Method for separating stearic acid lactone from mixed fatty acid

Abstract

The invention discloses a method for separating stearic acid lactone from mixed fatty acid, which comprises the following steps: dispersing an oleic acid isomerization hydrogenation product in an organic solvent which is one of normal hexane, methanol, ethanol, ethyl acetate and acetonitrile, then carrying out freezing crystallization, then carrying out solid-liquid separation, taking the liquid, and carrying out reduced pressure distillation to obtain the stearic acid lactone. The stearic acid lactone is obtained. The method for separating the stearic acid lactone from the mixed fatty acid has the advantages of simplicity in operation, high separation efficiency, low energy consumption, mild conditions, high purity of the separated stearic acid lactone and the like, and is suitable for large-scale industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of fatty acid compound separation, and particularly relates to a method for separating stearic acid lactone from mixed fatty acids. Background Art

[0002] Stearic acid lactone is usually made from oleic acid (the double bond on the oleic acid molecule is protonated to form a carbocation, which migrates to the fourth or fifth position on the carbon chain of the oleic acid molecule, and then cyclizes with the carboxyl functional group at the end of the oleic acid molecular chain). It contains a five-membered or six-membered ring structure and thus has high reactivity. It can not only be used as a raw material for preparing oxygen-containing fatty acid amides, polyhydroxy fatty alcohols, polyhydroxy fatty acid esters (PHA; lactone polymerization method), lubricants, and mold release agents, etc., but also high-purity lactone can be used directly as a fragrance in food and detergents. Isostearic acid is called the "universal chemical raw material" and is a mixture of saturated methyl and ethyl branched-chain stearic acids. Due to its branched-chain structure, it is liquid at room temperature and has good low-temperature fluidity. And because it does not contain unsaturated double bonds, it has good stability and antioxidant properties, and these characteristics make it widely used in industrial production. However, although isostearic acid widely exists in nature, due to its difficult extraction, its output has always been relatively limited and it is difficult to fully meet the market demand.

[0003] At present, in the industrial process of producing isostearic acid from zeolite isomerized oleic acid, it is inevitable to produce stearic acid lactone by-products (the C=C double bond of oleic acid breaks under the action of acidic active centers on the catalyst surface and forms a carbonium ion with a three-membered or four-membered ring, but the carbonium ion is very unstable and will open the ring under the action of high temperature and high pressure to form isomerized oleic acid with methyl or ethyl branched chains. The unsaturated double bonds of oleic acid and isomerized oleic acid may be affected by the acidic sites on the catalyst surface and cause carbocation migration, thus forming stearic acid lactone and isostearic acid lactone). And the output of stearic acid lactone by-products is relatively large, and there is currently a lack of effective separation means, resulting in the unreasonable application of this part of by-products. Common separation methods for fatty acid compounds include molecular distillation, urea inclusion, supercritical fluid extraction, vacuum distillation, etc. These methods generally have problems such as the need for expensive equipment and high energy consumption in the separation process. And because lactones and fatty acids have the same number of carbon atoms and branched-chain structures, these methods are not suitable for separating lactones and fatty acids.

[0004] Therefore, it is of great significance to develop a method for separating stearic acid lactone from mixed fatty acids with simple operation and high separation efficiency. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for separating stearic acid lactone from mixed fatty acids.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for separating stearic acid lactone from mixed fatty acids comprises the following steps: dispersing the isomerized and hydrogenated product of oleic acid in an organic solvent, which is one of n-hexane, methanol, ethanol, ethyl acetate, and acetonitrile, then performing freeze crystallization, then performing solid-liquid separation, and taking the liquid for vacuum distillation to obtain stearic acid lactone.

[0008] Preferably, a method for separating stearic acid lactone from mixed fatty acids comprises the following steps: dispersing the isomerized and hydrogenated product of oleic acid in an organic solvent, which is one of n-hexane, methanol, ethanol, ethyl acetate, and acetonitrile, then performing freeze crystallization, then performing solid-liquid separation, then dispersing the liquid in an organic solvent and performing freeze crystallization again, the organic solvent is one of n-hexane, methanol, ethanol, ethyl acetate, and acetonitrile, then performing solid-liquid separation again, and taking the liquid for vacuum distillation to obtain stearic acid lactone.

[0009] Preferably, the lactone acid ratio of the isomerized and hydrogenated product of oleic acid is 0.08 - 0.20.

[0010] Preferably, the organic solvent is acetonitrile.

[0011] Preferably, the mass ratio of the isomerized and hydrogenated product of oleic acid to the organic solvent is 1:2 - 12.

[0012] More preferably, the mass ratio of the isomerized and hydrogenated product of oleic acid to the organic solvent is 1:4 - 6.

[0013] Preferably, the freeze crystallization is carried out at a temperature of -25°C to 5°C.

[0014] Preferably, the time for freeze crystallization is 2h - 12h.

[0015] Preferably, the way of solid-liquid separation is suction filtration.

[0016] Preferably, the post-treatment process of the solid obtained by solid-liquid separation comprises the following operations: washing the solid obtained by solid-liquid separation, then redissolving it with a solvent, and then performing vacuum distillation to obtain fatty acids.

[0017] Preferably, the way of vacuum distillation is rotary evaporation.

[0018] Preferably, the organic solvent separated by vacuum distillation is recovered and used for dispersing the isomerized and hydrogenated product of oleic acid.

[0019] The beneficial effects of the present invention are as follows: The method for separating stearic acid lactone from mixed fatty acids of the present invention has the advantages of simple operation, high separation efficiency, low energy consumption, mild conditions, and high purity of the separated stearic acid lactone, and is suitable for large-scale industrial application.

[0020] Specifically:

[0021] 1) The present invention separates stearolactone from mixed fatty acids by single solvent freeze crystallization, which has the advantages of simple operation, high separation efficiency, low energy consumption, mild conditions, high purity of the separated stearolactone, etc. Moreover, the organic solvent used in the crystallization process can be recovered and recycled, making it suitable for large-scale industrial production;

[0022] 2) The method for separating stearolactone from mixed fatty acids of the present invention does not require high-temperature treatment, avoiding the ring-opening polymerization reaction of stearolactone under high-temperature conditions, which will not affect the yield and quality of stearolactone, and also reduces energy consumption and saves costs;

[0023] 3) The stearolactone obtained by the method for separating stearolactone from mixed fatty acids of the present invention has high purity and has very broad application prospects in the fields of chemical production, food processing, etc. Specific Embodiments

[0024] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0025] Example 1:

[0026] A method for separating stearolactone from mixed fatty acids is as follows:

[0027] 5 g of the isomerized hydrogenated product of oleic acid (the mass percentage content of stearolactone is 7.49%, the mass percentage content of fatty acids is 90.5%, and the lactone-acid ratio is 0.083) is fully dispersed in 20 g of acetonitrile at 35°C, and then placed in a constant temperature water bath at -10°C for 8 h of freezing. After suction filtration, the filtrate is subjected to rotary evaporation (the separated organic solvent is recovered and used for the dispersion of the isomerized hydrogenated product of oleic acid) to obtain stearolactone. The solid obtained by filtration is washed with 10 g of acetonitrile, redissolved with 30 g of ethyl acetate, and then subjected to rotary evaporation to obtain fatty acids.

[0028] After testing (gas chromatography analysis), the mass percentage content of stearolactone in the stearolactone product obtained in this example is 37.25%, the mass percentage content of fatty acids is 58.91%, the lactone-acid ratio is 0.632, the concentration ratio is 7.614, the recovery rate of stearolactone is 47.10%, and the mass percentage content of fatty acids in the fatty acid product is 95.94%, indicating that the stearolactone in the isomerized hydrogenated product of oleic acid has been effectively separated and enriched.

[0029] Note:

[0030] Lactone acid ratio = mass percentage of stearic acid lactone in the mixture / mass percentage of fatty acid in the mixture.

[0031] Concentration ratio = lactone acid ratio of stearic acid lactone product / lactone acid ratio of raw material.

[0032] Recovery rate of stearic acid lactone (%) = mass of stearic acid lactone product / mass of stearic acid lactone in oleic acid isomerization hydrogenation product × 100%.

[0033] Example 2:

[0034] A method for separating stearic acid lactone from mixed fatty acids, the steps are as follows:

[0035] 5 g of oleic acid isomerization hydrogenation product (mass percentage of stearic acid lactone is 7.49%, mass percentage of fatty acid is 90.5%, lactone acid ratio is 0.083) is fully dispersed in 30 g of acetonitrile at 35°C, then placed in a constant temperature water bath at 0°C and frozen for 6 h, filtered by suction, and the filtrate is taken for rotary evaporation (the separated organic solvent is recovered and used for the dispersion of oleic acid isomerization hydrogenation product) to obtain stearic acid lactone. The solid obtained by filtration is washed with 10 g of acetonitrile, redissolved with 30 g of ethyl acetate, and then rotary evaporated to obtain fatty acid.

[0036] After testing (gas chromatography analysis), the mass percentage of stearic acid lactone in the stearic acid lactone product obtained in this example is 28.25%, the mass percentage of fatty acid is 68.87%, the lactone acid ratio is 0.410, the concentration ratio is 4.940, the recovery rate of stearic acid lactone is 64.12%, and the mass percentage of fatty acid in the fatty acid product is 96.08%, indicating that the stearic acid lactone in the oleic acid isomerization hydrogenation product has been effectively separated and enriched.

[0037] Example 3:

[0038] A method for separating stearic acid lactone from mixed fatty acids, the steps are as follows:

[0039] Disperse 100 g of the isomerized and hydrogenated product of oleic acid (the mass percentage content of stearolactone is 7.49%, the mass percentage content of fatty acids is 90.5%, and the lactone-acid ratio is 0.083) in 400 g of acetonitrile at 35°C, then place it in a constant temperature water bath at -10°C and freeze for 6 h. Then, perform suction filtration. Take 3 g of the filtrate (denoted as filtrate 1), disperse it in 12 g of acetonitrile at 35°C, and then place it in a constant temperature low-temperature refrigerator at -25°C and freeze for 6 h. Then, perform suction filtration. Take the filtrate (denoted as filtrate 2) and perform rotary evaporation (the separated organic solvent is recovered and used for the dispersion of the isomerized and hydrogenated product of oleic acid) to obtain stearolactone. Take the filtered solid (the solids obtained from the two suction filtrations), wash it with 100 g of acetonitrile, then redissolve it with 250 g of ethyl acetate, and then perform rotary evaporation to obtain fatty acids.

[0040] After testing (gas chromatography analysis), the mass percentage content of stearolactone in filtrate 1 obtained in this example is 38.54%, the mass percentage content of fatty acids is 58.00%, the lactone-acid ratio is 0.664, and the concentration ratio is 8.000. The mass percentage content of stearolactone in filtrate 2 is 69.35%, the mass percentage content of fatty acids is 21.95%, the lactone-acid ratio is 3.159, and the concentration ratio is 38.060. This shows that the content of stearolactone in the isomerized and hydrogenated product of oleic acid has been further improved after two solvent freezing crystallizations.

[0041] Example 4:

[0042] A method for separating stearolactone from mixed fatty acids, the steps are as follows:

[0043] Disperse 5 g of the isomerized and hydrogenated product of oleic acid (the mass percentage content of stearolactone is 16.09%, the mass percentage content of fatty acids is 81.85%, and the lactone-acid ratio is 0.197) in 30 g of acetonitrile at 35°C, then place it in a constant temperature water bath at -5°C and freeze for 4 h. Then, perform suction filtration. Take the filtrate and perform rotary evaporation (the separated organic solvent is recovered and used for the dispersion of the isomerized and hydrogenated product of oleic acid) to obtain stearolactone. Take the filtered solid, wash it with 10 g of acetonitrile, then redissolve it with 30 g of ethyl acetate, and then perform rotary evaporation to obtain fatty acids.

[0044] After testing (gas chromatography analysis), the mass percentage content of stearolactone in the stearolactone product obtained in this example is 29.80%, the mass percentage content of fatty acids is 67.32%, the lactone-acid ratio is 0.443, and the concentration ratio is 2.249. The recovery rate of stearolactone is 48.33%. The mass percentage content of fatty acids in the fatty acid product is 90.21%. This shows that the stearolactone in the isomerized and hydrogenated product of oleic acid has been effectively separated and enriched.

[0045] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for separating stearolactone from mixed fatty acids, characterized in that, It includes the following steps: Disperse the isomerized and hydrogenated product of oleic acid in an organic solvent, which is one of n-hexane, methanol, ethanol, ethyl acetate, and acetonitrile, then carry out freeze crystallization, followed by solid-liquid separation. Take the liquid and perform vacuum distillation to obtain stearic acid lactone.

2. The method for separating stearolactone from mixed fatty acids according to claim 1, characterized in that: The lactone acid ratio of the isomerized and hydrogenated product of oleic acid is 0.08 - 0.

20.

3. The method for separating stearolactone from mixed fatty acids according to claim 1 or 2, characterized in that: The organic solvent is acetonitrile.

4. The method for separating stearolactone from mixed fatty acids according to claim 1 or 2, characterized in that: The mass ratio of the isomerized and hydrogenated product of oleic acid to the organic solvent is 1:2 - 12.

5. The method for separating stearolactone from mixed fatty acids according to claim 1 or 2, characterized in that: The freeze crystallization is carried out under the condition that the temperature is -25°C to 5°C.

6. The method for separating stearolactone from mixed fatty acids according to claim 1 or 2, characterized in that: The time of the freeze crystallization is 2h - 12h.

7. The method for separating stearolactone from mixed fatty acids according to claim 1 or 2, characterized in that: The way of the solid-liquid separation is suction filtration.

8. The method for separating stearolactone from mixed fatty acids according to claim 1 or 2, characterized in that: The post-treatment process of the solid obtained by the solid-liquid separation includes the following operations: Wash the solid obtained by the solid-liquid separation, then redissolve it with a solvent, and then perform vacuum distillation to obtain fatty acid.

9. The method for separating stearolactone from mixed fatty acids according to claim 1 or 2, characterized in that: The way of the vacuum distillation is rotary evaporation.

10. The method for separating stearolactone from mixed fatty acids according to claim 1 or 2, characterized in that: The organic solvent separated by the vacuum distillation is recovered and used for the dispersion of the isomerized and hydrogenated product of oleic acid.