CN107620206B

CN107620206B - Process for amidooximation of cyano compounds

Info

Publication number: CN107620206B
Application number: CN201710790380.7A
Authority: CN
Inventors: 王宁; 陈辉; 王东; 赵雪媚
Original assignee: University of Electronic Science and Technology of China; Hainan University
Current assignee: University of Electronic Science and Technology of China; Hainan University
Priority date: 2017-09-05
Filing date: 2017-09-05
Publication date: 2020-02-07
Anticipated expiration: 2037-09-05
Also published as: CN107620206A

Abstract

The invention relates to an amidoximation method of a cyano compound, and belongs to the technical field of amidoxime group material preparation. The technical problem to be solved by the invention is to provide an amidoximation method of a cyano compound with high cyano conversion rate. The method comprises the step of reacting hydroxylamine salt solution with a cyano compound in a supercritical fluid to obtain an amidoxime group material. The method of the invention can accelerate the reaction rate and shorten the reaction time. Meanwhile, the conversion rate of the cyano can be improved. In addition, the method of the invention has the advantages of simplicity, low equipment requirement, less investment and easy realization of large-scale industrial production.

Description

Process for amidooximation of cyano compounds

Technical Field

The invention relates to an amidoximation method of a cyano compound, and belongs to the technical field of amidoxime group material preparation.

Background

Amidoxime-based materials containing-C (NOH) NH₂The material of the structure has lone pair electrons in hydroxylamine oxime group and amino group, and the valence electron orbit of the metal cation is empty, so the material is easy to chelate with metal ions. Due to excellent metal ion chelating performance, diversified varieties, high selectivity and high adsorption capacity, the amidoxime group material can be applied to the metal ion adsorption process in many fields, and can also be applied to the fields of heterogeneous catalysts, dye degradation, light control, photocatalysis, electro-corrosion and the like.

Currently, most amidoxime materials are obtained by reducing a cyano group with hydroxylamine hydrochloride, and the reaction equation is as follows:

amidoximation of cyano compounds has long been studied, and researchers at home and abroad have been improving the amidoxime reaction process in order to achieve higher yield and simplify the control of the reaction process, thereby making the method suitable for industrial production.

In the thesis of "amidoxime polyacrylonitrile fiber preparation and research on uranyl and competitive ion adsorption performance" (Zhao Huan, 4 months 2015) by Master academic academy, PAN fiber and hydroxylamine hydrochloride were reacted to adjust pH to 7.0, and the influence of reaction temperature and time on the conversion rate of cyano group was studied, and from the test results, the conversion rate of cyano group was 53% at the maximum. The conversion rate is low and needs to be further improved.

The invention patent with publication number CN1313278A discloses a method for synthesizing amidoxime, which comprises the steps of synthesizing amidoxime by taking a cyano compound and hydroxylamine as raw materials, heating in a sectional manner, stirring at a lower temperature for a certain time, heating to continue stirring for a certain time, distilling under reduced pressure to remove a solvent, and recrystallizing to obtain an amidoxime product. The method needs sectional heating, the process is complex, and additional materials are added to promote the reaction. In addition, the yield of the method is different according to the cyano compound, and the yield can be basically improved to more than 80 percent to be further improved.

Therefore, the existing method has low conversion rate or yield of the cyano group, and the process is complex or the reaction time is too long, so that the cost is too high, and the method is not suitable for industrial production.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide a method for amidoximation of a cyano compound with high conversion rate of a cyano group.

The amidoxime method of the cyano compound of the invention is that hydroxylamine salt solution reacts with the cyano compound in supercritical fluid to obtain amidoxime material.

Preferably, hydroxylamine salt solution with the pH value of 6-10 and a cyano compound are added into a high-pressure reaction kettle, carbon dioxide is introduced into the high-pressure reaction kettle, the pressure is adjusted to enable the carbon dioxide to be in a supercritical state, and the mixture is reacted for more than 2 hours at the temperature of 45-110 ℃ to obtain the amidoxime group material.

Preferably, the reaction is carried out for 4 to 12 hours at a temperature of between 45 and 110 ℃.

Preferably, the pressure is 8-25 MPa.

More preferably, the molar ratio of the cyano group of the cyano compound to the hydroxylamine group of the hydroxylamine salt is 1:1 to 8.

Preferably, the concentration of the hydroxylamine salt solution is 0.2-1.5 mol/L.

Further preferably, the solvent of the hydroxylamine salt solution is at least one of water, methanol, ethanol, N-Dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

Preferably, the pH value of the hydroxylamine salt solution is adjusted to 6-10 by adding a pH adjusting agent, wherein the pH adjusting agent is at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate.

Further preferably, the hydroxylamine salt is hydroxylamine hydrochloride or hydroxylamine sulfate.

More preferably, the stirring speed during the reaction is 500 to 2000 r/min.

Preferably, the cyano compound is polyacrylonitrile, phenylacetonitrile or acrylonitrile.

Compared with the prior art, the invention has the following beneficial effects:

the invention can accelerate the reaction rate and shorten the reaction time by carrying out the reaction in the supercritical fluid. Meanwhile, the conversion rate of the cyano can be improved.

The method is simple, has low equipment requirement and less investment, and is easy to realize large-scale industrial production.

Drawings

FIG. 1 is an infrared spectrum of a PAN fiber and a product after amidoximation according to example 1 of the invention.

Detailed Description

Supercritical fluids, such as supercritical carbon dioxide, water, methanol, ethanol, isopropanol, ammonia, benzene, toluene, p-xylene, methane, hexane, propane, cyclohexane, ethylene, propylene, etc., have both gas-like diffusion properties with zero interfacial tension, "pore-free" and liquid-like solvency. The inventors of the present invention have found that the conversion rate of a cyano compound can be improved by performing a conventional amidoxime reaction in a supercritical fluid.

Preferably, the supercritical fluid is supercritical carbon dioxide. The supercritical carbon dioxide is a common supercritical fluid, has no toxicity, no pollution, inertia, low price and environmental protection, and the supercritical state (the critical temperature is 31.1 ℃, and the critical pressure is 7.38Mpa) is easy to realize, has low requirement on equipment, has small investment and is easy to realize large-scale industrial production. And the supercritical carbon dioxide is easy to separate from the product, impurities are not easy to generate, and the recovery and the recycling of the carbon dioxide can be realized. In a supercritical fluid system, amidoximation is carried out on a cyano compound, so that the reaction rate is favorably accelerated, and carbon dioxide plays a certain catalytic role in the process of converting cyano into amidoxime, thereby achieving the purpose of further improving the conversion rate of cyano.

Specifically, the following specific method is preferably employed: adding a hydroxylamine salt solution with the pH value of 6-10 and a cyano compound into a high-pressure reaction kettle, introducing carbon dioxide into the high-pressure reaction kettle, adjusting the pressure to enable the carbon dioxide to be in a supercritical state, and reacting at 45-110 ℃ for 2-12 hours to obtain the amidoxime group material.

The volume of the added reactants cannot exceed half of the volume of the reaction kettle for the safety of the reaction and the smooth progress of the reaction.

In the present invention, the amidoxime material is obtained by carrying out the post-reaction treatment process depending on the type of the cyano compound. For example, if some cyano compounds are not dissolved in the solvent of the hydroxylamine salt solution, the final reaction product is solid particles, and is washed by deionized water and filtered; some cyano compounds are soluble in the above solvents, and are treated by centrifugation or recrystallized depending on the intended use of the reaction product.

The reaction time has a certain influence on the conversion rate of the cyano group, the conversion rate of the cyano group increases along with the extension of the reaction time at the beginning of the reaction, the conversion rate can basically reach more than 80% after 4 hours of reaction, and the conversion rate tends to be stable after 12 hours, so the preferable reaction time is 4-12 hours.

Preferably, the pressure is 8-25 MPa. Specific pressures favor amidooximation of cyano compounds.

The solvent of the hydroxylamine salt solution is a commonly used solvent such as at least one of water, methanol, ethanol, N-Dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO).

Preferably, the hydroxylamine salt solution with the pH value of 6-10 can be obtained by adding alkali and adjusting the pH value of the hydroxylamine salt solution to 6-10, wherein the alkali is at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate.

The conventional hydroxylamine salt is suitable for the present invention, and preferably, the hydroxylamine salt is hydroxylamine hydrochloride or hydroxylamine sulfate.

For better reaction, the reaction of the invention is preferably stirred, and the stirring speed is 500-2000 r/min.

Preferably, the hydroxylamine salt solution has a pH of 7; during reaction, the pressure is 20MPa, and the stirring speed is 1600 r/min; the reaction was carried out at 80 ℃ for 4 h.

All cyano-containing compounds can be amidoximized using the process of the invention, for example, cyano-containing polymers such as polyacrylonitrile or acrylonitrile copolymers, cyano-containing monomers such as phenylacetonitrile, acrylonitrile, and the like.

The following examples are provided to further illustrate the embodiments of the present invention and are not intended to limit the scope of the present invention.

Example 1

Adding 1.6g of hydroxylamine hydrochloride into a 100mL beaker, adding a mixed solution of 30mL of water and 20mL of methanol, adding a certain amount of sodium hydroxide to adjust the pH value of the solution to 7.0 after the solution is completely dissolved, pouring the prepared solution into a 100mL high-temperature high-pressure magnetic stirring reaction kettle, adding 0.2g of Polyacrylonitrile (PAN) fiber, and finally introducing carbon dioxide into the kettle under the reaction condition of 80 ℃; 20 MPa; 1600 r/min; and 4 h. And (3) taking out the fiber after the reaction is finished, soaking the fiber in deionized water for more than 1h, repeatedly washing the fiber with the deionized water until the fiber is nearly neutral, and drying the fiber in a vacuum oven at the temperature of 60 ℃ for 24 h to obtain the amidoxime polyacrylonitrile fiber (AO-PAN). After drying, the weight was 0.3111g, and the cyano conversion was 89.27%. The infrared spectrum is shown in figure 1.

The cyano conversion was calculated using the following formula:

in the formula, CR_nIs the conversion (%) of cyano groups in cyano compounds;

W₀mass (g) of polyacrylonitrile fiber before reaction;

W_tmass (g) of the reacted polyacrylonitrile fiber;

M₀is-CH in the fibre₂Molecular weight of CHCN (53 g/mol);

M_tis NH₂Molecular weight of OH (33 g/mol).

Comparative example 1

Adding 1.6g of hydroxylamine hydrochloride into a 100mL beaker, adding a mixed solution of 30mL of water and 20mL of methanol, adding a certain amount of sodium hydroxide to adjust the pH value of the solution to 7.0 after the solution is completely dissolved, pouring the prepared solution into a 100mL high-temperature high-pressure magnetic stirring reaction kettle, adding 0.2g of polyacrylonitrile fiber, and carrying out sealed reaction under the reaction condition of 80 ℃; 1600 r/min; and 4 h. And (3) taking out the fiber after the reaction is finished, soaking the fiber in deionized water for more than 1h, repeatedly washing the fiber with the deionized water until the fiber is nearly neutral, and drying the fiber in a vacuum oven at the temperature of 60 ℃ for 24 h to obtain the amidoxime polyacrylonitrile fiber. After drying, weighing was performed and cyano conversion was calculated to be 5.46%.

Comparative example 2

Adding 1.6g of hydroxylamine hydrochloride into a 100mL beaker, adding a mixed solution of 30mL of water and 20mL of methanol, adding a certain amount of sodium hydroxide to adjust the pH value of the solution to 7.0 after the solution is completely dissolved, pouring the prepared solution into a 100mL high-temperature high-pressure magnetic stirring reaction kettle, adding 0.2g of polyacrylonitrile fiber, and carrying out sealed reaction under the reaction condition of 80 ℃; 1600 r/min; and (4) 12 h. And (3) taking out the fiber after the reaction is finished, soaking the fiber in deionized water for more than 1h, repeatedly washing the fiber with the deionized water until the fiber is nearly neutral, and drying the fiber in a vacuum oven at the temperature of 60 ℃ for 24 h to obtain the amidoxime polyacrylonitrile fiber. After drying, weighing was performed and cyano conversion was calculated to be 56.45%.

Examples 2 to 5

By adopting the method of example 1, only part of the parameters are changed to obtain the amidoxime polyacrylonitrile fiber, the changed parameters are detailed in table 1, and the infrared spectrum of the amidoxime polyacrylonitrile fiber is similar to that in fig. 1. The cyano group conversion was calculated according to the method of example 1, and the results are shown in Table 1.

TABLE 1

	Example 1	Example 2	Example 3	Example 4	Example 5
						Amount of hydroxylamine hydrochloride added (g)	1.6	1.6	5	1.6	0.7
pH value	7	6	8	9	10
						Polyacrylonitrile addition amount (g)	0.2	1.2	0.6	0.16	0.2
Reaction temperature (. degree.C.)	80	110	45	60	90
						Pressure (MPa)	20	15	25	8	10
Rotating speed (r/min)	1600	2000	500	1000	1800
						Reaction time (h)	4	10	2	12	8
Cyano conversion (%)	89.27	85.76	67.45	86.16	83.68

Example 6

Adding 1.9g of hydroxylamine sulfate into a 100mL beaker, adding a mixed solution of 30mL of water and 20mL of methanol, adding a certain amount of sodium hydroxide to adjust the pH value of the solution to 7.0 after the solution is completely dissolved, pouring the prepared solution into a 100mL high-temperature high-pressure magnetic stirring reaction kettle, adding 0.2g of benzyl cyanide, and finally introducing carbon dioxide into the kettle under the reaction condition of 80 ℃; 20 MPa; 1600 r/min; and 4 h. And (3) taking out the fiber after the reaction is finished, soaking the fiber in deionized water for more than 1h, repeatedly washing the fiber with the deionized water until the fiber is nearly neutral, and drying the fiber in a vacuum oven at the temperature of 60 ℃ for 24 h to obtain the amidoxime polyacrylonitrile fiber. After drying, 0.2482g were weighed, and the yield was 94.2%. The yield is the amount of the target product (actually) produced per the theoretical amount of the target product × 100%.

Example 7

Adding 1.6g of hydroxylamine hydrochloride into a 100mL beaker, adding a mixed solution of 30mL of water and 20mL of methanol, adding a certain amount of sodium hydroxide to adjust the pH value of the solution to 7.0 after the solution is completely dissolved, pouring the prepared solution into a 100mL high-temperature high-pressure magnetic stirring reaction kettle, adding 0.2g of acrylonitrile, and finally introducing carbon dioxide into the kettle under the reaction condition of 80 ℃; 20 MPa; 1600 r/min; and 4 h. After completion of the reaction, the solvent was distilled off under reduced pressure, and the solid residue was purified by recrystallization from toluene. After drying, 0.3015g was weighed, and the yield was 92.9%.

Claims

1. Process for amidooximation of a cyano compound, characterized in that: reacting hydroxylamine salt solution with a cyano compound in a supercritical fluid to obtain an amidoxime group material; the specific operation is as follows: adding a hydroxylamine salt solution with the pH value of 6-10 and a cyano compound into a high-pressure reaction kettle, introducing carbon dioxide into the high-pressure reaction kettle, adjusting the pressure to enable the carbon dioxide to be in a supercritical state, and reacting at 45-110 ℃ for 4-12 hours to obtain an amidoxime material; the pressure is 8-25 MPa; the cyano compound is polyacrylonitrile, phenylacetonitrile or acrylonitrile.

2. The amidoximation method of a cyano compound according to claim 1, wherein: the molar ratio of the cyano group of the cyano compound to the hydroxylamine group of the hydroxylamine salt is 1: 1-8.

3. Process for amidoximation of cyano compounds according to claim 1 or 2, characterized in that: the concentration of the hydroxylamine salt solution is 0.2-1.5 mol/L.

4. The amidoximation method of a cyano compound according to claim 3, wherein: the solvent of the hydroxylamine salt solution is at least one of water, methanol, ethanol, N-dimethylformamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide.

5. Process for amidoximation of cyano compounds according to claim 1 or 2, characterized in that: the pH value of the hydroxylamine salt solution is adjusted to be 6-10 by adding alkali, wherein the alkali is at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate.

6. Process for amidoximation of cyano compounds according to claim 1 or 2, characterized in that: the hydroxylamine salt is hydroxylamine hydrochloride or hydroxylamine sulfate.

7. Process for amidoximation of cyano compounds according to claim 1 or 2, characterized in that: stirring at a speed of 500-2000 r/min during reaction.