 5 hours. This reaction is preferably carried out in acidic medium, in particular with a pH ranging from 2.5 to 7.0.

In particular, acid catalysts for this reaction, such as organic or inorganic acids or their salts, may be used. There may be mentioned the use of acetic acid, sulfuric acid, methanesulphonic acid, ion exchange resins of carboxylic or sulfonic type. These resins can be on a fixed bed in the reactor.

At the end of the reaction, it is preferable to neutralize the catalyst, in particular by adding a base. For example, sodium carbonate or sodium hydroxide may be mentioned. Unreacted aldehyde and ketone can be removed by simple distillation. It is possible to separate the dioxolane formed from the reaction medium by distillation, preferably under reduced pressure. To carry out the distillation, one or more distillation columns can be used. In particular, the different compounds can be distilled on the same distillation column by varying the temperature, and possibly the pressure; for example, to distill the ketone or aldehyde, then increase the temperature to distill the water, and then increase the temperature to distill the dioxolane formed. Temperatures between 60 and 190 ° C are usually used and pressures between 2 and 1000 mbar are used. A specific language is used in the description so as to facilitate understanding of the principle of the invention. It should nevertheless be understood that no limitation of the scope of the invention is envisaged by the use of this specific language. In particular, modifications, improvements and improvements may be considered by a person familiar with the technical field concerned on the basis of his own general knowledge.

The term and / or includes the meanings and, or, as well as all other possible combinations of elements connected to this term. Other details or advantages of the invention will emerge more clearly in the light of the examples given below solely for information purposes.

EXPERIMENTAL PART

The commercially available crude glycerol has the following composition: 79.3% by weight of glycerol, 15.8% by weight of water, 1.61% by weight of Na + and 2.56% by weight of Cl-. Example 1

To 15.13 g of crude glycerol are added 180.4 g of acetone at room temperature. The mixture is heated to 45 ° C and stirred for 15 minutes until glycerol is dissolved in acetone and an insoluble phase is formed. The liquid phase is filtered using a PTFE filter with a pore diameter of 0.2 μm and 191.23 g of clear solution is recovered. 307.9 mg of methanesulfonic acid are then added at room temperature and the mixture is stirred for 1 hour. The appearance of flocculates is observed. 3. 140 g of sodium carbonate are then added and the liquid phase is recovered by filtration. The volatile compounds are then evaporated under vacuum at a temperature of 60 ° C. and a pressure of 0.3 bar absolute.

92 g of product are recovered which is analyzed by various techniques:

2,2-dimethyl-1,3-dioxolane-4-methanol: 94.2% (gas chromatography)

- water: 0.8% (gas chromatography)

glycerol: 5% (gas chromatography)

Na +: 0.07% (atomic absorption)

- Cl-: 0.04% (argentimetry)

The ketal can be further purified by distillation. Example 2

To 120.2 g of crude glycerol are added at room temperature 2464 g of acetone. The mixture is stirred for 15 minutes until dissolution of the glycerol in acetone and formation of an insoluble phase. The liquid phase is filtered using a PTFE filter with a pore diameter of 0.2 m and the solvent is evaporated under vacuum at a temperature of 60 ° C and a pressure of 0.3 bar absolute. The amount of purified glycerol recovered is 88.93 g.

Analyzes :

glycerol: 97.5% (GPC) - water: 1, 5% (GIC)

- Na +: 0, 12% (Atomic absorption)

- Cl-: 0.18% (Argentimetry) Synthesis of 2,2-dimethyl-1,3-dioxolane-4-methanol

30.77 g of 97.5% glycerol obtained in the preceding step and 38.04 g of acetone at 40 ° C. (acetone / glycerol molar ratio = 2) are introduced into a stirred reactor. 95.7 mg of methanesulfonic acid is then added and the mixture is stirred for 1 hour. The gas phase chromatographic analysis of the medium consisting of a single perfectly homogeneous liquid phase shows a glycerol conversion of 56% and the corresponding formation of 2,2-dimethyl-1,3-dioxolane-4-methanol. The ketal can be separated from the mixture by distillation.

Example 3

150.8 g of crude glycerol are added at room temperature 91.3 g of ethanol and 1754.3 g of acetone. The mixture is stirred for 20 minutes until dissolution of glycerol in acetone and formation of an insoluble phase. The liquid phase is filtered using a PTFE filter with a pore diameter of 0.2 μm. The solvent is then evaporated under vacuum at a temperature of 75 ° C. and a pressure of 0.3 bar absolute.

The amount of purified glycerol recovered is 106.7 g.

Analyzes :

glycerol: 98.3% (GPC)

- Na +: 0.32% (Atomic absorption)

Cl - 0.46% (argentiometry)

Synthesis of 2,2-dimethyl-1,3-dioxolane-4-methanol

30.62 g of 98.3% glycerol obtained in the preceding step and 38.10 g of acetone at 40 ° C. (molar ratio acetone / glycerol = 2) are introduced into a stirred reactor. 94.6 mg of methanesulfonic acid is then added and the mixture is stirred for 1 hour. Gas Chromatographic Analysis medium consisting of a single perfectly homogeneous liquid phase shows a glycerol conversion of 54% and the corresponding formation of 2,2-dimethyl-1,3-dioxolane-4-methanol. The ketal can be separated from the mixture by distillation. Example 4

140.3 g of 2,2-dimethyl-1,3-dioxolane-4-methanol (commercial product) and 2190 g of acetone are added at 140.7 g of crude glycerol. The mixture is stirred for 20 minutes until dissolution of glycerol in acetone and formation of an insoluble phase. The liquid phase is filtered using a PTFE filter with a pore diameter of 0.2 μm. The most volatile compounds are evaporated under vacuum at a temperature of 75 ° C. and a pressure of 0.3 bar absolute.

The amount of glycerol / 2,2-dimethyl-1,3-dioxolane-4-methanol mixture is 221.25 g.

Analysis:

glycerol: 44.2% (GPC)

2,2-dimethyl-1,3-dioxolane-4-methanol: 55.5% (GPC)

Na + 0.2% (atomic absorption)

- Cl-: 0, 15% (argentimetry)

Synthesis of 2,2-dimethyl-1,3-dioxolane-4-methanol

44.8 g of purified glycerol / 2,2-dimethyl-1,3-dioxolane-4-methanol mixture obtained in the preceding step and 25.3 g of acetone at 40 ° C. are introduced into a stirred reactor ( acetone / glycerol molar ratio = 2). 63.7 mg of methanesulfonic acid is then added and the mixture is stirred for 1 hour. The gas phase chromatographic analysis of the medium consisting of a single perfectly homogeneous liquid phase shows a glycerol conversion of 41% and the corresponding formation of 2,2-dimethyl-1,3-dioxolane-4-methanol. The ketal can be separated from the mixture by distillation. Example 5 (comparative)

Synthesis of 2,2-dimethyl-1,3-dioxolane-4-methanol using crude glycerol 37.86 g of crude glycerol (corresponding to 30.0 g of pure glycerol) and 38.04 are introduced into a stirred reactor. g of acetone at 40 ° C. (acetone / glycerol molar ratio = 2). 95.4 mg of methanesulfonic acid is then added and the mixture is stirred for 1 hour. The gas chromatographic analysis of the medium, corresponding to a mixture of two liquid phases and a white precipitate (predominantly composed of NaCl), shows a glycerol conversion of only 17% and the corresponding formation of 2,2-dimethyl 1,3-dioxolane-4-methanol.

Claims

1. A process for producing dioxolane comprising at least the following steps:

(b) separating the insoluble phase and the liquid phase;

(c) optionally separating the solvent and glycerol from the liquid phase;

(e) recovery of dioxonale.

2. Method according to claim 1, characterized in that the crude glycerol comes from renewable raw materials.

3. Method according to claim 1 or 2, characterized in that the crude glycerol is obtained during the manufacture of biodiesel or during the transformation of fats or oils, particularly animal or vegetable fats or oils.

4. Process according to any one of the preceding claims, characterized in that the ketone is chosen from the group comprising acetone, cyclohexanone, methyl cyclohexanone, cyclopentanone, methyl cyclopentanone and methyl isobutyl ketone.

5. Process according to any one of the preceding claims, characterized in that the aldehyde is chosen from the group comprising formaldehyde, acetaldehyde and furfuraldehyde.

6. Process according to any one of the preceding claims, characterized in that the alcohol is chosen from the group comprising ethanol, methanol and isopropanol.

7. Process according to any one of the preceding claims, characterized in that the ketal or the acetal is a dioxolane.

8. Process according to any one of the preceding claims, characterized in that the mass ratio between the crude glycerol and the solvent (crude glycerol / solvent) is between 1/1 and 1/50.

9. Method according to any one of the preceding claims, characterized in that the separation of step b) is carried out by filtration.

10. Process according to any one of the preceding claims, characterized in that the separation of step c) is carried out by evaporation.

1 1. Process according to any one of the preceding claims, characterized in that the dioxolane corresponds to the following general formula (I):

in which R and R1 independently of one another represent a hydrogen atom or an alkyl chain comprising from 1 to 10 carbon atoms.

12. Method according to any one of the preceding claims, characterized in that the reaction medium of step d) comprises an acid catalyst.

13. Method according to any one of the preceding claims, characterized in that the reaction medium of step d) comprises a selected acid catalyst in the group comprising acetic acid, sulfuric acid, methanesulfonic acid and carboxylic or sulfonic ion exchange resins.