JPH0227985B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a method for economically producing aromatic urethane using converter gas as inexpensive carbon monoxide. [Technical background of the invention and its problems] Aromatic urethanes are also used as raw materials for carbamate-based concentrates, but aromatic isocyanates (raw materials for polyurethanes used in soft and hard foams, paints, fibers, etc.) It is a chemical substance useful as a raw material for Conventionally, urethane isocyanates have been produced by reacting aromatic amines obtained by hydrogen reduction of aromatic nitro compounds with phosgene. However, this method has problems such as the complicated process, the use of toxic phosgene, and the production of large amounts of hydrogen chloride. Therefore, in recent years, inexpensive manufacturing methods that do not use phosgene have been proposed. These methods are roughly divided into two types: (1) direct method and (2) urethane-mediated method. The first method is to directly obtain an aromatic isocyanate from an aromatic nitro compound in the presence of a palladium-based catalyst in an inert solvent. This method has drawbacks such as harsh reaction conditions, low catalytic activity and poor yield, and simultaneous occurrence of side reactions. The second method targeted by the present invention is
Reacting an aromatic nitro compound with carbon monoxide in a compound having a hydroxyl group in the presence of a platinum group metal catalyst or a selenium catalyst to obtain an aromatic urethane;
This is a method of obtaining aromatic isocyanate by then thermally decomposing the urethane. Although this method shows fairly excellent results with a urethane yield of 80 to 90% even when dinitro compounds are used as raw materials, a more economical method is desired for industrialization. Against this background, Japanese Patent Application Laid-Open No. 55-7227
The publication proposes the presence of hydrogen in the reaction system in a method for producing urethane by reacting an aromatic nitro compound with a compound containing carbon monoxide and a hydroxyl group in the presence of a palladium catalyst. Although the presence of hydrogen increases the urethane yield, this method uses relatively high-purity CO and _H2 , and the purification and separation of these gases is quite expensive. Furthermore, JP-A-57-185253 proposes a method for producing aromatic urethane in which an aromatic amine compound and an aromatic nitro compound are reacted with an organic hydroxyl compound, hydrogen, and carbon monoxide in the presence of a similar catalyst. There is. In this reaction, aromatic amines and aromatic nitro compounds, which are more expensive than aromatic nitro compounds, are used as raw materials, and synthesis gas is used as hydrogen and carbon monoxide sources. On the other hand, converter gas discharged from an oxygen steelmaking furnace at a steelworks contains nitrogen and carbon dioxide, but contains very little sulfur and dust, so it can be considered an excellent source of carbon monoxide. In particular, in the case of bottom blowing furnaces, the carbon monoxide concentration is over 80%. [Object of the Invention] In view of the above, the present invention provides a method for producing aromatic urethane by using converter gas with a hydrogen content of 1% or less as a carbon monoxide (gas) source. The purpose is to provide a more economical method for producing aromatic urethane. [Summary of the Invention] The gist of the present invention to achieve the above object is to react an aromatic nitro compound, an organic compound containing carbon monoxide, and a hydroxyl group in a liquid phase in the presence of a platinum group metal catalyst to form an aromatic compound. The method for producing aromatic urethane is characterized in that a converter gas having a hydrogen content of 1% or less is used as a carbon monoxide source. That is, the present invention effectively uses converter gas, which is normally used only as a fuel, as a carbon monoxide source in the production of aromatic urethane, thereby reducing the cost of producing inexpensive aromatic urethane (and by extension, the cost of raw materials for polyurethane). The aim is to produce aromatic isocyanates (aromatic isocyanates) with a yield comparable to that of pure carbon monoxide sources. [Specific Examples of the Invention] The present invention will be further explained in detail. The aromatic nitro compound used as a main raw material in the production method of the present invention may be either a mononitro compound or a polynitro compound. For example, these include nitrobenzenes, dinitrobenzenes, dinitrotoluenes, nitronaphthalenes, nitroanthracenes, nitrobiphenyls, bis(nitrophenyl)alkanes, bis(nitrophenyl)ethers, nitrodiphenoxyalkanes, Alternatively, there are heteroaromatic compounds such as 5-nitropyridine. In the above compounds, 1, such as nitro, nitroalkyl, alkyl, alkenyl, alkoxy, halogen, carboxy, alkyl, cyano, isocyanate,
It may be substituted with one or more substituents. Specific compounds include nitrobenzene, o
-, m- and p-nitrotoluene, o-nitro-p-xylene, 1-nitronaphthalene, m- and p-dinitrobenzenes, 2,4- and 2,6-dinitrotoluene, dinitromesitylene, 4,4' -dinitrobiphenyl, 2,4'-dinitrobiphenyl, 4,4'-dinitrodibenzyl,
Bis(4-nitrophenyl)methane, bis(4-
nitrophenyl) ether, bis(4-nitrophenoxy)ethane, α,α′-dinitro-p-xylene, o-, m- and p-chloronitrobenzene, 1-chloro-2,4-dinitrobenzene, 1
-bromo-4-nitrobenzene, 1-fluoro-
2,4-dinitrobenzene, o-, m- and p
-Nitroanthol, 2,4-dinitrophenethole, m-nitrobenzaldehyde, ethyl-p
-nitrobenzoate, 3,3'-dimethyl-4,
Examples include 4'-dinitrobiphenyl and 1,5-dinitronaphthalene. Furthermore, isomers or mixtures of these aromatic nitro compounds can also be used, and homologs can also be used. The hydrous acid group compounds used in the production method of the present invention include monohydric alcohols or polyhydric alcohols and monohydric phenols or polyhydric phenols containing primary, secondary or tertiary hydroxyl groups. If alcohol is represented by R(OH)n, R is a linear or branched alkyl, cycloalkyl, alllene, cycloalkylene or aralkyl,
n is 1 or 2 or more. They may also contain substituents containing oxygen, nitrogen or halogen atoms, such as carbonyls, carboxylic acid ester groups, amines, amides or halogens. Specific examples of R(OH)n include methyl alcohol, ethyl alcohol, n- and iso-propyl alcohol, n-, iso- and tert-butyl alcohol, linear or branched amyl alcohol, hexyl alcohol, cyclohexyl alcohol, lauryl alcohol, cetyl alcohol,
Monohydric alcohols such as benzyl alcohol, chlorobenzyl alcohol and methoxybenzyl alcohol, dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trihydric alcohols such as glycerol, hexanetriol, and even more. Examples include functional polyols. Among these, particularly preferred alcohols are methanol and ethanol. Phenols used include phenol, chlorphenol, cresol, ethylphenol or linear or branched propylphenol, butyl and higher alkylphenols, catechol, resorcinol, 4,4'-dihydroxydiphenylmethane, 2,2 '-isopropylidene diphenol, anthranol, phenanthrol, pyrogallol, phloroglucinol, and the like. Of these, phenols are particularly advantageous. The main components of the platinum group metal catalyst used in the method of the present invention are palladium, rhodium, platinum, ruthenium, and osmium alone or in combinations of one or more of these. The chemical forms of these platinum group metal compounds include halides, oxides, sulfates, nitrates, acetylacetonate salts, carbonyl compounds, and complexes with organophosphorus compounds such as triphenylphosphine. It will be done. Among these, palladium and rhodium alone or as a compound are particularly preferred. Specific examples of catalysts suitable for use are palladium chloride, palladium acetate, palladium oxide, palladium nitrate, rhodium trichloride, rhodium sesquioxide, platinum sulfate, platinum nitrate, platinum acetate, platinum dichloride, ruthenium trichloride, ruthenium dioxide. , osmium tetrachloride, etc. Also included in the above examples are platinum group metal compounds in the form of complex salts, such as soluble compounds such as potassium and sodium tetrachloroparadate, potassium tetrachloroplatinate, and the like. These main catalyst components may be used in the reaction as they are, with or without the use of a physical support. As the support, alumina, silica, activated carbon, barium sulfate, calcium carbonate, asbestos, diatomaceous earth, ion exchange resin, magnesium silicate, aluminum silicate, molecular sieves, etc. are used. In the method of the present invention, Lewis acids are widely used as cocatalysts. These Lewis acids include:
Compounds obtained from elements of groups A to V and subgroups IB to VB of the Periodic Table which undergo redox reactions under the reaction conditions are suitable. for example,
Halides and oxyhalides of tin, titanium, zirconium, vanadium, niobium, germanium, aluminum, iron, nickel, molybdenum, tungsten, manganese, cobalt, etc.
sulfates, phosphates, nitrates, oxides, acetylacetonates and/or oxyacetylacetonates. When using oxides or hydroxides, it is preferred to add certain activated halides, especially activated chlorides. Examples of suitable Lewis acids include the following compounds. copper () chloride, copper () chloride,
Copper acetate (), thallium () chloride, tin ()
Chloride, tin () chloride, bismuth () chloride, vanadium () chloride, chromium () chloride, aluminum () chloride, molybdenum () chloride, tungsten () chloride, tungsten () chloride , manganese () chloride,
Iron () chloride, iron () chloride, iron () oxychloride, cobalt () chloride, copper () oxide, copper () hydroxide, thallium () hydroxide, tin () oxide, Tin () hydroxide, vanadium () oxide, molybdenum () oxide, tungsten () oxide, manganese () oxide, iron () hydroxide, iron () oxide, particularly preferred among these Lewis acids include iron() chloride, iron() chloride and oxychloride. In the catalyst system of the present invention, it is preferable to use a nitrogen-containing heteroaromatic compound together with a Lewis acid as a cocatalyst. Here, the nitrogen-containing heteroaromatic compound refers to a nitrogen-containing heteroaromatic cyclic compound, which may be unsubstituted or may have an appropriate substituent such as a halogen atom, an alkyl group, an aryl group, It may contain substituents such as an alkenyl group, a cyano group, an aldehyde group, an alkoxy group, a phenoxy group, a carbalkoxy group, a carbamyl group, and a carboallyloxy group. Further, single salts of nitrogen-containing heteroaromatic compounds such as nitrates, hydrohalides, sulfates, acetates, etc. are also used. Furthermore, quaternary salts of nitrogen-containing heteroaromatic compounds and oxides of nitrogen-containing heteroaromatic compounds can also be used. Specific examples include 1-methylpyrrole, 1-phenylpyrrole, 1-methylimidazole, 1-
Methylindole, 1-phenylindole, 1
-Methylcarbazole, pyridine, 2-chloropyridine, 2-bromopyridine, 2-fluoropyridine, 4-phenylpyridine, 2-methylpyridine, 2-methyl-5-ethylpyridine, 2,6-
Dimethylpyridine, 2,4,6-trimethylpyridine, 2-styrylpyridine, 3-chloropyridine, 2,6-dichloropyridine, 2-chloro-4
-methylpyridine, 2-methoxypyridine, 4,
4-dimethylaminopyridine, α-picolinate phenyl ester, γ-picolinate methyl ester, 2,6-dicyanopyridine, α-picolinaldehyde, α-picolinamide, 5,6,7,8
-tetrahydroquinoline, 2,2'-dipyridyl,
quinoline, isoquinoline, 2-chloroquinoline,
Acridine, phenanthridine, benzoquinoline, benzisoquinoline, naphthyridine, pyrazine, 4,6-dimethylpyrazine, 2,6-dimethylpyrazine, pyridazine, pyrimidine, quinosaline, 2,3-dimethylquinoxaline, quinazoline, phthalazine, phenazine, cinnoline , pteridine, etc. These nitrogen-containing heteroaromatic compounds can be added to the reactor separately from other catalyst components, or they can be treated in advance with other components of the catalyst system to form suitable compounds such as complexes and adducts. You can also do it.
It is well known that nitrogen-containing heteroaromatic compounds in particular form complexes with platinum group compounds or Lewis acids. For example, complexes of pyridine, quinoline, isoquinoline, etc. with halides, cyanides, and isocyanides such as palladium, rhodium, and platinum, specifically palladium() chloride-pyridine represented by Pd(pyridine) ₂ Cl ₂ Examples include complexes. Also, complexes of pyridine, quinoline, isoquinoline, γ-picoline, etc., and iron, tin, etc., such as iron() chloride-pyridine complexes represented by Fe(pyridine) ₂ Cl ₂ and Sn(pyridine) ₂ Cl ₄ ; A tin() chloride-pyridine complex is mentioned. In the process of the invention, the molar ratio of the platinum group element in the catalyst consisting of a platinum group metal to the aromatic nitro compound can vary over a wide range, ie from 1:5 to 1:2000, but the preferred range is from 1:10 to 1. :1000. Here, mole has the same meaning as gram equivalent or formula weight for a single platinum group metal or its compound. The Lewis acid used as a promoter is used in a molar ratio of 0.1:1 to 1000:1, preferably 1:1 to 100:1, relative to the platinum group metal or its compound. In addition, the amount of the nitrogen-containing heteroaromatic compound to be added is determined in molar ratio to the above-mentioned platinum group metal alone or its compound as the main catalyst.
It ranges from 0.1:1 to 1000:1, preferably from 1:1 to 100:1. In the method of the present invention, it is important to maintain the hydrogen content in the raw material converter gas below a predetermined concentration, and as a result, the production efficiency of the target aromatic urethane is significantly increased, and the pure carbon monoxide raw material with the same partial pressure is It reaches the same level as when using . This permissible hydrogen content is 1.0 vol% based on the converter gas, preferably
It is 0.5 vol%, more preferably 0.1 vol% or less. Converter gas composition varies depending on operating standards, but typically contains 55-75% carbon monoxide and 10% carbon dioxide.
~18%, nitrogen 10-20%, hydrogen 1-5%, oxygen 0.1
It is expressed as a volume ratio of ~0.6%. There are no particular restrictions on the method of adjusting the hydrogen content to 1% or less, and there are physical methods such as selective adsorption or storage of hydrogen, combustion with oxygen, and catalytic dehydrogenation using a halogen catalyst. Chemical methods can also be used.
Alternatively, it may be obtained by mixing with a gas having a lower hydrogen content. Although the method of the present invention can be carried out without the presence of a solvent, it may also be carried out diluted with a solvent inert to the reaction. Suitable solvents include n-hexane,
Aliphatic or aromatic hydrocarbons such as benzene, toluene, xylene, nitriles such as acetonitrile, benzonitrile, 1,1,2-trichloro-1,2,2-trifluoroethane, monochlorobenzene, dichlorobenzene and aliphatic or aromatic halogenated hydrocarbons such as trichlorobenzene, or ketones, esters, tetrahydrofuran, 1,4-dioxane, 1,2-
Examples include dimethoxyethane. In the reaction, the nitro group of the aromatic nitro compound, which is the main raw material,
It is desirable to use at least an equivalent molar amount of carbon monoxide and a hydrous acid group compound. There are no particular restrictions on the charging method and order of addition of raw materials and catalysts, and they can be changed within the limitations of the equipment used. The reaction may be carried out in a batch, semi-continuous or continuous manner. The reaction temperature is generally 100
It is kept in the range of 140 to 250℃, but especially 140 to 250℃.
A range of 190°C is preferred. The reaction pressure is in the range of 10 to 1000 Kg/cm ² -G, more preferably 30 to 300 Kg/cm ² -G as a partial pressure of carbon monoxide. The reaction time varies depending on various factors such as the nature of the aromatic nitro compound used, reaction temperature, reaction pressure, type and amount of catalyst, and reaction equipment, but generally it is 0.5 to 10
Time is enough. After the reaction is complete, the reaction mixture is cooled to room temperature and depressurized. The reaction product is then treated by conventional methods including filtration, distillation, extraction, or other suitable separation methods to separate the target aromatic urethane from unreacted products, by-products, solvents, catalysts, etc. . The separated and recovered catalyst can be recycled as it is, or after being purified by an appropriate method such as a solvent washing method and having its composition adjusted. [Examples and Comparative Examples] The effects of the present invention will be described below using Examples and Comparative Examples. The converter gases with different hydrogen contents used in the reaction were obtained by using a palladium molybdenum catalyst synthesized with reference to the method described in JP-A-50-15496 and by changing the coexisting oxygen gas supply. It was adjusted. In addition, a shaking autoclave made of stainless steel was used for all reactions. Conversion rates and yields are based on molar amounts calculated from the results of gas chromatography and high performance liquid chromatography analyses. Examples 1 to 4 0.820 g of nitrobenzene, commercially available 5% by weight, 0.130 g of palladium activated carbon, 0.280 g of ferric chloride, 0.290 g of pyridine, and 10 ml of dehydrated ethanol were charged into an autoclave with an internal volume of 30 ml, and the gas composition inside was adjusted to monoxide. 68% carbon, 15% carbon dioxide, 14% nitrogen
%, hydrogen at 2.5%, and oxygen at 0.5%, and then pressurized until the partial pressure of carbon monoxide reached 70 kg/cm ² -G. Immerse the autoclave in a pre-heated oil bath and raise the temperature while stirring to 155-160℃.
The mixture was kept at ℃ and allowed to react for 2 hours. After the reaction was completed, the mixture was cooled to room temperature and evacuated, and insoluble matter was separated and washed with 10 ml of dehydrated ethanol. The liquid and washing liquid were combined and the products in the liquid were analyzed. In Examples 2 to 4, the hydrogen content of the converter gas was 1.4 vol%, 0.8 vol%,
The content was changed to 0.4vol%. Table 1 shows the nitrobenzene reaction rate (%) and the yield (%) of ethyl N-phenylcarbamate (urethane). Comparative example 1 Carbon monoxide 70%, carbon dioxide 15.5%, nitrogen 14
The reaction was carried out in the same manner as in the example except that a gas having a composition of 0.5% and 0.5% oxygen was used. The results are shown in Table 1. Comparative Example 2 The reaction was carried out in the same manner as in Example, except that pure carbon monoxide was used. The results are shown in Table 1.

【table】

〔Effect of the invention〕

As described above, according to the present invention, when converter gas adjusted to have a hydrogen content of 1 vol% or less is used as a carbon monoxide source, the amount of nitrobenzene produced is the same as that of the conventional method using a carbon monoxide source. Reaction rates and urethane yields can be obtained which are therefore significantly more economical.

Claims (1)

[Claims] 1. In a method for producing aromatic urethane by reacting an aromatic nitro compound, carbon monoxide, and an organic compound containing a hydroxyl group in a liquid phase in the presence of a platinum group metal catalyst, hydrogen content is used as a carbon monoxide source.
A method for producing aromatic urethane characterized by using converter gas at a concentration of 1 vol% or less.