GB1596651A - Process for the recovery of laevulinic acid in the form of its internal ester alphaangelica lactone from mixtures of compounds of similar boiling-point - Google Patents

Description

(54) PROCESS FOR THE RECOVERY OF LAEVULINIC ACID IN THE FORM OF ITS INTERNAL ESTER, ALPHA-ANGELICA LACTONE, FROM MIXTURES OF COMPOUNDS OF SIMILAR BOILING-POINT (71) We, BP CHEMICALS LIMI TED, of Britannic House, Moor Lane, London, EC2Y 9BU, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method bv which it is to be performed, to be particularly described in and by the following statement: The present invention relates to laevulinic acid and in particular to its recovery in the form of its internal ester, alpha-angelica lactone (4-hydroxypent-3-enoic acid lactone) from a mixture of compounds of similar boiling-point, in particular, from the highboiling residues otherwise known as 'heavy ends' obtained as a by-product in the production of lower carboxylic acids by the oxidation of paraffinic hydrocarbons at elevated temperature and pressure.

The liquid phase oxidation of lower paraffins, e.g. paraffins containing from 4 to 8 carbon atoms in the molecule, with molecular oxygen at elevated temperatures and pressures is disclosed in British Patent Specification Nos. 743,989; 743,990; 771,991; 767,290 and 771,992. The products produced by the process may be classified as (ass volatile non-acidic oxidation products of boiling-point up to 990C in the presence of water, hereinafter referred to as "low-boilers" or "light ends", (b) water, (c) aliphatic monocarboxylic acids containing from 1 to 4 carbon atoms and (d) higher-boiling materials, including acids, otherwise known as heavy ends.

Typically, a hydrocarbon feedstock, such as naphtha, is fed to a reactor maintained at elevated temperature and pressure in which it is intimately contacted with molecular oxygen.

The liquid oxidation products are withdrawn from the base of the reactor and fed to a first distillation column wherein low-boiling materials or "light ends", containing a significant proportion of acetone and esters, are removed overhead. The product taken from the base of the first distillation column, sometimes referred to as "topped aqueous product" or "TAP", is passed to a second distillation column wherein a fraction, sometimes referred to as "crude wet acid" or "CWA", comprising a mixture of formic, acetic, propionic and some butyric acids, together with water, is recovered overhead. Individual acids are reccvered from the CWA by further distillation.

The high-boiling residue recovered from the base of the second distillation column is passed to a third column generally operated under reduced pressure, wherein lower-boiling materials are stripped out and recycled to the second distillation column. The third column base product hereinafter to be referred to as heavy ends, is a comolex mixture of highboiling materials. Whilst the composition of heavy ends is not known in detail, compounds which have been detected and in some cases estimated are butyric and higher monobasic acids, dibasic acids such as succinic, glutaric and adipic acids, lactones such as butyrolactone and valerolactone and ketoacids such as laevulinic acid. Normally the heavy ends contain from 5 to 150/o by wt laevulinic acid and lesser amounts of alpha-angelica lactone (4-hydroxypent-3-enoic acid lactone).

Laevulinic acid is a material having many potential industrial applications arising from its antimicrobial, bactericidal and virucidal activity. Thus, it has been suggested as an effective disinfectant for air and, as an aqueous solution containing also gelatin and glycerol, a mould inhibiting coating for food wrappers, as a levelling agent in metal electroplating baths, and as a component in shampoos, amongst many other applications. In the form of its metal salts it has been suggested as an automobile coolant permanent antifreeze and as a component of greases. Hitherto, laevulinic acid has been produced from wood residues and other cellulose-containing waste products by a complicated process involving heating with dilute mineral acid under pressure. A desirable objective would be to recover the laevulinic acid present in the heavy ends produced in paraffin oxidation processes. It has so far proved impossible to recover pure laevulinic acid from heavy ends by straight distillation, even under reduced pressure, because of decomposition in the distillation column. Another approach to the problem described in Japanese Patent Application No.

Showa 47(1972)-96449 is to recover the laevulinic acid, in the form of an ester, by distillation, and thereafter, hydrolyse the ester.

The present invention provides a process for recovering laevulinic acid in the form of its internal ester, alpha-angelica lactone, from a mixture containing laevulinic acid and compounds of similar boiling-point which process comprises removing from the mixture lowerboiling compounds, dehydrating the remaining matcrial under conditions which effect dehydration of the laevulinic acid to alphaangelica lactone and recovering a fraction containing alpha-angelica lactone therefrom.

In a preferred embodiment of the invention the mixture containing laevulinic acid in admixture with compounds of similar boilingpoint is the heavy ends, as hereinbefore defined, recovered from the products of the oxidation of paraffinic hydrocarbons.

Compounds boiling lower than laevulinic acid may be removed from the heavy ends by feeding the heavy ends to a first distilaltion column, provided with conventional kettle, condensing and refluxing facilities, operating at sub-atmospheric pressure wherein a distillate fraction comprising compounds having a boiling-point at atmospheric pressure below about 2GOOC is separated overhead from a residue fraction. The residence time of the heavy ends tin the first distillation column during removal of the distillate fraction is preferably the minimum consistent with removing the lower-boiling compounds and avoiding decomposition of laevulinic acid. The distillate fraction may contain acids with a boiling-point up to and including butyric and valeric acids, and may comprise up to 50% of the total heavy ends fed to the column, the actual amount depending upon the composition of the initial feed to the oxidation reaction. Preferably the distillate fraction is recycled to the paraffinic hydrocarbon and oxidation. Other methods of removing compounds having a boiling-point at atmospheric pressure below 2000C from the heavy ends, such as flash distillation, may be employed.

After removal of low-boiling compounds the residue fraction remaining is subjected to dehydration. This may be effected in the first distillation collumn bv modifving the operating conditions to conditions which favour the dehydration of laevulinic acid to alpha-angelica lactone. Thus the kettle temperature may be adjusted to a value in the range 150 to 2000 C, at a pressure in the range 25 to 100 mm Hg.

As dehydration proceeds there are formed alDha-angelica lactone and other low-boiling dehydration products which are simultaneously removed overhead as a low-boiling distillate fraction at a fixed, pre-determined column head temperature i.e. under isothermal distillation conditions. The fixed column head temperature should preferably be at least as high as the boiling-point of alpha-angelica lactone under the conditions prevailing in the column. Essentially complete dehydration of laevulinic acid may be effected over a period of between 5 and 20 hours. Alternatively, the residue fraction remaining after removal of the low-boilers from the heavy ends may be fed to a separate dehydration vessel which may be, for example a second distillaton column, maintained at a temperature in the range 150 to 2000C and a piessure in the range 25 to 100 mm Hg for a period of be tween 5 and 20 hours to produce a low boiling fraction containing alpha-angelica lactone. It is believed that the following reaction occurs during dehydration:

laevulinic acid alpha-angelica lactone A catalyst may be added to promote the dehydration, though its presence is not essential. Any conventional dehydration catalyst, such as concentrated sulphuric acid, may be employed.

The low-boiling fraction from the dehydration stage may contain, in addition to alphaangelica lactone, impurities such as butyric acid, propionic acid, acrylic acid, cyclohexanone, gamma-butyrolactone, crotonic acid and valerolactone. The low-boiling fraction may if desired, be purified by, for example further distillation or crystallisation.

Laevulinic acid may be removed from this fraction, either after removal of the aforesaid impurities therefrom or in the presence of the impurities contained therein, by hydrolysis and removal of compounds having a boilingpoint lower than laevulinic acid.

Hydrolysis of the alpha-angelica lactone added by the addition of a hydro'ysis catalyst, though the presence of a catalyst is not essential. Any conventional hydrolysis catalyst may be employed.

The process may be operated bathwise, semi-continuously or continuously.

The invention will now be illustrated by reference to the following Examples.

Production of Heavy Ends.

Naphtha and air were continuously fed to a stainless steel cylindrical reactor fitted wth an internal draught tube to promote liquid circulation. All feed and recycle streams were fed into the top of the draught tube. Air was introduced at the base of the reactor through a sparge ring. Liquid products were withdrawn from the base through a pressure reducing valve. Organic vapours issuing from the head of the reactor were condensed and returned.

Waste gases were vented to atmosphere. The liquid product drawn from the base of the reactor was fed to a first distillation column, the base of which was maintained at a temperature of about 125"C. Low-boiling materials of 'light ends' were removed overhead. The 'light-ends' were divided two ways, part being recycled to the reactor and part going forward to the acetone recovery system. The product from the first distillation column, (TAP), was fed to a second distillation column which was operated at a base temperature of about 140"C.

From the top of the second distillation column was taken an overhead fraction consisting of a mixture of lower carboxylic acids and water, (CWA). This fraction consists of formic, acetic and propionic acids with some butyric acid.

The CWA fraction was passed to further distillation steps in which the individual acids were recovered. The high-boiling residue from the base of the second distillation column was fed to a third distillation column which was operated under reduced Dressure at a base temperature of about 1SO"C. Lower-boiling materials were stripped out overhead and returned, to the second distillation column.

The complex mixture of products taken from the base of the third column was th heavy ends used as a feedstock for the process of the process invention. The heavy ends contained butyric and higher monobasic acids, dibasic acids such as succinic, glutaric, adipic acids etc., lactones such as butyrolactone, valerolactone etc., ketoacids such as laevulinic acid and other unknown high-boilers. The amounts of the main components of interest were analysed as follows: alpha-angelica lactone - 1.5% by weight n-butyric acid - 8.0% by weight buytrolactone - 3.0% by weight valerolactone - 2.0% by weight laevulinic acid - 6.0% by weight Example 1.

A. Recovery of Laevulinic Acid in the form of its Internal Ester Alpha-Angelica Lactone.

(a) Removal of lower-boiling compounds the mixture.

1,000 g of heavy ends of the above composition were distilled batchwise using a 25 plate, 2 inch diameter glass Oldershaw column under a pressure of 85 mm Hg. Distillate was removed under partial reflux conditions until the column head temperature reached 109 111"C. This distillate (primary distillate) amounted to 365 g in total and contained essentially all of the angelica lactone and n-butyric acid present in the original sample of heavy ends.

(b) Dehydration of the remaining material and recovery of a fraction containing alphaangelica lactone.

The operating conditions were mcdified to those favouring the dehydration of laevulinic acid, i.e. the kettle temperature was allowed to rise to 182"C. The kettle was then maintained at this temperature for a further 16 hours, during which time the column head temperature was maintained at 111 C by adjusting the ratio of distillate removed to distillate returned to the column as reflux. In this way a further 146 g of distillate (secondary distillate) was removed which contained 36% by weight of a-angelica lactone, equivalent, within the limits of experimental accuracy, to an almost quantitative yield on the laevulinic acid present in the original sample of heavy ends.

B. Purification of alpha-angelica lactone.

1. By distillation.

The secondary distillates from a number of experiments of the type described in Example 1A were bulked. 1,000 g of the bulked distillate containing 430 g of a-angeliica lactone were further distilled in the sam batch distillation column at a pressure of 40 mm Hg and a reflux ratio of 4:1. 96% of the a-angelica lactone in the charge was recovered in the distillate collected up to a column head temperature of 820 C, and a fraction collected at a column head temperature of 81"C was found to be angelica lactone of 95.3% purity.

2. By crystallisation.

A sample of the secondary distillate obtained by the method described in A above was cooled to less than 170C. A crystalline solid came out of solution, the solid being shown by analysis to be 98% pure alphaangelica lactone.

Example 2.

Recovery of laevulinic acid from alphaangelica lactone.

To a samnle of secondary distillate from an experiment of the type described in Example 1A above, containing 36% angelica lactone, was added water in an amount equivalent to three times the amount calculated to react with the z-angelica lactone. 0.5 g of an ion exchange resin (Amberlite* IR120) was added to 10 mls of this mixture, which was then stirred for 48 hours at room temperature. By analysis it was shown that more than 90% of the 5Z-angelica lactone has been converted to laevulinic acid.

WHAT WE CLAIM IS: 1. A process for recovering laevulinic acid in the form of its internal ester, alpha-angelica lactone, from a mixture containing laevulinic acid and compounds of similar boiling point which process comprises removing from the mixture lower-boiling compounds, dehydrating the remaining material under conditions which effect dehydration of the laevulinic acid to alpha-angelica lactone and recovering a fraction containing alpha-angelica lactone therefrom.

2. A process according to claim 1 wherein the mixture containing laevulinic acid and compounds of similar boiling-point is the heavy ends, as hereinbefore defined, recovered from the oxidation of paraffinic hydrocarbons.

3. A process according to claim 2 wherein those compounds boiling below laevulinic acid are removed from the heavy ends by feeding the heavy ends to a first distillation column provided with conventional kettle, condensing and rev'fluxing facilities operating at sub-atmo spheric pressure wherein a distillate fraction comprising compounds having a boiling-point at atmospheric pressure below about 200"C is separated overhead from a residue fraction.

4. A process according to claim 3 wherein the residence time of the heavy ends in the first distillation column during removal of the distillate fraction is the mirimum consistent with removing the lower-boiling compounds and avoiding decomposition of laevulinic acid.

5. A process according to either one of claims 3 ind 4 wherein the distillate fraction is recycled to the paraffinic hydrocarbon oxidation.

6. A process according to any one of claims 3 to 5 wherein the residue fraction is dehydrated in the first distillation column by modifying the operating conditions to conditions which favour the dehydration of laevulinic acid to alpha-angelica lactone.

7. A process according to claim 6 wherein the kettle temperature is adjusted to a value in the range 150 to 2000C at a pressure in the range 25 to 100 mm Hg.

8. A process according to either one of *Amberlite is a Registered Trade Mark.

claims 6 and 7 wherein alpha-anglica lactone and other low-boiling dehydration products are simultaneously removed overhead as a low-boiling distillate fraction at a fixed, predetermined column head temperature which is at least as high as the boiling-point of the alpha-angelica lactone under the conditions prevailing in the column.

9. A process according to any one of claims 6 to 8 wherein dehydration is effected ovr a period of between 5 and 20 hours.

10. A process according to any one of claims 3 to 5 wherein the residue fraction is fed to a separate dehydration vessel maintained at a temperature in the range 150 to 2000C and a pressure in the range 25 to 100 mm Hg for a period of between 5 and 20 hours to produce a low-boiling fraction containing alpha-angelica lactone.

11. A process according to claim 10 wherein the dehydration vessel is a second distillation column.

12. A process according to any one of claims 6 to 11 wherein a catalyst is added to promote the dehydration.

13. A process according to claim 12 wherein the catalyst is sulphuric acid.

14. A process according to any one of the preceding claims wherein the fraction containing alpha-angelica lactone is purified by further distillation or by crystallisation.

15. A process for recovering laevulinic acid in the form of its internal ester, alpha-angelica lactone, from a mixture containing laevulinic acid and compounds of similar boiling-point substantially as hereinbefore described with reference to Example 1.

16. Laevulinic acid in the form of its internal ester, alpha-angelica lactone, whenever recovered by a process as claimed in any on of the preceding claims.

17. A process for recovering laevulinic acid from the fraction containing alpha-angelica lactone recovered by a process as claimed in any one of claims 1 to 15 which process comprises hydrolysing the fraction containing alpha-angelica lactone either after removal of impurities therefrom or in the presence of the impurities contained therein and removing compounds having a boiling point lower than laevulinic acid.

18. A process according to claim 17 wherein a hydrolysis catalyst is added.

19. A process for recovering laevulinic acid from the fraction containing alphaangelica lactone substantially as hereinbefore described with reference to Example 2.

20. Laevulinic acid whenever recovered by a process as claimed in any one of claims 17 to 19.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (20)

**WARNING** start of CLMS field may overlap end of DESC **. an experiment of the type described in Example 1A above, containing 36% angelica lactone, was added water in an amount equivalent to three times the amount calculated to react with the çz-angelica lactone. 0.5 g of an ion exchange resin (Amberlite* IR120) was added to 10 mls of this mixture, which was then stirred for 48 hours at room temperature. By analysis it was shown that more than 90% of the 5Z-angelica lactone has been converted to laevulinic acid. WHAT WE CLAIM IS:

1. A process for recovering laevulinic acid in the form of its internal ester, alpha-angelica lactone, from a mixture containing laevulinic acid and compounds of similar boiling point which process comprises removing from the mixture lower-boiling compounds, dehydrating the remaining material under conditions which effect dehydration of the laevulinic acid to alpha-angelica lactone and recovering a fraction containing alpha-angelica lactone therefrom.

2. A process according to claim 1 wherein the mixture containing laevulinic acid and compounds of similar boiling-point is the heavy ends, as hereinbefore defined, recovered from the oxidation of paraffinic hydrocarbons.

3. A process according to claim 2 wherein those compounds boiling below laevulinic acid are removed from the heavy ends by feeding the heavy ends to a first distillation column provided with conventional kettle, condensing and rev'fluxing facilities operating at sub-atmo spheric pressure wherein a distillate fraction comprising compounds having a boiling-point at atmospheric pressure below about 200"C is separated overhead from a residue fraction.

4. A process according to claim 3 wherein the residence time of the heavy ends in the first distillation column during removal of the distillate fraction is the mirimum consistent with removing the lower-boiling compounds and avoiding decomposition of laevulinic acid.

5. A process according to either one of claims 3 ind 4 wherein the distillate fraction is recycled to the paraffinic hydrocarbon oxidation.

6. A process according to any one of claims 3 to 5 wherein the residue fraction is dehydrated in the first distillation column by modifying the operating conditions to conditions which favour the dehydration of laevulinic acid to alpha-angelica lactone.

7. A process according to claim 6 wherein the kettle temperature is adjusted to a value in the range 150 to 2000C at a pressure in the range 25 to 100 mm Hg.

8. A process according to either one of *Amberlite is a Registered Trade Mark.

claims 6 and 7 wherein alpha-anglica lactone and other low-boiling dehydration products are simultaneously removed overhead as a low-boiling distillate fraction at a fixed, predetermined column head temperature which is at least as high as the boiling-point of the alpha-angelica lactone under the conditions prevailing in the column.

9. A process according to any one of claims 6 to 8 wherein dehydration is effected ovr a period of between 5 and 20 hours.

10. A process according to any one of claims 3 to 5 wherein the residue fraction is fed to a separate dehydration vessel maintained at a temperature in the range 150 to 2000C and a pressure in the range 25 to 100 mm Hg for a period of between 5 and 20 hours to produce a low-boiling fraction containing alpha-angelica lactone.

11. A process according to claim 10 wherein the dehydration vessel is a second distillation column.

12. A process according to any one of claims 6 to 11 wherein a catalyst is added to promote the dehydration.

13. A process according to claim 12 wherein the catalyst is sulphuric acid.

14. A process according to any one of the preceding claims wherein the fraction containing alpha-angelica lactone is purified by further distillation or by crystallisation.

15. A process for recovering laevulinic acid in the form of its internal ester, alpha-angelica lactone, from a mixture containing laevulinic acid and compounds of similar boiling-point substantially as hereinbefore described with reference to Example 1.

16. Laevulinic acid in the form of its internal ester, alpha-angelica lactone, whenever recovered by a process as claimed in any on of the preceding claims.

17. A process for recovering laevulinic acid from the fraction containing alpha-angelica lactone recovered by a process as claimed in any one of claims 1 to 15 which process comprises hydrolysing the fraction containing alpha-angelica lactone either after removal of impurities therefrom or in the presence of the impurities contained therein and removing compounds having a boiling point lower than laevulinic acid.

18. A process according to claim 17 wherein a hydrolysis catalyst is added.

19. A process for recovering laevulinic acid from the fraction containing alphaangelica lactone substantially as hereinbefore described with reference to Example 2.

20. Laevulinic acid whenever recovered by a process as claimed in any one of claims 17 to 19.