Mitsui Toatsu Chemicals, Incorporated

Makoto Aiga

Katsuharu Miyata

Yutaka Hirai

Seiji Hasegawa

Masanobu Ajioka

Akihiro Tamaki

Masafumi Kataita

Katsuharu Miyate

Hexamethylene diisocyanate (HDI) is prepared by introducing a hexamethylenediamine (HDA) solution and an equivalent amount or more of hydrogen chloride gas simultaneously into a turbulent zone in the vicinity of an agitating blade in an inert organic solvent held under agitation within a tank-shaped reactor and allowing them to undergo a successive salt-forming reaction so as to obtain a high-concentration slurry of hexamethylenediamine hydrochloride (HDA.multidot.HCl) and then reacting the slurry with phosgene. The phosgenation is effected by charging an HDA.multidot.HCl slurry of a high concentration, such as that obtained by the above process, into a tank-shaped reactor held under a pressure above the atmosphere pressure but below 5 kg/cm.sup.2 G and controlling the amount of phosgene, which is to be blown into the reactor, at a level 1-18 molar times per hour the total amount of HDA.multidot.HCl and HDI in the reaction mixture. In a preferred embodiment of the phosgenation, the phosgenation reaction is effected in a continuous two-step tank-shaped reactor while controlling the degree of conversion in the first step within 70-95%. This is a rationalized preparation process of hexamethylene diisocyanate since it requires a shorter overall phosgenation time.

Preparation process of hexamethylene

Aromatic urethanes can be produced by interacting an aromatic primary amino compound having a nitro group, a nitroso group or a carbamate group, an organic compound having at least one hydroxyl group, and carbon monoxide in the presence of a catalytic system composed of a platinum group metal and/or a compound thereof serving as catalyst and a Lewis acid and/or a compound thereof as promoter under high temperature and high pressure conditions. For instance, the interaction of 2-amino-4-nitrotoluene, ethanol and carbon monoxide in the presence of palladium chloride and a ferrous chloride-pyridine complex under high temperature and high pressure conditions can yield 2,4-diethylcarbamatetoluene.

Process for preparing aromatic urethanes

An aromatic urethane is obtained at high yield without involving corrosion of a stainless steel reactor by interacting an aromatic nitro compound, an organic compound having at least one hydroxyl group therein and carbon monoxide in the presence of a catalyst composed of (1) palladium, ruthenium, rhodium or compounds thereof, (2) a Lewis acid, and (3) a tertiary amine. For instance, 2,4-dinitrotoluene, ethanol and carbon monoxide placed in a SUS-32 reactor are interacted in the presence of a catalyst composed of (1) 5% palladium on carbon, (2) ferric chloride, and (3) pyridine to obtain 2,4-diethyldicarbamatetoluene without corrosion of the reactor. After completion of the reaction, the catalyst and reaction product are separated from the reaction system; e.g., the insoluble catalyst is first separated and then the reaction solution is cooled down, e.g., to room temperature, to separate the reaction product as crystals, followed by separation of the crystals by filtration. Then, the reaction may be repeated by adding fresh 2,4-dinitrotoluene and ethanol and the separated catalyst to the resultant fitrate under pressurized conditions of a carbon monoxide atmosphere. By repeating the reaction in this manner, 2,4-diethyldicarbamatetoluene with a purity of 98% can be obtained at a yield of 90%.

Process for producing an aromatic urethane

In a process for preparing an aromatic urethane which comprises reacting an aromatic nitro compound, an organic compound containing at least one hydroxyl group, and carbon monoxide at elevated temperature and pressure in the presence of a catalytic system composed of a catalyst consisting of a platinum metal, a platinum metal compound, and/or a platinum metal compound-containing compound and a promoter consisting of a Lewis acid and/or a Lewis acid-containing compound, an organic primary amino compound, a urea compound, a biuret compound, an allophanate compound, or a mixture thereof is added to the reaction system whereby the reaction rate is increased and the yield of the desired product is enhanced. For example, 2,4-diethylcarbamatetoluene can be prepared in quantitatively high yield by reacting 2,4-dinitrotoluene, ethanol, carbon monoxide, and a small amount of aminonitrotoluene at elevated temperature and pressure in the presence of palladium chloride and ferrous chloride-pyridine complex.

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Omuta, Japan

Makoto Aiga