JPH0611743B2 - Process for producing aromatic isocyanate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an aromatic isocyanate useful as a raw material for polyurethane, agricultural chemicals and the like. More specifically, it relates to a method for directly producing a corresponding isocyanate from an aromatic nitro compound and carbon monoxide.

[Conventional technology]

The current industrial production method of aromatic isocyanate is a method of reducing a nitro compound to give an amine, and then reacting phosgene separately synthesized from carbon monoxide and chlorine with the amine to obtain the isocyanate. However, without using hydrogen or chlorine in the middle, and without dealing with highly toxic phosgene,
It would be desirable if an aromatic isocyanate could be produced by reacting the nitro group directly with carbon monoxide to convert it to an isocyanate group in one step. This direct isocyanate method is economically advantageous because the isocyanate can be produced from the nitro compound in a one-step reaction without producing hydrochloric acid as a by-product.

An aromatic nitro compound and carbon monoxide are reacted under high temperature and pressure in the presence of a suitable catalyst containing a noble metal compound as a main component according to the formula (1), and Ar (NO ₂ ) n + 3nCO → Ar (NCO) n + 2nCO ₂ ... (1) A method for directly synthesizing an aromatic isocyanate is known, and many various catalyst systems using a noble metal compound as a main catalyst have been proposed.

That is, many methods have been proposed in which a noble metal, a compound of a noble metal or a complex compound thereof is used as a main catalyst and various promoters are used.

For example, as a method using a vanadium compound as a cocatalyst, a method using an oxide of vanadium is disclosed in JP-B-45-22.
722, JP-B-45-35774 and JP-B-48-42632, a method using a chloride of vanadium is described in JP-B-48-43110.

Further, a method in which vanadium oxide and phosphorus acid halide are mentioned as co-catalysts is described in Japanese Patent Publication No. 45-35774.

However, in all cases, the reaction rate is slow in spite of the large amount of the main catalyst used, and the conversion and yield of aromatic isocyanate are low.

On the other hand, using a catalyst selected from the group consisting of a palladium halide, its pyridine or quinoline complex, and a mixture of palladium halide and vanadium oxide as the main catalyst, the reaction is carried out in the presence of a hydroxy-substituted hydrocarbon. A special method for producing aromatic isocyanate
48-43113. However, as shown in the examples, the yield is low and a large amount of catalyst is required, which is considered to be insufficient for industrial practice.

[Problems to be solved by the invention]

As mentioned above, in the method for producing an aromatic isocyanate from an aromatic nitro compound and carbon monoxide, a method using various cocatalyst systems to improve the reaction by using palladium or its compound as a main catalyst is proposed. However, in the known method, a large amount of an expensive noble metal main catalyst has to be used for the starting nitro compound due to the low activity and selectivity of the catalyst, and the yield of the target product is low.

Further, the main catalyst is decomposed during the reaction and is deposited (adhered out) on the reactor wall (plate out), which further lowers the catalytic activity and makes it difficult to recover the catalyst.

The present invention has been made from the above viewpoint, and the object of the present invention is to use a new catalyst system and to use an extremely small amount of a noble metal catalyst in combination with an additive,
An object of the present invention is to provide a method for producing an aromatic isocyanate with a high yield and a simplified process.

[Means for solving problems]

The present inventors have earnestly studied to achieve the above object, and finally arrived at the present invention.

That is, the present invention, an aromatic nitro compound and carbon monoxide, palladium or a mixture of the compound and a nitrogen-containing heterocyclic compound, a palladium complex coordinated with the nitrogen-containing heterocyclic compound, and the complex In the method for producing an aromatic isocyanate, which comprises reacting at high temperature and high pressure in the presence of at least one catalyst selected from the group consisting of a mixture with the nitrogen-containing heterocyclic compound, the reaction is carried out by reacting an active hydrogen compound An aromatic fragrance, characterized in that it is carried out in the presence of a cocatalyst system consisting of a halogenated phosphorus compound, a vanadium compound and a tertiary amine, and the aromatic isocyanate is separated from the resulting reaction product by distillation. It is a method for producing a group isocyanate.

The aromatic nitro compound used as a raw material in the present invention is an aromatic mono- or poly-nitro compound, and may contain an isocyanate group and a substituent that does not react with this. Representative examples include nitrobenzene, o-, m- and p-nitrotoluene, o-nitro-p-xylene, nitromesitylene, 1-chloro-2-nitrobenzene, 1,
2-dichloro-4-nitrobenzene, 1-bromo-4-
Nitrobenzene, 1-fluoro-4-nitrobenzene,
1-trifluoromethyl-4-nitrobenzene, o-,
m- and p-nitrophenyl isocyanate, o- and p-nitroanisole, o- and p-nitrophenol, nitrobenzaldehyde, nitrobenzoyl chloride, methyl nitrobenzoate, nitrobenzenesulfonyl chloride, nitrobenzonitrile, 2-isocyanato-4-nitrotoluene, 2-nitro-4-isocyanatotoluene, 2-isocyanato-6-nitrotoluene,
Nitronaphthalene, 5-nitronaphthyl isocyanate, nitroanthracene, (4-isocyanatophenyl) (4'-nitrophenyl) methane, m-dinitrobenzene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, α, α'-dinitro-p-xylene, dinitromesitylene, 1-chloro-2,4-dinitrobenzene, 2,4-dinitroanisole, 1,5-dinitronaphthalene, 4,4'-dinitrobiphenyl, 3,3 ' −
Dimethyl 4,4'-dinitrobiphenyl, bis (p-nitrophenyl) methane, bis (p-nitrophenyl) ether, bis (p-nitrophenyl) thioether, bis (p-nitrophenyl) sulfone, trinitrobenzene and the like can be mentioned.

Among these, especially nitrobenzene, 2,4- and 2,
6-Dinitrotoluene, 1,2-dichloro-4-nitrobenzene, 1,5-dinitronaphthalene, bis (p-nitrophenyl) methane and the like are preferably used practically.

The active hydrogen compound used in the method of the present invention is a compound that reacts with an isocyanate and is stable at room temperature and easily dissociates at a high temperature to react as an isocyanate, that is, a compound that forms a blocked isocyanate. In the method of the present invention, the dissociation initiation temperature (the temperature at which the weight loss by differential thermal analysis is 5%) is 200.
Represents a compound having an active hydrogen which forms a blocked isocyanate at a temperature of ℃ or below. Examples of the active hydrogen compound used in the present invention include the following.

That is, cyano compounds such as hydrogen cyanide and ethyl cyanoacetate, malonates, acetoacetyl compounds such as acetylacetone and ethyl acetoacetate, hydroxylamine or oxime derivatives such as hydroxylamine and acetone oxime, N-such as N-methylaniline and diphenylamine. Substituted aromatic amines, aliphatic and aromatic mercaptans, aromatic hydroxy compounds such as phenols and 6-hydroxytetralin, lactams such as α-pyrrolidone and caprolactam, 1-phenol-3-methyl-5-pyrazolone, etc. 5-pyrazolone compounds, imidazoles and triazoles. Examples of the phenols used in the present invention include phenol, chlorophenol, cresol, ethylphenol, alkylphenols such as linear or branched propyl-, butyl-, nonylphenol, catechol, resorcin, pyrogallol, phloroglucinol, 4,4. Examples include ′ -dihydroxydiphenylmethane, 2,2′-isopropylidenediphenol, α and β-naphthol, anthranol, phenanthrol and the like. These phenols may be substituted with a substituent inert to this reaction, for example, a monovalent substituent such as a halogen atom, an alkyl group and a carboxylic acid ester group, and an alkylene group, an oxy group, a carbonyl group and the like. It does not matter if it is crosslinked with a divalent substituent.

Use of these active hydrogen compounds in a small amount, compared with the case where they are not used at all, is effective in accelerating the reaction and improving the yield. Usually 0.05 for the nitro group of aromatic nitro compounds
It is used in a molar ratio or more, preferably 0.1 molar ratio or more. It is not economically advantageous to use a large excess of the aromatic nitro compound, and the yield tends to decrease. Usually, it is used in a molar ratio of not more than 10 and preferably not more than 5 with respect to the nitro group of the aromatic nitro compound.

Ordinary alcohols, on the other hand, react with isocyanates to form urethane, but the urethane formed has a high dissociation initiation temperature of 250 ° C. or higher and is therefore not included in the category of active hydrogen compounds of the method of the present invention.

Examples of the noble metal compound used as the main catalyst include palladium and palladium halides, nitrates, isocyanides, carbonates, carboxylates, oxides, chelates and other inorganic compounds and carbonyl, alkyl, olefin, π-allyl group, and other compounds. An organic complex containing a ligand is mentioned. Preferred are halogen-containing compounds such as palladium chloride, palladium bromide, palladium iodide, sodium chloropalladate, tetraamminepalladium chloride, dichlorodiamminepalladium, bis (ethylene) palladium chloride, bis (π-allyl) palladium chloride. Etc. In the case of a noble metal compound containing no halogen, it is desirable to separately add a halogen-containing compound such as hydrogen halide, phosgene, halogenated hydrocarbon and acid halide.

Examples of the nitrogen-containing heterocyclic compound that acts as a ligand for the noble metal of the main catalyst include pyrrole, N-methylpyrrole, pyrazole, imidazole, triazole, pyridine, α-, β- or γ-picoline, 4-phenylene. Phenyl pyridine, 4-vinyl pyridine, 2-fluoro pyridine, 2
-Chloropyridine, 3-chloropyridine, 2-bromopyridine, 3-hydroxypyridine, 2-methoxypyridine, α-picolinaldehyde, α-picolinic acid methyl ester, α-picolinamide, 2,6-dimethylpyridine, 2- Methyl-4-ethylpyridine, 2-chloro-4
-Methylpyridine, 2,6-dicyanopyridine, 5,
6,7,8-tetrahydroquinoline, 5,6,7,8-
Tetrahydroisoquinoline, quinoline, isoquinoline,
Acridine, benzoquinoline, benzisoquinoline, phenanthridine, pyridazine, pyrimidine, pyrazine,
Cinnoline, quinazoline, quinoxaline, phthalazine,
Examples include naphthyridine and phenazine.

Representative examples of complexes of noble metal halides with nitrogen-containing heterocyclic compounds include, for example, dichlorobis (pyridine) palladium, dibromobis (pyridine) palladium, diiodobis (pyridine) palladium, dichlorobis (α-picoline) palladium, dichlorobis (quinoline). Examples thereof include palladium, dichlorobis (isoquinoline) palladium, dichlorocarbonyl (pyridine) palladium, dichlorocarbonyl (2,6-dimethylpyridine) palladium and the like.

The process according to the invention is characterized by the use of a cocatalyst system which comprises a combination of a special compound consisting of a halogenated phosphorus compound, a vanadium compound and a tertiary amine in addition to the main catalyst palladium or a compound thereof.

In order to effectively carry out the method of the present invention, the use of each catalyst component is indispensable, but the addition of a halogenated phosphorus compound is particularly effective, and at the same time enhances the activity of the catalyst system and accelerates the reaction. , It suppresses the generation of by-products and increases the selectivity of the target substance.

Examples of the halogenated phosphorus compound used in the method of the present invention include phosphorus trifluoride, phosphorus trichloride, phosphorus tribromide, phosphorus triiodide, phosphorus pentafluoride, phosphorus pentachloride, phosphorus pentabromide and tetratetrafluoromethane. Phosphorus halide compounds such as diphosphorus chloride and diphosphorus tetraiodide; alkyl or aryl substituted phosphorous compounds such as dimethylbromophosphine, diphenylchlorophosphine and ethylphosphorus tetrachloride;
Phosphoryl fluoride, phosphoryl chloride, phosphoryl bromide,
Phosphoryl oxyhalides such as phosphoryl monofluoride difluoride, phosphoryl difluoride monofluoride, pyrophosphoryl chloride, and oxyethyl phosphorus dichloride; quaternary phosphonium halides such as tetraethylphosphonium chloride; phosphonyl halides such as ethylphosphonic acid dichloride Kind;
Examples include alkyl phosphates and halogenides such as methyl phosphate and dichloride.

In these halogenated phosphorus compounds, 0.05 to 20 gram atom, preferably 0.1 to 10 gram atom, is used as phosphorus for 1 gram atom of palladium. Further, it is desirable to use 1 × 10 ⁻³ mol or more with respect to 1 mol of the raw material nitro compound, and to use 1 × 10 ⁻⁴ g or more with respect to 1 kg of the whole reaction liquid as the concentration in the reaction liquid.

Any vanadium compound can be used as the vanadium compound. The valence of vanadium of the vanadium compound used is not particularly limited.

Examples of vanadium compounds that can be used in the method of the present invention include chlorides such as vanadium trichloride and vanadium tetrachloride, salts of chlorides such as potassium vanadium (IV) chloride, vanadium dichloride oxide, vanadium trichloride chloride and the like. Substance, vanadium oxide (III), vanadium oxide (I
V), oxides such as vanadium oxide (V), vanadates such as pyrovanadate and metavanadate, sodium orthovanadate, ammonium metavanadate, vanadate salts such as potassium metavanadate, vanadium sulfate (II)
I) Vanadium salts of acids such as ammonium and vanadium (III) oxalate, vanadium oxysulfate (IV), vanadyl salts of acids such as vanadium oxyoxalate, vanadium (I
V) Acetylacetone salts such as oxyacetylacetonate and hexacarbonyl vanadium.

These vanadium compounds are used in an amount of 0.05 to 20 gram atoms, preferably 0.1 to 10 gram atoms in terms of vanadium with respect to 1 gram atom of vanadium. If it is less than 0.05 gram atom, the activity is low, and use of 20 gram atom or more reduces the selectivity. Also, 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ mol, preferably 1 ×, relative to 1 mol of the starting nitro compound
It is preferably used in the range of 10 ^{−3 to} 5 × 10 ⁻² mol.

As the tertiary amine, aliphatic, aliphatic-aromatic, alicyclic, aromatic tertiary amines and nitrogen-containing heterocyclic compounds are used. These may be in the unsubstituted form, or may be a suitable substituent inert to the reaction, for example, a halogen atom,
It may have a substituent such as an alkyl group, an aryl group, an alkenyl group, a cyano group, an aldehyde group, an alkoxy group, a phenoxy group, an alkylthio group, a phenylthio group, a carbamyl group, a carboalkoxy group and a thiocarbamyl group. Among these, for example, aliphatic tertiary amines such as trimethylamine, triethylamine, tripropylamine and tributylamine, N, N-dimethylaniline, N,
Aliphatic aromatic amines such as N-diethylaniline and N, N-diisopropylaniline, N, N-dimethylcyclohexylamine, N, N-diethylcyclohexylamine, N, N-diisopropylcyclohexylamine,
Aliphatic tertiary amines such as 1,4-diazabicyclo [2,2,2] octane, aromatic tertiary amines such as triphenylamine, nitrogen-containing heterocyclic compounds such as pyridine, quinoline, and isoquinoline Is included. Among them, nitrogen-containing heterocyclic compounds show remarkable effects from the viewpoint of improving the yield of urethane and the reaction rate. Further exemplifying effective nitrogen-containing heterocyclic compounds other than the above, 1-methylpyrrole, 1-phenylpyrrole, 1-methylimidazole,
1-methylindole, 1-phenylindole, indolenine, 2-isobenzazole, indolizine, 1-
Methylcarbazole, 2-chloropyridine, 2-bromopyridine, 2-fluoropyridine, 4-phenylpyridine, 2-, 3- and 4-methylpyridine, 2-methyl-5-ethylpyridine, 2,6-dimethylpyridine. ,
2,4,6-trimethylpyridine, 2-vinylpyridine, 2-styrylpyridine, 3-chloropyridine, 2,
6-dichloropyridine, 2-chloro-4-methylpyridine, 4-phenylthiopyridine, 2-methoxypyridine, 4-dimethylaminopyridine, α-picolinic acid phenyl ester, γ-picolinic acid methyl ester, 2,6
-Dicyanopyridine, α-picolinaldehyde, α-picolinamide, 5,6,7,8-tetrahydroquinoline, 2,2-dipyridyl, 2-chloroquinoline, acridine, phenanthridine, benzoquinoline, benzisoquinoline, naphthyridine, Examples thereof include pyrazine, 4,6-dimethylpyrazine, 2,6-dimethylpyrazine, pyridazine, pyrimidine, quinoxaline, 2,3-dimethylquinoxaline, quinazoline, phthalazine, phenazine, cinnoline and pteridine. These can also be used as a polymer such as polyvinyl pyridine. These tertiary amines may be added to the reactor separately from the raw materials and other catalyst components, or a part of them may be treated with a part of other components of the catalyst system in advance to obtain a suitable complex or adduct. It can also be used by changing to other compounds. As an example, palladium chloride and pyridine can be separately added to the reactor and reacted, but a palladium chloride-pyridine complex is prepared in advance, and the complex, other raw materials, a catalyst component, and a tertiary The amine can be added and reacted.

The amount of the tertiary amine used is 0.05 mol ratio or more, preferably 0.1 mol ratio or more based on the nitro group of the nitro compound used as the raw material. If it is less than 0.05 mol ratio, the reaction becomes very slow and the selectivity is lowered.

Furthermore, the present invention can be carried out by using one or more kinds of conventionally known various co-catalyst additives such as Lewis acids, metal compounds and organic / inorganic compounds in combination with the above catalyst system.

Although the method of the present invention can be carried out without using a solvent, it is preferable to dilute the aromatic nitro compound with a solvent for reaction. The solvent used is all effective as long as it is a liquid inert to the raw materials and products, and is not particularly limited, but usually heptane, cyclohexane,
Aliphatic, alicyclic and aromatic hydrocarbons such as benzene, toluene, xylene and various petroleum fractions, for example halogenated hydrocarbons such as dichloromethane, perchloroethylene, tetrachloroethane, chlorobenzene, dichlorobenzene and chloronaphthalene. Kinds and the like are used.

The amount of the solvent used is not particularly limited and is completely arbitrary, and the appropriate amount varies depending on the reaction mode. However, the amount used is usually in the range of 3 to 50% by weight as the concentration of the aromatic nitro compound in the solvent. The method of mixing the solvent is not particularly limited,
The aromatic nitro compound, the main catalyst and the cocatalyst can be mixed in absolutely any order and proportions.

The amount of carbon monoxide consumed as the reaction raw material is stoichiometrically 3 mol per mol of the nitro group according to the formula (1),
At the same time, 2 mol of carbon dioxide is produced as a by-product. The amount of carbon monoxide actually charged in the reactor depends on the concentration of the aromatic nitro compound, the amount of catalyst used, the type of reactor, the reaction temperature,
Although the appropriate amount varies depending on the reaction pressure and the like, the minimum amount is required to be 3 times the molar amount of the nitro group in the reactor, usually 5 to 100 times the molar amount, and preferably 7 to 20 times the molar amount. The reaction can also be carried out in a batch mode while containing carbon dioxide produced as a by-product, but while removing carbon dioxide that increases according to the progress of the reaction from the reactor, at the same time recycling and supplementing carbon monoxide, It is desirable to carry out the reaction while keeping the molar ratio of carbon dioxide to carbon oxide in the reactor small.

The reaction temperature is 100 to 250 ° C, preferably 150 to 230 ° C.

The reaction pressure used is in the range of 10 to 1000 kg / cm ² , usually 50 to 500 kg / cm ² .

The reaction time is usually in the range of 0.5 to 10 hours, and the practical optimum time is determined within this range depending on the selection of the above-mentioned conditions.

To elaborate on the embodiments of the present invention, the reaction can be carried out batchwise, semi-continuously or continuously. Usually, the solution in which the aromatic nitro compound is dissolved in the solvent and each component of the catalyst are mixed prior to the reaction or separately supplied into the reactor. The reactor is pressurized to reaction pressure with carbon monoxide and kept at reaction temperature. In the continuous mode, the carbon dioxide mixed gas in the reactor is continuously discharged and carbon monoxide is injected under pressure.

After a lapse of a predetermined time, the reaction mixture is cooled or the gas is separated. The reaction mixture obtained is subjected to distillation and divided into product isocyanate, solvent, catalyst and by-products. The recovered catalyst and solvent are used for the reaction again as they are or, if necessary, after appropriate treatment. If a small amount of raw material or a nitroisocyanate intermediate in the case of using a polynitro compound as a raw material remains in the reaction mixture, these are also separated and circulated to the reactor at the same time. The product isocyanate is subjected to a conventional refining operation depending on the application.

Thus, according to the process of the present invention, it is possible to economically produce the corresponding isocyanates from aromatic nitro compounds in high yields by using highly active catalyst systems.

〔Example〕

 The present invention will be specifically described with reference to Examples or Comparative Examples.

In the following Examples or Comparative Examples, all reactions were carried out using an electromagnetic stirring type autoclave made of stainless steel (SUS-316L).

The conversion and yield in the examples are 15% silicon DC550 /
Calculated from the results of gas chromatographic analysis using gas chromium Q, 150 ° C., and biphenyl internal standard.

In the examples, dinitrotoluene is abbreviated as DNT, tolylene diisocyanate is abbreviated as TDI, and nitrotolyl isocyanate is abbreviated as NIT. When it is necessary to indicate the position of a substituent,
For example, 2,4-dinitrotoluene is prepended with a position number, such as 2,4-DNT.

Example-1 30 g of 2,4-DNT, 3.1 g of phenol and 0.3 g of dichlorobis (pyridine) palladium were placed in an autoclave having an internal volume of 500 ml.
78g, phosphoryl chloride 0.346g, vanadium trichloride oxide
0.096 g, quinoline 9.8 g, o-dichlorobenzene 172 g
Was prepared.

The inside of the autoclave was replaced with nitrogen, and carbon monoxide was 160 kg.
The pressure was increased to / cm ² G. The temperature was raised to 210 ° C. with stirring, and the reaction was carried out at the same temperature for 300 minutes. During the process, carbon monoxide was replenished under pressure up to 260 kg / cm ² G each time the pressure dropped to 240 kg / cm ² G.

After completion of the reaction, the autoclave was not cooled and the pressure was released while maintaining the reaction temperature, and o-dichlorobenzene, phenol and a part of quinoline accompanying the exhaust gas were condensed and collected through a condenser. After evacuation to normal pressure, a part of the reaction solution in the autoclave was taken and analyzed.
It was found that 22.1 g of 4-TDI was contained. This corresponds to a yield of 77 mol% based on 2,4-DNT charged.

The autoclave is gradually depressurized, then a fraction consisting of a mixture of quinoline and 2,4-TDI which is subsequently distilled off under reduced pressure is collected, and the fraction is distilled using a conventional rectification column,
21.5 g of 2,4-TDI (120-117 ° C / 15-9 mmHg) was obtained.

Comparative Example-1 and Examples-2 to 7 In order to show the effect of the active hydrogen compound in the method of the present invention, the case where no phenol is used is Comparative Example-1, and the case where the amount of phenol used is changed is Example-2 to. As 4,
Instead of phenol, husband and wife p-phenylphenol,
The case of using ε-caprolatum or acetone oxime is shown in Table 1 as Examples-5 to 7.

Other amounts and methods used are the same as in Example-1 Is.

Comparative Example-1 in which neither active hydrogen compound was used
It is shown that the reaction rate was increased as compared with the above, the nitro group conversion rate was improved, the yield of 2,4-TDI and the total yield of 2,4-TDI + NIT were also increased, and the selectivity was improved.

Comparative Examples-2 to 3 Comparative Examples to show the effect of the cocatalyst in the method of the present invention-
In Example 2, the phosphoryl chloride was not used, and in Comparative Example-3, 2,4-DNT and carbon monoxide were reacted in the same manner as in Example-1 except that vanadium trichloride was not used. Again with the results of Example-1, Table-2
Shown in.

The lack of any of the cocatalyst components of the process of the present invention resulted in a decrease in nitro group conversion and total isocyanate yield.

Examples-8 to 12 Table 3 shows the results of the same reaction as in Example-2 except that a part of the charged raw materials or the catalyst in Example-1 was changed to the type or the usage amount shown in Table 3.

Example-13 Crude DNT 31.3 g (2,4) obtained by nitration of toluene
-DNT 24 g, 2,6-DNT 6 g, and a small amount of nitrotoluene and 2,3-, 3,4- and 2,5-DNT isomers) phenol 34.0 g, dichlorobis (quinoline) palladium 0.492 g, phosphoryl chloride 0.173 g, vanadium trichloride 0.096 g, quinoline 4.9 g, and o-dichlorobenzene 145 g were used, and the reaction was performed in the same manner as in Example 1 except that the reaction was performed at a reaction temperature of 190 ° C. for 3.5 hours. As a result of analyzing the reaction solution in the autoclave after exhaustion, unreacted DNT
And no intermediate NIT, 2,4- and 2,
A total of 24.4 g of 6-TDI was contained. This corresponds to a yield of 85% based on 2,4- and 2,6-DNT charged. The reaction solution in the autoclave was distilled in the same manner as in Example 1 to give 2,4- and 2,6-TDI in total of 23.8 g.
Got

〔The invention's effect〕

According to the method of the present invention, an aromatic isocyanate can be produced in high yield from an aromatic nitro compound and carbon monoxide under mild conditions by a simple process.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B01J 31/36 C07B 61/00 300

Claims (1)

[Claims] 1. A mixture of an aromatic nitro compound and carbon monoxide, palladium or a mixture of the compound and a nitrogen-containing heterocyclic compound, a palladium complex coordinated with the nitrogen-containing heterocyclic compound, and the complex. In the method for producing an aromatic isocyanate, which comprises reacting at high temperature and high pressure in the presence of at least one catalyst selected from the group consisting of a mixture with the nitrogen-containing heterocyclic compound, the reaction is carried out by reacting an active hydrogen compound. An aromatic fragrance, characterized in that it is carried out in the presence of a cocatalyst system consisting of a halogenated phosphorus compound, a vanadium compound and a tertiary amine, and the aromatic isocyanate is separated from the resulting reaction product by distillation. For producing a group isocyanate.