CN1226261C - Liquid-liquid extraction method of diethoxymethane and ethanol aqueous solution - Google Patents

Abstract

The liquid-liquid extraction method of diethoxymethane (DEM) and ethanol aqueous solution: use polyhydric alcohol as extractant, carry out liquid-liquid extraction to diethoxymethane and ethanol aqueous solution, after layer separation, extractive phase rectification treatment, processing After the solvent is recycled, the raffinate contains higher purity DEM. The optimization scheme is: adopt cross-current extraction and counter-current extraction: the aqueous solution of raw material DEM and ethanol is sent into the extraction tower and the extraction agent glycerin flowing into the extraction tower is reversely contacted, and the raffinate is passed through static stratification section 3 (the liquid is in this section stop flow time of more than 10 minutes), the raffinate contains more than 99.6% of DEM, the extraction agent mixture at the bottom of the extraction tower is separated through the rectification tower, and the ethanol solution is obtained at the top of the rectification tower. The invention can effectively separate DEM and ethanol aqueous solution, after separation, the purity of DEM reaches more than 99.6%, and the yield of DEM reaches more than 98.9%.

Description

Liquid-liquid extraction method of diethoxymethane and ethanol aqueous solution

technical field

The invention relates to a chemical extraction process, in particular to a liquid-liquid extraction method of diethoxymethane (DEM) and ethanol aqueous solution.

Background technique

Diethoxymethane (DEM) is an important solvent and pharmaceutical intermediate, and it is generally produced by acid catalysis and chloramphenicol by-product method. Regardless of the acid catalysis method or the chloramphenicol by-product method, in the separation process, the precision rectification method is used to separate the mixed product. Since the boiling point of DEM in the product is close to the azeotropic point of ethanol and water, the reflux ratio (R) of the rectification method is used. Controlling it at about 30:1 not only consumes a lot of energy, but also only about 95% of DEM can be obtained. At present, there are no reports on DEM extraction and purification at home and abroad. Therefore, the development of effective separation technology is not only conducive to improving product purity, but also conducive to reducing energy consumption.

Contents of the invention

The purpose of the invention is to provide a new DEM extraction and purification technology, so that the mixture of DEM and ethanol aqueous solution can be effectively separated, so that the DEM purity can reach more than 99.6%, and the DEM yield can reach more than 98.9%.

The technical scheme for accomplishing the above-mentioned invention task is: use polyhydric alcohol as extraction agent, the mass ratio of raw material and solvent is 1: 0.5～4, carry out liquid-liquid extraction to the ethanol aqueous solution of diethoxymethane, after layer separation, extraction phase Rectification treatment, the raffinate contains higher purity DEM, and the solvent is recycled after treatment. The "polyol" mentioned here is the key technology of the present invention: select a kind of solvent (S) that is insoluble in DEM, easily soluble in ethanol and water, and by extraction, the raffinate phase can obtain more than 99.6% of DEM, and the extraction phase After being rectified in a rectifying tower, the solvent (S) is recycled. From the perspective of stratification, halogenated hydrocarbons, halogenated aromatics, esters, and ethers are easily soluble in DEM and ethanol, but insoluble (slightly soluble) in water. Without the above conditions, organic acids, ethylene glycol, and ammonia and sulfones have no stratification phenomenon, and do not have extraction conditions, only polyols exhibit stratification phenomenon, so to study the distribution of DEM, ethanol and water in several polyols, the mass ratio of raw materials and solvents is 1:1 The measured results are shown in Table 1. From table 1 result, glycerol has separation effect preferably, in conjunction with other factors, it is comparatively suitable to determine that glycerol is extractant, so the first-selected glycerol of the present invention is extractant. Under the condition of different mass ratios of raw materials and solvents, the distribution coefficient measurement results are shown in Figure 3, and the results in Figure 3 show that when the mass ratios of raw materials and solvents are 1:1-2, the separation effect is the best.

Table 1:

Partition coefficients of DEM, ethanol and water in polyols

Table 2 Liquid-liquid extraction separation results material composition raw material F Solvent Si one extraction secondary extraction triple extraction E1 R1 E2 R2 E3 R3 flow 20 20 29.810 10.190 20.239 9.951 20.064 9.887 DEM 0.5000 0.0000 0.0142 0.9670 0.0130 0.9899 0.0088 0.9962 ethanol 0.4500 0.0000 0.8842 0.0316 0.9851 0.0080 0.9901 0.0023 water 0.0500 0.0000 0.1016 0.0014 0.0019 0.0015 0.0011 0.0015

The specific flow of the extraction process is: firstly, the liquid-liquid extraction process diagram shown in Figure 1 and Figure 2 is designed, and the countercurrent extraction is adopted in Figure 2: the ethanol aqueous solution of the raw material DEM is sent into the extraction tower and the extraction agent glycerin flowing into the extraction tower is in reverse contact , the raffinate is through static layering section 3 (the liquid stops flowing in this section for more than 10 minutes), the raffinate contains more than DEM99.6%, and the extraction agent mixed solution at the bottom of the extraction tower is separated through a rectification tower, and the rectification tower The ethanol aqueous solution is obtained at the top, and the extractant (S) at the bottom of the tower is recycled.

Advantages of the present invention: using the extraction process shown in Fig. 1 and Fig. 2 and the determined extractant can effectively separate DEM and ethanol aqueous solution, after separation, the purity of DEM reaches more than 99.6%, and the yield of DEM reaches more than 98.9%, and the extraction phase is rectified The tower 4 is processed, and the ethanol aqueous solution containing DEMO.21% can be obtained at the top of the tower, which can be processed into absolute ethanol for recycling. The extraction process can be carried out at normal temperature, and the energy consumption in the production process is low, which is about 35% lower than that of the rectification method.

Description of drawings

Fig. 1 is the cross-flow extraction process flowchart of embodiment 1;

Fig. 2 is a countercurrent extraction process flow chart;

Fig. 3 is a graph showing the influence of solvent mass ratio on partition coefficient.

Detailed ways

Embodiment 1, with reference to Fig. 1, process diagram shown in Fig. 2, raw material is the aqueous ethanol solution of DEM, and the content of DEM, ethanol and water is respectively 50%, 45%, 5% (mass content), raw material is 20Kg, pure extraction Agents S1-S3 are 20Kg respectively. In the case of 298.2K, according to the process flow shown in Figure 1, the mixed solution is sent to the extractor and fully stirred with the inflowing extractant glycerin, and the layers are separated, the extraction phase (E1～E3) and the raffinate phase (R1～R3) Equilibrium is reached in each stage of extractor, and the final extraction phase E1+E2+E3 is processed by a rectifying tower. After separation, the composition of E1～E3 and R1～R3 is shown in Table 2 (excluding the amount of solvent). The results of Table 2 show that , after three extractions, the yield of DEM reaches 98.9%, and the purity can reach 99.6% (mass content). After the treatment, the solvent (S) is recycled, and the tower top (E) is further processed to obtain ethanol. The process is suitable for the extraction and separation of the mixture of DEM and ethanol water in any ratio, and the ratio of the extractant to the mixture is 1-4:1. In the extraction process Fig. 2, raw material (F) is fed into the extraction static section 1 of the extraction tower and the extraction agent (S) flowing into the extraction tower is reversely contacted in the extraction section 2, and the raffinate is passed through the static stratification section 3 (liquid In this section stop flow time more than 10 minutes), the raffinate contains more than DEM99.6%, and the extraction agent mixed solution at the bottom of the extraction tower is separated through the rectification tower 4 (5 is the feed position among the figure), and the rectification tower 4 top Obtain ethanol aqueous solution, and the extractant (S) at the bottom of the tower is recycled. The extraction section 2 can use different fillers or trays, but the actual number of plates is more than 6. The extraction phase is left to stand in the static section 1, and the residence time of the liquid in this section should be more than 10 minutes. The actual plate number of the rectifying tower 4 reaches more than 5.

Claims (6)

1, a kind of liquid-liquid extraction method of diethoxymethane and ethanol aqueous solution: take polyhydric alcohol as extraction agent, the mass ratio of raw material and solvent is 1: 0.5～4, carries out liquid-liquid extraction to diethoxymethane and ethanol aqueous solution After extraction and layer separation, the extract phase is rectified, and the solvent is recycled after treatment, and the raffinate contains diethoxymethane with relatively high purity. 2. The liquid-liquid extraction method of diethoxymethane and ethanol aqueous solution according to claim 1, characterized in that the mass ratio of the raw material to the solvent is 1:1-2. 3, according to the liquid-liquid extraction method of diethoxymethane and ethanol aqueous solution described in claim 2, it is characterized in that, concrete steps are: the extraction that raw material (F) is sent into extraction tower through feeding position (5) leaves standstill Section (1) is in reverse contact with the extractant (S) flowing into the extraction tower in the extraction section (2), and the raffinate is left to stand for stratification. More than 99.6% of diethoxymethane, the extractant mixed solution at the bottom of the extraction tower is separated through the rectification tower (4), and the rectification tower (4) tops to obtain an aqueous ethanol solution, and the extractant (S) at the bottom of the tower is recycled. 4. The liquid-liquid extraction method of diethoxymethane and ethanol aqueous solution according to claim 1, 2 or 3, characterized in that the actual number of plates in the extraction section is more than 6. 5. The liquid-liquid extraction method of diethoxymethane and ethanol aqueous solution according to claim 4, characterized in that the actual number of plates in the rectification column is more than 5. 6. The liquid-liquid extraction method of diethoxymethane and ethanol aqueous solution according to claim 1, 2 or 3, characterized in that the actual number of plates in the rectification column is more than 5.

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