KR0164447B1 - Process for nitration of aromatic compound - Google Patents

Abstract

The present invention relates to a method of dissolving an aromatic compound in an organic solvent together with a small amount of nitric acid and nitrogen dioxide or nitrogen dioxide containing nitrogen monoxide and blowing ozone into a reaction vessel to perform a nitration reaction without using mixed acid even at a low temperature. .

A feature of the present invention is that a small amount of nitric acid is used directly as a nitration reaction reagent, and since dinitrogen pentoxide produced by nitrogen dioxide and ozone mostly reacts with water produced during the nitration reaction to produce nitric acid again, The nitric acid production reaction is carried out in series so that the concentration of nitric acid remains constant without dropping. As a result, it is possible to prevent nitration reactivity from decreasing the concentration of nitric acid due to water generation, and thus, it is possible to control the reactivity and selectivity that cannot be expected by the conventional mixed acid method by nitrifying widely even in the case of aromatic compounds having weak reactivity. have.

Description

Nitrification Method of Aromatic Compounds

1 shows gas chromatography of a product according to an embodiment of the present invention.

In the present invention, a small amount of nitric acid, nitrogen dioxide (NO ₂ ), and ozone (O ₃ ) in an organic solvent are used instead of a mixed acid method using a mixed acid composed of concentrated nitric acid and concentrated sulfuric acid, which is a method generally used in most nitration processes. By adding and reacting, the reaction conditions are milder than those of the conventional process, there is no generation of waste acid, and the position selectivity of the nitration reaction can be controlled. In particular, even the aromatic compounds in which benzene nuclei are inactivated, such as chlorobenzene, are mononitrified. In addition, it relates to a new process that can arbitrarily control the denitration reaction.

Aromatic nitro compounds produced by the nitration process are widely used as raw materials for petrochemicals and fine chemicals such as pesticides, medicines, dyes, gunpowder and rubber chemicals or intermediates thereof.

The nitration process is one of the most important processes of the organic unit process, and important petrochemical products requiring large nitration processes are diphenylmethane diisocyanate (MDI), which is a raw material of aniline, toluidine, and polyurethane, which are starting materials for dye synthesis. ) And tolene diisocyanate (TDI). Recently, due to the rapid development of the fine chemical industry, the production of related products has been increasing by more than 10% per year since 1990. However, the nitrification process used here still uses the blending method for more than 100 years.

Currently, the most commonly used mixed acid method in the nitration process is concentrated nitric acid and concentrated sulfuric acid (Euler, H, Ann. Chem. 1093, 330, 280). There are many problems with the process. First of all, when using such mixed acid, the generation of huge amount of waste sulfuric acid is inevitable, and the amount of waste water including washing water input in the washing process is estimated to be at least 300,000 tons per year based on the production of domestic nitro compounds. This wastewater generation problem is emerging as a problem that must be solved in the future in terms of environmental aspects. In addition, the reaction in such strong acid conditions is dangerous to work, promote corrosion of the reactor, as well as difficult to automate the operation due to the enormous reaction heat generated during the reaction. In order to solve these problems, developed countries are known to be conducting research on new nitration processes in various angles, but no clear alternatives are available. However, most plants still use the nitration process using a mixture of nitric acid and sulfuric acid. It is done.

The water produced in the nitration reaction of aromatic compounds causes serious waste acid treatment problems as mentioned above, and this problem is even more serious in the current mixed acid reaction of nitric acid and sulfuric acid. In addition, in the case of such mixed acid-based reactions, the reaction is not easy to control the reaction, and in the nitration reaction of some compounds such as toluene, highly explosive substances such as acylnitrate may be generated as by-products.

Therefore, instead of using strong acid such as sulfuric acid as an acid catalyst, nitric acid itself is used as it is, but there is a risk of explosion even when the concentration of nitric acid is high. Thus, in 1956, Olah and Kuhn introduced the nitric acid-HF-BF ₃ method (Olah, GA, Kuhn, SJ Chem) as a new nitration reaction to solve the problem of mixed acid nitration reaction. Ind. 1956. p. 98; Olah, GA, Kuhn, SJ, Mlinko, AJ Chem. Soc. 1956, p, 4257.), and thereafter NO ₂ BF ₄ was subjected to nitration reaction by Henion et al. Although it has been reported to be used (Thomas, RJ, Anzilotti, W, F., Hennion, GF Ind, Eng. Chem. 1940, 32, 408; Hennion, GFUS Patent, 2,314,212 (1943)), because the reagents are very expensive. Not economical, still corrosive, and HBF ₄ produced as a by-product is undesirable because of the high risk of explosion.

Nitrate-anhydrous acetic acid system (Redlich, O., Hood, GC Discuss Faraday Sox. 1957, 24, 87.) or Ostromyslenkskii and Werner studied as another nitration reagent In the case of the developed C (NO ₂ ) ₄ (Ostromyslenkskli, II Chem. Ber. 1920, 53, 1537; Werner, A. Chem. Ber. 1908, 42, 4326), the risk of explosion is still present, in addition to the weakness of reactivity. It is known that there are many problems to apply to the industry because it cannot be solved. Recently, Suzuki et al., Kyoto University, announced that nitrification can be carried out relatively easily in an organic solvent using gaseous nitrogen dioxide and ozone as an oxidant (Suzuki H., et al., Chem Letters, pp. 1421-1424, 1993; Suzuki H., et al., JCS Chem. Commun. 1049, 1991; EP 0 497 989 Al, 1991), which is still in the research stage and has no strong nitration reactivity compared to the reference method In the case of nitration reaction of weakly reactive aromatic compounds, such as dinitrolation is known to be difficult to proceed.

Therefore, the present invention is not inferior in terms of reactivity compared to the mixed acid method currently used in the large-scale nitration process, it is possible to freely make the desired isomer freely, and the problem of treating many acidic waste waters generated after the reaction and strong mixed acid reaction It is to provide a new nitration reaction process that can solve problems such as reducing the operational risk due to conditions.

In the present invention, in the use of nitric acid as an nitration reagent in an organic solvent, dinitrogen pentoxide (N ₂ O ₅ ) obtained by oxidizing nitrogen dioxide to ozone reacts with water generated during the nitration reaction to continuously supply nitric acid. It is based on easily and selectively proceeding the nitration reaction of aromatic compounds with a small amount of nitric acid without using an acid catalyst.

In the present invention, the nitration reaction temperature is preferably set to -30 ° C to + 30 ° C. In the present invention, a mixture of nitrogen monoxide and nitrogen dioxide, and a mixture of ozone and air instead of ozone may be used instead of nitrogen dioxide.

The nitration reaction of the aromatic compound proceeds through the mechanism of electrophilic substitution reaction, in particular the electrophile of the nitration reaction is known as nitronium ion (NO ₂ ⁺ ). According to the present invention then processes the nitrogen dioxide to ozone oxidation as diphosphorus pentoxide nitrogen, is diphosphorus pentoxide nitrogen is NO ₂ ^+, and NO ₃ ^- at the same time utilizing a NO ₂ ⁺ generated when digested with a electrophile in the nitration reaction NO ₃ ^- which was used to remove the by-product water which acts as a determining factor in the reactivity decreases. The reaction could be selectively controlled according to the choice of organic solvent, the flow rate of ozone, and the equivalent of nitrogen dioxide, and in some cases aromatic compounds could be used as reactants and solvents, especially for aromatic compounds with relatively low nitration reactivity such as chlorobenzene. In this case, the reactivity and the selectivity of the reaction were significantly increased, and the reaction could be easily proceeded to dinitration. Looking at this in detail from the reaction mechanism side as follows.

First, a double bond of an aromatic compound is attacked by nitronium ions present in nitric acid, and a nitro group is introduced through an arerenium intermediate. At this time, water is produced as a by-product, and the generated water reacts with NO ₃ ⁻ generated by decomposition of dinitrogen pentoxide, which is oxidized by ozone, to form nitric acid again, so that the concentration of nitric acid can be maintained at the same level as the initial reaction. have. Further, it is possible to generate the NO ₂ at the same time the decomposition of diphosphorus pentoxide Nitrogen ⁺ attack the double bonds of an aromatic compound directly to the nitration reaction of the electrophile, thereby further increasing the reactivity. This reaction takes the form of a chain reaction and can maintain nitric acid at a high concentration without a strong strong acid catalyst.

The decrease in nitric acid concentration due to the production of water has been pointed out as the most important factor to reduce the nitration reactivity (Ridd, JH Draper, MRJ Chem. Soc., Perkin II. 1981, 94.). It is the biggest reason to go to the mountain. In the case of mixed nitrification, sulfuric acid is used as an acid catalyst for oxidizing nitric acid more than 50% of nitric acid, and if nitric acid is nitrated by itself, a considerable amount of nitric acid is required to maintain nitric acid concentration. As a result, not only problems such as waste acid treatment but also increase the risk of work.

The throughput and duration of nitric acid should be adjusted appropriately depending on the reactants and conditions. Details thereof will be described in detail by way of examples.

Example 1

In a three-necked round bottom flask equipped with a dry ice cooler, 5 mmol chlorobenzene, 30 mmol (6.0 equivalents) of liquid nitrogen dioxide, and 5 mmol (1.0 equivalents) of nitric acid were dissolved in different solvents, respectively, for 3 hours at a flow rate of 5 mmol / h. Ozone was blown in while. At this time, the reaction temperature was maintained at 0 ℃. After the reaction, nitrogen gas was blown to blow out the ozone mixed in the solution, and then depressurized to completely remove the unreacted nitrogen dioxide remaining in the product. In this case, the yield was slightly different depending on the reaction conditions, but was more than 97%. Analysis of specific isomers was carried out through gas chromatography, the aspects of the gas chromatography is shown in Figure 1, the analysis results are shown in Table 1.

Example 2

In a three-necked round bottom flask equipped with a dry ice cooler, 10 mmol toluene, 30 mmol (3.0 equivalents) of liquid nitrogen dioxide, and 10 mmol (1.0 equivalents) of nitric acid were dissolved in different solvents, respectively, at a flow rate of 20 mmol / h for 2 hours. Ozone was blown in. At this time, the reaction temperature was maintained at 0 ℃. At this time, the yield was slightly different depending on the conditions of the reaction, but showed more than 97%, and the analysis results of specific isomers by the same analysis as in Example 1 are shown in Table 2.

Example 3

In a three-necked round bottom flask equipped with a dry ice cooler, 10 mmol toluene, 30 mmol (3.0 equivalents) of liquid nitrogen dioxide, and 10 mmol (1.0 equivalents) of nitric acid were dissolved in 40 ml of different solvents, respectively, at a flow rate of 10 mmol / h. Ozone was blown in for an hour. At this time, the reaction temperature was maintained at 0 ℃. At this time, the yield was slightly different depending on the conditions of the reaction, but most were 97% or more, and the analysis results of specific isomers by the same analysis as in Example 1 are shown in Table 3.

Example 4

In a three-necked round-bottomed flask equipped with a dry ice cooler, 5 mmol chlorobenzene, 12.5 mmol (2.5 equivalents) of liquid nitrogen dioxide, and 12.5 mmol (2.5 equivalents) of nitric acid were added to 10 ml of carbon tetrachloride. Ozone was blown in for an hour. At this time, the reaction temperature was maintained at 0 ℃.

At this time, the yield was 97% or more, and the analysis results of specific isomers by the same analysis as in Example 1 are shown in Table 4.

Example 5

In a three-necked round-bottomed flask equipped with a dry ice cooler, 5 mmol chlorobenzene, 50 mmol (10 equivalents) of liquid nitrogen dioxide, and 5 mmol (1.0 equivalents) of nitric acid were dissolved in carbon tetrachloride and ozone was applied for 12 hours at a flow rate of 5 mmol / h. Blow it in. After 8 hours, an additional 25 mmol (5 equivalents) of nitrogen dioxide was added. At this time, the reaction temperature was maintained at 0 ℃. The yield showed an average of 97% or more, and the analysis results of specific isomers by the same analysis as in Example 1 are shown in Table 5.

Example 6

In a three-neck round-bottomed flask equipped with a dry ice cooler, 5 mmol chlorobenzene, 12.5 mmol (2.5 equivalents) of liquid nitrogen dioxide and 12.5 mmol (2.5 equivalents) of nitric acid were added to 10 ml of carbon tetrachloride, and the flow rate was 7.5 at 5 mmol / h. Blowing a mixture of ozone and air for a time. 12.5 mmol (2.5 equiv) of nitrogen dioxide was added every 3 hours. At this time, the reaction temperature was maintained at 0 ℃. The yield showed an average of 97% or more, and the analysis results of specific isomers by the same analysis as in Example 1 are shown in Table 6.

Example 7

In a three-necked round-bottomed flask equipped with a dry ice cooler, 10 ml of carbon tetrachloride and 12.5 mmol (2.5 equivalents) of nitric acid in liquid form containing 5 mmol 2-nitrochlorobenzene and 12.5 mmol (2.5 equivalents) of nitrogen monoxide were added. , A mixture of ozone and air was blown for 5 hours at a flow rate of 5 mmol / h. At this time, the reaction temperature was maintained at 0 ℃. The yield showed an average of 97% or more, and the analysis results of specific isomers by the same analysis as in Example 1 are shown in Table 7.

Example 8

In a three-necked round-bottomed flask equipped with a dry ice cooler, 10 ml of carbon tetrachloride and 12.5 mmol (2.5 equivalents) of nitric acid and liquid nitrogen dioxide containing 5 mmol 4-nitrochlorobenzene and 12.5 mmol (2.5 equivalents) of nitrogen monoxide were added. , Was blown into ozone for 12 hours at a flow rate of 5 mmol / h. 12.5 mmol (2.5 equivalents) of liquid nitrogen dioxide was added every 3 hours. At this time, the reaction temperature was maintained at 0 ℃. The yield was an average of 97% or more, and the analysis results of specific isomers by the same analysis as in Example 1 are shown in Table 8.

Example 9

In a three-necked round-bottomed flask equipped with a dry ice cooler, 20 mmol of chlorobenzene (197 mmol) was added 20 mmol of liquid nitrogen dioxide and 10 mmol of nitric acid, and ozone for 3 hours at a flow rate of 5 mmol / h. Blown in. At this time, the reaction temperature was maintained at 0 ℃. As a product, 7.7 mmol of mononitro compound was obtained, and the results of analysis of specific isomers by the same analysis as in Example 1 are shown in Table 9.

Example 10

In a three-necked round-bottomed flask equipped with a dry ice cooler, 10 mmol of toluene, 25 mmol (2.5 equivalents) of liquid nitrogen monoxide and 25 mmol (2.5 equivalents) of nitric acid were added to 40 ml of carbon tetrachloride, and the flow rate was 20 mmol / h for 1 hour. Blow into ozone. At this time, the reaction temperature was maintained at 0 ℃. The yield showed an average of 97% or more, and the analysis results of specific isomers by the same analysis as in Example 1 are shown in Table 10.

Example 11

In a three-necked round-bottomed flask equipped with a dry ice cooler, 10 mmol 4-nitrotoluene, 12.5 mmol (2.5 equivalents) of liquid nitrogen dioxide and 25 mmol (2.5 equivalents) of nitric acid were added to 40 ml of carbon tetrachloride, and the flow rate was 20 mmol / h. Blowed in ozone for 1 hour. At this time, the reaction temperature was maintained at 0 ℃. The yield showed an average of 97% or more, and the analysis results of specific isomers by the same analysis as in Example 1 are shown in Table 11.

Example 12

In a three-necked round-bottomed flask equipped with a dry ice cooler, 5 mmol benzene, 12.5 mmol (2.5 equivalents) of liquid nitrogen dioxide, and 12.5 mmol (2.5 equivalents) of nitric acid are placed in 10 ml of carbon tetrachloride and 30 minutes at a flow rate of 5 mmol / h. While blowing in ozone. At this time, the reaction temperature was maintained at 0 ℃. Nitrobenzene was obtained in 100% yield.

Example 13

In a three-necked round-bottomed flask equipped with a dry ice cooler, 5 mmol benzene, 12.5 mmol (2.5 equivalents) of liquid nitrogen dioxide, and 12.5 mmol (2.5 equivalents) of nitric acid were placed in 10 ml of carbon tetrachloride, and 2.5 hours at a flow rate of 5 mmol / h. While blowing in ozone. At this time, the reaction temperature was maintained at 0 ℃. Meta-dinitrobenzene showing an average yield of at least 98% was obtained.

Example 14

In a three-necked round bottom flask equipped with a dry ice cooler, 5 mmol benzene, 15 mmol (3 equivalents) of liquid nitrogen dioxide, and 5 mmol (1.0 equivalents) of nitric acid were placed in 10 ml of carbon tetrachloride and ozone for 2 hours at a flow rate of 5 mmol / h. After the mononitration reaction was completed, 12.5 mmol (2.5 equivalents) of liquid nitrogen dioxide and 12.5 mmol (5 equivalents) of nitric acid were added thereto, and ozone was added at the same flow rate for 3 hours. At this time, the reaction temperature was maintained at 0 ℃. Meta-dinitrobenzene was obtained with an average yield of 97% or more.

As described above, the present invention provides an effect of allowing nitration to be performed in a less dangerous reaction than the mixed acid method. In addition, the present invention does not use concentrated sulfuric acid, and also reduces the amount of concentrated nitric acid to significantly reduce the amount of wastewater generated by the use of a large amount of these inorganic acids to provide an effect to protect the environment. Although the present invention has been described in detail only with respect to the above-described embodiments, it will be apparent to those skilled in the art that the present invention may be changed or modified within the spirit and scope of the present invention, and such changes or modifications are attached to the appended claims. Should be limited by

Claims (5)

In the nitrification of an aromatic compound using nitric acid, the aromatic compound and nitric acid are dissolved or dispersed in an organic solvent, and nitrogen dioxide or a mixture of nitrogen monoxide and nitrogen dioxide and ozone or a mixture of ozone and air are added thereto. Process for nitration of aromatic compounds. The nitration reaction of the aromatic compound according to claim 1, wherein the aromatic compound is used simultaneously as a reactant and a solvent. The method for nitrating the aromatic compound according to claim 1, wherein the amount of nitric acid (HNO ₃ ), nitrogen dioxide, and ozone is selectively controlled to control mononitrolation, dinitrolation, and trinitrolation. The nitration method of the aromatic compound according to claim 1, wherein the nitration reaction is performed at a temperature range of -30 to + 30 ° C. The method for nitrating the aromatic compound according to claim 1, wherein the organic solvent is one or a mixture of two or more organic halogen compounds of dichloromethane, trichloromethane and carbon tetrachloride.