JPS585895B2 - Separation method of organic acids - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating formic acid or formic acid and acetic acid from an aqueous organic acid solution containing them.

Regarding the method of fractionally extracting organic acids and mineral acids from aqueous solutions containing organic acids and mineral acids using solvent extraction technology, the present inventors have disclosed Japanese Patent Application No. 46-55377 and Japanese Patent Application No. 49-79882.
No., Special Publication No. 13794, or Special Publication No. 1979-
Although it is disclosed in No. 11148, it has the drawback that the recovery concentration is low.

Particularly, even if the organic acid or mineral acid is recovered from the discharged aqueous solution, there is a problem in that it is difficult to dispose of the recovered acid if water balance cannot be maintained between the site and the place where it is used.

Furthermore, there is a drawback that organic acids cannot be separated from each other using acids such as formic acid and acetic acid.

The present invention was made for the purpose of improving the deficiencies of the above-mentioned conventional methods.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows a flow sheet of a method for separating formic acid from an aqueous solution containing formic acid according to the present invention.

First, in the formic acid extraction step, the formic acid-containing liquid is brought into contact with an organic solvent diluted with an extractant selected from the amine group with a petroleum-based hydrocarbon diluent to extract formic acid into the organic solvent. The formic acid is separated and recovered by contacting it with sulfuric acid in a formic acid stripping step to strip the formic acid in sulfuric acid, or by directly applying heat in the formic acid stripping step to distill off the formic acid.

The extractant selected from the amine group used in the method of the present invention is an amine selected from the group of primary amines to quaternary amines, and the primary amine is represented by RNH, where R is generally an alkyl amine having 4 to 20 carbon atoms.

A typical primary amine is the following formula (1) The following amines can be listed.

As the secondary amine (R2NH), those in which R represents an alkyl group having 4 to 20 carbon atoms are used, and the amine represented by the following formula (2) can be listed as a representative example.

The tertiary amine (R3N) is an amine in which R is an alkyl group having 4 to 20 carbon atoms, and a typical example is an amine represented by the following formula (3).

Quaternary amines are represented by (R3N-CH3)x, where R is 4
An alkyl group of ~20 carbon atoms, where X is a halogen or a hydroxyl group.

R in the above-mentioned secondary amines to quaternary amines may be the same or different, and although representative examples are only given for each amine, amines within the range specified for R may be used. can be used, and any mixture of primary to quaternary amines can also be used.

In addition, the group of phosphoric acid esters refers to phosphorus-containing compounds represented by the following formula: (In the above formula, R may be the same or different from each other, and 4 to 1
is an alkyl or aromatic group of 8 carbon atoms) (
Representative examples of each group from (a) to (d) are (a)
(b) dibutylbutylphosphonate (DBBP), (c) ethyldiphenylphosphinate (EDPP), and (d) trioctylphosphine oxide (TOPO).

A mixture of (a) to (d) can also be used.

The diluent used in the present invention may be an aromatic hydrocarbon, an aliphatic hydrocarbon, or a mixture thereof, but kerosene is preferred.

The concentration of the extractant in the organic solvent is 2-30% by volume.

If necessary, a higher alcohol containing 8 to 34 carbon atoms may be added to the organic solvent as a modifier.

FIG. 2 shows a flow sheet of a method for separately recovering each acid from formic acid and acetic acid.

The separation and recovery of formic acid and acetic acid will be explained below with reference to FIG.

Aqueous solution containing formic acid and acetic acid (liquid containing formic acid monoacetic acid)
Formic acid is selectively extracted according to the formula shown below by contacting an extractant selected from the amine group with an organic solvent diluted with a diluent hydrocarbon (extractant concentration 10 to 80% by volume) (where = part Acetic acid is also co-extracted): R3N+HCOO−+H”=R3NH”HCOO−
(5) Next, by bringing the organic solvent containing formic acid into contact with an aqueous solution containing a large amount of formic acid in a washing step, acetic acid co-extracted with formic acid in the formic acid extraction step is back-extracted into the formic acid aqueous solution.

The organic solvent containing an amine as an extractant is back-extracted into an acetic acid:formic acid aqueous solution according to the following formula: The Jingjun aqueous solution from which acetic acid has been back extracted is sent before the formic acid extraction step, and a new formic acid-monoacetic acid-containing aqueous solution is extracted. The aqueous solution remaining after the formic acid extraction is sent to the acetic acid extraction step.

The organic solvent from which acetic acid has been back-extracted in the washing process is sent to the formic acid stripping process, where the formic acid is separated from the organic solvent by treatment similar to the formic acid stripping process shown in Figure 1 or by contacting with an aqueous solution containing an alkali metal. The organic solvent is then regenerated and recycled to the formic acid extraction step.

On the other hand, the formic acid extraction process raffinate aqueous solution sent to the acetic acid extraction process is mixed with an organic solvent diluted with a hydrocarbon diluent using phosphoric acid ester as an extractant, and acetic acid is extracted into the organic solvent in the acetic acid extraction process. Either the acetic acid is removed and recovered from the organic solvent by contacting the organic solvent with water in the acetic acid stripping step, or the acetic acid is distilled and recovered by applying heat in the acetic acid stripping step, and the organic solvent is regenerated and sent to the acetic acid extraction step. Recirculate.

The aqueous solution containing a large amount of formic acid that is introduced into the washing process to back-extract acetic acid is a solution that has a higher concentration of formic acid than the formic acid in the organic solvent that has undergone the formic acid extraction step, and allows back-extraction of acetic acid according to equation (6). Concentration of formic acid, and more formic acid than other parts《
refers to an aqueous solution containing formic acid in an organic solvent that has undergone an extraction process,
It can be easily determined by knowing the acetic acid concentration.

The present invention will be specifically described below with reference to Examples.

Example 1 Formic Acid Extraction Step The following aqueous solutions containing formic acid and formalin were used in the experiments: was extracted.

Extraction was performed according to a conventional method. The results listed in Table 1 were obtained.

In the table, the secondary amine is the amine of formula (2) above.
Equilibrium extraction curves (room temperature) at nominal formic acid concentrations using the concentrations and types of extractants shown in the table are shown in Section 3 (7.5% secondary amine), Fig. 5 (25% TOPO), and Fig. 6 ( 3
0%TBP+30%DBBP).

3 Formic acid stripping step (1) Stripping with sulfuric acid Formic acid in the initial organic phase shown in Table 2 was stripped using H2SO4 at a concentration of 57.8 g/l as a stripping solution.

The exfoliation is carried out by the following reaction: The results are listed in Table 2 below: Figure 4 shows the exfoliation equilibrium curve for each formic acid concentration using H2S04 at a concentration of 57.8 g/l. .

(2) Stripping by heating distillation The results of heating distillation are listed in Table 3: The organic solvents (a) to (c) after stripping were used for re-extraction, and it was confirmed that there was no difference in extraction performance from before distillation. Example 2 Formic acid extraction step Table 4 lists the results of performing the formic acid extraction step in the formic acid extraction step in Figure 2 from the aqueous solution containing formic acid and acetic acid described in Table 4 below: Both acetic acid and formic acid When an aqueous solution containing
O, residual kerosene organic solvent) and Figure 6 (30% T
As shown in (BP+30% DBBP, residual kerosene organic solvent), acetic acid and formic acid exhibit almost the same extraction and distribution ratio, indicating that they are co-extracted and that selective stripping is not easy.

However, as shown in Table 4 above, formic acid is mainly selectively extracted using an organic solvent containing an amine.

Furthermore, looking at FIG. 3, it is even clearer that formic acid is extracted more selectively than acetic acid.

Washing process Table 4 and Figure 3 show that acetic acid is also slightly co-extracted in the formic acid extraction process.

While the extraction and distribution ratio of formic acid is 1.7, the extraction and distribution ratio of acetic acid is as low as 0.2.

Therefore, if an organic solvent containing formic acid and acetic acid is washed with an aqueous solution containing a large amount of formic acid, the formic acid in the organic solvent (organic phase) is extracted and the acetic acid is stripped from the organic phase.

Table 5 shows the results when an amine organic solvent containing formic acid monoacetic acid was washed with a formic acid aqueous solution of about 13 g/l to about 19 g/l: As can be seen from the above table, acetic acid co-extracted into the organic phase was extracted. By contacting with an aqueous solution containing a large amount of formic acid with a high distribution ratio, only acetic acid can be selectively washed from the organic phase.

Alternatively, when H2S04 is brought into contact, only HCOOH can be separated from the organic phase if the contact ratio is such that the operating line is located above the equilibrium curve shown by the Rollo line in FIG.

Peeling Step (1) Peeling with Sulfuric Acid (Washing) A formic acid-containing organic solvent containing co-extracted acetic acid can also selectively peel off phosphoric acid by bringing it into contact with sulfuric acid.

Table 6 shows the results when 60 g/l of sulfuric acid was used as the cleaning solution (stripping solution): It can be seen from the above table that most of the formic acid was removed.

(2) Stripping by Distillation In order to strip the formic acid in the three types of organic solvents shown in the organic phase after equilibrium in Table 5, the formic acid in the residual liquid after distillation was measured at 125° C. to 140° C.

The results are shown in Table 7: Acetic acid extraction process An acetic acid aqueous solution (initial aqueous phase in Table 8 below) which simulates the acetic acid-containing raffinate after formic acid has been extracted from the formic acid extraction process was added to the phosphorus described in Table 6. The results of extraction using an organic solvent containing an acid ester extractant (the diluent is n-paraffin with a boiling point of 210°C) are listed in Table 8.

[Brief explanation of the drawing]

Figures 1 and 2 are flow sheets for carrying out the method of the present invention, Figure 3 is the extraction equilibrium curve of formic acid and acetic acid in an organic solvent containing an amine extractant, and Figure 4 is a flowchart for the extraction of formic acid or acetic acid in an organic solvent containing an amine. The peeling equilibrium curves using sulfuric acid and FIGS. 5 and 6 are the equilibrium curves for formic acid and acetic acid extraction using organic solvents containing phosphate ester extractants.

Claims (1)

[Claims] 1. An organic solvent obtained by diluting an extractant selected from the amine group selected from primary amines to quaternary amines with a petroleum-based hydrocarbon diluent in an aqueous solution containing formic acid. It is characterized by selectively extracting formic acid in the aqueous solution by contacting it, and removing the formic acid and regenerating the organic solvent by contacting the organic solvent from which the formic acid has been extracted with sulfuric acid or by heating and distilling it. A method for separating organic acids. 2. By contacting an aqueous solution containing mainly formic acid and acetic acid with an extractant selected from the group of primary amines to quaternary amines and an organic solvent diluted with a petroleum-based hydrocarbon diluent, a small proportion of mainly formic acid is added. of acetic acid is extracted, the co-extracted acetic acid is selectively removed from the organic solvent by contacting the organic solvent with an aqueous solution containing a large amount of formic acid, and the remaining organic solvent containing formic acid is brought into contact with sulfuric acid. , the organic solvent is regenerated by stripping the formic acid from the organic solvent by distillation, and the raffinate aqueous solution after contacting the aqueous solution containing formic acid and acetic acid with the organic solvent is treated with an extractant selected from the group consisting of phosphoric acid esters. An organic method characterized by extracting acetic acid into an organic solvent by contacting it with an organic solvent diluted with a hydrocarbon diluent, and exfoliating the acetic acid from the organic solvent by heating the organic solvent or contacting it with water. Method of separating acids.