CN118594022A - Extraction agent and extraction distillation separation method - Google Patents

Abstract

The invention provides an extractant and an extractive distillation separation method. The extractant comprises any two of calcium chloride, magnesium chloride and magnesium sulfate. The extractant provided by the invention can break the azeotropic system of trioxymethylene and water, so that trioxymethylene can be separated simply and efficiently. Meanwhile, the extractant has the advantages of high boiling point and good thermal stability, can be stable in liquid raw materials, is not easy to volatilize and pyrolyze, and avoids the extra separation and recovery energy consumption caused by the traditional extractant escaping into the vapor phase with the trioxymethylene. In addition, the extractant itself is low in price, which reduces the cost of extractive distillation separation.

Description

Extraction agent and extraction distillation separation method

Technical Field

The invention belongs to the technical field of trioxymethylene separation, and in particular relates to an extractant and an extractive distillation separation method.

Background Art

Trioxane is widely used in life as a disinfectant, additive, stabilizer, pesticide, binder, high-quality solid fuel, etc. As an important chemical raw material, it is considered to be a good substitute for formaldehyde, especially when used to replace formaldehyde in anhydrous environments, trioxane plays an extremely important role. Trioxane is also mainly used to produce polyoxymethylene engineering plastics, polyoxymethylene dimethyl ether, a series of bulk chemicals and fine chemicals, etc., and plays a key role in the modern chemical industry. At the same time, trioxane is an important platform compound for the development of methanol downstream. Vigorously developing the trioxane industry will have great strategic significance for absorbing excess production capacity in the methanol industry and promoting the development of coal chemical industry.

The sulfuric acid method is the most mature method for synthesizing trioxymethylene in the world and is also the most widely used method for synthesizing trioxymethylene in my country. This method usually uses a 60.0wt% formaldehyde aqueous solution as a raw material, and then uses sulfuric acid as a catalyst under heating conditions to distill the product after the reaction. The top distillate is mainly composed of trioxymethylene + water + formaldehyde + impurities, among which trioxymethylene and water have an azeotropic point, which is not conducive to subsequent separation and purification operations.

In order to separate and purify trioxymethylene, the researchers used the cooling crystallization method, taking advantage of the fact that the solubility of a solute in a solvent changes with temperature. As the temperature decreases, the solubility of trioxymethylene in various solvents shows a downward trend. By cooling the vapor phase distillate of the crude trioxymethylene product, most of the cooled trioxymethylene can be obtained, and then the crystals are separated, melted and distilled to remove impurities again to obtain high-purity trioxymethylene. However, cooling crystallization requires a lot of energy, and the quality of the trioxymethylene particles obtained by filtration is difficult to guarantee, and it is easy to form a crust on the surface of the heat exchanger in the subsequent process. In addition, the industrial scale-up of the cooling crystallization method for separating trioxymethylene is limited, which is not conducive to continuous operation.

To make up for the above defects, the researchers also adopted the extraction-distillation method, adding the extractant to the binary or multicomponent system, and using the different solubility of solutes in different solvents, the extractant can extract the target product from the original solvent, and then separate the extractant from the target product by distillation. The most important of these is the extraction process; however, commonly used extractants such as benzene, toluene, dichloromethane and other organic solvents have certain toxicity and volatility. These extractants will inevitably evaporate during the operation, which will not only cause environmental damage, but also threaten human health. In addition, the amount of extractant used is large, and the energy consumption of solvent recovery is high.

In summary, there is currently no extraction agent that can achieve simple, efficient and pollution-free extraction of trioxymethylene.

Summary of the invention

The invention provides an extractant, which is used to solve the problem in the prior art that it is difficult to separate trioxymethylene in a simple, efficient and low-energy manner, and has little pollution to the environment.

The invention provides an extraction and rectification separation method, which adopts the above-mentioned extractant to participate in the extraction and rectification separation treatment of the trioxymethylene crude solution. The method is simple and easy to implement, has low energy consumption for extraction and rectification separation, and does not pollute the environment.

In one aspect, the present invention provides an extractant comprising any two of calcium chloride, magnesium chloride and magnesium sulfate.

Furthermore, the mass ratio of any two salts among the calcium chloride, the magnesium chloride and the magnesium sulfate is (0.1-0.9): (0.1-0.9).

On the other hand, the present invention provides an extractive distillation separation method for a crude trioxymethylene solution, which uses the extractant according to claim 1 or 2 to participate in the extractive distillation separation treatment of the crude trioxymethylene solution.

Further, the trioxymethylene crude solution comprises trioxymethylene, formaldehyde, water and impurities;

Wherein, the mass ratio of the trioxymethylene, the formaldehyde, the water and the impurities is (0.1-90): (0-15): (10-84.9): (0-10);

Wherein, the impurities include at least one of formic acid, methanol, methylal and methyl formate.

Furthermore, the mass ratio of the extractant to the crude trioxymethylene solution is (0.01-1):1.

Furthermore, when the mass ratio of the trioxymethylene, the formaldehyde, the water and the impurities is (60-90):(0-15):(10-25):(0-3), the mass ratio of any two salts of the calcium chloride, the magnesium chloride and the magnesium sulfate is (0.4-0.6):(0.4-0.6).

Furthermore, the temperature of the extraction distillation separation treatment is 90-150°C.

Furthermore, the method further comprises: condensing the vapor phase material obtained by the extraction, rectification and separation treatment to obtain a trioxymethylene extract; allowing at least a portion of the trioxymethylene extract to participate in the extraction, rectification and separation treatment again;

Wherein, the reflux ratio of the trioxymethylene extract is (0.1-10):1.

Furthermore, the method further comprises: performing secondary distillation or cooling crystallization treatment on at least part of the trioxymethylene extract to obtain a trioxymethylene product.

Furthermore, it also includes:

The liquid phase material obtained by the extraction, rectification and separation treatment is subjected to reduced pressure rotary evaporation treatment to obtain a formaldehyde aqueous solution, and the formaldehyde aqueous solution is used as a reaction raw material to participate in the synthesis of trioxymethylene.

The extractant provided by the present invention can break the azeotropic system of trioxymethylene and water, so that trioxymethylene can be separated simply and efficiently. At the same time, the extractant has the advantages of high boiling point and good thermal stability, can be stable in liquid raw materials, is not easy to volatilize and pyrolyze, and avoids the additional separation and recovery energy consumption caused by the traditional extractant escaping with trioxymethylene into the vapor phase. In addition, the extractant itself is low in price, which reduces the cost of extraction, distillation and separation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is an extractive distillation separation device used in an embodiment of the present invention;

FIG. 2 is a gas chromatographic detection of the vapor phase material obtained in Example 1 of the present invention.

Description of reference numerals:

1: Feed inlet;

2: First thermometer;

3: Heating belt;

4: Second thermometer;

5: Condenser;

6: Vapor phase sampling port;

7: Valve;

8: Liquid sampling port;

9: Heating unit;

10: Magnetic stirring bar;

11: Extraction distillation unit.

DETAILED DESCRIPTION

In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

In one aspect, the present invention provides an extractant comprising any two of calcium chloride, magnesium chloride and magnesium sulfate.

The extractant provided by the invention comprises calcium chloride, magnesium chloride and magnesium sulfate. The synergistic effect of calcium chloride, magnesium chloride and magnesium sulfate can significantly enhance the electrostatic effect between the extractant and water molecules, so that the water molecules gather around the ions, and finally the water molecules and the ions are combined in the form of ion pairs or water molecules surrounding the ions, thereby greatly reducing the activity of water, increasing the relative volatility of trioxymethylene with respect to water, breaking the azeotropic system of trioxymethylene and water, and realizing the extraction and rectification separation of trioxymethylene; meanwhile, the extractant provided by the invention has low price, high boiling point and good thermal stability, so the extractant can be stable in the liquid phase and will not escape into the vapor phase with trioxymethylene, thus avoiding the evaporation loss and pyrolysis loss of traditional organic solvents, reducing the cost of raw materials, and further avoiding the subsequent separation energy consumption and recovery energy consumption caused by the traditional extractant distilling out of the trioxymethylene vapor phase system, thereby greatly reducing the extraction and rectification separation cost.

The extractant provided by the present invention can break the azeotropic system of trioxymethylene and water, so that trioxymethylene can be separated simply and efficiently. At the same time, the extractant has the advantages of high boiling point and good thermal stability, can be stable in liquid raw materials, is not easy to volatilize and pyrolyze, and avoids the additional separation and recovery energy consumption caused by the traditional extractant escaping with trioxymethylene into the vapor phase. In addition, the extractant itself is low in price, which reduces the cost of extraction, distillation and separation.

Furthermore, the mass ratio of any two salts among calcium chloride, magnesium chloride and magnesium sulfate is (0.1-0.9):(0.1-0.9).

The inventors have found that when the ratio of each component in the extractant provided by the present invention is further limited, it is easier to break the azeotropic system of trioxymethylene and water, increase the volatility of trioxymethylene relative to water, and further improve the effect of separating and extracting trioxymethylene.

On the other hand, the present invention provides a method for extracting and rectifying the trioxymethylene crude solution, which uses the above-mentioned extractant to participate in the extracting and rectifying separation treatment of the trioxymethylene crude solution.

At present, in the crude trioxymethylene solution obtained by synthesizing trioxymethylene in industry, trioxymethylene and water have an azeotropic point, which is difficult to separate by ordinary distillation operation; therefore, the present invention provides an extractant capable of simply and efficiently extracting and distilling trioxymethylene, so that the extractant can participate in the extracting and distilling separation treatment of the crude trioxymethylene solution;

Specifically, in the extractive distillation separation treatment, a raw material system including a crude trioxymethylene solution and an extractant is subjected to an extractive distillation separation treatment to obtain a vapor phase material rich in trioxymethylene and a liquid phase material rich in a formaldehyde aqueous solution; the extractive distillation separation treatment can break the azeotropic point of trioxymethylene and water, reduce the activity of water, and increase the volatility of trioxymethylene relative to water, thereby realizing the extractive distillation separation treatment of trioxymethylene; since the extractant provided by the present invention has the advantages of high boiling point, good thermal stability, etc., it can be stable in the liquid phase raw material and is not easy to volatilize or pyrolyze, thereby avoiding the extra separation and recovery energy consumption caused by the traditional extractant escaping into the vapor phase with the trioxymethylene, and reducing the cost of extractive distillation separation.

The present invention provides an extraction and distillation separation method, which adopts the above-mentioned extractant to participate in the extraction and distillation separation treatment of the trioxymethylene crude solution. The method is simple and easy to implement, has low energy consumption for extraction and distillation separation, is pollution-free to the environment, and can simply and efficiently implement the extraction and distillation separation treatment of trioxymethylene.

The trioxymethylene crude solution includes trioxymethylene, formaldehyde, water and impurities;

Wherein, the mass ratio of trioxymethylene, formaldehyde, water and impurities is (0.1-90): (0-15): (10-84.9): (0-10);

Wherein, the impurities include at least one of formic acid, methanol, methylal and methyl formate.

It can be understood that the crude trioxymethylene solution obtained by the current industrial synthesis of trioxymethylene includes trioxymethylene, formaldehyde, water and impurities, wherein the impurities include at least one of formic acid, methanol, methylal and methyl formate; since trioxymethylene and water have an azeotropic point, the content of each component in the crude trioxymethylene solution affects the separation effect. The inventors have found that when the mass ratio of trioxymethylene, formaldehyde, water and impurities is (0.1-90): (0-15): (10-84.9): (0-10), the effect of extractive distillation separation can be further improved, the concentration of trioxymethylene in the vapor phase obtained by extractive distillation separation can be further improved, and it is more conducive to breaking the azeotropic system of trioxymethylene and water.

Furthermore, the mass ratio of the extractant to the crude trioxymethylene solution is (0.01-1):1.

The amount of extractant used is related to the extraction and distillation separation effect of trioxymethylene. The inventors have found through a lot of creative work that when the mass ratio of the extractant to the crude trioxymethylene solution is (0.01-0.2):1, the extractant can better play its role, which is more conducive to breaking the azeotropic point of trioxymethylene and water at a low cost and improving the extraction and distillation separation effect of trioxymethylene.

In a specific embodiment, when the mass ratio of trioxymethylene, formaldehyde, water and impurities is (60-90):(0-15):(10-25):(0-3), the mass ratio of any two salts of calcium chloride, magnesium chloride and magnesium sulfate is (0.4-0.6):(0.4-0.6).

Specifically, when the mass ratio of trioxymethylene, formaldehyde, water and impurities is (60-90):(0-15):(10-25):(0-3), by further limiting the ratio of each component of the extractant, the synergistic effect between calcium chloride, magnesium chloride and magnesium sulfate can be further utilized to extract trioxymethylene in the trioxymethylene crude solution, thereby better realizing the efficient separation of trioxymethylene.

Optionally, the temperature of the extractive distillation separation treatment is 90-150°C.

The extraction temperature has an important influence on the extraction distillation separation method. The temperature will affect the vaporization and condensation process of the substance, thereby affecting the separation effect and product purity. The inventors found that when the extraction distillation separation treatment provided in the present application adopts the conditions of 90-150°C, the efficiency of the extraction distillation separation can be further improved.

Furthermore, the method further comprises: condensing the vapor phase material obtained by the extraction, rectification and separation treatment to obtain a trioxymethylene extract; allowing at least a portion of the trioxymethylene extract to participate in the extraction, rectification and separation treatment again;

Wherein, the reflux ratio of the trioxymethylene extract is (0.1-10):1.

It can be understood that, through the extraction and distillation separation process, a vapor phase material rich in trioxymethylene can be obtained, and the vapor phase material is condensed to obtain a trioxymethylene extract; and at least a portion of the trioxymethylene extract is re-involved in the extraction and distillation separation process, so that formaldehyde and other substances in the trioxymethylene extract can be further recovered, and the trioxymethylene concentration in the trioxymethylene extract can be further increased;

The reflux ratio of the trioxymethylene extract in the present invention refers to the ratio of the reflux part to the produced part. When the reflux ratio is (0.1-10):1, the trioxymethylene concentration can be further increased.

Furthermore, the method further comprises: performing secondary distillation or cooling crystallization treatment on at least part of the trioxymethylene extract to obtain a trioxymethylene product.

It can be understood that since the concentration of trioxymethylene in the trioxymethylene extract is greatly increased compared with the concentration before the extraction and distillation, performing secondary distillation or cooling crystallization at this time will not cause a large energy consumption.

Optionally, the method further comprises: subjecting the liquid material obtained by the extraction, rectification and separation treatment to a reduced pressure rotary evaporation treatment to obtain a formaldehyde aqueous solution, and using the formaldehyde aqueous solution as a reaction raw material to participate in the synthesis of trioxymethylene.

Hereinafter, an extractant provided by the present invention is described in detail through specific examples.

Example 1

The extractive distillation separation device used in this embodiment is shown in FIG1 ; the extractive distillation separation device comprises: an extractive distillation unit 11 (an improved Othmer vapor-liquid equilibrium kettle), a first thermometer 2 (a high-precision mercury thermometer) and a second thermometer 4 (a high-precision mercury thermometer), a heating belt 3, a condenser 5, and a heating unit 9 (a heat-collecting constant-temperature heating magnetic stirrer);

The extraction and rectification unit 11 is used to implement the extraction and rectification separation process, the first thermometer 2 is used to monitor the temperature of the liquid phase material obtained by the extraction and rectification separation process, the second thermometer 4 is used to monitor the temperature of the vapor phase material obtained by the extraction and rectification separation process, the heating belt 3 is used to heat the vapor phase material obtained by the extraction and rectification separation process to prevent it from condensing and precipitating, the condenser 5 is used to condense the vapor phase material, and the heating unit 9 is used to provide heat for the extraction and rectification separation process;

The extraction and distillation unit 11 is provided with a feed port 1, a vapor sampling port 6, a valve 7, and a liquid sampling port 8; and a magnetic stirrer 10 is placed in the extraction unit and the heating unit 9, and the magnetic stirrer 10 is used to make the oil bath temperature and the vapor-liquid phase equilibrium system temperature uniform.

This embodiment includes the following steps:

(1) adding 60 g of trioxymethylene, 40 g of a 15.0 wt % formaldehyde aqueous solution of trioxymethylene and an extractant comprising 4.8 g of calcium chloride and 3.2 g of magnesium chloride into an improved Othmer vapor-liquid equilibrium reactor through a feed inlet, and performing extractive distillation separation at 120° C. to obtain a vapor phase material and a liquid phase material;

(2) The vapor phase material is condensed at 50°C to obtain a trioxymethylene extract; after the vapor and liquid phases reach equilibrium (at this time, the temperatures of the vapor and liquid phases are consistent), sampling and analysis are performed.

Example 2

The difference between this embodiment and embodiment 1 is that the extractant is 5g of magnesium chloride and 5g of magnesium sulfate.

Example 3

The difference between this embodiment and embodiment 1 is that the extractant is 4 g of magnesium sulfate and 6 g of calcium chloride.

Example 4

The difference between this embodiment and embodiment 1 is that the temperature of the extraction distillation separation treatment is 160°C.

Example 5

The difference between this embodiment and embodiment 1 is that the crude trioxymethylene solution is 60g trioxymethylene, 40g 37.5wt% formaldehyde aqueous solution

Example 6

The difference between this embodiment and embodiment 1 is that the crude trioxymethylene solution contains 60 g trioxymethylene and 40 g water.

Example 7

The difference between this embodiment and embodiment 1 is that the crude trioxymethylene solution is 70 g trioxymethylene and 30 g 15.0 wt % formaldehyde aqueous solution.

Example 8

The difference between this embodiment and embodiment 1 is that the crude trioxymethylene solution is 80 g trioxymethylene and 20 g 15.0 wt % formaldehyde aqueous solution.

Embodiment 9

The difference between this embodiment and embodiment 1 is that the crude trioxymethylene solution is 90 g trioxymethylene and 10 g 15.0 wt % formaldehyde aqueous solution.

Comparative Example 1

The difference between this comparative example and Example 1 is that no extractant is added.

Comparative Example 2

The difference between this comparative example and Example 5 is that no extractant is added.

Comparative Example 3

The difference between this comparative example and Example 6 is that no extractant is added.

Comparative Example 4

The difference between this comparative example and Example 7 is that no extractant is added.

Comparative Example 5

The difference between this comparative example and Example 8 is that no extractant is added.

Comparative Example 6

The difference between this comparative example and Example 9 is that no extractant is added.

Comparative Example 7

The difference between this comparative example and Example 1 is that the extractant is 10.0 g of magnesium sulfate.

Comparative Example 8

The difference between this comparative example and Example 1 is that the extractant is 10.0 g of sodium bisulfate.

Comparative Example 9

The difference between this comparative example and Example 1 is that the extractant is 10.0 g of lithium sulfate.

Comparative Example 10

The difference between this comparative example and Example 1 is that the extractant is 8.0 g of calcium chloride.

Comparative Example 11

The difference between this comparative example and Example 1 is that the extractant is 8.0 g of magnesium chloride.

Comparative Example 12

The difference between this comparative example and Example 1 is that the extractant is 6.0 g of potassium chloride.

Comparative Example 13

The difference between this comparative example and Example 1 is that the extractant is 5.0 g of sodium chloride.

Comparative Example 14

The difference between this comparative example and Example 1 is that the extractant is 10.0 g of sodium bromide.

Comparative Example 15

The difference between this comparative example and Example 1 is that the extractant is 10.0 g of sodium nitrate.

Comparative Example 16

The difference between this comparative example and Example 1 is that the extractant is 10.0 g of sodium sulfate.

Comparative Example 17

The difference between this comparative example and Example 1 is that the extractant is 10.0 g of potassium sulfate.

Comparative Example 18

The difference between this comparative example and Example 1 is that the extractant is 10.0 g of zinc sulfate.

Test Example 1

The trioxymethylene content in the vapor phase material and the liquid phase material was analyzed by gas chromatography, wherein the gas chromatography detection diagram of the vapor phase material obtained in Example 1 is shown in FIG2 ; the formaldehyde content in the vapor phase material and the liquid phase material was determined by sodium sulfite acid-base titration method; the water content in the vapor phase material was determined by Karl Fischer moisture analyzer;

The above test results are shown in Table 1.

Table 1

As can be seen from Table 1, no extractant was added to Comparative Examples 1-6, and the content of trioxymethylene in the azeotropic composition was about 70%. However, from the experimental data of Examples 1, 7-9, it can be seen that after using the extractant proposed by the present invention, the azeotropic system formed by trioxymethylene and water can be effectively broken, and the separation effect of trioxymethylene can be significantly improved. Moreover, compared with Comparative Examples 7-18, the extractant of the present invention has a better effect. From the experimental data of Examples 1, 5, 6 and Comparative Examples 1, 2, 3, it can be seen that the presence of formaldehyde in the system will further promote the extractant to break the azeotropic equilibrium, which is beneficial to the purification and separation of trioxymethylene.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. An extractant, characterized in that it comprises any two of calcium chloride, magnesium chloride and magnesium sulfate. 2. The extractant according to claim 1, characterized in that the mass ratio of any two salts of the calcium chloride, the magnesium chloride and the magnesium sulfate is (0.1-0.9): (0.1-0.9). 3. A method for extracting and distilling a crude trioxymethylene solution, characterized in that the extractant according to claim 1 or 2 is used to participate in the extracting and distilling separation treatment of the crude trioxymethylene solution. 4. The extractive distillation separation method according to claim 3, characterized in that the crude trioxymethylene solution comprises trioxymethylene, formaldehyde, water and impurities; Wherein, the mass ratio of the trioxymethylene, the formaldehyde, the water and the impurities is (0.1-90): (0-15): (10-84.9): (0-10); Wherein, the impurities include at least one of formic acid, methanol, methylal and methyl formate. 5. The extractive distillation separation method according to claim 3 or 4, characterized in that the mass ratio of the extractant to the crude trioxymethylene solution is (0.01-1):1. 6. The extractive distillation separation method according to any one of claims 3 to 5, characterized in that when the mass ratio of the trioxymethylene, the formaldehyde, the water and the impurities is (60-90):(0-15):(10-25):(0-3), the mass ratio of any two salts of calcium chloride, magnesium chloride and magnesium sulfate is (0.4-0.6):(0.4-0.6). 7. The extractive distillation separation method according to any one of claims 3 to 6, characterized in that the temperature of the extractive distillation separation treatment is 90-150°C. 8. The extractive distillation separation method according to any one of claims 3 to 7, characterized in that it further comprises: condensing the vapor phase material obtained by the extractive distillation separation process to obtain a trioxymethylene extract; allowing at least a portion of the trioxymethylene extract to participate in the extractive distillation separation process again; Wherein, the reflux ratio of the trioxymethylene extract is (0.1-10):1. 9. The extraction and distillation separation method according to claim 8, characterized in that it further comprises: subjecting at least part of the trioxymethylene extract to secondary distillation or cooling crystallization to obtain a trioxymethylene product. 10. The extractive distillation separation method according to claim 8 or 9, characterized in that it also comprises: The liquid phase material obtained by the extraction, rectification and separation treatment is subjected to reduced pressure rotary evaporation treatment to obtain a formaldehyde aqueous solution, and the formaldehyde aqueous solution is used as a reaction raw material to participate in the synthesis of trioxymethylene.