Continuous preparation process of nitro-alcohol

Abstract

The invention discloses a continuous preparation process of nitro-alcohol, which comprises the following steps: S1, placing a catalyst N in a polycondensation reactor, then pressurizing a formaldehyde solution, a reaction solvent and nitro-alkane respectively by using a pressure pump, uniformly mixing at a position close to an inlet of the reactor, and conveying the mixture into the polycondensation reactor, s2, controlling the pressure in the polycondensation reactor to be 0.05-0.2 Mpa, and S3, after the reaction is finished, collecting a nitro alcohol reaction solution at the outlet of the reactor; and collecting the nitro-alcohol reaction liquid flowing out of the outlet of the reactor, and detecting to obtain the nitro-alcohol with the yield of 99.61%. The adopted self-made modified catalyst N has the characteristic of improving the stability of the reaction product nitro-alcohol and reducing the decomposability of the nitro-alcohol, the service life of the catalyst is greatly prolonged, continuous operation can be performed for 3-6 months, the risk that impurity salts are generated by adopting acid neutralization after the condensation reaction is finished by adopting a homogeneous base catalyst is avoided, the post-treatment procedures are reduced, and the production cost is reduced. And meanwhile, the production cost is also reduced.

Description

Technical Field

[0001] The invention relates to a preparation technology of nitro alcohol, and in particular to a continuous preparation process of nitro alcohol. Background Art

[0002] Amino alcohol is an organic compound containing amino and hydroxyl functional groups. It has a wide range of uses in industrial production, medicine and organic synthesis. Many amino alcohol products can be obtained by condensing nitro hydrocarbons and aldehydes and then reducing them, such as 2-amino-1,3-propanediol (APD), 2-amino-2-ethyl-1,3-propanediol (AEPD), 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol (AMP), etc. AMP is a multifunctional additive. As a pigment dispersant, it can effectively improve the pH stability, viscosity, corrosion resistance and odor of coatings. It is widely used in the coating and papermaking industries. It is also favored by many customers in the pharmaceutical, cosmetic and pesticide intermediate industries. The latest research shows that AMP is also a very effective CO2 chemical ion exchange resin. Tris is an important biochemical and pharmaceutical intermediate. It is widely used in acute metabolic and respiratory acidosis and is an important alkaline buffer. 2-Amino-1,3-propanediol is an important pharmaceutical intermediate and an important raw material for synthesizing the radiocontrast agent iopamidol.

[0003] Primary and secondary nitroalkanes and aldehydes and ketones undergo condensation reaction in an alkaline solution, and the resulting product is nitroalcohol. Using nitroalcohol as a raw material, amino alcohol is prepared by hydrogenation reduction reaction under the action of Raney nickel and palladium carbon catalyst. In the disclosed patent technology, the first step of condensation reaction of preparing nitroalcohol using nitroalkanes as raw materials mostly adopts a reactor device for intermittent production. Patents CN 104262160B, CN114105788A, and CN116813484A disclose a process for preparing 2-nitro-2-methyl-1-propanol. In an alkaline solution, a certain reaction temperature is controlled, and 2-nitropropane and formaldehyde solution are condensed to prepare 2-nitro-2-methyl-1-propanol, and an acid solution is added for neutralization after the reaction is completed.

[0004] CN113200877B discloses a method for preparing trimethylolnitromethane. Methanol, paraformaldehyde, and alkaline catalyst are sequentially added to a reactor and stirred for 20-40 minutes until the solution becomes colorless and transparent; nitromethane is slowly added dropwise, and oxalic acid is added after the reaction to adjust the pH to 8-9; CN 201753333 U discloses a synthesis device for trimethylolnitromethane, wherein the reaction materials paraformaldehyde, methanol, and KOH are placed in a condensation reactor, stirred and heated until completely dissolved, nitromethane is slowly added dropwise, and a certain temperature is maintained until the reaction is completed. The preparation of nitro alcohols is mostly carried out intermittently in a reactor device, which has many inconveniences in industrial production, high labor intensity, and affects production efficiency. Most nitro alcohol preparation processes use inorganic bases (such as sodium hydroxide, potassium hydroxide, potassium carbonate, etc.) or organic amines (trimethylamine, triethylamine, etc.) homogeneous bases as catalysts. The preparation method of nitro alcohol in patent CN104254516A uses alkaline silica, alkaline alumina or alkaline resin as catalysts. However, ordinary alkaline resins have the disadvantage of short life, and need to be regenerated repeatedly in production. The regeneration steps are complicated and a large amount of wastewater is generated. Patent CN118005515 A discloses a continuous synthesis method of amine compounds. The intermediate nitro compound is synthesized continuously using a homemade catalyst. After repeated experiments by researchers, it is easy to pulverize and the catalyst active substance is easy to lose during actual use, which affects the service life of the catalyst.

[0005] Homogeneous bases such as inorganic bases or organic amines are used as catalysts, which need to be removed after the polycondensation reaction. Most of the existing technologies use inorganic acids, acidic ion exchange resins, HZSM-5, phosphotungstic heteropoly acids, etc. for neutralization treatment (CN108976128B). During the neutralization process, trace amounts of nitro alcohols will decompose to produce nitroalkanes. Patents CN117800854A, CN116813484A, and CN1107172029B mention that the concentration needs to be diluted to 10%-50% before the reduction reaction using nitro alcohol as a raw material. In actual use, it is found that nitro alcohols will also slightly decompose during the dilution process. The nitroalkanes produced by the decomposition are further reduced to produce impurities during the hydrogenation process, which not only affects the product quality but also increases the separation cost. Summary of the invention

[0006] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a continuous preparation process for improving the stability of nitroalcohol products. According to the technical solution provided in the embodiment of the present application, a continuous preparation process of nitro alcohol comprises the following steps: S1, a catalyst N is built into a polycondensation reactor, and then a formaldehyde solution, a reaction solvent, and a nitroalkane are pressurized by a pressure pump, mixed evenly near the reactor inlet, and then transported to the polycondensation reactor, wherein the molar ratio of the formaldehyde solution, the reaction solvent, and the nitroalkane is 1:1.0~4.0:1.0~5.0; S2, controlling the pressure in the polycondensation reactor to be between 0.05-0.2Mpa, and maintaining the reaction temperature in the polycondensation reactor to be between 25-80°C, the residence time of the polycondensation raw materials in the polycondensation reactor is controlled to be between 0.2-3h, at which time the concentration of the nitro alcohol product in the reaction solution is 10%-60%, and the reaction temperature is continued to be controlled between 30-80°C and allowed to stand; S3. After the reaction is completed, the nitro alcohol reaction liquid at the reactor outlet is collected; the nitro alcohol reaction liquid flowing out of the reactor outlet is collected for detection, and the yield is 99.61% (nitro alcohol); The catalyst N is composed of a macroporous strong alkaline anion resin modified by a transition metal, an auxiliary agent and a stabilizer, wherein; The transition metal is a transition metal salt, preferably one or more of the nitrates of cobalt, zinc, nickel, copper and chromium. The auxiliary agent is a tungsten salt, preferably one of tungsten oxide, potassium tungstate, sodium tungstate or ammonium tungstate; The stabilizer is preferably one or more of zinc stearate, chromium stearate, calcium stearate, and barium stearate; The macroporous strong basic anion resin is one of D201, D202, D254, D113 and D301; The transition metal content in the catalyst N is 0.01-0.5% of the dry weight of the macroporous strong basic anion resin; The content of the stabilizer in the catalyst N is 0.001-2% of the dry weight of the macroporous strong basic anion resin.

[0007] The content of the auxiliary agent in the catalyst N is 0.0001-0.005% of the dry weight of the macroporous strong basic anion resin.

[0008] In the present invention, further, the solvent used in the preparation of the modified resin is one or more of pyridine, DMF, DMSO, dichloromethane, n-hexane and isooctane.

[0009] In the present invention, further, the molar ratio of the nitroalkane to formaldehyde is 1:1-3.

[0010] In the present invention, further, the preparation process of the catalyst N is as follows: add macroporous polystyrene alkaline resin and stabilizer to the solvent, heat to boiling and reflux, react for 10-20 hours, cool, wash, dry, take the prepared modified resin, add an aqueous solution of transition metal salt and auxiliary salt, stir at room temperature for 4 hours, and dry at 60°C in a nitrogen atmosphere for 4 hours to obtain catalyst N.

[0011] In summary, the beneficial effects of the present application are as follows: the present process does not use homogeneous alkaline catalysts such as sodium hydroxide, potassium hydroxide, triethylamine, dimethylamine, and diethylamine, and uses a self-made modified catalyst N which has the characteristics of increasing the stability of the reaction product nitro alcohol, reducing the decomposition of nitro alcohol, and greatly extending the service life of the catalyst, which can be continuously operated for 3-6 months, avoiding the risk of producing impurity salts by acid neutralization after the condensation reaction using a homogeneous alkaline catalyst, reducing the post-processing process, and also reducing the production cost. DETAILED DESCRIPTION

[0012] The present application will be further described in detail below in conjunction with the embodiments. It will be appreciated that the specific embodiments described herein are only used to explain the related inventions, rather than to limit the invention. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the embodiments.

[0013] Example 1 To prepare catalyst N, weigh 40 g of pyridine, add 60 g of D201 resin and 0.2 g of zinc stearate, heat to reflux, react for 15 h, cool to room temperature, filter, wash the obtained solid twice with 20 ml of deionized water, dry it in a nitrogen atmosphere at 40 ° C for 2 h, take the prepared modified resin, add 0.45 g of cobalt nitrate and 0.05 g of sodium tungstate aqueous solution, stir at room temperature for 4 h, and dry it in a nitrogen atmosphere at 60 ° C for 4 h to obtain catalyst N.

[0014] The obtained catalyst N was loaded into the reactor, and the reaction raw materials 2-nitropropane 35g, 37% formaldehyde aqueous solution 32g, and methanol 23g were configured, mixed evenly, and continuously fed into the reactor equipped with catalyst N. The reaction temperature was controlled at 35°C, the raw material residence time was 20min, and the outlet material concentration was detected. The conversion rate of 2-nitropropane was 99.8%, the yield of 2-nitro-2-methyl-1-propanol was 99.6%, the concentration of 2-nitro-2-methyl-1-propanol in the reaction solution was 51.73%, and the concentration of 2-nitropropane was 0.078%. The reaction solution was allowed to stand for 48h for concentration monitoring. The concentration of 2-nitro-2-methyl-1-propanol was 51.72%, and the concentration of 2-nitropropane was 0.078%. The obtained reaction solution was diluted to a concentration of 25%, and the concentration of 2-nitropropane was 0.039%. After the catalyst was continuously operated for 3000h, The conversion rate of 2-nitropropane was 99.78%, and the yield of 2-nitro-2-methyl-1-propanol was 99.61%.

[0015] Example 2 To prepare catalyst N, 40 g of N,N-dimethylformamide was weighed, 60 g of D201 resin and 0.025 g of zinc stearate were added, and the mixture was heated to reflux for 15 h. The mixture was cooled to room temperature and filtered. The solid was washed twice with 20 ml of deionized water and dried in a nitrogen atmosphere at 40 °C for 2 h. The modified resin was taken and 0.5 g of nickel nitrate and 0.005 g of tungsten oxide aqueous solution were added. The mixture was stirred at room temperature for 4 h and dried in a nitrogen atmosphere at 60 °C for 4 h to obtain catalyst N.

[0016] The obtained catalyst N was loaded into the reactor, and 35 g of nitromethane and 141.89 g of 52% formaldehyde methanol solution as reaction raw materials were prepared and mixed evenly. The mixture was continuously fed into the reactor containing the catalyst N. The reaction temperature was controlled at 40°C, and the residence time of the raw materials was 25 min. The concentration of the outlet material was detected. The conversion rate of nitromethane was 99.8%, the yield of trimethylolnitromethane was 99.6%, the product concentration in the reaction solution was 56.24%, and the concentration of raw material nitromethane was 0.04%. The reaction solution was allowed to stand for 48 h for concentration monitoring. The trimethylolnitromethane was 56.22%, and the concentration of nitromethane was 0.04%. The obtained reaction solution was diluted to a concentration of 20%, and the concentration of nitromethane was 0.02%. After the catalyst was continuously operated for 3000 h, the conversion rate of nitromethane was 99.79%, and the yield of trimethylolnitromethane was 99.58%. Comparative Example 1 The reactor was filled with 60 g of commercially available macroporous anion resin D202, and the reaction raw materials 35 g of 2-nitropropane, 34 g of 37% formaldehyde aqueous solution, and 21 g of methanol were prepared and mixed evenly. The catalyst was continuously fed into the reactor, the reaction temperature was controlled at 35 ° C, the raw material residence time was 40 min, and the outlet material concentration was detected. The conversion rate of 2-nitropropane was 99.6%, the yield of 2-nitro-2-methyl-1-propanol was 99.3%, the concentration of 2-nitro-2-methyl-1-propanol in the reaction solution was 51.58%, and the concentration of 2-nitropropane was 0.158%. The obtained reaction solution was allowed to stand for 48 hours, and the concentration of 2-nitro-2-methyl-1-propanol decreased to 50.72%, and the concentration of 2-nitropropane increased to 0.5%; the obtained reaction solution was directly diluted to 25% concentration, and the concentration of 2-nitropropane in the reaction solution increased to 0.7%. The catalyst was continuously operated for 100 hours, and the conversion rate of 2-nitropropane decreased to 98.2%. The concentration of 2-nitro-2-methyl-1-propanol in the reaction decreased to 50.75%.

[0017] Comparative Example 2 Weigh 60 g of D254 resin, add 0.022 g of zinc tungstate aqueous solution, stir at room temperature for 4 h, and dry at 60° C. in a nitrogen atmosphere for 4 h to obtain catalyst N.

[0018] The obtained catalyst N was loaded into a reactor, and reaction raw materials 2-nitropropane 35g, 37% formaldehyde aqueous solution 33g, and isopropanol 22g were prepared and mixed uniformly. The catalyst N was continuously fed into the reactor, the reaction temperature was controlled at 40°C, the raw material residence time was 40min, the outlet material concentration was detected, the 2-nitropropane conversion rate was 99.7%, the 2-nitro-2-methyl-1-propanol yield was 99.4%, the 2-nitro-2-methyl-1-propanol concentration in the reaction solution was 51.65%, and the 2-nitropropane concentration was 0.12%. The obtained reaction solution was allowed to stand for 48h, the 2-nitro-2-methyl-1-propanol concentration decreased to 50.82%, and the 2-nitropropane concentration increased to 0.3%; the obtained reaction solution was directly diluted to a concentration of 25%, and the 2-nitropropane concentration in the reaction solution increased to 0.6%. The catalyst was continuously operated for 500h, and the 2-nitropropane conversion rate decreased to 98%.

[0019] Comparative Example 3 Weigh 40g of tetrahydrofuran, add 60g of D202 resin and 0.025g of calcium stearate, heat to reflux, react for 18h, cool to room temperature, filter, wash the obtained solid twice with 20ml of deionized water, dry in a nitrogen atmosphere at 40℃ for 2h, take the prepared modified resin, add 0.015% mass fraction nickel tungstate aqueous solution, stir at room temperature for 4h, and dry in a nitrogen atmosphere at 60℃ for 4h to obtain catalyst N.

[0020] The obtained catalyst N was loaded into the reactor, and the reaction raw materials 2-nitropropane 35g, 37% formaldehyde aqueous solution 28g, and methanol 23g were prepared and mixed evenly. The reactor containing the catalyst N was continuously fed, and the reaction temperature was controlled at 35°C, the raw material residence time was 20min, and the outlet material concentration was detected. The conversion rate of 2-nitropropane was 99.6%, the yield of 2-nitro-2-methyl-1-propanol was 99.3%, the concentration of 2-nitro-2-methyl-1-propanol in the reaction solution was 51.58%, and the concentration of 2-nitropropane was 0.158%. The reaction solution was left to stand for 48h for concentration monitoring. The concentration of 2-nitro-2-methyl-1-propanol was 51.578%, and the concentration of 2-nitropropane was 0.158%. After continuous operation for 499h, the conversion rate of 2-nitropropane dropped to 98%.

[0021] The above description is only an explanation of the preferred embodiments of the present application and the technical principles and other schemes used. At the same time, the scope of the invention involved in the present application is not limited to the technical scheme formed by a specific combination of the above technical features, but also includes other technical schemes formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present application (but not limited to) to form a technical scheme.

Claims

1. A continuous process for preparing nitro alcohol, characterized in that: The following steps are involved: S1, a catalyst N is built into a polycondensation reactor, and then a formaldehyde solution, a reaction solvent, and a nitroalkane are pressurized by a pressure pump, mixed evenly near the reactor inlet, and then transported to the polycondensation reactor, wherein the molar ratio of the formaldehyde solution, the reaction solvent, and the nitroalkane is 1:1.0~4.0:1.0~5.0; S2, controlling the pressure in the polycondensation reactor between 0.05-0.2Mpa, and maintaining the reaction temperature in the polycondensation reactor between 25-80°C, the residence time of the polycondensation raw materials in the polycondensation reactor is controlled between 0.2-3h, at which time the concentration of the nitro alcohol product in the reaction solution is 10%-60%, and the reaction temperature is continued to be controlled between 30-80°C, and the reaction is continued for 3000h; S3. After the reaction is completed, the nitro alcohol reaction liquid at the reactor outlet is collected; the nitro alcohol reaction liquid flowing out of the reactor outlet is collected for detection, and the yield is 99.61% of nitro alcohol; The catalyst N is composed of a macroporous strong alkaline anion resin modified by a transition metal, an auxiliary agent and a stabilizer, wherein; The transition metal is a transition metal salt, preferably one or more of the nitrates of cobalt, zinc, nickel, copper and chromium. The auxiliary agent is a tungsten salt, preferably one of tungsten oxide, potassium tungstate, sodium tungstate and ammonium tungstate; The stabilizer is preferably one or more of zinc stearate, chromium stearate, calcium stearate, and barium stearate; The macroporous strong basic anion resin is one of D201, D202, D254, D113 and D301; The transition metal content in the catalyst N is 0.01-0.5% of the dry weight of the macroporous strong basic anion resin; The content of the stabilizer in the catalyst N is 0.001-2% of the dry weight of the macroporous strong basic anion resin.

2. A continuous process for preparing nitro alcohol according to claim 1, characterized in that: The reaction solvent is one or more of methanol, ethanol, isopropanol and water.

3. A continuous process for preparing nitro alcohol according to claim 1, characterized in that: The molar ratio of the nitroalkane to formaldehyde is 1:1-3.

4. A continuous process for preparing nitro alcohol according to claim 1, characterized in that: The preparation process of the catalyst N is as follows: adding macroporous polystyrene alkaline resin and stabilizer to a solvent, heating to boiling and reflux, reacting for 10-20 hours, cooling, washing, drying, taking the prepared modified resin, adding a transition metal salt solution, stirring at room temperature for 4 hours, and drying in a nitrogen atmosphere at 60°C for 4 hours to obtain the catalyst N.

5. A continuous process for preparing nitro alcohol according to claim 1, characterized in that: The solvent is one or more of pyridine, DMF, DMSO, dichloromethane, n-hexane and isooctane.