CN111440090A - Preparation method of malononitrile and malononitrile prepared by same - Google Patents
Preparation method of malononitrile and malononitrile prepared by same Download PDFInfo
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Abstract
The invention relates to the technical field of chemical synthesis methods, in particular to a preparation method of malononitrile and the malononitrile prepared by the preparation method, wherein the preparation method comprises the following steps: mixing cyanoacetamide, a catalyst and a solvent, heating and refluxing, and introducing phosgene to synthesize malononitrile; wherein, the mass ratio of the cyanoacetamide to the catalyst to the solvent is (2.5-3.5): (0.005-0.02): (7.5-10.5); the solvent is any one of dichloromethane, dichloroethane or toluene; the catalyst is any one or more of diethylamine, N-dimethylformamide or pyridine. The method adopts cyanoacetamide to synthesize malononitrile in one step under the action of phosgene, the required raw materials are cheap and easy to obtain, the synthesis reaction steps are few, harsh conditions are avoided, the operation is simple and stable, the controllability is good, the yield of the prepared malononitrile can reach more than 93 percent and is far higher than other process schemes, and the preparation method has lower three-waste treatment cost and objective economic benefit.
Description
Technical Field
The invention relates to the technical field of chemical synthesis methods, in particular to a preparation method of malononitrile and the malononitrile prepared by the same.
Background
Malononitrile is an important organic synthesis starting material. The malononitrile molecule contains two cyano functional groups, and the cyano is a strong polar group and has strong electron-withdrawing performance. Due to the action of the two cyano groups, the electron cloud of the malononitrile molecule is transferred to the nitrogen atom on the cyano group, so that the two hydrogen atoms on the methylene group in the malononitrile molecule are also quite active. Because both cyano and methylene can react, malononitrile is a compound with very active chemical properties, and can perform a series of reactions such as addition, condensation, substitution, cyclization, polymerization and the like to synthesize a series of important chemical products. The formula of malononitrile is as follows:
therefore, malononitrile is widely used in the fields of medicines, pesticides, dye materials, and the like. In the aspect of medicine, the compound can be used for synthesizing a series of important medicines such as vitamin B1, aminopterin, triamterene and the like. In the aspect of pesticides, the herbicide oxapyrim, propyribac-sodium, thiazopyrim and the like can be synthesized. In the aspect of dyes, the dye can be used for synthesizing raw materials containing cyano dyes, and the cyano dyes are generally very bright, pure in color and good in fastness performance. For example, the new product Foron Brill blue S-R of the Daoshi company of Switzerland is a blue disperse dye taking malononitrile as a main raw material, which is called as 'blue king' and is suitable for various dyeing processes and is also suitable for direct printing and anti-pollination printing. The output of the terylene fiber in China is increased year by year, the demand of the disperse dye is correspondingly increased, and therefore, the variety of the disperse dye taking malononitrile as the dye is also increased year by year. It can also be used as gold extractant. In recent years, organic conductive materials mainly composed of tetracyano compounds prepared from malononitrile have been increasingly used in the field of electric appliances.
At present, the synthesis method of malononitrile is various, such as allene oxidation ammonolysis method, acetonitrile chloronitrile gas phase method, acetonitrile high temperature pyrolysis method, styrene method, acrylonitrile and aminoacetonitrile method, etc. However, these methods all need to adopt high temperature and high pressure, have large equipment investment and high requirements, and especially have the problem of environmental protection because the gas phase reaction generates virulent cyanogen gas, chlorine gas, hydrogen cyanide and the like.
Therefore, the development of a new process for synthesizing malononitrile to overcome the problems of high cost, large solid waste amount and high difficulty in treating phosphorus-containing wastewater in the prior art is a problem to be solved in the field.
Disclosure of Invention
The invention aims to provide a preparation method of malononitrile, which has the advantages of strong safety and stability, low cost and no generation of solid waste.
The invention provides a preparation method of malononitrile, which comprises the following steps:
mixing cyanoacetamide, a catalyst and a solvent, heating and refluxing, and introducing phosgene to synthesize malononitrile;
wherein, the mass ratio of the cyanoacetamide to the catalyst to the solvent is (2.5-3.5): (0.02-0.04): (7-11);
the solvent is any one of dichloromethane, dichloroethane or toluene;
the catalyst is any one or more of diethylamine, N-dimethylformamide or pyridine;
the synthetic route is as follows:
at present, the domestic malononitrile is mainly prepared by elimination reaction of cyanoacetamide and phosphorus oxychloride, but the method has the problems of high cost, large solid waste amount, high difficulty in treating phosphorus-containing wastewater and the like. In order to solve the problem, the method adopts cyanoacetamide to synthesize malononitrile in one step under the action of phosgene, adopts pyridine, diethylamine or N, N-Dimethylformamide (DMF) as a catalyst, adopts dichloroethane, dichloromethane or toluene as a solvent, and completes dehydration elimination reaction of cyanoacetamide under the action of phosgene.
Further, the method specifically comprises the following steps:
s1, mixing cyanoacetamide, a catalyst and a solvent, and uniformly stirring;
s2, when the temperature of the mixed system is raised to 40-110 ℃, continuously introducing phosgene, and carrying out reflux reaction for 10-20 h;
s3, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 30-95 ℃, introducing nitrogen to empty phosgene;
and S4, sequentially carrying out normal pressure distillation and reduced pressure distillation to obtain the malononitrile product.
In the preparation method, firstly, cyanoacetamide and a catalyst are completely dissolved in a solvent, phosgene is continuously introduced when the temperature of a mixed solution is raised to 40-110 ℃, a dehydrating agent is provided for the elimination reaction of cyanoacetamide, the phosgene is used as the dehydrating agent, malononitrile can be obtained in one step, and the reaction is discharged in the form of hydrogen chloride. When the reaction is about to be completed, judging the reaction process by a visual method and a gas chromatography detection method, wherein in the visual method, part of reaction feed liquid is taken out firstly, after the reaction feed liquid is cooled to 40 ℃, no crystal precipitation is observed, and the reaction can be judged to be basically completed, and then, the gas chromatography detection method is further used, and the reaction can be judged to be completed if the reactant is remained below 1.5%. After the reflux reaction is finished, nitrogen is needed to evacuate phosgene in the reaction system so as to be beneficial to the post-treatment, after the phosgene is evacuated, normal pressure distillation and reduced pressure distillation are sequentially carried out for post-treatment, the solvent in the reaction liquid is mainly removed by the normal pressure distillation, and the reduced pressure distillation mainly aims to remove impurities and trace solvent so as to obtain a white or yellowish transparent liquid product.
Further, the flow rate of the phosgene is 5-20L/h.
Phosgene is always fed at a flow rate of 5-20L/h, if the flow rate is too high, the content of phosgene is increased, and byproducts generated in the reaction are correspondingly increased, on the other hand, after the content of phosgene is excessive, the difficulty of treatment after the reaction is increased, such as the time for removing light is prolonged, the light removal is not thorough, and the like.
Further, the flow rate of the nitrogen gas is 5-20L/h.
Nitrogen is introduced at a flow rate of 5 to 20L/h, so that on the one hand the phosgene of the reaction system is completely evacuated and on the other hand evaporation of the solvent is avoided.
Further, during the atmospheric distillation, the distillation gas with the distillation range of 50-120 ℃ is removed, and the crude malononitrile with the distillation range of more than 50-120 ℃ is obtained.
In the invention, the boiling point of the solvent dichloromethane is 39.8 ℃, the boiling point of dichloroethane is 83.5 ℃ and the boiling point of toluene is 110.6 ℃, so that most of reagents can be removed to obtain a crude product of malononitrile when the temperature of a reaction system is raised to 50-120 ℃ during atmospheric distillation and no fraction is generated, and the removed solvent can be further recycled in a reaction kettle of the initial reaction for reuse.
Further, during the reduced pressure distillation, the crude malononitrile is placed under the vacuum degree of-0.09 to-0.1 MPa, the fraction with the distillation range below 95 ℃ is removed, and the fraction with the distillation range above 95 ℃ is collected, so that the refined malononitrile is obtained.
And during reduced pressure distillation, putting the crude malononitrile into a vacuum degree of-0.09 to-0.1 MPa, firstly collecting fractions below 95 ℃ to remove low-boiling-point substances and trace solvents in the crude malononitrile, and collecting fractions with the distillation range of more than 95 ℃ after impurities are basically removed to obtain the refined malononitrile. Here, in order to further improve the product yield, the vacuum distillation may be repeated with the recovery of the front distillate.
Further, the method specifically comprises the following steps:
s1, mixing cyanoacetamide, pyridine and dichloroethane, and uniformly stirring;
s2, when the temperature of the mixed system is raised to 70-75 ℃, continuously introducing phosgene at the speed of 10-15L/h, and carrying out reflux reaction for 10-20 h;
s3, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 50-70 ℃, continuously introducing nitrogen at the speed of 10-15L/h to empty phosgene, so as to obtain a feed liquid containing malononitrile;
and S4, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 110 ℃ to obtain a crude malononitrile product with the distillation range above 110 ℃, distilling the crude malononitrile product at a vacuum degree of-0.09 to-0.1 MPa under reduced pressure to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
Further, the method specifically comprises the following steps:
s1, mixing cyanoacetamide, diethylamine and dichloromethane, and stirring uniformly;
s2, when the temperature of the mixed system is raised to 35-40 ℃, continuously introducing phosgene at the speed of 5-10L/h, and carrying out reflux reaction for 10-20 h;
s3, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 30-35 ℃, continuously introducing nitrogen at the speed of 5-10L/h to empty phosgene, so as to obtain a feed liquid containing malononitrile;
and S4, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 50 ℃ to obtain a crude malononitrile product with the distillation range above 50 ℃, distilling the crude malononitrile product at a vacuum degree of-0.09 to-0.1 MPa under reduced pressure to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain the refined malononitrile product.
Further, the method specifically comprises the following steps:
s1, mixing cyanoacetamide, N-dimethylformamide and toluene, and uniformly stirring;
s2, when the temperature of the mixed system is raised to 95-110 ℃, continuously introducing phosgene at the speed of 15-20L/h, and carrying out reflux reaction for 10-20 h;
s3, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 85-95 ℃, continuously introducing nitrogen at the speed of 15-20L/h to empty phosgene, so as to obtain a feed liquid containing malononitrile;
and S4, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 120 ℃ to obtain a crude malononitrile product with the distillation range above 120 ℃, distilling the crude malononitrile product at a vacuum degree of-0.09 to-0.1 MPa under reduced pressure to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
The malononitrile prepared by the preparation method.
The malononitrile prepared by the invention is white or yellowish transparent liquid, the purity is over 99.8 percent, the yield can reach over 93 percent, and the method is far higher than other process schemes.
Compared with the prior art, the preparation method of malononitrile has the following advantages:
1. according to the method, cyanoacetamide is adopted to synthesize malononitrile in one step under the action of phosgene, the required raw materials are cheap and easy to obtain, the synthesis reaction steps are few, harsh conditions are avoided, and the method is simple and stable to operate and good in controllability;
2. the solvent produced in the synthetic process is easy to recycle, the production cost is greatly reduced, and no absorbent is required to be added in the three-waste treatment process, wherein in the photochemical reaction, the discharged hydrogen chloride and excessive phosgene waste gas are absorbed by clear water to generate byproduct hydrochloric acid; the micro-amount vacuum wastewater solution generated in the invention can be discharged after reducing various indexes through acid-base neutralization; in the production process, no solid residue is produced, so the preparation method has lower three-waste treatment cost and objective economic benefit;
3. the yield of the malononitrile obtained by the preparation method can reach more than 93 percent, which is far higher than that of other process schemes.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a gas chromatogram of malononitrile prepared in example 1 of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise. Furthermore, the terms "mounted," "connected," and "connected" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Example 1
S11, mixing 300g of cyanoacetamide, 3g of pyridine and 900g of dichloroethane, and uniformly stirring;
s12, when the temperature of the mixed system is raised to 75 ℃, continuously introducing phosgene at the speed of 10L/h, carrying out reflux reaction for 10h, taking out part of feed liquid, cooling to 40 ℃, observing that no crystal is separated out, and judging that the reaction is finished;
s13, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 60 ℃, continuously introducing nitrogen at the speed of 10L/h to empty phosgene, and obtaining feed liquid containing malononitrile;
and S14, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 110 ℃ to obtain a crude malononitrile product with the distillation range above 110 ℃, carrying out reduced pressure distillation on the crude malononitrile product under the vacuum degree of-0.097 MPa to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
Example 2
S21, mixing 250g of cyanoacetamide, 2g of pyridine and 700g of dichloroethane, and uniformly stirring;
s22, when the temperature of the mixed system is raised to 70 ℃, continuously introducing phosgene at the speed of 15L/h, carrying out reflux reaction for 15h, taking out part of feed liquid, cooling to 40 ℃, observing that no crystal is separated out, and judging that the reaction is finished;
s23, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 60 ℃, continuously introducing nitrogen at the speed of 15L/h to empty phosgene, and obtaining feed liquid containing malononitrile;
and S24, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 110 ℃ to obtain a crude malononitrile product with the distillation range above 110 ℃, carrying out reduced pressure distillation on the crude malononitrile product under the vacuum degree of-0.097 MPa to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
Example 3
S31, mixing 350g of cyanoacetamide, 4g of pyridine and 1000g of dichloroethane, and uniformly stirring;
s32, when the temperature of the mixed system is raised to 75 ℃, continuously introducing phosgene at the speed of 15L/h, carrying out reflux reaction for 15h, taking out part of feed liquid, cooling to 40 ℃, observing that no crystal is separated out, and judging that the reaction is finished;
s33, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 60 ℃, continuously introducing nitrogen at the speed of 15L/h to empty phosgene, and obtaining feed liquid containing malononitrile;
and S34, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 110 ℃ to obtain a crude malononitrile product with the distillation range above 110 ℃, carrying out reduced pressure distillation on the crude malononitrile product under the vacuum degree of-0.097 MPa to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
Example 4
S41, mixing 300g of cyanoacetamide, 4g of diethylamine and 1000g of dichloromethane, and uniformly stirring;
s42, when the temperature of the mixed system is raised to 38 ℃, continuously introducing phosgene at the speed of 5L/h, carrying out reflux reaction for 20h, taking out part of feed liquid, cooling to 40 ℃, observing that no crystal is separated out, and judging that the reaction is finished;
s43, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 30 ℃, continuously introducing nitrogen at the speed of 5L/h to empty phosgene, and obtaining feed liquid containing malononitrile;
and S44, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 50 ℃ to obtain a crude malononitrile product with the distillation range above 50 ℃, distilling the crude malononitrile product under the vacuum degree of-0.097 MPa to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
Example 5
S51, mixing 320g of cyanoacetamide, 4g N, N-dimethylformamide and 900g of toluene, and uniformly stirring;
s52, when the temperature of the mixed system is raised to 105 ℃, continuously introducing phosgene at the speed of 20L/h, carrying out reflux reaction for 15h, taking out part of feed liquid, cooling to 40 ℃, observing that no crystal is separated out, and judging that the reaction is finished;
s53, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 90 ℃, continuously introducing nitrogen at the speed of 20L/h to empty phosgene, and obtaining feed liquid containing malononitrile;
and S54, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 120 ℃ to obtain a crude malononitrile product with the distillation range above 120 ℃, distilling the crude malononitrile product under the vacuum degree of-0.097 MPa to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
Example 6
S61, mixing 300g of cyanoacetamide, 3g of diethylamine and 900g of dichloroethane, and uniformly stirring;
s62, when the temperature of the mixed system is raised to 75 ℃, continuously introducing phosgene at the speed of 10L/h, carrying out reflux reaction for 15h, taking out part of feed liquid, cooling to 40 ℃, observing that no crystal is separated out, and judging that the reaction is finished;
s63, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 60 ℃, continuously introducing nitrogen at the speed of 10L/h to empty phosgene, and obtaining feed liquid containing malononitrile;
and S64, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 110 ℃ to obtain a crude malononitrile product with the distillation range above 110 ℃, distilling the crude malononitrile product under the vacuum degree of-0.097 MPa to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
Example 7
S71, mixing 300g of cyanoacetamide, 3g N, N-dimethylformamide and 900g of dichloroethane, and uniformly stirring;
s72, when the temperature of the mixed system is raised to 75 ℃, continuously introducing phosgene at the speed of 10L/h, carrying out reflux reaction for 15h, taking out part of feed liquid, cooling to 40 ℃, observing that no crystal is separated out, and judging that the reaction is finished;
s73, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 60 ℃, continuously introducing nitrogen at the speed of 10L/h to empty phosgene, and obtaining feed liquid containing malononitrile;
and S74, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 110 ℃ to obtain a crude malononitrile product with the distillation range above 110 ℃, distilling the crude malononitrile product under the vacuum degree of-0.097 MPa to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
Example 8
S81, mixing 300g of cyanoacetamide, 2g of pyridine, 1g of diethylamine and 900g of dichloroethane, and uniformly stirring;
s82, when the temperature of the mixed system is raised to 75 ℃, continuously introducing phosgene at the speed of 10L/h, carrying out reflux reaction for 15h, taking out part of feed liquid, cooling to 40 ℃, observing that no crystal is separated out, and judging that the reaction is finished;
s83, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 60 ℃, continuously introducing nitrogen at the speed of 10L/h to empty phosgene, and obtaining feed liquid containing malononitrile;
and S84, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 110 ℃ to obtain a crude malononitrile product with the distillation range above 110 ℃, distilling the crude malononitrile product under the vacuum degree of-0.097 MPa to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
To examine and compare the yields and purities of the fine malononitrile products prepared in examples 1 to 8, the malononitrile products prepared in examples 1 to 8 were respectively subjected to gas chromatography. Table 1 shows the chromatographic data for malononitrile prepared in example 1; table 2 shows the reactant ratios of examples 1-8, and Table 3 shows the product yield data of examples 1-8.
TABLE 1 data for the chromatographic analysis of malononitrile prepared in example 1
| Retention time (min) | Peak area (uV S) | Content (%) | |
| Malononitrile | 2.5 | 2081638.4 | 99.57 |
Table 2 examples 1-8 reactant ratios
Table 3 shows the product yield data of examples 1 to 8
As can be seen from tables 2 and 3, when pyridine was used as a catalyst and dichloroethane was used as a solvent to prepare malononitrile, the product yields were all 93% or more, and the product purities were also high, all 99.5% or more. The yield of the product is only between 90 and 91.8 percent and the purity is only about 98 percent by taking the diethylamine or DMF as the catalyst, so that the pyridine has the highest catalytic activity compared with the diethylamine and the DMF. When dichloromethane is used as a solvent, the solubility of reactants is poor, so that the yield and the purity of the product are low, the solubility of the reactants can be improved by toluene, but the boiling point of the toluene is high, the required reaction energy consumption is relatively high, the toxicity of the toluene is high, the harm to workers is large, and the cost for treating waste liquid is relatively high.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A preparation method of malononitrile is characterized by comprising the following steps:
mixing cyanoacetamide, a catalyst and a solvent, heating and refluxing, and introducing phosgene to synthesize malononitrile;
wherein, the mass ratio of the cyanoacetamide to the catalyst to the solvent is (2.5-3.5): (0.02-0.04): (7-11);
the solvent is any one of dichloromethane, dichloroethane or toluene;
the catalyst is any one or more of diethylamine, N-dimethylformamide or pyridine.
2. The preparation method according to claim 1, comprising the following steps:
s1, mixing cyanoacetamide, a catalyst and a solvent, and uniformly stirring;
s2, when the temperature of the mixed system is raised to 40-110 ℃, continuously introducing phosgene, and carrying out reflux reaction for 10-20 h;
s3, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 30-95 ℃, introducing nitrogen to empty phosgene;
and S4, sequentially carrying out normal pressure distillation and reduced pressure distillation to obtain the malononitrile product.
3. The method according to claim 2, wherein the phosgene is introduced at a flow rate of 5 to 20L/h in step S2.
4. The method according to claim 2, wherein the nitrogen gas is introduced at a flow rate of 5 to 20L/h in step S3.
5. The method according to claim 2, wherein in step S4, the distillation gas having a boiling range of 50 to 120 ℃ or lower is removed during the atmospheric distillation to obtain a crude malononitrile having a boiling range of more than 50 to 120 ℃.
6. The preparation method of claim 5, wherein in the step S4, during the reduced pressure distillation, the crude malononitrile is placed under a vacuum degree of-0.09 to-0.1 MPa, the fraction with the distillation range below 95 ℃ is removed, and the fraction with the distillation range above 95 ℃ is collected to obtain the refined malononitrile.
7. The preparation method according to claim 1, comprising the following steps:
s1, mixing cyanoacetamide, pyridine and dichloroethane, and uniformly stirring;
s2, when the temperature of the mixed system is raised to 70-75 ℃, continuously introducing phosgene at the speed of 10-15L/h, and carrying out reflux reaction for 10-20 h;
s3, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 50-70 ℃, continuously introducing nitrogen at the speed of 10-15L/h to empty phosgene, so as to obtain a feed liquid containing malononitrile;
and S4, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 110 ℃ to obtain a crude malononitrile product with the distillation range above 110 ℃, distilling the crude malononitrile product at a vacuum degree of-0.09 to-0.1 MPa under reduced pressure to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
8. The preparation method according to claim 1, comprising the following steps:
s1, mixing cyanoacetamide, diethylamine and dichloromethane, and stirring uniformly;
s2, when the temperature of the mixed system is raised to 35-40 ℃, continuously introducing phosgene at the speed of 5-10L/h, and carrying out reflux reaction for 10-20 h;
s3, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 30-35 ℃, continuously introducing nitrogen at the speed of 5-10L/h to empty phosgene, so as to obtain a feed liquid containing malononitrile;
and S4, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 50 ℃ to obtain a crude malononitrile product with the distillation range above 50 ℃, distilling the crude malononitrile product at a vacuum degree of-0.09 to-0.1 MPa under reduced pressure to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain the refined malononitrile product.
9. The preparation method according to claim 1, comprising the following steps:
s1, mixing cyanoacetamide, N-dimethylformamide and toluene, and uniformly stirring;
s2, when the temperature of the mixed system is raised to 95-110 ℃, continuously introducing phosgene at the speed of 15-20L/h, and carrying out reflux reaction for 10-20 h;
s3, after the reflux reaction is finished, when the temperature of the mixed system is reduced to 85-95 ℃, continuously introducing nitrogen at the speed of 15-20L/h to empty phosgene, so as to obtain a feed liquid containing malononitrile;
and S4, distilling the feed liquid at normal pressure, removing the distillation gas with the distillation range below 120 ℃ to obtain a crude malononitrile product with the distillation range above 120 ℃, distilling the crude malononitrile product at a vacuum degree of-0.09 to-0.1 MPa under reduced pressure to remove the fraction with the distillation range below 95 ℃, and collecting the fraction with the distillation range above 95 ℃ to obtain a refined malononitrile product.
10. Malononitrile produced by the production method according to any one of claims 1 to 9.
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