PROCESS FOR PRODUCING A URETHANE AND A CARBONIC ACID ESTER

Abstract: The present invention relates to a process for producing a urethane and a carbonic acid ester which comprises reacting a primary amine, an organic compound containing a hydroxyl group(s), carbon monoxide and molecular oxygen with one another by using a catalyst comprising mainly copper.

Description: The present invention relates to a process for producing a urethane and a carbonic acid ester which comprises reacting a primary amine, an organic compound containing at least one hydroxyl group, carbon monoxide and molecular oxygen by using a catalyst comprising mainly copper. Urethanes are important compounds as substrate for carbamate based agricultural chemicals. Since they can easily be converted by heat treatment into isocyanates for producing polyurethanes, there has recently been desired a process for producing urethanes at low costs as intermediates for producing isocyanates without using phosgene which is poisonous. On the other hand, carbonic acid esters are useful not only as starting materials for producing polycarbonates, but also as esterifying agents or solvents. Urethanes and carbonic acid esters have heretofore been produced by reacting phosgene with primary amines or alcohols, but in recent years, there have been proposed various methods using no phosgene which is very poisonous. The methods for producing urethanes without using phosgene are roughly divided into two group, namely, methods using nitro compounds as starting materials and methods using primary amines as starting materials. The methods using nitro compounds as starting materials comprise reacting a nitro compound such as nitrobenzene, an organic compound containing at least one hydroxyl group, such as an alcohol, and carbon monoxide in the the presence of a catalyst comprising mainly a compound of an element of the platinum group, e.g., palladium or rhodium, or selenium, and thereby producing a urethane reductively. These methods are disclosed for example, in GB-A-1080094 and 1402379. Japanese Patent Kokai (Laid-Open) Nos. 57-32250 and 57-32251 disclose methods for producing a urethane and a carbonic acid ester at the same time by reacting an aromatic nitro compound, on organic compound containing at least one hydroxyl group, and carbon monoxide in the presence of a catalyst comprising mainly palladium. On the other hand, the methods using primary amines as starting materials comprise using molecular oxygen or a nitro compound as an oxidizing agent, reacting a primary, amine such as aniline, an organic compound containing at least one hydroxyl group, and carbon monoxide in the presence of a catalyst comprising mainly a compound of an element of the platinum group, e.g., palladium, rhodium or ruthenium, and thereby producing a urethane oxidatively. These oxidative carbonylation methods are disclosed, for example, in CA-A-1150292, US-A-4490551, US-A-4297501 and US-A-4547322. EP-A-173457 discloses a process for producing a carbamate ester comprising reacting an aromatic amine with carbon monoxide and an alcohol in the presence of a protonic acid and a catalyst comprising (a) at least one metal selected from the group palladium, rhodium, ruthenium, iridium and cobalt and (b) copper. In the methods using a nitro compound of a primary amine as a starting material, as described in US-A-4678856, a catalyst comprising a compound of an element of the platinum group or selenium is used, but since the main catalyst itself has onlyalow urethane synthesizing activity, there have been developed catalytic systems consisting of combinations of the main catalyst and co-catalysts such as iron chloride, iron oxychloride, vanadium oxychloride, lithium hydroxide, halides and Lewis acids, or ligands such as pyridine and quinoline. Employment of these co-catalysts or ligands, however, is disadvantageous in that although the urethane synthesizing activity is improved, a complicated catalyst composed of many components is used, so that a troublesome procedure and great costs are required for recovering, for reuse, the expensive compound of element of the platinum group efficiently from the reaction mixture after the reaction. It is the object of the present invention to provide an improved process for producing a urethane and a carbonic acid ester. Said object is achieved by a process for producing a urethane and a carbonic acid ester which comprises reacting a primary amine, carbon monoxide, molecular oxygen and an organic compound containing at least one hydroxyl group characterized in that the reaction is carried out at a temperature of 100 to 250°C and under a pressure of 1961 to 29420 kPa (20 to 300 kg/cm²) by using a catalytic system comprising at least one member selected from the group consisting of copper and copper compounds and at least one halogen selected from the group consisting of iodine, chlorine and bromine. It is preferred to conduct the reaction in the presence of an oxygen-containing organic sulfur compound in an amount of 1 mole or more per mole of the amino group of the primary amine because the urethane yield can be greatly improved. In this case high yields can be attained particularly when an aliphatic primary amine is used as a starting material. According to the claimed process a high urethane-synthesizing activity can be attained in an oxidative carbonylation reaction of a primary amine. In the process of the present invention, one and the same catalytic system permits production of a urethane and a carbonic acid ester. It is believed that two reactions represented by the following general formulas proceed at the same time: R₁(NH₂) n + n·CO + 1/2n·O₂ + n·R₂OH → R₁(NHCOOR₂) n + n·H₂O (1) 2R₂OH + Ca + 1/2·O₂ → CO(OR₂)₂ + H₂O (2) wherein each of R₁ and R₂ is an alkyl group or an aryl group, and n is an integer of 1 or more. As the copper catalyst used in the process of the present invention, any catalyst may be used as long as it contains copper as a component, and either metallic copper or a component constituting a copper compound may be used. The copper catalyst may be supported on a carrier, for example, active carbon, graphite, silica, or alumina. Copper compounds usable as the catalyst include, for example, inorganic compounds such as copper iodide, copper bromide, copper chloride, copper oxide, copper sulfate or copper nitrate; copper salts of organic acids, such as copper acetate, copper oxalate or copper formate; and copper salts or copper complex compounds which contain ammonia, amines, phosphine, carbon monoxide or chelate ligands. The amount of the copper catalyst used is 0.001 to 100 g atoms, preferably 0.01 to 10 g atoms in terms of copper atom per mole of the amino group of the primary amine. When the amount is less than 0.001 g atom, the reaction rate is too slow. When the amount exceeds 100 g atoms, no adverse effect is brought about but such an amount is not economical. Therefore, the above range is practical. The halogen used in the present invention is selected from iodine, bromine and chlorine. These halogens may be used alone or as a mixture of two or more. Among them, iodine is particularly preferred. The halogen may be used in the form of either the halogen molecule itself or an organic or inorganic halogen-containing compound. The halide includes, for example, halides of metals such as alkali metals or alkaline earth metals; halogenated onium compounds, e.g., ammonium salts and phosphonium salts; oxoacids of halogens or salts thereof; and organic halides, e.g., methyl halides and ethyl halides. The amount of the halogen used is 0.01 to 100 g atoms, preferably 0.1 to 10 g atoms in terms of halogen atom per g atom of copper. Although the catalyst of the present invention contains mainly copper and the halogen as active ingredients, there can be properly used in combination therewith other elements, for example, tellurium, sulfur, antimony, bismuth, zinc, tin, vanadium, iron, cobalt, nicyel, manganese, thallium, chromium, molybdenum, and tungsten. The oxygen-containing organic sulfur compound which is optionally used includes sulfones and sulfoxides. Specific examples of the oxygen-containing organic sulfur compound include dimethyl sulfone, sulfolane, 2-methyl sulfolane, diphenyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetramethyl sulfoxide, and diphenyl sulfoxide. Among them, sulfolane is particularly preferred. The amount of the oxygen-containing organic sulfur compound used is 1 mole or more, preferably 2 to 20 moles per mole of the amino group of the primary amine. When the amount is less than 1 mole, the addition of said compound has only insufficient effect. When the amount is more than 20 moles, the space time yield is lowered. Therefore, the above range is practical. The primary amine as starting material in the present invention includes aliphatic, aromatic, alicyclic and heterocyclic compounds having at least one amine group in the molecule. The aromatic or heterocyclic amines include, for example, aniline, 1,2-diaminobenzene, 1,4-diaminobenzene, isomers of chloroaniline, 3,4-dichloroaniline, 4-isopropylaniline, p-toluidine, chlorotoluidine, xylidine, alkoxyanilines, isomers of nitroaniline, 2,3-diaminotoluene, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,5-diaminotoluene, 3,4-diaminotoluene, 3,5-diaminotoluene, 2-amino-4-nitrotoluene, 2-amino-3-nitrotoluene, 2-amino-5-nitrotoluene, aminophenols, diaminoxylene, aminonitroxylenes, aminonaphthalenes, aminoanthracenes, chloroaminobenzoic acids, aminobenzenesulfonic acids, 4,4-diaminodiphenylmethane, 2,2-diaminodiphenylmethane, 2,4-diaminodiphenylmethane, tris(4-aminophenyl)methane, aminopyridines, aminoquinolines, aminopyrroles, aminofurans, aminothiophenes, and 2-aminobenzothiazoles. The alicyclic amines include, for example, aminocyclobutane, aminocyclopentane, cyclohexylamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, and bis(aminocyclohexyl)methanes. The aliphatic amines include, for example, methyl amine, ethylamine, 1-propylamine, 2-propylamine, 1-butylamine, 2-butylamine, isobutylamine, t-butylamine, 1-pentylamine, 1-hexylamine, 1-heptylamlne, 1-octylamine, 1-decylamine, 1-dodecylamine, ethylenediamine, diaminopropanes, diaminobutanes, diaminopentanes, diaminohexanes such as 1,6-hexamethylenediamine, diaminooctanes, diaminodecanes, benzylamine, bis(aminomethyl)cyclohexanes, and bis(aminomethyl)benzenes such as m-xylenediamine. The organic compound containing at least one hydroxyl group used in the present invention includes alcohols and phenols. The alcohols include, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, t-butanol, n-pentanol, n-hexanol, cyclohexanol, benzyl alcohol, cycloethanol, ethylene glycol, diethylene glycol, propylene glycol, glycerol, and trimethylolpropane. The phenols include, for example, phenol, naphthols, anthranol, phenanthrol, and hydroxybenzofurans. The amount of these organic compounds containing at least one hydroxyl group used is 1 mole or more, preferably 5 moles or more per mole of the amino group of the primary amine. Although not critical, the upper limit of the amount is 200 moles or less in practice. When the amount exceeds 200 moles, the space time yield is lowered. Therefore, it is not desirable. Although the process of the present invention does not particularly require a solvent, solvents inert towards the reaction can be used in said process. The solvents include, for example, aliphatic hydrocarbons such as pentane, hexane, heptane or octane; alicyclic hydrocarbons such as cyclohexane or tetralin; aromatic hydrocarbons such as benzene, toluene or xylene; nitriles such as acetonitrile or benzonitrile; ethers such as tetrahydrofuran or 1,4-dioxane; ketones such as acetone or methyl ethyl ketone; esters such as ethyl acetate or ethyl benzoate; and halogenated hydrocarbons such as chlorobenzene, dichlorobenzene, chlorohexane or trichlorotrifluoroethane. As the molecular oxygen used in the present invention, pure oxygen and air can be used as they are or after being diluted with other gases which do not inhibit the reaction, for example, inert gases such as argon, helium, nitrogen or carbon dioxide. As the carbon monoxide used in the present invention, there can be used pure carbon monoxide, and mixed gases of carbon monoxide, the above-mentioned inert gases and if necessary, hydrogen or hydrocarbon gases. The reaction temperature in the present invention is 100° to 250°C. When it is lower than 100°C, the reaction rate is decreased. When it is higher than 250°C, side reactions are promoted. The reaction pressure is 1961 to 29420 kPa (20 to 300 kg/cm²G). Although varied depending on the catalytic system, the amount of catalyst or the reaction conditions, the reaction time is usually several minutes to several hours. The present invention can be suitably conducted either in a batchwise manner or continuously. The reaction mixture in the present invention is first freed from the catalyst by filtration and then heated and evaporated to be concentrated or dried up, after which the urethane precipitated is separated by filtration or solvent extraction. The distillate obtained by the evaporation is separated into the compound containing at least one hydroxyl group (an alcohol), a carbonic acid ester, the unreacted amine, and low-boiling by-products, followed by recovery. The present invention is a process for producing a urethane and a carbonic acid ester from a primary amine, an organic compound containing a hydroxyl group(s), carbon monoxide and molecular oxygen, and is advantageous in that unlike conventional processes, it neither requires handling of phosgene which is highly poisonous, nor yields hydrochloric acid as a by-product. Conventional catalytic systems comprise mainly expensive elements of the platinum group, such as palladium, rhodium and ruthenium, or selenium which is poisonous, and they are disadvantageous in that there is no choice but to use co-catalysts containing foreign metallic elements, ligands or additives, in a large amount in order to secure the activity and stability of the catalyst, so that the catalytic systems tend to be composed of many components and to become complicated. On the other hand, the process of the present invention is advantageous in that a high activity can be attained by means of a catalytic system comprising mainly copper which is not expensive, and since the catalyst is a simple system and does not contain any foreign metal, the catalyst can be smoothly recovered and reused. Thus, according to the process of the present invention, by the oxidative carbonylation reaction of an aromatic or aliphatic primary amine in the presence of an organic compound containing at least one hydroxyl group, corresponding urethanes and carbonic esters can be efficiently produced. Therefore, said process is industrially advantageous. The process which additionally uses an oxygen-containing organic sulfur compound is advantageous particularly for producing an aliphatic urethane which can be used as a material for hexamethylene diisocyanate and m-xylene diisocyanate. The process of the present invention is illustrated by the following examples. Example 1 An autoclave made of Hastelloy having a capacity of 100 ml was charged with 1 g (10.7 m moles) of aniline 25 g (543 m moles) of ethanol and 0.48 g (2.52 m moles) of copper iodide, and hermetically sealed. Carbon monoxide, and air were put in the autoclave to adjust their partial pressures to 7355 kPa (75 kg/cm²G) and 3432 kPa (35 kg/cm²G), respectively, and the reaction was carried out at a temperature of 158°C for 2 h. After completion of the reaction, the residual gas was purged while cooling the autoclave, and the reaction mixture was analyzed by an internal standard method by high performance liquid chromatography and gas chromatography. The urethane (ethyl N-phenylcarbamate) yield based on aniline was 92.3%, and 0.91 m moles of diethyl carbonate was found to be produced at the same time. Examples 2 to 5 Reaction was carried out in the same manner as in Example 1, except that the reaction temperature was changed to 175°C, 165°C, 145°C or 132°C. The urethane yield based on aniline and the amount of diethyl carbonate obtained are shown in Table 1. Example No. Reaction temp. (°C) Urethane yield mol% Amount of diethyl carbonate obtained m mol 2 175 50.4 2.10 3 165 86.5 4.38 4 145 82.3 0.77 5 132 68.6 - Example 6 Reaction was carried out in the same manner as in Example 1, except for using 0.16 g (2.52 m moles) of metallic copper and 0.38 g (2.52 m moles) of sodium iodide as catalysts. The urethane yield based on aniline was 42.2% and the amount of diethyl carbonate obtained was 7.05 m moles. Example 7 The same autoclave as in Example 1 was charged with 1 g (8.61 m moles) of 1.6-hexamethylenediamine, 25 g (780 m moles) of methanol and 0.48 g (2.52 m moles) of copper iodide in the same manner as in Example 1. Carbon monoxide and air were put in the autoclave to adjust their partial pressures to 7355 kPa (75 kg/cm²G) and 3432 kPa (35 kg/cm²G), respectively, and the reaction was carried out at a temperature of 175°C for 1 h. The diurethane (dimethyl 1.6-hexamethylenecarbamate) yield based on 1,6-hexamethylenediamine was 66.6% and 4.45 m moles of dimethyl carbonate was produced at the same time. Example 8 Reaction was carried out in the same manner as in Example 7, except for using 1 g (7.34 m moles) of m-xylenediamine as a starting material. The diurethane [dimethyl 1,3-phenylenebis(methylene)biscarbamate] yield based on m-xylenediamine (hereinafter referred as MXDA) was 66.8% and the amount of dimethyl carbonate obtained was 7.53 m moles. Example 9 Reaction was carried out in the same manner as in Example 8, except for using 0.25 g (2.52 m moles) of copper chloride as a catalyst. The diurethane yield based on MXDA was 37.9% and 7.11 m moles of dimethyl carbonate was produced at the same time. Example 10 An autoclave made of Hastelloy having a capacity of 100 ml was charged with 1 g (7.34 m moles) of MXDA, 8 g (250 m moles) of methanol, 6 g (49.9 m moles) of sulfolane and 0.48 g (2.52 m moles) of copper iodide, and hermetically sealed. Carbon monoxide and air were put in the autoclave to adjust their partial pressures to 7355 kPa (75 kg/cm²G) and 3432 kPa (35 kg/cm²G), respectively, and the reaction was carried out at a temperature of 165°C for 2 h. After completion of the reaction, the residual gas was purged while cooling the autoclave, and the reaction mixture was analyzed by an internal standard method by high performance liquid chromatography and gas chromatography. The diurethane [dimethyl 1,3-phenylenebis(methylene)biscarbonate] yield based on MXDA was 91.9%, and 1.86 m moles of dimethyl carbonate was found to be produced at the same time. Example 11 and 12 Reaction was carried out in the same manner as in Example 10, except that the molar ratio of sulfolane to the amino group was changed to 4.54 or 9.65. The diurethane yield based on MXDA and the amount of dimethyl carbonate obtained are shown in Table 2. Example No. Sulfolane Amino Group mol/mol Urethane yield mol% Amount of dimethyl carbonate obtained m mol 11 4.54 89.2 3.31 12 9.65 92.0 1.84 Example 13 Reaction was carried out in the same manner as in Example 10, except that 17 g (218 m moles) of dimethyl sulfoxide was used in place of sulfolane. The diurethane yield based on MXDA was 85.5% and the amount of dimethyl carbonate obtained was 5.81 m moles. Example 14 Reaction was carried out under the same conditions as in Example 1, except for using 8 g (174 m moles) of ethanol as an alcohol material. The diurethane [diethyl 1,3-phenylenebis(methylene)biscarbamate] yield based on MXDA was 89.0% and the amount of diethyl carbonate obtained was 0.59 m moles. Example 15 The same autoclave as in Example 10 was charged with 1 g (8.61 m moles) of 1,6-hexamethylenediamine as amine material, 8 g (250 m moles) of methanol, 6 g (49.9 m moles) of sulfolane and 0.48 g (2.52 m moles) of copper iodide. Carbon monoxide and air were put in the autoclave under pressure to adjust their partial pressures to 7355 kPa (75 kg/cm²G) and 3432 kPa (35 kg/cm²G), respectively, and the reaction was carried out at a temperature of 175°C for 1 h. The diurethane (dimethyl 1,6-hexamethylenecarbamate) yield based on 1,6-hexamethylenediamine was 82.3% and 3.21 m moles of dimethyl carbonate was produced at the same time. Example 16 The same autoclave as in Example 10 was charged with 1 g (10.7 m moles) of aniline, 8 g (173.6 m moles) of ethanol, 8 g (66.6 m moles) of sulfolane and 0.48 g (2.52 m moles) of copper iodide. Carbon monoxide and air were put in the autoclave under pressure to adjust their partial pressures to 7355 kPa (75 kg/cm²G) and 3432 kPa (35 kg/cm²G), respectively, and the reaction was carried out at a temperature of 158°C for 2 h. The urethane (ethyl N-phenylcarbamate) yield based on aniline was 95.8% and the amount of diethyl carbonate obtained was 0.52 m moles. Comparative Example 1 The same autoclave as in Example 1 was charged with 1 g (7.34 m moles) of MXDA and 8 g (250 m moles) of methanol as starting materials and 0.48 (2.52 m moles) of copper iodide, and they were reacted in the same manner as in Example 10 without sulfolane. The diurethane yield based on MXDA was 60.9% and 2.47 m moles of dimethyl carbonate was produced at the same time. Comparative Example 2 Reaction was carried out in the same manner as in Example 13, except that 17 g (151 m moles) of chlorobenzene was used in place of sulfolane. The diurethane yield based on MXDA was 60.3% and the amount of dimethyl carbonate obtained was 1.43 m moles. Comparative Example 3 Reaction was carried out in the same manner as in Example 10, except that the molar ratio of sulfolane to the amino group was changed to 0.85. The diurethane yield based on MXDA was 64.8% and 4.76 m moles of dimethyl carbonate was produced at the same time.

Claims: A process for producing a urethane and a carbonic acid ester which comprises reacting primary amine, carbon monoxide, molecular oxygen and an organic compound containing at least one hydroxyl group characterized in that the reaction is carried out at a temperature of 100 to 250°C and under a pressure of 1961 to 29420 kPa (20 to 300 kg/cm²) by using a catalytic system comprising at least one member selected from the group consisting of copper and copper compounds and at least one halogen selected from the group consisting of iodine, chlorine and bromine. The process of claim 1, wherein a catalyst comprising at least one member selected from the group consisting of copper and copper compounds and iodine are used. The process of claim 1 further comprising an oxygen-containing organic sulfur compound in an amount of 1 mole or more per mole of the amino group of the primary amine. The process of claim 3, wherein the primary amine is aliphatic. The process of claim 3, wherein the oxygen-containing organic sulfur compound is a sulfone or sulfoxide. The process of claim 3, wherein the oxygen-containing organic sulfur compound is sulfolane.

Inventors: ISOGAI, NOBUO, OKAWA, TAKASHI, TSUJI, TOMOJI
Applicants: MITSUBISHI GAS CHEMICAL COMPANY, INC.
Application year: 1988
Main classification: C07C271
IPC codes: C07C68, C07C271