JPS6220172B2 - - Google Patents

Description

[Detailed description of the invention]

(1) Background Technical Field of the Invention The present invention relates to a method for separating aliphatic glycols from non-glycols such as monools and hydrocarbons having boiling points close to these glycols. Long-chain aliphatic glycols having 5 to 19 carbon atoms are useful compounds as raw materials for synthetic resins, lubricating oils, paints, adhesives, fragrances, and the like. Glycols can also be produced synthetically, for example, by hydrogenating the corresponding dicarboxylic acid.
In such cases, expensive raw materials and auxiliary agents and many steps are required, and the resulting glycols are expensive. On the other hand, when producing higher alcohols for detergents or plasticizers through the oxation reaction of long-chain olefins, a small amount of glycols is released from the diolefins contained in the raw material olefins. By recovering these by-product glycols, glycols can be obtained at low cost. However, in the glycol fraction obtained by distilling the by-product oil during the production of higher alcohols,
It contains monools and hydrocarbons with similar boiling points, and it is difficult to selectively separate glycols from such a fraction by distillation. Prior art As a separation method for glycols, acetonitrile-water or acetonitrile-formamide-
A method is known in which glycols are selectively extracted into a polar solvent phase by liquid-liquid extraction using a polar solvent consisting of water and a non-polar solvent consisting of a saturated aliphatic hydrocarbon. (USP3088982) However, these polar solvents mainly composed of acetonitrile have low solubility in glycol,
When this method is applied to crude glycol containing a large amount of linear glycol, a precipitate is formed at room temperature. Further, when a large amount of branched glycol is included, normal phase separation may not occur. Therefore, in the method using these polar solvents mainly composed of acetonitrile, the liquid-liquid extraction operation cannot be performed satisfactorily, especially when separating glycols from by-product oil during the production of higher alcohols. Further, when such a nitrogen-containing compound is used as an extraction solvent, a trace amount of the nitrogen-containing compound remains even after the solvent is removed, which adversely affects the quality of the product glycol. (2) Summary of the Invention The present invention aims to solve the above problems, and attempts to achieve this aim by using a polar solvent consisting of methanol and water. Therefore, the method for separating glycols according to the present invention can separate aliphatic glycols having 5 to 19 carbon atoms,
In a method for separating non-glycols with boiling points close to those of non-glycols by liquid-liquid extraction using polar and non-polar solvents,
It is characterized by using a mixture of 65% by weight or more of methanol and 35% by weight or less of water. Effects By using a polar solvent consisting of methanol and water, glycols can be efficiently separated from by-product oil during the production of higher alcohols, and glycols can be obtained at low cost. Note that even if a small amount of methanol remains in the product, unlike acetonitrile, it has almost no effect on the quality of the glycol. Furthermore, linear glycols, branched glycols, and non-glycols can be separated from a fraction containing a mixture of linear and branched glycols and non-glycols, respectively. Glycols separated in this way are useful compounds as described above. (3) Detailed Description of the Invention Extraction Solvent The water content in the polar solvent used in the method of the present invention is 35% by weight or less, but its optimum value differs depending on the glycols and non-glycols to be separated. Generally, as the water content increases, the selectivity for separation of glycols and non-glycols increases, but the extraction rate of glycols decreases. Therefore, it is appropriate to use a solvent with a high water content for lower glycols with high solubility, and to use a solvent with a low water content for higher glycols with low solubility. Specifically, for example, a polar solvent with a water content of about 30% by weight is used for a glycol with a carbon number of around 5, and a polar solvent containing almost no water is used for a glycol with a carbon number of around 19. However, for glycols having about 8 to 16 carbon atoms, polar solvents with a water content of about 15 to 25% by weight are particularly preferred. Suitable non-polar solvents usually have a carbon number of about
12 or less saturated aliphatic and alicyclic hydrocarbons. Typical examples include hexane, heptane, octane, cyclohexane, and mixtures thereof. Furthermore, when a polar solvent with a low water content is used, it is appropriate to use a non-polar solvent with a large carbon number, such as dodecane, in order to improve phase separation. Volume ratio of polar solvent to non-polar solvent (ml/ml)
The optimum value is determined by the composition of glycol and non-glycol components, but it is usually 1/5.
A range of 5 to 5 is used. Extraction conditions The ratio of the extraction solvent (polar solvent + non-polar solvent) to the glycol-non-glycol mixture (hereinafter referred to as crude glycol) is approximately 1 (ml/g) or more, but generally a smooth extraction operation is performed. For this purpose, 3 or more is preferable. The optimal ratio varies depending on the composition of the crude glycol, the composition of the extraction solvent, the purity and recovery rate of the desired glycol, or the extraction method, but is usually 50%
It is as follows. The extraction temperature is 0°C to the boiling point of the extraction solvent, usually 20 to
A range of 40°C is used. Although it is desirable to heat the mixture to a temperature slightly higher than room temperature to promote dissolution, subsequent operations such as phase separation can be carried out at room temperature. The extraction method may be either a batch method or a continuous method. Depending on the required purity of glycol, the number of extractions in a batch system or the number of stages in a continuous system is appropriately selected. Application method Glycols obtained by the method of the present invention are usually a mixture of linear components and branched components, but in order to further separate this into linear components and branched components, conventionally known methods In this method, this mixture can be heated and dissolved in an aromatic solvent and then cooled to selectively crystallize the linear components. (for example,
USP3067260) Conversely, the method of the present invention can be used to crystallize and separate linear glycol from crude glycol in advance by a known method, and then separate glycols and non-glycols mainly consisting of remaining branched components. You can also do it. Furthermore, according to the method of the present invention, crude glycol is dissolved in a polar solvent and a non-polar solvent, and then cooled to below room temperature or left at room temperature for a long time to precipitate crystals mainly composed of linear glycols, Thereafter, it is also possible to separate the three components at once by obtaining branched glycols from the polar solvent of the mother liquor and obtaining non-glycols from the non-polar solvent. Experimental Examples Example 1 Distillation of heavy residues produced when producing detergent alcohols with 14 and 15 carbon atoms by hydroformylation of a mixture of linear olefins with 13 and 14 carbon atoms. A fraction containing linear and branched glycols (161-200°C/0.7mmHg) was obtained. The composition of this product is 56.3% glycol, 43.7% non-glycol consisting mainly of monoalcohols,
The ratio of linear forms of glycol was 55.0%. To 10.0 g of this crude glycol, 25.0 ml of a polar solvent consisting of 76% methanol and 24% water and n
- Add 25.0 ml of heptane and heat to about 40°C to dissolve. No solid formation was observed even after about 2 hours of standing at room temperature, and phase separation was easily performed. After removing the solvent from each phase, the water-methanol phase contained 89.7% glycol and 10.3% non-glycol.
5.3 g of a white solid consisting of
4.5 g of a highly viscous liquid was obtained. The ratio of the amount of glycol extracted into the polar solvent to the amount of glycol contained in the crude glycol (hereinafter referred to as glycol yield) was 84.4%. Comparative Example A polar solvent consisting of 1.0 g of the crude glycol used in Example 1, 65% by weight of acetonitrile, and 35% by weight of water.
2.5 ml and n-heptane 2.5 ml were added, and the mixture was heated and dissolved at about 70°C. As soon as the solution was taken out of the water bath, solids adhered to the walls of the vessel, making smooth phase separation impossible. Example 2 An experiment similar to Example 1 was carried out by varying the water content in the polar solvent and the ratio of extraction solvent to crude glycol. The water content in the polar solvent was 12% by weight, 24% by weight, and 35% by weight. The volume ratio of polar solvent to nonpolar solvent was fixed at 1/1, and the ratio of total solvent to crude glycol (hereinafter referred to as ml/g solvent ratio) was varied from 3 to 36. The purity of the obtained glycol was as shown in Table-1.

[Table] As the solvent ratio increases, in both cases,
The purity of the glycol is increased, and with a large excess of solvent, 100% purity can be obtained in just one extraction. Furthermore, for the crude glycol of this composition, a polar solvent of methanol (76) and water (24) is optimal. Example 3 The entire heavy residue produced as a by-product during the production of detergent alcohols having 12 and 13 carbon atoms by hydroformylation of a mixture of linear olefins having 11 and 12 carbon atoms was used as a sample. The composition of this stuff is glycol
17.8%, of which the proportion of linear forms was 63.8%. To 4.0 g of this crude glycol were added 20.0 ml of a polar solvent consisting of 65% methanol and 35% water and 40.0 ml of n-hexane, and the same extraction as in Example 1 was carried out. As a result, the purity of the glycol obtained from the polar solvent phase was 91.6%, and the yield was 68.4%. Example 4 In an experiment similar to Example 1, crude glycol was dissolved in polar and non-polar solvents and 1
When left standing day and night, a white solid was formed. As a result of separation into the solid phase, polar solvent phase, and non-polar solvent phase, the purity of glycol in the solid phase was 89.0%, the ratio of linear forms was 79.4%, the yield was 46.4%, and the purity of glycol in the polar solvent phase was 89.0%. The ratio of linear products was 41.2%, and the yield was 47.8%. Example 5 When the polar solvent phase separated in Example 4 was further left at room temperature for one day and night, crystals mainly composed of linear glycol precipitated again. The solvent was removed from the mother liquor from which the crystals were separated to obtain a white solid rich in branched glycols. Add the non-glycol components in the heavy residue to this, and add the glycol
A crude glycol having a composition of 48.0% and a linear proportion of 4.4% was prepared. This crude glycol was subjected to the same extraction operation as in Example 1, and as a result, the purity of the glycol obtained from the polar solvent phase was 91.9% and the yield was 90.7%. Example 6 A mixture of 2.0 g of 1,5-pentanediol and 2.0 g of n-decyl alcohol was added to 65% by weight of methanol.
- 10.0 ml of polar solvent consisting of 35% by weight of water and n-
It was dissolved in 10.0 ml of heptane and extracted in the same manner as in Example 1. As a result, the purity of the glycol obtained from the polar solvent phase was 92.4%, and the yield was 69.9%. Also, methanol 76% by weight - water 24% by weight
When a polar solvent consisting of the following was used, the purity of the glycol was 83.5% and the yield was 80.3%. Example 7 Using oleyl alcohol as a raw material, in the presence of a catalyst consisting of cobalt carbonyl and tri-n-octylphosphine, synthesis gas (H ₂ /CO molar ratio 2/1) was applied at 70 Kg/cm ² at 200°C for 6 hours. A hydroformylation reaction was carried out under the following conditions, and the product was recrystallized from toluene to obtain a glycol having 19 carbon atoms. A mixture of 0.5 g of this glycol and 0.5 g of non-glycol components obtained from the heavy residue by-produced during the production of detergent alcohol was used as a sample, and 10.0 ml of methanol was added as a polar solvent and 5.0 ml of n-dodecane was added as a non-polar solvent. Extraction was carried out using the result,
The purity of the glycol obtained from the polar solvent phase was 60.3%.
The yield was 89.6%.

Claims (1)

[Claims] 1 aliphatic glycols having 5 to 19 carbon atoms;
In a method for separating non-glycols with boiling points close to those of non-glycols by liquid-liquid extraction using polar and non-polar solvents,
A method for separating glycols, characterized by using a mixture of 65% by weight or more of methanol and 35% by weight or less of water.