JPS6111222B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing urethane by reacting an aromatic nitro compound with an organic compound containing a hydroxyl group and carbon monoxide in the presence of a palladium catalyst. Aromatic isocyanates are important compounds as raw materials for polyurethane, and have conventionally been produced by reacting aromatic amines obtained by hydrogenating aromatic nitro compounds with phosgene. However, because the method using phosgene has a large fixed cost burden and the toxicity of phosgene, research has been actively conducted in recent years on methods for producing isocyanates that do not use phosgene, and many methods for producing isocyanates are already known. It is being These known methods are broadly classified into two types. The first method is to directly obtain aromatic isocyanates by carbonylating aromatic nitro compounds in the presence of a palladium catalyst in an inert solvent such as C-dichlorobenzene. Due to the low activity of the catalyst, a large amount of expensive palladium, which is the main catalyst, must be used, and because the aromatic isocyanate produced is an unstable compound, side reactions such as polymerization and decomposition occur, resulting in low yields. It has drawbacks such as: The second method produces esters of the corresponding carbamic acids by reacting aromatic nitro compounds with carbon monoxide and alcohols or phenols in the presence of a noble metal or selenium catalyst in an alcoholic or phenolic solvent. This is a method in which so-called urethane is obtained and then the urethane is decomposed by a method such as thermal decomposition to obtain aromatic isocyanate. Catalysts used in the second method include, for example, rhodium carbonyl chloride (Japanese Patent Publication No. 42-1420), group metal carbonyls, and catalysts consisting of salts of metals having the property of existing in two or more valence states ( Japanese Patent Publication No. 43-23939) is known, but all of these have low yields of urethane and are difficult to implement industrially. In addition, a method using a catalyst consisting of palladium and Lewis acid with improved urethane yield (U.S. Patent No.
3531512) has also been proposed, but this method is difficult to put into practical use because Lewis acids such as ferric chloride are highly corrosive to reaction vessels. In addition to this,
The method using a catalyst consisting of urethane and a base (Japanese Unexamined Patent Publication No. 49-62420) has an excellent yield of urethane, but there are no prospects for industrialization because a method for recovering toxic selenium or selenium compounds has not been established. Not standing. Recently, by using catalysts combining palladium, Lewis acids and tertiary amines,
A method was proposed (Japanese Unexamined Patent Publication No. 1982-98240) for suppressing corrosion of the reactor while ensuring a high urethane yield. However, even this method cannot be said to be sufficient in terms of catalyst activity, and the solubility of the complex formed by Lewis acids, especially ferric chloride, and tertiary amines in alcoholic solvents is low. Since the amount used is large, a slurry with high density must be handled, which is very disadvantageous for industrial processes. The present inventors searched for a catalyst that does not have the drawbacks of the prior art described above, and found that a catalyst consisting of palladium, vanadium oxytrichloride or vanadium oxydichloride, and a tertiary amine has high activity. discovered that urethane can be obtained in high yield by reacting an aromatic nitro compound with a hydroxyl group-containing organic compound and carbon monoxide in the presence of , and that the reaction solution is easy to handle, and the present invention was achieved based on this discovery. This is what I did. That is, an object of the present invention is to provide an industrially advantageous method for producing urethane, which involves reacting an aromatic nitro compound with an organic compound containing a hydroxyl group and carbon monoxide in the presence of a catalyst. In the method for producing urethane, metallic palladium or a palladium compound is used as a catalyst,
This can be easily achieved by using a catalyst consisting of vanadium oxytrichloride or vanadium oxydichloride and a tertiary amine. The present invention will be explained in detail below. As the aromatic nitro compound, both mononitro compounds and polynitro compounds can be used in the method of the present invention. Specifically, nitrobenzene, O-, m- and p-nitrotoluene, O-nitro-p-xylene, O-, m- and p-chloronitrobenzene, 1-bromo-4-
Nitrobenzene, O-, m- and p-nitrophenyl carbamate, O-, m- and p-nitroanisole, m-nitrobenzaldehyde, p
- Mononitrobenzenes such as nitrobenzoyl chloride, ethyl p-nitrobenzoate, m-nitrobenzenesulfonyl chloride, 3-nitrophthalic anhydride, m- and p-dinitrobenzene, 2,4-dinitrotoluene, 2,6-dinitrobenzene, etc. Nitrotoluene, dinitromesitylene, 1-chloro-
2,4-dinitrobenzene, 1-fluoro-2.
dinitrobenzenes such as 4-dinitrobenzene,
Trinitrobenzenes such as 2,4,6-trinitrotoluene, mono- or polynitro-substituted condensed ring compounds such as 1-nitronaphthalene and 1,5-dinitronaphthalene, 4,4'-dinitrobiphenyl,
Nitrobiphenyl such as 2,4-dinitrobiphenyl, 3,3'-dimethyl-4,4'-dinitrobiphenyl, bis(4-nitrophenyl)methane,
Bis(nitrophenyl) alkanes such as 4,4′-nitrobenzyl, bis(4-nitrophenyl)
ether, bis(nitrophenyl) ethers such as bis(2,4-dinitrophenyl) ether,
Bis(nitrophenyl)thioethers such as bis(4-nitrophenyl)thioether, bis(4-nitrophenyl)thioether, etc.
Bis(nitrophenyl)sulfones such as -nitrophenyl)sulfone, bis(nitrophenoxy)alkanes such as bis(4-nitrophenoxy)ethane, heteroaromatic nitro compounds such as 5-nitropyrimidine, or α・α′-dinitro- p
-xylene, α·α′-dinitro-m-xylene, and the like. The initial concentration of these aromatic nitro compounds in the reaction solution is usually selected within the range of 1 to 70% by weight, preferably 5 to 30% by weight. The organic compound containing a hydroxyl group in the method of the invention is selected from monohydric alcohols, polyhydric alcohols, monohydric phenols and polyhydric phenols. Specifically, linear or branched alkanols such as methanol, ethanol, propanol, butanol, amyl alcohol, hexanol, lauryl alcohol, cetyl alcohol, cycloalkanols such as cyclohexyl alcohol, benzyl alcohol, chlorobenzyl alcohol, methoxy Aralkyl alcohols such as benzyl alcohol are listed as monohydric alcohols, and polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, hexanetriol, etc.
Listed as alcohol. In addition, monohydric phenols include phenol, chlorophenol, cresol, ethylphenol, propylphenol, butylphenol, higher alkylphenols, β-naphthol, anthrol, phenanthrol, and catechol, resorcinol, 4-4 Examples of polyhydric phenols include '-dihydroxydiphenylmethane, 2,2'-isopropylidene diphenol, pyrogallol, and phloroglucin. These alcohols or phenols may be further substituted with a substituent such as a halogen atom, sulfoxide, sulfone, or carboxylic acid ester group. The amount of alcohol or phenol used above is
It is necessary to use at least one molecule per nitro group of the aromatic nitro compound used as a raw material, and it is usually used in large excess with respect to the aromatic nitro compound, and in many cases, the reaction solvent It is also used as. The catalyst used in the process of the invention is a three-component catalyst consisting of metallic palladium or a palladium compound, vanadium oxytrichloride or vanadium oxydichloride and a tertiary amine. Metal palladium or palladium compounds that are the main components of the catalyst include simple metals such as palladium black, divalent palladium such as halogenated palladium, cyanide palladium, thiocyanide palladium, isocyanide palladium, palladium oxide, sulfate palladium, and nitrate palladium. Palladium inorganic salts, divalent palladium organic acid salts such as palladium acetate, tertiary amines such as triethylamine, pyridine, and isoquinoline, tertiary organic phosphorus compounds such as triphenylphosphine, carbon monoxide, etc. Examples include divalent palladium complexes coordinated with neutral ligands or Ovalent palladium complexes obtained by reducing divalent palladium complexes, and these include activated carbon, graphite, alumina, silica, barium sulfate, and calcium carbonate asbestos. , bentonite, diatomaceous earth, ion exchange resin, magnesium silicate, aluminum silicate, titanium silicate, molecular sieve, and the like. Metallic palladium or palladium compounds are
The concentration in the reaction solution is converted to palladium alone.
It is used in an amount of 0.001 to 1% by weight, preferably 0.005 to 0.1% by weight. Vanadium oxytrichloride (VOCl ₃ ) or vanadium oxydichloride (VOCl ₂ ), which is the second component of the catalyst, must be used at least 1 mole per gram atom of palladium, but there is an upper limit on the amount used. There are no particular controls on this. However, if the amount exceeds 1000 mol per gram atom of palladium, little increase in effectiveness is expected and it is economically disadvantageous, so it is usually used within the range of 10 to 100 mol per gram atom of palladium. be done. The tertiary amine, which is the third component of the catalyst, is
Aliphatic tertiary amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, aliphatic tertiary amines such as N·N-dimethylaniline, N·N-diethylaniline, N·N-dipropylaniline, Alicyclic tertiary amines such as N·N-dimethylcyclohexylamine, N·N-diethylcyclohexylamine, N·N-dipropylcyclohexylamine, 1,4-diazabicyclo(2·2·2)-octane, 1・8-
Diazabicyclo(5.4.0)-undecene-
Heterocyclic tertiary amines such as 7,1,5-diazabicyclo(4,3,0)-nonene-5, aromatic tertiary amines such as triphenylamine, heteroaromatics such as pyridine, quinoline, isoquinoline, etc. Examples include tertiary amines. In particular, heteroaromatic tertiary amines are effective for improving the yield of urethane, and specifically, pyridine, 2-chloropyridine, 2-bromopyridine, 2-fluoropyridine, 3-chloropyridine , 2,6-dichloropyridine, 4-phenylpyridine, α-picoline,
γ-picoline, 2-methyl-5-ethylpyridine, 2,6-lutidine, γ-collidine, 2-vinylpyridine, 2-chloro-4-methylpyridine,
4-phenylthiopyridine, 2-methoxypyridine, 2,6-dicyanopyridine, 4-dimethylaminopyridine, α-phenyl picolinate, γ-methyl picolinate, α-picolinaldehyde, α-
Pyridine derivatives such as picolinamide, 2,2'-dipyridyl; quinoline or quinoline derivatives such as 2-chloroquinoline, 5,6,7,8-tetrahydroquinoline; acridine, phenanthridyl
benzoquinoline such as benzoquinoline, 5,6-benzoquinoline, 6,7-benzoquinoline, 7,8-benzoquinoline; isoquinoline; 1-methylpyrrole, 1-
Pyrrole derivatives such as phenylpyrrole; imidazole derivatives such as 1-methylimidazole; indole derivatives such as 1-methylindole and 1-phenylindole; carbazole derivatives such as 1-methylcarbazole; pyrazine, 2,6-dimethylpyrazine, Examples include diazines such as pyridazine and pyrimidine; benzodiazines such as quinoxaline, 2,3-dimethylquinoxaline, quinazoline, phthalazine, cinnoline, and phenazine; indolenine; indolizine; naphthyridine; and pteridine. It is also possible to use it in the form of a polymer such as polyvinylpyridine. The amount of tertiary amine used may be 1 mol or more per 1 mol of vanadium oxytrichloride or vanadium oxydichloride, but usually 1 to 50 mol, preferably 1 mol.
Selected within the range of ~20 moles. In the method of the present invention, as mentioned earlier,
In many cases, the reaction is carried out in the presence of an excess amount of an organic compound containing a hydroxyl group, which also serves as a solvent, but a solvent inert to the reaction can also be used.
Specifically, aromatic hydrocarbons such as benzene, toluene and xylene, nitriles such as acetonitrile and benzonitrile, sulfones such as sulfolane, 1.
Halogenated aliphatic hydrocarbons such as 1,2-trichloro-1,2,2-trifluoroethane, halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene, trichlorobenzene, tetrahydrofuran, 1,4-dioxane, 1 - Ethers such as 2-dimethoxyethane, ketones, esters, etc. can be used. To carry out ^the present invention, an aromatic nitro compound, an organic compound containing a hydroxyl group, a catalyst and optionally an inert compound for the reaction are added under a partial pressure of carbon monoxide of 1 to 500 Kg/cm ² , preferably 10 to 200 Kg/cm 2 . The reaction solution containing the appropriate solvent is heated to a temperature of 100 to 240°C, preferably 140 to 200°C.
It may be heated for 10 minutes to 6 hours. After the completion of the reaction, the product liquid taken out from the reaction system contains, in addition to the reaction product urethane, a catalyst, an organic compound containing a hydroxyl group, and in some cases a solvent inert to the reaction, and an aromatic nitro compound as a raw material. Usually, almost all of it is reacted, so it is hardly contained. The reaction product liquid may be cooled after separating the palladium component or carrier present in a solid state by a method such as filtration, or if desired, a part or most of the organic compound containing a hydroxyl group may be separated by distillation or the like. By cooling it later, it can be separated into the urethane that crystallizes and the mother liquor. Since the mother liquor contains a catalyst component, it is normally recycled to the reaction system after appropriately adjusting its concentration. In addition, in the method of the present invention, the nitro group of the aromatic nitro compound is reduced and aromatic amines or urea derivatives are produced as by-products, but the aromatic amine easily becomes urethane by being subjected to the reaction together with the aromatic nitro compound. Therefore, by circulating the mother liquor containing by-products such as aromatic amines into the reaction system, the yield of urethane can be increased, which is economically advantageous. As detailed above, the catalyst of the present invention has extremely high activity, low corrosiveness to the reactor, and good solubility of catalyst components other than the palladium component, so that the reaction solution can be used in a concentrated slurry. It has the advantage of being easy to handle because it does not form a solid state, and does not precipitate when the urethane is crystallized after the reaction, so it is less likely to contaminate the urethane, and has high industrial value. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1 25 mmol of 2,4-dinitrotoluene, 50 ml of ethanol, and palladium chloride were placed in a vertically stirred autoclave lined with titanium and having an internal volume of 200 ml.
After charging 33.3 mg of vanadium oxytrichloride, 3.25 mmol of vanadium oxytrichloride, and 20 mmol of pyridine, the inside of the autoclave was purged three times with 30 Kg/cm ² of nitrogen gas.
The temperature was raised to 140℃. Next, when carbon monoxide was pressurized to 75 kg/cm ² into the autoclave, the reaction started and the temperature rose to 160°C due to heat generation. Maintain the temperature inside the autoclave at 160℃
After reacting for 100 minutes, the autoclave was cooled, the pressure was released, and the reaction product liquid was taken out. As a result of analyzing the obtained reaction product liquid by high performance liquid chromatography, the reaction rate of 2,4-dinitrotoluene was 100%, and the yield of diethyltolylene-2,4-dicarbamate was 76%. Ta. 〓〓〓〓〓
Example 2 Instead of 33.3 mg of palladium chloride, metallic palladium (hereinafter referred to as 2
It is written as %Pd/C. ) using 1 g and reaction time
The experiment was conducted in the same manner as in Example 1 except that the time was changed to 180 minutes. As a result, the reaction rate of 2,4-dinitrotoluene was 100%, and the yield of diethyltolylene-2,4-dicarbamate was 69%. Furthermore, the reaction product liquid from which the activated carbon had been removed was a homogeneous solution. Example 3 The amount of vanadium oxytrichloride used was 6.5 mmol
The experiment was conducted in the same manner as in Example 1, except that the reaction time was changed to 180 minutes. As a result, the reaction rate of 2,4-dinitrotoluene was 100%.
The yield of diethyltolylene-2,4-dicarbamate was 58%. Examples 4 to 9 Experiments were conducted in the same manner as in Example 2, except that various tertiary amines listed in Table 1 were used in place of pyridine. The results are shown in Table-1.

[Table] Examples 10 to 15 The experiment was conducted in the same manner as in Example 1, except that the amount of pyridine used was varied as shown in Table 2, and the reaction time was changed to 180 minutes. The results are shown in Table-2.

[Table] 〓〓〓〓〓

[Table] Example 16 The amount of ethanol used was changed to 30 ml, the amount of O-dichlorobenzene was changed to 20 ml as an inert solvent, the amount of pyridine used was changed to 10 mmol, and the reaction time was changed to 180 minutes. The experiment was conducted in the same manner as in Example 1 except for the above. the result,
The reaction rate of 2,4-dinitrotoluene was 100%, and the yield of diethyltolylene-2,4-dicarbamate was 62%. Examples 17 to 19 Experiments were conducted according to Example 2, with the type and amount of catalyst, type of alcohol, reaction temperature, or reaction time changed as shown in Table 3.
The reaction rate of 2,4-dinitrotoluene is
It was 100%. Dialkyltrilene-2,4-
The yield of dicarbamate is shown in Table 3.

[Table] Example 20 An experiment was carried out in the same manner as in Example 1, except that 50 mmol of nitrobenzene was used instead of 25 mmol of 2,4-dinitrotoluene, and the amount of pyridine used was changed to 10 mmol. As a result, the reaction rate of nitrobenzene was 100%, and the yield of ethyl carbanilate was 89%. Example 21 An experiment was conducted in the same manner as in Example 20, except that 50 ml of isopropyl alcohol was used instead of 50 ml of ethanol, and the reaction time was changed to 180 minutes. As a result, the reaction rate of nitrobenzene was 100%, and the yield of isopropyl carbanilate was 92%. Comparative Example An experiment was conducted in the same manner as in Example 2 except that 3.25 mmol of ferric chloride was used instead of 3.25 mmol of vanadium oxytrichloride. As a result, 2.4
The reaction rate of -dinitrotoluene was 100%, and the yield of diethyltolylene-2,4-dicarbamate was 51%. In addition to active transport, bulky crystals containing iron and pyridine were precipitated in the reaction product solution. Comparative Example 2 An experiment was conducted in the same manner as in Example 1 except that vanadium oxytrichloride was not used and the reaction time was changed to 90 minutes. As a result, the reaction rate of 2,4-dinitrotoluene was 24%, but no formation of diethyltolylene-2,4-dicarbamate was observed, and only a trace of ethyl-nitrotolylene-monocarbamate was formed. Ta. Comparative Example 3 Same as Example 2 except that vanadium oxytrichloride was not used and the reaction time was changed to 105 minutes.
I conducted an experiment. As a result, the reaction rate of 2,4-dinitrotoluene was 31%, but no formation of diethyltolylene-2,4-dicarbamate was observed, and only a trace of ethyl-nitrotolylene-monocarbamate was formed. Ta. 〓〓〓〓〓

Claims (1)

[Claims] 1. A method for producing urethane by reacting an aromatic nitro compound with an organic compound containing a hydroxyl group and carbon monoxide in the presence of a catalyst, in which metallic palladium or a palladium compound as a catalyst,
A method for producing urethane, which comprises using a catalyst consisting of vanadium oxytrichloride or vanadium oxydichloride and a tertiary amine.