CN111646923B

CN111646923B - Method for purifying hydroxyacetonitrile by freeze concentration

Info

Publication number: CN111646923B
Application number: CN202010561439.7A
Authority: CN
Inventors: 申剑; 刘文静; 张洪; 刘晓青
Original assignee: Shanxi Science And Technology Resources And Large Instruments Open Sharing Center
Current assignee: Shanxi Science And Technology Resources And Large Instruments Open Sharing Center
Priority date: 2020-06-18
Filing date: 2020-06-18
Publication date: 2022-11-15
Anticipated expiration: 2040-06-18
Also published as: CN111646923A

Abstract

The invention discloses a method for purifying hydroxyacetonitrile by freeze concentration, which comprises the steps of adjusting the pH value of a hydroxyacetonitrile solution containing water to 1-2, cooling the solution to-5 to-10 ℃, stirring for the first time, crystallizing for 2-6 hours, then continuously cooling to-20 to-30 ℃, stirring again, crystallizing for 12-24 hours, filtering out ice crystals, and melting the ice crystals at room temperature to obtain the concentrated hydroxyacetonitrile. The content of the hydroxyl acetonitrile separated and purified by the method is between 90 and 95 percent, and the average yield is more than 97 percent. If higher content of hydroxyl acetonitrile is needed, the content of the hydroxyl acetonitrile can be further increased to 96-98 percent by vacuum evaporation.

Description

Method for purifying hydroxyacetonitrile by freeze concentration

Technical Field

The invention relates to the field of chemical processes, in particular to a method for purifying hydroxyacetonitrile by freeze concentration.

Background

Hydroxy acetonitrile: also known as Glycolonitrile, glycolonitrile, chemical formula HOCH ₂ CN, with a molecular weight of 57.05, a boiling point of 183 ℃, a freezing point of-72 ℃, a specific gravity of 1.104, generally a colorless oily liquid, is a hydrocyanic acid derivative and is the simplest cyanohydrin.

As an important cyanohydrin organic intermediate, hydroxyacetonitrile is widely applied to the fields of food, medicine, pesticide, dye and the like, and is a main raw material for producing fine chemical products such as glycine, creatine (food additive), hydantoin (medical intermediate), glyphosate (pesticide), indigo blue (dye) and the like. Because industrial formaldehyde solution which is a main raw material for synthesizing the hydroxyacetonitrile usually contains a large amount of water, the concentration of the commercially available hydroxyacetonitrile solution is low, the hydroxyacetonitrile content is only 45-50%, and the water content is about 50%, so that the large amount of water can increase the difficulty and the cost of post-treatment separation of downstream products and can directly influence the use effect of the hydroxyacetonitrile in other fields such as mineral flotation, metal plating and the like. In addition, the hydroxyacetonitrile is easy to polymerize and has poor thermal stability, and is easy to decompose under heating to generate hydrocyanic acid highly toxic gas, so that the conventional distillation method for purifying the hydroxyacetonitrile is low in yield and has great potential safety hazard.

In the prior art, the conventional method for purifying the hydroxyacetonitrile is to extract the hydroxyacetonitrile in a hydroxyacetonitrile solution by using diethyl ether, then dry and remove water, distill and remove the diethyl ether under normal pressure, then distill under reduced pressure, and collect fractions at about 100 ℃ (1.33 kPa) to obtain a high-concentration hydroxyacetonitrile product. The method needs to consume ether, drying agent and other chemical reagents, the distillation temperature is high (more than 100 ℃) to cause the partial decomposition of the hydroxy acetonitrile, the potential safety hazard of highly toxic gas leakage exists, and the experimental operation and the device design are complex.

In the patent ZL201611170164.4, a first extractant n-hexane is used for extracting nonpolar organic impurities in a hydroxyacetonitrile solution, a second extractant ether is used for extracting the hydroxyacetonitrile in the residual hydroxyacetonitrile solution, then drying and dewatering are carried out, reduced pressure distillation is carried out for removing the ether, then nitrogen protection and reduced pressure distillation are carried out on the hydroxyacetonitrile in a Schlenk line system, and fractions of 50-60 ℃ (0.20 kPa) are collected to obtain a high-concentration hydroxyacetonitrile product. The method needs to consume chemical reagents such as normal hexane, diethyl ether, drying agent and the like, the distillation temperature is higher (more than 60 ℃) to cause the partial decomposition of the hydroxy acetonitrile, a small amount of highly toxic gas leakage potential safety hazards exist, and the experimental operation and the device design are complex.

Therefore, in order to solve the above problems of the prior art, a new method for purifying hydroxyacetonitrile needs to be found.

Disclosure of Invention

One aspect of the invention provides a method for purifying hydroxyacetonitrile by freezing concentration, aiming at the defects that in the prior art, hydroxyacetonitrile is easy to be decomposed by heating, the yield is low, the energy consumption is high, and the design of experimental operation and devices is complicated.

The technical scheme provided by the invention is as follows:

a method for purifying hydroxyacetonitrile by freeze concentration comprises the steps of adjusting the pH value of a hydroxyacetonitrile solution containing water to 1-2, cooling the solution to-5 to-10 ℃, stirring for the first time, crystallizing for 2-6 hours, then continuously cooling to-20 to-30 ℃, stirring again, crystallizing for 12-24 hours, filtering out ice crystals, and melting the ice crystals at room temperature to obtain the concentrated hydroxyacetonitrile.

Compared with the traditional evaporation concentration, the freeze concentration method for purifying the hydroxyacetonitrile solution in the technical scheme of the invention is more suitable for the thermosensitive aqueous solution.

Preferably, the hydroxyacetonitrile to be subjected to freeze concentration and purification in the present invention is an aqueous hydroxyacetonitrile solution.

In addition, the above-mentioned aqueous hydroxyacetonitrile solution may contain nonpolar impurities, which may be removed by a conventional method. For example, a method described in "a method for separating and purifying hydroxyacetonitrile" (patent No. ZL 201611170164.4). Preferably, in one embodiment of the present invention, a step of removing the non-polar impurities with an extractant is further included before the pH adjustment. The extractant may be, for example, petroleum ether, cyclohexane.

More preferably, the water-containing hydroxyacetonitrile solution contains water in a proportion of 49 to 54wt%.

More preferably, the hydroxyacetonitrile to be subjected to freeze concentration and purification in the invention is a hydroxyacetonitrile solution containing only an aqueous phase.

Further, in one embodiment of the present invention, the above-mentioned hydroxyacetonitrile solution containing only an aqueous phase contains water in a proportion of 49 to 54% by weight.

Preferably, in one embodiment of the present invention, the stirring rate for the initial stirring and crystallization is 100 to 150rpm.

In a preferred mode of the present invention, a nucleating agent may also be added. Preferably, in one embodiment of the present invention, a nucleating agent is added during the first stirring and crystallization to a final concentration of 1 to 10 g/L.

In the present invention, any suitable nucleating agent can achieve the objects of the present invention, but preferably, the nucleating agent is nanosilica.

Nano silicon dioxide (English name nano-silicon dioxide) is an inorganic chemical material, commonly called white carbon black. Due to the ultrafine nanometer scale, the size range is 1-100 nm, so the material has a plurality of unique properties, such as optical performance for resisting ultraviolet rays, and the aging resistance, the strength and the chemical resistance of other materials can be improved.

Preferably, in one embodiment of the present invention, the stirring rate for the re-stirring and crystallization is 200 to 250rpm.

Preferably, in one embodiment of the present invention, the adjustment of the pH value to 1 to 2 is performed by using one or more of sulfuric acid, phosphoric acid or hydrochloric acid. More preferably, the adjustment of the pH value to 1-2 is performed using dilute sulfuric acid.

In the invention, the steps of initial freezing, deep freezing and filtering can be repeatedly and circularly carried out, thereby increasing the effect of freeze concentration and purification. Preferably, the filtrate after filtering out the ice crystals is continuously circulated and repeated for adjusting the pH value and the subsequent steps.

Preferably, the step of further concentrating the obtained concentrated hydroxyacetonitrile by vacuum evaporation is further included after the ice crystals are melted at room temperature to obtain the concentrated hydroxyacetonitrile. Namely, the obtained concentrated hydroxyacetonitrile is transferred into a negative pressure resistant container, and is vacuumized and evaporated at room temperature until the weight of the hydroxyacetonitrile does not change, so that the high-purity hydroxyacetonitrile is obtained.

The invention has the beneficial effects that:

the freeze concentration method of the invention has the following advantages:

1) The whole process is operated at low temperature/room temperature, thereby avoiding the thermal sensitive component of the hydroxyacetonitrile from being heated and decomposed and improving the recovery rate of the hydroxyacetonitrile;

2) The production of hydrocyanic acid is avoided, and the potential safety hazard of highly toxic gas leakage is eliminated;

3) No new chemical reagent is introduced, so that the raw material cost is saved, and the three wastes are greatly reduced;

4) The experimental operation is simple, and the production efficiency and the operation safety are improved;

5) The experimental device is simple, and the equipment investment is reduced;

6) Less three wastes (only a small amount of waste liquid with low content is generated), low energy consumption, environmental protection and energy saving.

Through analysis and calculation, the separated and purified hydroxyacetonitrile content is between 90 and 95 percent, and the average yield is more than 97 percent. If high-concentration hydroxy acetonitrile which can be obtained by vacuum evaporation is needed, the content of the hydroxy acetonitrile is further increased to 96-98 percent.

Drawings

FIG. 1 is a process flow diagram of the present invention for purifying hydroxyacetonitrile by freeze concentration.

Detailed Description

The invention discloses a method for purifying hydroxyacetonitrile by freezing concentration, which can be realized by appropriately improving process parameters by taking the contents of the method as reference by a person skilled in the art. It is expressly intended that all such alterations and modifications which are obvious to those skilled in the art are deemed to be incorporated herein by reference, and that the techniques of the invention may be practiced and applied by those skilled in the art without departing from the spirit, scope and range of equivalents of the invention.

In the present invention, unless otherwise specified, scientific and technical terms used herein have the meanings that are commonly understood by those skilled in the art.

In order to make those skilled in the art better understand the technical solution of the present invention, the following detailed description of the present invention is provided with reference to specific embodiments.

Example 1:

adjusting the pH value of a glycolonitrile water solution with water content of 48% to 1.8 by using dilute sulfuric acid, cooling to-8 ℃, adding a nano-silicon dioxide nucleating agent under the stirring condition (the stirring speed is 130 rpm), keeping the temperature and stirring for 4 hours, then continuously cooling to-25 ℃, stirring and crystallizing for 18 hours (the stirring speed is 230 rpm), filtering out ice crystals, melting at room temperature to obtain high-concentration glycolonitrile, and recycling the filtrate. Through analysis and calculation, the average content of the separated and purified hydroxyacetonitrile is 92.6 percent, and the average yield reaches 97.4 percent.

Example 2:

adjusting the pH value of a glycolonitrile water solution with water content of 48% to 1.5 by using dilute sulfuric acid, cooling to-10 ℃, adding a nano-silica nucleating agent under the stirring condition (the stirring speed is 130 rpm), keeping the temperature and stirring for 3 hours, then continuously cooling to-20 ℃, stirring and crystallizing for 24 hours (the stirring speed is 230 rpm), filtering out ice crystals, melting at room temperature to obtain high-concentration glycolonitrile, and recycling the filtrate. Through analysis and calculation, the average content of the separated and purified hydroxyacetonitrile is 91.8 percent, and the average yield reaches 98.2 percent.

Example 3:

adjusting the pH value of a hydroxyacetonitrile water solution with water content of 48% to 1.8 by using dilute sulfuric acid, cooling to-10 ℃, adding a nano silicon dioxide nucleating agent under the stirring condition (the stirring speed is 150 rpm), keeping the temperature and stirring for 4h, then continuously cooling to-25 ℃, stirring and crystallizing for 24h (the stirring speed is 250 rpm), filtering out ice crystals, melting at room temperature to obtain high-concentration hydroxyacetonitrile, and recycling the filtrate. Through analysis and calculation, the average content of the separated and purified hydroxyacetonitrile is 90.5 percent, and the average yield reaches 98.6 percent.

Example 4:

adjusting the pH value of a hydroxyacetonitrile water solution with water content of 45% to 2.0 by using diluted phosphoric acid, cooling to-6 ℃, adding a nano silicon dioxide nucleating agent under the stirring condition (stirring speed of 130 rpm), keeping the temperature and stirring for 6h, then continuously cooling to-25 ℃, stirring and crystallizing for 12h (stirring speed of 250 rpm), filtering out ice crystals, melting at room temperature to obtain high-concentration hydroxyacetonitrile, and recycling the filtrate. Through analysis and calculation, the average content of the separated and purified hydroxyacetonitrile is 93.2 percent, and the average yield reaches 97.1 percent.

Example 5:

adjusting the pH value of a hydroxyacetonitrile aqueous solution with water content of 45% to 1.5 by using dilute hydrochloric acid, cooling to-5 ℃, adding a nano-silica nucleating agent under the stirring condition (the stirring speed is 100 rpm), keeping the temperature and stirring for 2 hours, then continuously cooling to-28 ℃, stirring and crystallizing for 24 hours (the stirring speed is 200 rpm), filtering out ice crystals, melting at room temperature to obtain high-concentration hydroxyacetonitrile, and recycling the filtrate. Through analysis and calculation, the average content of the separated and purified hydroxyacetonitrile is 90.3 percent, and the average yield reaches 97.6 percent.

Example 6:

adjusting the pH value of a hydroxyacetonitrile water solution with water content of 45% to 1.0 by using dilute sulfuric acid, cooling to-5 ℃, keeping the temperature and stirring for 6h (stirring speed of 100 rpm), then continuously cooling to-30 ℃, stirring and crystallizing for 18h (stirring speed of 250 rpm), filtering out ice crystals, melting at room temperature to obtain high-concentration hydroxyacetonitrile, and recycling the filtrate. Through analysis and calculation, the average content of the separated and purified hydroxyacetonitrile is 83.3 percent, and the average yield reaches 95.5 percent.

Example 7:

adjusting the pH value of a hydroxyacetonitrile water solution with water content of 45% to 1.5 by using dilute sulfuric acid, cooling to-5 ℃, adding a nano silicon dioxide nucleating agent under the stirring condition (stirring speed 100 rpm), keeping the temperature and stirring for 2h, then continuously cooling to-28 ℃, stirring and crystallizing for 12h (stirring speed 200 rpm), filtering out ice crystals, melting at room temperature to obtain high-concentration hydroxyacetonitrile, and recycling the filtrate.

The high concentration hydroxyacetonitrile (consisting of hydroxyacetonitrile and a trace amount of water) obtained above was transferred to a negative pressure resistant vessel and the hydroxyacetonitrile solution was evaporated under vacuum at room temperature and 0.2kPa until the mass did not decrease. Through analysis and calculation, the average content of the separated and purified hydroxyacetonitrile is 97.8 percent, and the average yield reaches 97.1 percent.

Comparative example 1:

adjusting the pH value of a glycolonitrile water solution with the water content of 48 percent to 1.5 by using dilute sulfuric acid, cooling to-25 ℃, stirring and crystallizing for 35 hours (the stirring speed is 230 rpm), filtering out ice crystals, melting at room temperature to obtain more concentrated glycolonitrile, and recycling the filtrate. The average content of the separated and purified hydroxyacetonitrile is 78.5 percent by analysis and calculation, and the average yield reaches 95.8 percent.

Comparative example 2:

adjusting the pH value of the hydroxyl acetonitrile water solution with water content of 48 percent to 1.5 by using dilute sulfuric acid, cooling to-20 ℃, stirring and crystallizing for 40 hours (the stirring speed is 230 rpm), filtering out ice crystals, melting at room temperature to obtain more concentrated hydroxyl acetonitrile, and recycling the filtrate. Through analysis and calculation, the average content of the separated and purified hydroxyacetonitrile is 76.3 percent, and the average yield reaches 96.6 percent.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.

Claims

1. A method for purifying hydroxyacetonitrile by freeze concentration is characterized in that the pH value of a hydroxyacetonitrile solution containing water is adjusted to 1-2, the solution is cooled to-5 to-10 ℃, stirred for the first time and crystallized for 2-6 hours, then the temperature is continuously reduced to-20 to-30 ℃, stirred again and crystallized for 12-24 hours, ice crystals are filtered out, and the condensed hydroxyacetonitrile is obtained by melting the ice crystals at room temperature;

the hydroxyacetonitrile to be frozen, concentrated and purified is a hydroxyacetonitrile solution only containing an aqueous phase; the hydroxyl acetonitrile solution only containing the water phase contains 49-54 wt% of water.

2. The method of claim 1, wherein the hydroxyacetonitrile solution containing water is adjusted to a pH of 1.8.

3. The method of claim 1, wherein the stirring rate for the initial stirring and crystallization is 100 to 150rpm.

4. The method according to claim 1 or 3, wherein a nucleating agent is added during the primary stirring and crystallization to a final concentration of 1 to 10 g/L.

5. The method of claim 4, wherein the nucleating agent is nanosilica.

6. The method according to claim 1, wherein the stirring rate for the re-stirring and crystallization is 200 to 250rpm.

7. The method of claim 1, wherein the adjusting the pH to 1-2 is performed using one or more of sulfuric acid, phosphoric acid, or hydrochloric acid.

8. The method of claim 7, wherein the adjusting the pH to 1-2 is performed using dilute sulfuric acid.

9. The method of claim 1, wherein the filtrate after filtering out ice crystals is continuously circulated to repeat the steps of adjusting pH and thereafter.

10. The method as claimed in claim 1, wherein the step of further concentrating the obtained concentrated hydroxyacetonitrile by vacuum evaporation after the ice crystals are melted at room temperature to obtain the concentrated hydroxyacetonitrile.