JPS6056132B2 - Production method of aromatic carbamate ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing aromatic carbamate esters, and more specifically, the present invention relates to a method for producing aromatic carbamate esters. The present invention relates to an improvement in a method for producing group carbamic acid esters.

For example, aromatic isocyanates such as tolylene diisocyanate are useful as raw materials for polyurethane, and are usually produced by reacting aromatic amines obtained by hydrogen reduction of aromatic nitro compounds with phosgene. There is.

However, this method has drawbacks such as complicated steps, the use of phosgene, which is a harmful gas, and the generation of hydrogen chloride during the phosgenation reaction, which causes equipment corrosion. Therefore, in recent years, several new methods for producing isocyanates that do not use phosgene have been proposed.
A known method is to produce a corresponding aromatic carbamate ester by reacting with carbon monoxide and alcohol or phenol, and then to thermally decompose the ester to obtain an aromatic isocyanate.

In this method, the technical point is the catalyst for producing the aromatic carbamate ester, and various catalysts have been proposed to obtain high conversion and selectivity. Among these catalysts, the catalyst containing palladium-vanadium-tertiary amine is particularly excellent in terms of reaction. However, when this catalyst is used, the inside of the reactor is severely corroded even if a stainless steel or titanium reactor is used.

In order to reduce the corrosiveness, it is possible to reduce the catalyst component or add additives for corrosion inhibition. , the catalytic activity will decrease. In view of the above circumstances, the present inventors conducted various studies to find a method for improving only the corrosivity of a catalyst containing palladium-vanadium tertiary amine without losing its activity. The present invention has been completed by discovering that this object can be achieved by coexisting with a catalyst.

That is, the gist of the present invention is to provide a method for producing an aromatic carbamic acid ster by reacting an aromatic nitro compound with an organic compound having a hydroxyl group and carbon monoxide in the presence of a catalyst, in which palladium-vanadium-tertiary amine The present invention relates to a method for producing an aromatic carbamate ester, which is characterized by using a catalyst containing the above and allowing a salt of a zinc group metal or an iron group metal to coexist in the reaction system.

The present invention will be explained in detail below.

As the aromatic nitro compound to be used in the present invention, both mononitro compounds and polynitro compounds can be used.

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,
Mononitrobenzenes such as m-nitrobenzaldehyde, p-nitrobenzoyl chloride, ethyl-p-nitrobenzoate, m-nitrobenzenesulfonyl chloride, 3-nitrophthalic anhydride, m- and p-dinitrobenzene, 2,4-dinitrotoluene , 2,6-dinitrotoluene, dinitromesitylene, 1-chloro2,
Dinitrobenzenes such as 4-dinitrobenzene and 1-fluoro-2,4-dinitrobenzene, trinitrobenzenes such as 2,4,6-trinitrotoluene, mono- or polynitro-substituted condensation of 1-nitronaphthalene, 15-dinitronaphthalene, etc. Ring compounds, nitrobiphenyls such as 4,4''-dinitrobiphenyl, 2,4-dinitrobiphenyl, 3,3-dimethyl-4,4'-dinitrobiphenyl, bis(4-nitrophenyl)methane, 4,4''-
Bis(nitrophenyl) alkanes such as dinitrobenzyl, bis(4-nitrophenyl) ether, bis(2
, 4-dinitrophenyl) ether, and bis(4-nitrophenyl) thioether. (nitrophenyl)thioethers, bis(nitrophenyl)sulfones such as bis(4-nitrophenyl)sulfone, bis(nitrophenoxy)alkanes such as bis(4-nitrophenoxyethane), 5-
Examples include heteroaromatic nitro compounds such as nitropyrimidine, α, α″-dinitro p-xylene, α, α5-dinitro m-xylene, etc. The initial concentration of these aromatic nitro compounds in the reaction solution is usually 1 ~7
It is selected within the range of 5% to 3%, preferably 5% to 3%. On the other hand, in the method of the present invention, the organic compound containing a hydroxyl group 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, and cetyl alcohol, cycloarylecanols such as cyclohexyl alcohol, benzyl alcohol, and chlorobenzyl alcohol. Examples of monohydric alcohols include aralkyl alcohols such as , methoxybenzyl alcohol, and polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, and hexanetriol. In addition, monohydric phenols include phenol, glolphenol, cresol, ethylphenol, propylphenol, butylphenol, and higher alkylphenols, β-naphthol, anthrol, phenanthrol, and catechol, resorcinol, 4,45
Examples of the polyhydric phenol include -dihydroxydiphenylmethane, 2,7-isopropylidenephenol, pyrogallol, and phloroglucin. These alcohols or phenols may be further substituted with a substituent such as a halogen atom, sulfoxide, sulfone, carbonyl, or carboxylic acid ester group.

The amount of alcohol or phenol used must be at least one molecule per nitro group of the aromatic nitro compound used as a raw material, and usually in large excess relative to the aromatic nitro compound. In many cases, it is also used as a reaction solvent.

In the present invention, a catalyst containing palladium-vanadium-tertiary amine is used. First, as the palladium component, for example, palladium metal, palladium halide, palladium cyanide, palladium thiocyanide, palladium isocyanide, palladium oxide, etc. Examples include palladium, palladium sulfate, palladium nitrate, palladium acetate, and the like.

Palladium catalysts such as those mentioned above are typically activated carbon, graphite, alumina, silica, silica-alumina, barium sulfate, calcium carbonate, asbestos, bentonite, diatomaceous earth, ion exchange resins, magnesium silicate, calcium silicate, aluminum silicate, titanium silicate, mole. It is used by being supported on a carrier such as Kyura Thief or zeolite.

The palladium component supported on the carrier undergoes reduction under the reaction conditions, so it can be used as is without undergoing reduction treatment before being subjected to the reaction, but it can be used as is without undergoing reduction treatment. It is preferable to perform a reduction treatment using a reducing agent and then use it as a catalyst.

Through the reduction treatment, part or all of the palladium component is reduced to a metallic state. The amount of palladium used is 0.0001 to 1% by weight in terms of metal palladium, preferably 0.001 to 0.1% by weight, based on the reaction solution. The amount is 0.05 to 2% by weight, preferably 0.2 to 5% by weight in terms of metal palladium. Examples of tertiary amines include aliphatic tertiary amines such as trimethylamine, triethylamine, tripropylamine, and tributylamine, and fatty acids such as N,N-dimethylaniline, N,N-diethylaniline, and N,N-dipropylaniline. Aromatic tertiary amines, 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-7,1,5-diazabicyclo(4
Heterocyclic tertiary amines such as ,3,0)-nonene-5, aromatic tertiary amines such as triphenylamine, pyridine,
Examples include heteroaromatic tertiary amines such as quinoline and isoquinoline.

In particular, heteroaromatic tertiary amines are effective for improving the yield of aromatic carbamate esters, and specifically, pyridine, 2-chloropyridine, 2-bromopyridine, 2-fluoropyridine, 3-chlorpyridine,
2,6-dichloropyridine, 4-phenylpyridine, α
-Picoline, γ-picoline, 2-methyl-5-ethylpyridine, 2,6-lutidine, γhycolidine, 2-vinylpyridine, 2-chloro-4-methylpyridine, 4-phenylthiopyridine, 2-methoxypyridine, 2,6 Pyridine derivatives such as -dicyanopyridine, 4-dimethylaminopyridine, α-phenyl picolinate, γ-methyl picolinate, α-picolinaldehyde, α-picolinamide, 2, goudipyridyl; quinoline or 2-chloroquinoline, 5, Quinoline derivatives such as 6,7,8-tetrahydroquinoline; acridine, phenanthridine, 5,6
-benzoquinoline, 6,7-benzoquinoline, 7,8-
Benzoquinoline such as benzoquinoline; Isoquinoline; 1
- Pyrrole derivatives such as meurvirol and 1-phenylpyrrole; imidazole derivatives such as 1-methylimidazole; indole derivatives such as 1-methylindole and 1-phenylindole; carbazole derivatives such as 1-methylcarbazole: pyrazine, 2, Examples include diazines such as 6-dimethylpyrazine, pyridazine, and pyrimidine; benzodiazines such as quinoxaline, 2,3-dimethylquinoxaline, quinazoline, phthalazine, cinnolene, and phenazine; indolenine; indolizine, ninaphthyridine, nipteridine, and the like. It is also possible to use it in the form of a polymer such as polyvinylpyridine. The amount of the tertiary amine to be used may be 1 mole or more per 1 gram atom of palladium, which will be described later, and is usually selected within the range of 1 to 50 moles, preferably 1 to 20 moles. Vanadium is used as a compound, specifically vanadium trichloride,
Chlorides such as vanadium tetrachloride, vanadium chloride (■), chlorides such as potassium chloride, oxychlorides such as vanadium oxydichloride, vanadium oxytrichloride, vanadium oxide (■), vanadium oxide (■), vanadium oxide (■
), vanadic acids such as pyropanadic acid and metavanadate, vanadates such as sodium orthovanadate, ammonium metavanadate, potassium metavanadate, ammonium vanadium sulfate (■), potassium vanadium (■) oxalate, etc. vanadium salts of acids, vanadyl salts of acids such as vanadium oxysulfate (vanadium oxyoxalate, etc.), acetylacetone salts such as vanadium (■) oxyacetylacetonate, V(CO), KV(CO)
),,v[(CH3)2PCH2CH2P(CH3)2
]3, VCl3[S(CH3)2]2, VCl4[0-
C6H4(AS(CH3)2)2]2, VO(CH2C
These include complex compounds coordinated with neutral ligands such as OCH2COCH3)2.C5H5N.

The compound containing vanadium is usually used at least 1 gram atom in terms of vanadium atom per gram atom of vanadium, and there is no particular restriction on the upper limit of the amount used.

However, for 1 gram atom of palladium, 100
Beyond gram atoms, little increase in effect is expected;
It is also economically disadvantageous, and the preferred amount to be used is 1 to 30 gram atoms per gram atom of palladium. In the present invention, it is an essential requirement that a salt of a zinc group metal or an iron group metal be present in the reaction system together with the above catalyst components.

These compounds include, for example, zinc, cadmium,
These include inorganic acid salts such as hydrochloride, nitrate, and sulfate, and organic acid salts such as acetate and isopropionate of zinc group metals consisting of mercury or iron group metals consisting of iron, cobalt, and nickel. Zinc chloride, ferric chloride, etc. are preferred. The amount of these salts present is usually 0.1 to 10 times the mole of the vanadium compound, preferably 0.5
~2 mole times. If the amount present is too small, corrosion within the reaction system cannot be sufficiently suppressed, while if it is too large, no improvement in effectiveness can be expected and it is not economical. In addition, in the present invention, by allowing the above-mentioned salt to exist in the reaction system, the reaction can be carried out without reducing the catalytic activity of palladium-vanadium-tertiary amine. This can significantly suppress corrosion inside the reactor. In the method of the present invention, the reaction is often 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 beazonitrile, sulfones such as sulfolane, and logenated fats such as 1,1,2-trichloro-1,2,2-trifluoroethane For example, halogenated aromatic hydrocarbons such as hydrocarbons such as trichlorobenzene, dichlorobenzene, and trichlorobenzene, ethers, ketones, and esters such as tetrahydrofuran, 1,4-dioxane, and 1,2-dimethoxyethane can be used. To practice the invention, 1 to 500k
9/Alfl preferably 10-200k9/Cll! A reaction solution containing an aromatic/group nitro compound, an organic compound containing a hydroxyl group, a catalyst, and optionally a solvent inert to the reaction under a partial pressure of carbon monoxide is heated at 100 to 240°C, preferably at 1
What is necessary is just to heat to the temperature of 40-240C for 1 to 6 hours.

After the reaction is complete, the product liquid taken out from the reaction system contains, in addition to the reaction product aromatic carbamate ester (hereinafter referred to as urethane), a catalyst component, an organic compound containing a hydroxyl group, and, in some cases, palladium. A solid catalyst, a solvent inert to the reaction, etc. are present, and almost all of the aromatic nitro compound used as a raw material is usually reacted, so it is hardly contained.

If the reaction is not carried out using a fixed bed of solid catalyst containing palladium, the solid catalyst will be included in the reaction product liquid that is taken out, so the solid catalyst can be removed by ordinary solid-liquid separation methods such as p-filtration and centrifugation. The urethane to be crystallized and the mother liquor can be separated by separating and cooling, or if desired, separating a part or most of the organic compound containing a hydroxyl group by vaporization or the like and then cooling.

Since the mother liquor contains catalyst components, it is normally recycled to the reaction system after adjusting the concentration appropriately. 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. However, the aromatic amine easily becomes urethane by being subjected to the reaction with the aromatic nitro compound. By circulating the mother liquor containing by-products such as aromatic amines through the reaction thread, the yield of urethane can be increased. As detailed above, according to the method of the present invention, the loss of expensive palladium can be extremely reduced, and the corrosion inside the reactor is also extremely small.
This is an industrially extremely advantageous method.

Example <Reaction test> Vertical stirring device and CO supply port were made of SUS3 200m1
In an autoclave, dinitrotoluene 6.4y1 activated carbon carrying 2wt% of palladium metal 1.4f1 vanadyl trichloride 0.8', pyridine 1.1f1 and the salt of the present invention shown in Table 1 were added to vanadyl trichloride. equimolar preparation,
Next, after adding 55y of ethanol, the inside of the system was replaced with N2 gas as a closed system, and the system was heated at 140°C under stirring at 4k9/min.
The temperature was raised to Clt, and further, CO gas was injected under pressure until the concentration reached 80k9/Cd, and the reaction was carried out at 160°C for 3 hours.

After the reaction was completed, the solid matter was filtered and the mother liquor was analyzed by liquid high performance chromatography to measure the yield of diethyltolylene-2,4-dicarbamate, and the results shown in Table 1 were obtained. <Corrosion test> 50 x 30 x 2rn/m (7) SUS3 in a glass container
A test piece of SUS3l6 was temporarily installed, and the same dinitrotoluene, palladium metal, vanadyl trichloride, and the salt shown in Table 1 as in the above reaction test example were charged, and further,
Add ethanol and heat at 65°C for 10 minutes in N2 gas atmosphere.
An immersion test between C@ was conducted to measure the degree of corrosion of the test piece.

As is clear from the above table, when the salt of the present invention was added, it was found that the corrosion resistance was significantly better than the example (No. 3) in which no salt was added.

Further, even when the salt of the present invention is added, the yield is almost the same as when no salt is added, indicating that there is no adverse effect on the reaction.
Note: Corrosion test (Tfn/year) After cleaning and drying the test piece before and after the corrosion test, accurately measure the surface area and weight, compare the amount of reduction before and after the corrosion test,
Based on this, the degree of corrosion over one year was calculated.

Claims (1)

[Claims] 1. A method for producing an aromatic carbamate ester by reacting an aromatic nitro compound with a compound having a hydroxyl group and carbon monoxide in the presence of a catalyst, using a catalyst containing palladium-vanadium-tertiary amine, and,
A method for producing an aromatic carbamate ester, which comprises coexisting a salt of a zinc group metal or an iron group metal in the reaction system.