JPS5810548A - Preparation of aromatic isocyanate - Google Patents

Abstract

PURPOSE:To prepare the titled compound usefual as a raw material of polyurethane, economically, with easy recovery and reuse of expensive catalyst, by reacting an aromatic nitro compound with CO in the presence of a catalyst composed of a noble metal and a nitrogen compound and a cocatalyst consisting of chlorine. CONSTITUTION:The titled compound is prepared by reacting an aromatic nitro compound with CO at high temperature and pressure, in the presence of a catalyst containing at least one material selected from the group of a mixture of a noble metal or its compound and a hetero-aromatic nitrogen compound, a complex of a noble metal coordinated to said nitrogen compound, and a mixture of said complex and said nitrogen compound, and a cocatalyst consisting of chlorine. The cocatalyst increases the activity and selectivity of the catalyst, and reduces the necessary amount of the expensive noble metal catalyst. since the catalyst can be recovered easily and has low corrosivity, the use of a particular reaction apparatus is not necessary, and the process is extremely economical.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for directly synthesizing corresponding incyanates from aromatic nitro compounds and carbon monoxide.

More particularly, the present invention provides a compound selected from the group consisting of a mixture of a noble metal or a compound thereof and a heteroaromatic nitrogen compound, a complex of a noble metal coordinated with the nitrogen compound, and a mixture of the complex and the nitrogen compound. The present invention relates to a method for directly producing a corresponding aromatic incyanate by reacting an aromatic nitro compound and carbon monoxide under high temperature and pressure by adding chlorine in the presence of at least one catalyst.

Isocyanates are extremely useful substances in practice, mainly as raw materials for polyurethane, and among them, tolylene diisocyanate is produced on the largest scale.9 The current industrial manufacturing method for inocyanates is to reduce nitro compounds. This is a method to obtain isocyanates by reacting an amine with phosgene, which is separately synthesized from carbon monoxide and chlorine.

However, it would be desirable if aromatic isocyanates could be produced by directly reacting a nitro group with carbon monoxide and converting it into an inocyanate group in one step without using hydrogen or chlorine as an intermediate and without handling highly toxic phosgene. This direct incyanatization method is economically advantageous because incyanates can be produced from a nitro compound in a one-step reaction without producing hydrochloric acid as a by-product.

An aromatic nitro compound and carbon monoxide are reacted at high temperature and pressure in the presence of a suitable catalyst containing a noble metal compound as the main component according to the following formula to produce aromatic isocyanate (NO2)yl +
311004Ar(Neo)n + 2nO02,,
, (1) - Direct synthesis methods are well known, and many various catalyst systems using noble metal compounds as main catalysts have been proposed, but none have been put into practical use yet. This is because a large amount of expensive main catalyst is required to carry out this reaction, and the recovery of the catalyst is difficult due to the use of complex metal co-catalysts and promoters, and the yield of incyanate is low. are doing.

As a method for directly synthesizing aromatic isocyanates according to reaction formula (1), for example, according to U.S. Pat. Although this method is known, even if a large amount of catalyst is used, the yield of isocyanate is low and it is not practical.

No. 3,884,952 discloses a method in which an aromatic nitro compound is vaporized and the vapor is reacted with carbon monoxide in the gas phase in the presence of an active palladium catalyst and a halogen-donating gas. However, even with this method, the isocyanate yield is extremely low, and useful dinitro compounds that are difficult to evaporate cannot be used as raw materials.

In JP-A-49-108001, the reaction is carried out in the presence of a catalyst consisting of a reduction metal and hydrogen or bromine.
Incyanato is only confirmed.

In addition, as a method using halogen derivatives, JP-A No. 4
A method of adding hydrogen halide is known in No. 8-99144, but the raw material 2,4-dinitrotoluene (hereinafter referred to as D
The yield of 2.4'-)lylene diisocyanate (hereinafter abbreviated as TDI) is as low as 38% even if 2.5 mol of palladium catalyst is used based on the amount of palladium catalyst (hereinafter abbreviated as TDI). Corrosion is a problem. Special Public Service 1977-
3577% obtained a TDI yield of 11.9% by using an acid halide (phosgene) in combination with vanadium oxide as a cocatalyst, but this method also lacks practicality.

On the other hand, in U.S. Pat. No. 3,481,968, a halogenated aromatic isocyanate is prepared by reacting an aromatic nitro compound with a halogenated oxide such as phosgene and carbon monoxide in the presence of a metal catalyst. We provide a method for synthesizing , albeit with a low yield.

As mentioned above, hydrogen, bromine, or halogen derivatives such as hydrogen halide and acid halides can be used as cocatalysts for the reductive carbonylation reaction of aromatic nitro compounds with carbon monoxide.
A method for producing incyanate used as a reaction promoter or a reaction reagent is known, but a method using chlorine as a cocatalyst or promoter is not known.

The above-mentioned known methods have the disadvantage that, due to low catalyst activity and selectivity, a large amount of an expensive precious metal main catalyst must be used relative to the starting nitro compound, and the yield of the target product is also low. be. In addition, the main catalyst decomposes during the reaction and deposits on the walls of the reactor (plates out), which further reduces the catalyst activity and makes it difficult to recover the catalyst. Furthermore, adding various known co-catalysts to increase the activity of the catalyst will make recovery of the catalyst even more complicated, which is not economical.

Corrosion of the reactor is also a problem.

In order to solve these drawbacks, the present inventors have diligently investigated the catalytic function of halogens, particularly chlorine, and have surprisingly found that chlorine can be used as a cocatalyst for the direct synthesis of incyanate, such as the aforementioned bromine, hydrogen or It has been found that it exhibits far more effective effects than halogen derivatives.

Further, by studying the usage pattern, it was determined that the above-mentioned drawbacks could be solved, and the present invention was completed.

The main object of the present invention is to react an aromatic nitro compound with carbon monoxide to form the corresponding isocyanate using a novel catalyst with excellent activity and selectivity at a low concentration.

Another object of the present invention is to make the catalyst extremely simple, and in the simplest case, the metal component in the catalyst is only the noble metal of the main catalyst, and by making the co-catalyst a volatile substance, it can be used as a catalyst. The purpose is to provide products that can be easily recycled and used.

Still another object is to provide a catalyst that is extremely corrosive and thus to provide a process that allows the use of conventional materials for the reactor.

That is, the present invention provides at least one member selected from the group consisting of a mixture of a noble metal or a compound thereof and a heteroaromatic nitrogen compound, a complex of a noble metal coordinated with the nitrogen compound, and a mixture of the complex and the nitrogen compound. This is a method for directly producing isocyanates by reacting an aromatic nitro compound with carbon monoxide at high temperature and pressure in the presence of a catalyst and a chlorine promoter.

Furthermore, the present invention can be carried out by using one or more of the conventionally known co-catalysts, promoters, additives, etc. consisting of various Lewis acids, metal compounds, organic and inorganic compounds in the above-mentioned catalyst system. can.

The aromatic nitro compound used as a raw material in the present invention is
It is an aromatic mono- and polynitro compound and may contain an incyanato group and a substituent that does not react with this. Representative examples include, for example, nitrobenzene, 0-lm- and p-nitrotoluene, 0-nitro-p-xylene, nitromesitylene, 1-chloro-l-nitrobenzene, 1.
2-cyclo-4-nitrobenzene, 1-promo 4-
Nitrobenzene, 1-fluoro-4-nitrobenzene,
1-) +7 fluoromethyl-4-nitrobenzene, o
-1m- and p-nitrophenyl isocyanate, 〇- and p-nitroanisole, 〇- and p-nitrophenetol, nitrobenzaldehyde, nitrobenzoyl chloride, methylnitrobenzoate, nitrobenzenesulfonyl chloride, nitrobenzonitrile, 2-Isocyanato-4-nitrotoluene, 2-nitro-4-isocyanatotoluene, 2-incyanato-6-nitrotoluene, nitronaphthalene, 5-nitronaphthylisocyanate, nitroanthracene, (4-goro-p-
xylene, dinitromesitylene, 1-chloro-2,4-
Dinitrobenzene, 2,4-dinitronitrobiphenyl, bis(p-nitrophenyl)methane, bis(p-nitrophenyl)ether, bis(p-nitrophenyl)thioether, bis(p-nitrophenyl)sulfone, IJ-') Robenin, etc.

Among these, nitrobenzene, 2.4- and 2.
6-cinitrotoluene, 1,2-dichloro-4-nitrobenzene, t,S-dinitronaphthalene, bis(p-nitrophenyl)methane, and the like are preferably used for practical purposes.

The noble metals or their compounds used as the main catalyst include ruthenium, rhodium, palladium, osmium,
Coordination of elemental substances such as iridium and platinum, or inorganic compounds such as halides, nitrates, isocyanides, carbonates, carboxylates, oxides, and chelates of these precious metals, and carbonyl, alkyl, olefin, and π-allyl groups. Examples include organic complexes containing children. Preferably, for example, palladium asbestos, palladium-carbon, palladium chloride, palladium bromide, palladium iodide, sodium chloride palladate, tetraammine chloride (radium, dichlorocyafamine palladium, rhodium chloride, rhodium bromide, rhodium iodide, chloride) These include sodium rhodate, ammonium rhodate chloride, bis-ethylene palladium chloride, bis-π-allyl palladium chloride, etc. As mentioned above, the main catalysts include, for example, silica, alumina, silica alumina, zeolite, carbon, celite, Bentonite, diatomaceous earth, activated clay, calcium carbonate, barium sulfate, asbestos, etc. can be used as sweep-supported materials or in combination.This can adjust the function of the catalyst and facilitate handling and recovery. can.

The heteroaromatic nitrogen compound that acts as a ligand to the noble metal of the main catalyst is a compound consisting of an aromatic ring containing a nitrogen atom, such as pyrrole, N-methylpyrrole, pyrazole, iadazole, triazole, pyridine, α, β- or γ-picoline, 4
-Phenylhyridine, 4-vinylpyridine, 2-fluoropyridine, 2-chloropyridine, 3-chloro-pyridine, 2-bromopyridine, 3-hydroxypyridine, 2
-methoxypyridine, α-picolinaldehyde, α-picolinate methyl ester, α-picolinamide, 2,6
-Simethylpyridine, 2-methyl-4-ethylpyridine, 2-chloro-4-methylpyridine, 2,6-dicyazpyridine, 5.6.7.8-tetrahydroquinoline, 5
, 6.7.8-tetrahydroisoquinoline, quinoline,
Examples include inquinoline, acridine, benzoquinoline, benzisoquinoline, phenanthridine, pyridazine, pyrimidine, pyrazine, cinnoline, quinazoline, quinoxaline, phthalazine, naphthyridine, phenazine, and the like.

Typical examples of complexes of noble metal halides with heteroaromatic nitrogen compounds include palladium and rhodium. For example, bis(pyridine)dichloropalladium (
II), bis(pyridine)dibromopalladium (■),
Bis(pyridine) short palladium (I[), bis(
α-picoline) dichloropalladium ([) 1 bis(quinoline) dichloropalladium (If), bis(isoquinoline) dichloropalladium, (pyridine) (carbonyl) dichloropalladium (■), (2,6-dimethylpyridine) (carbonyl)dichloropalladium(II), tris(pyridine)trichlororhodium(1), )lis(
tribromorhodium (pyridine), tris(γ-picoline) trichlororhodium (7), tris(isoquinoline) trichlororhodium (1), etc.

Although the production of incyanates by carbonylation of aromatic nitro compounds proceeds even in the presence of the above-mentioned main catalyst alone (US Pat. No. 3,576,835), the comparative example described below shows that the catalytic activity is surprisingly low. As a result, the yield of the desired isocyanates is extremely low.

The economics of direct production of isocyanates depends on the activity of the catalyst,
Selectivity and recovery are most involved. Therefore, it is most important to develop a co-catalyst that increases the activity and selectivity of the main catalyst containing precious metals and facilitates the recovery and reuse of expensive precious metal catalysts. The catalyst system was developed.

Chlorine used as a cocatalyst in the present invention has a remarkable effect of accelerating the reaction, and the amount of the noble metal main catalyst to be used can be greatly reduced by simply adding a catalytic amount.

Since the economic efficiency of the isocyanate direct production method is largely determined by the concentration of the catalyst used, this effect will significantly contribute to reducing production costs.

Further, chlorine is highly desirable in that, when used in an appropriate amount, it can exhibit the effect of increasing catalytic activity without significantly reducing reaction selectivity, unlike the general characteristics of other cocatalysts.

Under the conditions of use of the present invention, chlorine is surprisingly not found to act as a chlorinating agent for organic substances in the system during the reaction. Furthermore, it has been demonstrated through examples that the cocatalytic effect of chlorine has the above-mentioned desirable features that are clearly different from the reaction accelerating effect, which is accompanied by a drastic decrease in the selectivity of hydrogen chloride, which occurs when aromatic nuclei are chlorinated. Ru.

Furthermore, incyanate can be obtained in high yield even when no other metal auxiliary medium is used in the catalyst system of the present invention. In such a case, since the reaction solution does not contain a different metal, there is an advantage that the palladium main catalyst can be easily separated and recovered. Of course, the present invention can be used in combination with other known promoters, promoters, additives, etc. In this case as well, the use of chlorine has the effect of suppressing the decomposition of the main catalyst and facilitating its reuse. .

The reaction between aromatic nitro compounds and carbon monoxide uses a noble metal or its compound (main catalyst), a heteroaromatic nitrogen compound (ligand) and chlorine (co-catalyst) as essential catalyst components.
carried out in the presence of

The amount of noble metal used in the main catalyst is 0.00% relative to the nitro compound.
It ranges from 0.001 to 10 mol., preferably from 0.01 to 2 mol. The amount of the ligand of the heteroaromatic nitrogen compound is generally 1 to 500 times the mole of the main catalyst, preferably 2 to 100 times the mole of the main catalyst. The appropriate amount of chlorine as a co-catalyst varies depending on the reaction conditions, but it is usually 0.1 to 500 times the mole of the main catalyst.
Desirably, a range of 0.1 to 50 times the mole is used.

Chlorine is used in a gaseous, liquid or solution form.

The method of use of the catalyst component is not specified, and it can be used by bringing it into contact with the reaction raw material in a liquid phase by any method.

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 before reacting. Any solvent can be used as long as it is a liquid that is inert to the raw materials and products, and is not particularly limited, but usually examples include evaheptane, cyclohexane,
Aliphatic, cycloaliphatic and aromatic hydrocarbons such as Hensen, toluene, xylene, various petroleum fractions, halogens such as dichloromethane, perchlorethylene, tetrachloroethane, chlorobenzene, dichlorobenzene, chloronaphthalene. 2) Hydrocarbons, ethers, ketones, etc. are used.

The amount of the solvent to be used is not particularly limited and is arbitrary, and the appropriate amount varies depending on the type of reaction. 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, and there is no particular restriction on the method of mixing the aromatic nitro compound, the main catalyst, and the co-catalyst. According to the formula (D), the ratio is 3 mol per 1 mol of nitro group, and at the same time 2 mol of carbon dioxide is produced as a by-product. The amount used is in the range of 5 to 100 times the mole, preferably 7 to 20 times the mole, depending on the concentration of the aromatic nitro compound, the amount of the catalyst used, the type of reactor, the reaction temperature, the reaction pressure, etc. can be carried out batchwise while containing carbon dioxide as a by-product, but by removing carbon dioxide, which increases as the reaction progresses, from the reactor and at the same time recycling and replenishing carbon monoxide. It is preferable to carry out the reaction while keeping the molar ratio of carbon in the reactor small.

The reaction temperature is 100-250°C, preferably 150-2
A range of 30°C is used.

Reaction pressure is 10-1000 #/cd, usually 50-50
A range of 0#/cd is used.

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 conditions.

To elaborate on embodiments of the invention, the reaction can be carried out batchwise, semi-continuously or continuously.

Usually, a solution of an aromatic nitro compound dissolved in a solvent and each component of the catalyst are mixed before the reaction or are fed separately into the reactor. The reactor is pressurized with carbon monoxide to reaction pressure and maintained at reaction temperature.

In the continuous type, the carbon dioxide mixture gas in the reactor is continuously discharged, and -carbon oxide is injected under pressure.

After a predetermined period of time has elapsed, the reaction mixture is cooled, separated into gas and liquid, and then subjected to overdistillation, extraction, etc., and is separated into product incyanates, solvent, catalyst, and by-products. The separated and recovered catalyst and solvent are used again for the reaction after being used or, if necessary, subjected to appropriate treatment. Furthermore, if a small amount of raw materials or nitroisocyanate intermediates remain in the reaction mixture, these can also be separated and recycled to the reactor at the same time. The product isocyanates are subjected to conventional purification operations depending on the intended use.

Thus, according to the method of the present invention, the corresponding isocyanates can be economically produced in high yields from aromatic nitro compounds by using a highly active catalyst system.

EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Incidentally, the yield (or selectivity) from the nitro compound to the target incyanates can be easily increased by increasing the catalyst.

The present invention will be explained below with reference to Examples.

Example 1 D in an autoclave (S, XS-516, 500m)
NT15.0,9. Dichlorobis(quinoline)haladium Q, 4929. Quinoline 7,469 and chlorine gas 0.6
195 g of 0-dichlorobenzene in which 011 was dissolved was charged, and after substitution with carbon oxide twice, the pressure was increased to 160 #/Cd. The temperature was raised to 220°C with stirring, the reaction was incubated at the same temperature for 6 hours and 10 minutes, the pressure was released after cooling to room temperature, and the reaction solution was subjected to gas chromatography (15% silicon D0550).
/Gaschrome Q, 150°C1 biphenyl internal standard)
It was analyzed in

The product liquid does not contain the raw material DNT and has a TDI of 11,839.

A trace amount of 2-nitro-4-isocyanatotoluene (hereinafter abbreviated as 2N4IT) and 0.087. 4-nitro-2-incyanatotoluene (hereinafter abbreviated as 4N2IT). The yield for DNT is TDI of 8
2.5%, and its precursor 4N21T was 0.6%. Also, the obtained target product TD for the NO2 group in DNT
If the proportion of NOO groups in I and both precursors is taken as the NC0 yield, this is 82.8%.

After the reaction, no plateout of metallic palladium was observed from the palladium main catalyst, and palladium was recovered in the form of the charged complex.

Furthermore, no corrosion of the materials was observed in the reactors, such as autoclaves and stirring blades, in which the Examples described in this specification and the experiments pertaining to the present invention were repeatedly conducted.

Examples 2 to 7 The reaction was carried out in the same manner as in Example 1, except that the amounts of the main catalyst and chlorine co-catalyst used and the reaction time were as shown in Table 1, and that 46 mol of quinoline was used relative to DNT. The results are shown in Table 1.

Comparative Example 1 In order to demonstrate the effect of chlorine promoter, chlorine was not used,
The reaction was carried out under the same reaction conditions as in Examples 5 to 7 except that 148 g of DNT was used instead of 150 g. The results are also listed in Table 1.

The effect of the chlorine co-catalyst according to the present invention was compared with Examples 2 to 4 or 5 to 7 in which the amount of chlorine added was varied at a constant amount of palladium and quinoline, and the latter with Comparative Example 1 in which no chlorine was added. It becomes clear from the comparison. That is, by using chlorine, the DNT conversion rate increases, and 10
0%, and the desired TDI yield was improved by about 40 inches or more. This reaction promoting effect functions without significantly reducing reaction selectivity. It can be seen that in both the example series with different main catalyst concentrations, as the amount of chlorine used increases, the reaction promotion effect becomes more pronounced and the TDI yield generally increases.

Examples 8 to 11 The same procedure as in Example 2 was carried out, except that the amount of the main catalyst used was 0.2% by weight of Pd/DNT, and the reaction was carried out for 5 hours at the amount of chlorine shown in Table 2. The results are shown in Table 2.

Comparative Example 2 No chlorine, DNT15. 14 instead of Og(7).
The reaction was carried out under the same conditions as in Examples 8 to 11 except that 8 g was used.

Comparative Examples 3.4 and 5 The reaction was carried out in the same manner as in Example 9, except that bromine, iodine and phosgene dimer were added to the main catalyst at a molar ratio of 15, J' 15 and 8, respectively, instead of chlorine. Ta. The results are also listed in Table 2.

Comparative Example 6 Same as Example 8 except that hydrogen chloride was added as quinoline hydrochloride in place of chlorine at a molar ratio of 29 to the main catalyst, quinoline was used in a predetermined amount in total, and the reaction was carried out for 35 hours. I did the same. The results are also listed in Table 2.

From the consideration of Examples 8 to 11 and Comparative Example 2, the same promoter effect of chlorine as described above is recognized. It is generally known that in this type of sequential reaction, as the TDI yield increases, the selectivity of all isocyanates tends to decrease significantly, but in Examples 9 to 11, the TDI yield was approximately three times that of Comparative Example 2. Despite this improvement, the selectivity of all isocyanates remains almost unchanged. Therefore, it can be easily seen that chlorine in the catalyst of the present invention has the effect of increasing the reaction rate and significantly increasing the yield of TDI (diisocyaner) while suppressing a decrease in reaction selectivity.

Addition of halogens such as bromine or iodine rather significantly reduces the activity and selectivity of the catalyst, but chlorine has exactly the opposite desired effect? The following is clear from the correspondence between Comparative Example 3 or 4 and Example 9.

- Also, from the comparison between Example 9 and Comparative Example 5, chlorine as a cocatalyst gives higher DNT conversion, TDI yield and total incyanate selectivity than phosgene (easily produced by thermal decomposition of the dimer), and therefore the reaction It is clear that both the promoting effect and the selectivity improving effect are uniquely excellent. It can be seen from Table 2 that hydrogen chloride greatly accelerates the reaction, but extremely lowers the selectivity; on the other hand, chlorine increases T without decreasing the selectivity.
DI yield can be increased.

Example 12 A reaction was carried out in the same manner as in Example 9 except that nitrobenzene 203I was used instead of DNTO and the reaction was carried out for 3 hours. The yield of phenyl incyanate was 86.3%.

Example 13 The reaction was carried out in the same manner as in Example 6 except that palladium chloride o, ioog was used instead of dichlorobis(quinoline)palladium. Product yield TDI 74.0%;
2N4IT was 1.0% and 4N2IT was 5.2%.

Example 14 A reaction was carried out in the same manner as in Example 6 except that 115 g of rhodium trichloride O was used as the main catalyst and the reaction was carried out for 5 hours. Yield: TDI 40. Ochi, 2N4 IT 8.5” section and 4
N2IT 27. It was Ochi.

Example 15 Dichlorobis(pyridine)palladium 0.0% as the main catalyst.
The reaction was carried out in the same manner as in Example 10, except that pyridine 6 and Og were used in place of 095.9 and Kino 9F 6.

The nNT conversion rate was 974%, and the yield was TDI2B, 2%,
2N4IT was 13.3ch and 4N2IT was 28.6ch.

Comparative Example 7 Example 15. As a comparison, when chlorine is not used, D
NT conversion rate is 63.5%, yield is TDI 46%, 2N4
IT20. Oq6 and 4N21T '29.8 excellent.

Example 16 When 49 g of vanadium oxytrichloride o, o and phosphorus oxytrichloride [], 087p were used together as another promoter in Example 10, the yield was 61.2% TDI, 2N4 I
4.0% T and 12.3% 4N2IT were obtained.

Example 17 In Example 10, 0.183% of t-butyl chloride was added as another reaction accelerator. ! When 9 is used in combination, the yield is T
DI68.7ch, 2N4IT0.7% and 4N2IT5.
2 pieces were obtained.

Claims (1)

[Claims] (Aromatic nitro compound and carbon monoxide, a mixture of a noble metal or its compound and a heteroaromatic nitrogen compound, a complex of a noble metal coordinated with the nitrogen compound, and a mixture of the complex and the nitrogen compound) at least one selected from the group
1. A method for producing aromatic isocyanates, which comprises using chlorine as a co-catalyst in the method for producing isocyanates in which the reaction is carried out at high temperature and high pressure in the presence of a catalyst containing seeds.