WO1995006026A1

WO1995006026A1 - Dehydration of itaconic acid

Info

Publication number: WO1995006026A1
Application number: PCT/EP1994/002820
Authority: WO
Inventors: Auke Gerardus Talma; Anna Gerdine Bovenkamp-Bouwman; Hendrika Petronella Maria Verlaan-Hooft
Original assignee: Akzo Nobel NV
Current assignee: Akzo Nobel NV
Priority date: 1993-08-26
Filing date: 1994-08-25
Publication date: 1995-03-02
Anticipated expiration: 1996-02-26

Abstract

A process is disclosed for the dehydration of itaconic acid, said process comprising the step of heating itaconic acid to a temperature between 90° and 400 °C in the presence of 0.1 to 50 wt%, based on itaconic acid, of C1-C10 alkane sulphonic acid, the alkane group being optionally substituted with one or more halogen groups, for a time period sufficient to dehydrate at least some itaconic acid. The process according to the present invention proceeds rapidly and results in high conversions and high yields of either itaconic anhydride or citraconic anhydride.

Description

Dehydration of Itaconic Acid

The present invention relates to a process for the preparation of itaconic and/or citraconic anhydride from itaconic acid by dehydrati.on thereof.

Methods for the conversion of itaconic acid to itaconic anhydride are known in the art.

One method relates to the dehydration of itaconic acid in the presence of a catalyst. R. . McCabe et al., J. Chem. Research (S), 1985, pp. 356-357, discloses a process for the cyclisation of itaconic acid in the presence of a clay or zeolite in a refluxing solvent. The publication also mentions that the reaction may be carried out in the presence of para-toluene sulphonic acid (pTSA) . However, the dehydration reaction of itaconic acid in the presence of pTSA is very slow and yields are low.

In Thiotopics, a leaflet published by Atoche (Elf Aquitaine), methane sulphonic acid (MSA) is compared with para-toluene sulphonic acid in the context of catalysed esterification reactions. Though several advantages of the use of MSA in this process are discussed, the present process is not disclosed in this leaflet, nor is the use of MSA in such processes or the advantages acquired by its use.

The use of clay as a catalyst in the dehydration reaction of itaconic acid is also disclosed in European patent application 0317 394, where the reaction is carried out in a refluxing solvent. German patent application 3 321 703 describes the conversion of itaconic acid in solution into itaconic anhydride in the presence of a tertiary amine at reflux temperatures. However, this method may involve many difficulties, and long reaction times and low yields are not uncommon. Another method is the dehydration of itaconic acid with the aid of a compound such as acetic anhydride, acetyl chloride or (trimethylsilyl)ethoxyacetylene. European patent application 0495544 describes such a process for the preparation of itaconic anhydride from itaconic acid. The process comprises the reaction in refluxing xylene of itaconic acid with acetic anhydride to form itaconic anhydride. A comparable process is described by M.C. Galanti et al., J. Org. Chem., 47, 1982, pp. 1572-1574, and by A.V. Galanti et al., ,L Pol. Sci: Pol. Chem. Ed., Vol. 19, 1981, pp. 451-475. Here itaconic acid is reacted with acetyl chloride at reflux conditions to form itaconic anhydride. Y. Kita et al., J. Org. Chem., 51, 1986, pp. 4150-4158 describes the use of (trimethylsilyl)ethoxyacetylene at temperatures between 20° and 60°C. This method has the disadvantage that a by-product is formed during the reaction, which then has to be removed from the reaction mixture to isolate the itaconic anhydride.

In addition, German patent application 1 443826 describes a process for the dehydration of dicarboxylic acid in a refluxing solvent mixture of benzene and propionic or isobutyric acid. No mention is made of the use of a catalyst, nor of the dehydration of itaconic acid.

Accordingly, there is a need in the art for a process for the synthesis of itaconic anhydride which is fast and which produces itaconic anhydride in high yield.

Methods for the conversion of itaconic acid into citraconic anhydride are also known in the art.

Citraconic anhydride may be prepared from melted itaconic acid. British patent 827,638 describes this process at pressures between 20 and 500 mmHg and temperatures between 155° and 185°C. The process conditions are very extreme and, therefore, economically unattractive. US patent 2,966,498 reveals that it is also possible to melt itaconic acid in the presence of an alkali metal salt at temperatures of 165-190°C at atmospheric pressure to produce citraconic anhydride.

European patent application 0495 544 describes two additional processes for the preparation of citraconic anhydride from itaconic acid. The first process converts itaconic acid into citraconic anhydride by melting itaconic acid in a solvent in the presence of an alkali metal salt at 180°C. The second process is a two-step reaction. The first step comprises the reaction in xylene of itaconic acid with acetic anhydride to form itaconic anhydride. In the second step the formed itaconic anhydride is converted into citraconic anhydride in the presence of a tertiary amine at reflux temperatures. Due to the two steps involved and the formation of acetic acid as a by-product which has to be removed, this second process is very elaborate and, therefore, economically unattractive.

Accordingly, there is also a need for a simple process for the production of citraconic anhydride from itaconic acid in high yields and with good conversion.

The present invention relates to an improved process for the dehydration of itaconic acid, said process comprising the step of heating itaconic acid to a temperature between 90° and 400°C in the presence of 0.1 to 50 wt%, based on itaconic acid, of Cj-Cio alkane sulphonic acid, the alkane group being optionally substituted with one or more halogen groups, for a period of time sufficient to convert at least some itaconic acid to citraconic and/or itaconic anhydride.

The process of the present invention proceeds rapidly and results in high conversions and high yields of either citraconic or itaconic anhydride. The temperature of the process ranges from 90° to 400°C. While it is possible to carry out the process at subatmospheric pressure or superatmospheric pressure, it is preferred that the reaction be carried out in a temperature range between 90° and 200°C and at substantially atmospheric pressure. The temperature and pressure conditions allow the use of normal equipment with steam heating, which renders the process economically attractive in addition to the above- mentioned advantages.

Preferably, the process of the present invention is carried out in a liquid system having a boiling temperature above 100°C at atmospheric pressure. More preferably, the process is carried out under reflux conditions. For, some liquid systems may codistill with the water produced during the conversion, i.e. form an azeotrope with water, and the reflux conditions enable the removal of water from the reaction.

The liquid system serves primarily to regulate heat transfer to the itaconic acid. Although not necessary, it is preferred that the liquid system be capable of solubilizing at least some of the itaconic acid. The reaction proceeds faster when at least some of the itaconic acid is solubilized in the liquid system. Furthermore, when the process temperature is above 168°C at atmospheric pressure, i.e. the melting temperature of itaconic acid at atmospheric pressure, the itaconic acid melts and dissolves. Typically, the liquid system is present in an amount of 1-500% by weight of the itaconic acid.

Examples of components capable of solubilizing at least some itaconic acid include xylene, cumene, cymene, o-dichlorobenzene, ethylbenzene, 1,1,2,2-tetrachloroethane, petroleum ethers boiling above 100°C, and aliphatic hydrocarbons, such as n-octane.

The liquid system may comprise a second component in addition to the components mentioned above. This second component should be polar and may not influence the reaction, i.e. it has to be inert. Examples of these second components include dimethyl sulphoxide and propionic acid.

The process is preferably carried out with a liquid system boiling above 100°C at atmospheric pressure. More preferably, the process of the present invention is carried out with a liquid system having a boiling temperature between 120° and 200°C at atmospheric pressure. The conversion to anhydride is completed in a shorter time period then when a liquid system having a boiling temperature below 120°C is used. Furthermore, liquid systems having a boiling temperature below 200°C at atmospheric pressure allow the use of normal equipment with steam heating.

When the process is carried out at a temperature below the melting point of itaconic acid (168°C at atmospheric pressure), the dehydration process will favour the formation of. itaconic anhydride, whereas when the reaction temperature exceeds 168°C, citraconic anhydride formation is favoured over longer reaction times. Both processes provide good conversions and high yields of products.

Although we do not wish to be bound by any theory, it is believed that independent of temperature first itaconic anhydride is formed. Above

168°C, after some time, isomerization of itaconic anhydride to citraconic anhydride takes place.

The catalysts for the processes are either a C^-Cio alkane sulphonic acid, a halogenated CI-CIQ alkane sulphonic acid or mixtures of one or more of these compounds. The halogenated Cj-Cio alkane sulphonic acids may comprise one or more fluorine, chlorine, iodine and/or bromine atoms, with fluorine being the most preferred. The most preferred alkane is methane, thus making methane sulphonic acid and trifluoro methane sulphonic acids the most preferred catalysts. Preferably, the amount of Cj-Cχo alkane sulphonic acid or halogenated ^cl"^c10 alkane sulphonic acid is 0.5 to 15 wt%, based on the weight of the itaconic acid.

The formed anhydride may be removed and purified in conventional ways. For example, the product may be removed by distillation under reduced pressure or recrystallized from solution, for example chloroform.

Itaconic anhydride may be used as a precursor for the production of, for example, itaconic perester compounds. Citraconic anhydride may be used for the production of citraconimides.

The following examples are presented to further illustrate the present invention. Examples 1-8 are carried out at reflux conditions at atmospheric pressure. In view of the fact that the solvent systems form an azeotrope with water, the precise temperature at which these Examples are carried out cannot be given. The temperature will range from 90°C (lowest azeotropic temperature of water/liquid system) to the boiling temperature of the liquid system used.

Example 1

In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 20 g (156 mmoles) of itaconic acid and 0.2 g methane sulphonic acid (MSA: 1 wt%, based on itaconic acid) were suspended in 100 ml cumene at room temperature. The suspension was heated to reflux temperature. Upon heating the itaconic acid dissolved and a clear solution was formed from which the water was removed. After 4 hours at reflux, the cumene was distilled off and the itaconic anhydride isolated in a crude yield of 97%. Example 2

In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condenser, 20 g (156 mmoles) of itaconic acid and 5 wt%, based on itaconic acid, of trifluoro methane sulphonic acid (TFMSA) were suspended in 100 ml xylene at room temperature. The suspension was heated to reflux temperature. Upon heating the itaconic acid dissolved and a clear solution was formed from which the water was removed. After 4 hours at reflux, the xylene was distilled off and the crude itaconic anhydride isolated. A conversion of more than 95% was obtained.

Examples 3 and 4 and Comparative Example A

The procedure of Example 1 was followed, except that other solvents were substituted for cumene. The solvent systems used have the following boiling temperatures at atmospheric pressure: below 120°C for toluene, between 120° and 168°C for xylene, and above 168°C for decaline. The results obtained are listed in Table 1.

Table 1

IA = itaconic anhydride CA = citraconic anhydride

As is shown in Table 1, when itaconic anhydride is the desired product, a solvent system having a boiling temperature between 120° and 168°C gives the best performance of the three solvent systems compared. When citraconic anhydride is desired, the reaction has to be carried out above 168°C for some time, as is shown in Example 4. Comparative Examples B and C

The procedure of Example 1 was followed, except that para-toluene sulphonic acid (pTSA) was substituted for MSA. Itaconic anhydride was formed. The results obtained are given in Table 2. For comparison the results of Example 1 are also listed in the Table.

Table 2

As the results in Table 2 show, the use of MSA in the process of the present invention results in a higher conversion in a shorter time as compared with the use of pTSA.

Examples 5 and 6

The procedure of Example 1 was followed, except that in some examples xylene was substituted for cumene and in some examples a cosolvent was present during the reaction. Itaconic anhydride was formed. The results are listed in Table 3. For comparison the results of Examples 1 and 3 are also listed in the Table.

Table 3

prop. = propionic acid n.d. = not determined

Example 7

In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condensor, 20 g of itaconic acid and 10% MSA, based on the weight of itaconic acid, were suspended in 100 ml of Shell Ondina^® Oil. The suspension was heated to a temperature above the melting point of itaconic acid (>168°C), viz. 175°C, to produce in 18 hours citraconic anhydride with a conversion of 88%.

Example 8

In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condensor, 100 g of itaconic acid were suspended in 50 wt% MSA, based on the weight of itaconic acid. The suspension was heated to a temperature above the melting point of itaconic acid (>168°C), viz. 175°C, to produce in 8 hours citraconic anhydride with a conversion of 89% and in a yield of 49%.

Example 9

In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condensor, 1 wt.% methane sulphonic acid, based on the weight of the itaconic acid, was mixed with 20 g of itaconic acid. This mixture was heated, with stirring, to a temperature of about 155-160°C for a period of four hours to produce itaconic anhydride with a conversion of 29%.

The reaction mixture was then heated to 175°C for an additional 18 hours, forming citraconic anhydride with a conversion of 95%.

Example 10

In a 250 ml reactor vessel equipped with a mechanical stirrer and a Dean-Stark trap with a reflux condensor, 10 wt.% methane sulphonic acid, based on the weight of the itaconic acid, was mixed with 20 g of itaconic acid. This mixture was heated, with stirring, to a temperature of about 170°C for a period of 18 hours to produce citraconic anhydride with a conversion of 89% and a yield of 46%.

The foregoing examples have been presented for the purpose of illustration and description only and are not to be construed as limiting the scope of the invention in any way. The scope of the invention is to be determined by the claims appended hereto.

Claims

1. A process for the dehydration of itaconic acid, said process comprising the step of heating itaconic acid to a temperature between 90° and 400°C in the presence of 0.1 to 50 wt%, based on itaconic acid, of CJ-CIQ alkane sulphonic acid, the alkane group being optionally substituted with one or more halogen groups, for a period of time sufficient to dehydrate at least some itaconic acid.

2. Process according to claim.1, characterized in that it is carried out at a temperature between 90° and 200°C and at substantially atmospheric pressure.

3. Process according to any of the preceding claims, characterized in that it is carried out in a liquid system, said liquid system having a boiling temperature above 100°C at atmospheric pressure.

4. Process according to claim 3, characterized in that it is carried out under reflux conditions.

5. Process according to claim 3 or 4, characterized in that the liquid system is capable of solubilizing at least some of the itaconic acid.

6. Process according to claim 5, characterized in that the liquid system comprises at least one component selected from the group of xylene, cumene, cymene, o-dichlorobenzene, ethylbenzene, 1,1,2,2-tetrachloroethane, petroleum ethers boiling above 100°C, and aliphatic hydrocarbons.

7. Process according to claim 3, 4, 5, or 6, characterized in that the boiling temperature of the liquid system is between 120° and 200°C at atmospheric pressure.

8. Process according to any one of the preceding claims, characterized in that the amount of CJ-CIQ alkane sulphonic acid or halogenated CI-C^Q alkane sulphonic acid is 0.5-15 wt%, based on itaconic acid.

9. Process according to any one of the preceding claims wherein the Ci-Cio alkane sulphonic acid is methane sulphonic acid and the halogenated CJ-CIQ alkane sulphonic acid is trifluoromethane sulphonic acid.

10. Process according to any one of the preceding claims wherein the reaction temperature is above the melting point of the itaconic acid and the primary product is citraconic anhydride.

11. Process according to any one of claims 1-9 wherein the reaction temperature is below the melting point of the itaconic acid and the primary product is itaconic anhydride.