JPS6115868B2 - - 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-based 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 there are already many methods for producing isocyanates. Are known. 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 O-dichlorobenzene. Due to the low activity of the catalyst, large amounts of expensive palladium, which is the main catalyst, must be used.
Furthermore, since the aromatic isocyanate produced is an unstable compound, side reactions such as polymerization and decomposition occur, resulting in a low yield. 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, a method using a catalyst consisting of selenium and a base (Japanese Unexamined Patent Publication No. 49-62420) has an excellent yield of urethane, but a method for recovering toxic selenium or selenium compounds has not been established. There is no prospect of industrialization. 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, a vanadium compound, a tertiary amine, and hydrogen chloride was highly active. The present invention was achieved by discovering that a high yield of urethane can be obtained by reacting an aromatic nitro compound with an organic compound containing a hydroxyl group and carbon monoxide, and that the reaction solution is easy to handle. . 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 a vanadium compound, a tertiary amine and hydrogen chloride. 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
-Nitrobenzenes such as nitrobenzoyl chloride, ethyl p-nitrobenzoate, m-nitrobenzenesulfonyl chloride, 3-nitrophthalic anhydride, m- and p-dinitrobenzene, 2,2-dinitrotoluene, 2,6-di Nitrotoluene, dinitromesitylene, 1-chloro-
2,4-dinitrobenzene, 1-fluoro-2.
dinitrobenzenes such as 4-dinitrobenzene,
Tonitrobenzenes such as 2,4,6-trinitrotoluene, mono- or polynitro-substituted condensed ring compounds such as 1-nitronaphthalene and 1,5-dinitronaphthalene, 4,4'-dinitrobiphenyl, 2,
4-dinitrobiphenyl, 3,3'-dimethyl-
Nitrobiphenyls such as 4,4'-dinitrobiphenyl, bis(4-nitrophenyl)methane, 4,
Bis(nitrophenyl) alkanes such as 4'-dinitrobibenzyl, bis(nitrophenyl) ethers such as bis(4-nitrophenyl) ether, bis(2,4-dinitrophenyl) ether, bis(4-nitrophenyl) thioether, etc. Bis(nitrophenyl)thioethers, bis(4-
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 mentioned as monohydric alcohols, and ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, hexanetriol and the like are mentioned as polyhydric alcohols. 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 catalyst consisting of the following components: palladium metal or a palladium compound, a vanadium compound, a tertiary amine and hydrogen chloride. Metal palladium or palladium compounds that are the main components of the catalyst include simple metals such as palladium black, palladium halides, palladium cyanide, palladium thiocyanide, palladium isocyanide, palladium oxide, palladium sulfate, palladium nitrate, palladium nitrate, etc. Divalent palladium inorganic salts, divalent palladium organic acid salts such as palladium acetate, tertiary amines such as triethylamine, pyridine, isoquinoline, etc. to the above palladium salts,
Examples include tertiary organophosphorus compounds such as triphenylphosphine, divalent palladium complexes coordinated with neutral ligands such as carbon monoxide, and Ovalent palladium complexes obtained by reducing divalent palladium complexes. are activated carbon, graphite, alumina,
Silica, barium sulfate, calcium carbonate, asbestos, bentonite, diatomaceous earth, ion exchange resin,
It can also be used by being supported on a carrier such as magnesium silicate, aluminum silicate, titanium silicate, or molecular sieve. The metal palladium or palladium compound has a concentration in the reaction solution of 0.001 to 1% by weight, preferably 0.005 to 1% by weight in terms of palladium alone.
Used at 0.1% by weight. Any vanadium compound can be selected as the second component of the catalyst. In addition, since the reaction in the method of the present invention is a combination of the reduction reaction of a nitro compound with strong oxidizing power and the oxidation reaction of carbon monoxide with strong reducing power, the valence of the vanadium compound may change during the reaction.
It is thought that it exists in several valence states with a certain distribution. Therefore, the valence of vanadium in the vanadium compound that can be used is not particularly limited. Specific examples of vanadium compounds that can be used in the method of the present invention include chlorides such as vanadium trichloride and vanadium tetrachloride, chloride salts such as vanadium () potassium chloride, vanadium oxydichloride, vanadium oxytrichloride, etc. Oxychloride of, vanadium oxide (), oxides such as vanadium oxide (), vanadium oxide (), vanadic acid such as pyrovanadic acid, metavanadate, vanadic acid such as sodium orthovanadate, ammonium metavanadate, potassium metavanadate, etc. salts, vanadium salts of acids such as ammonium vanadium sulfate, potassium vanadium oxalate,
vanadyl salts of acids such as vanadium oxysulfate (), vanadium oxyoxalate, acetylacetone salts such as vanadium ()oxyacetylacetonate, V(CO) ₆ , KV(CO) ₆ ,

【formula】

, V[(CH ₃ ) ₂ PCH ₂ CH ₂ P(CH ₃ ) ₂ ] ₃ , VCl ₃ [S
(CH ₃ ) ₂ ] ₂ , VCl ₄ [OC ₆ H ₄ (As(CH ₃ ) ₂ ) ₂ ] ₂ ,
These include complex compounds coordinated with neutral ligands such as VO(CH ₂ COCH ₂ COCH ₃ ) ₂・C ₅ H ₅ N. It is necessary to use at least 1 gram atom of these vanadium compounds in terms of vanadium per 1 gram atom of palladium, but there is no particular restriction on the upper limit of the amount used. However, if the amount exceeds 1000 gram atoms per 1 gram atom of palladium, little increase in the effect is expected and it is economically disadvantageous, and it is usually within the range of 10 to 100 gram atoms per 1 gram atom of palladium. used in 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 2-chloroquinoline, quinoline derivatives such as 5,6,7,8-tetrahydroquinoline; acridine, phenanthridine, 5,6-benzoquinoline, 6・Benzoquinoline such as 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 polypynylpyridine. The amount of the tertiary amine used may be 1 mol or more per 1 gram atom of vanadium in the vanadium compound, but it is usually selected within the range of 1 to 50 mol, preferably 1 to 20 mol. . Hydrogen chloride, the fourth component of the catalyst, is in a gaseous state,
It is used in the form of a solution in a solvent such as water or alcohol, or in the form of a salt with the tertiary amine. The amount of hydrogen chloride used is 1 to 10 moles, preferably 1 to 5 moles, per 1 gram atom of vanadium in the vanadium compound, but preferably equal moles or less to the tertiary amine. Although the use of hydrogen chloride in excess of the tertiary amine does not cause any particular problem in the reaction in the method of the present invention, excess hydrogen chloride may corrode the reactor or the piping around the reactor. It is wise to avoid using excess hydrogen chloride. 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, Ethers such as 1,2-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 crystallized urethane 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.
33.3 mg, 1.63 mmol of vanadium pentoxide, and 10 mmol of pyridine hydrochloride (C ₅ H ₅ N HCl) were charged.
After purging the inside of the autoclave three times with nitrogen gas at 30 kg/cm ² , the temperature was raised to 140°C. Next, when carbon monoxide was pressurized to 75Kg/cm ² into the autoclave, the reaction started and the temperature rose due to heat generation.
The temperature rose to 160℃. Temperature in autoclave to 160
After keeping at ℃ and reacting for 180 minutes, it was cooled.
The autoclave was depressurized 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 65%. Ta. Examples 2 to 4, Comparative Example 1 Same as Example 1 except that the amount of pyridine hydrochloride used was changed and the molar ratio of pyridine hydrochloride to vanadium pentoxide was changed as shown in Table 1. I conducted an experiment. The results are shown in Table-1.

[Table] Dicarbamate Example 5 Using 1 g of metallic palladium supported on activated carbon (support rate 2% by weight) instead of palladium chloride,
Oxytriisopropoxyvanadium [VO(i-C ₃ H ₇ O) ₃ ] 3.25 m instead of vanadium pentoxide
The experiment was conducted in the same manner as in Example 1 except that mol was used. As a result, the reaction rate of 2,4-dinitrotoluene was 100%, and the reaction rate of 2,4-dinitrotoluene was 100%.
The yield of 2,4-dicarbamate was 45%. Comparative Example 2 When the experiment of Example 5 was repeated without using pyridine hydrochloride, the reaction rate of 2,4-dinitrotoluene was 32%, and the reaction rate of 2,4-dinitrotoluene was 32%.
-The yield of dicarbamate was 3%. Example 6 Vanadyl acetylacetonate [VO
An experiment was carried out in the same manner as in Example 5 except that 3.25 mmol of (CH ₂ COCH ₂ COCH ₃ ) ₂ was used. As a result, the reaction rate of 2,4-dinitrotoluene was 100
%, and the yield of diethyltolylene-2,4-dicarbamate was 31%. Example 7 37% by weight concentrated hydrochloric acid containing 10 mmol of pyridine and 10 mmol of hydrogen chloride was used instead of pyridine hydrochloride, and 2% pd/c1 was used instead of palladium chloride.
The experiment was conducted in the same manner as in Example 1 except that g was used. As a result, the reaction rate of 2,4-dinitrotoluene was 100%, and the reaction rate of 2,4-dinitrotoluene was 100%.
The yield of 2,4-dicarbamate was 18%. Example 8 An experiment was carried out in the same manner as in Example 7 except that 10 mmol of isoquinoline was used instead of pyridine. As a result, the reaction rate of 2,4-dinitrotoluene was 100%, and diethyltolylene-2,4-
The yield of dicarbamate was 21%.

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, characterized by using a catalyst consisting of a vanadium compound, a tertiary amine, and hydrogen chloride.