KR20010013407A - Method for the preparation of carbamates - Google Patents

Abstract

Method for the preparation of carbamates by reaction of aromatic amines with organic carbonates in the presence of a metal based catalyst on an inert carrier support.

Description

Method for the Preparation of Carbamates

<Start of invention>

The present invention relates to a process for preparing carbamate by reacting an aromatic amine with an organic carbonate using a catalyst on an inert support.

It is known to react amines with organic carbonates to obtain carbamates.

US-A 5,347,034 discloses poly (o-alkylurethanes) of diphenylmethanes by reacting corresponding amines with dialkyl carbonates in the presence of a catalyst, where the resulting poly (o-alkylurethanes) are cooled to provide high purity. A method for precipitating is described.

EP-A 391,473 firstly reacts an amine with (cyclo) alkyl carbonate in the presence of a carbamation catalyst to produce a mixture of carbamate and urea, followed by reaction of the urea with carbonate to A process for preparing carbamate using a reduced amount of catalyst is described by obtaining a barmate and finally recovering the carbamate from the reaction mixture.

DE-A 3,202,690 describes a process for producing aromatic urethanes by the reaction of aromatic amines and alkylcarbonates in the presence of alcohol compounds of alkali or alkaline earth metals.

US-A 4,268,684 describes a process for the preparation of carbamate in which organic carbonates are reacted with aromatic amines in the presence of certain zinc, tin or cobalt salts which are active only at temperatures above 200 ° C., and US-A 4,268,683 The use of zinc or tin salts which are dissolved in the reaction mixture is described.

EP-A 48,371 describes the preparation of N, O-disubstituted urethanes by reaction of primary amines with dialkylcarbonates in the presence of neutral or basic inorganic or organic lead, titanium, zinc or zirconium compounds.

JP-A 07,328,435 uses a catalyst comprising Zr and Si containing oxide compositions for the production of carbamates from liquid aliphatic amines and diester carbonates.

An improved method of preparing carbamates has been found by reacting aromatic amines with organic carbonates.

Accordingly, the present invention relates to a process for preparing carbamate by reacting an aromatic amine with an organic carbonate in the presence of a metal based catalyst on an inert carrier support.

The method facilitates recovery of the catalyst, thus improving the economics and environmental impact of the process.

Another aspect of the invention relates to a catalyst comprising an organometallic salt on an inert carrier support.

Such catalysts exhibit improved functionality in converting aromatic amines to carbamates through reaction with organic carbonates.

Aromatic amines that can be used in the process of the invention are mono-, di- or polyamines.

Suitable amines according to the process of the invention are, for example, phenylamine, 4-chlorophenylamine, 2-fluorophenyl amine, 3,4-dichlorodiphenylamine, aniline, tolylamine, diisopropyl phenylamine, 2,4'-diaminodiphenylmethane, 4,4'-diaminophenylmethane, 2,2'-diaminodiphenylmethane and higher homologues (polyaminopolyphenylmethane), 2,4-toluenediamine, 2 , 6-toluenediamine, m-phenylenediamine, 1,5-naphthylenediamine and mixtures thereof.

Preference is given to aromatic di- or polyamines, such as toluenediamine, diaminodiphenylmethane or polyaminopolyphenylmethane, or any mixture thereof.

Suitable organic carbonates are cyclic or alicyclic carbonates such as ethylene carbonate, propylene carbonate, styrene carbonate, diphenyl carbonate, methyl phenyl carbonate, dimethyl carbonate Acetate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dihexyl carbonate, methyl ethyl carbonate, methyl butyl carbonate and the like.

Organic or inorganic salts that can be used are, for example, acetate, chloride, nitrate, sulfonate, propionate, isopropanoate, butanoate, 2-ethylhexanoate, n-octanoate, isono Nanoate, benzoate, chlorobenzoate, naphthalenate, stearate, itaconate, pivalate, phenolate, acetylacetonate, alkoxide, C ₁₆ / Cl ₁₈ -alkenylsuccinoate (ASA), C ₁₂ Alkenylsuccinoate (DSA) and the like.

Alkanoates having 1 to 15 carbon atoms are preferred.

Suitable catalysts are, for example, zinc chloride, zinc acetate, zinc propionate, zinc octanoate, zinc benzoate, zinc p-chlorobenzoate, zinc naphthalene, zinc stearate, zinc itaconate, zinc pivalate, zinc phenolate, acetyl Zinc catalysts such as zinc acetosan, zinc methoxylate, lead catalysts such as lead acetate and lead octoate, tin catalysts such as tin chloride and tin octosan, and mixtures thereof.

Preferably, the metal in the catalyst is selected from the group consisting of Ti, Zr, Zn, Sn and Pb.

Heterogeneous metal based catalysts on a carrier may be prepared by impregnating the catalyst with the carrier or by precipitation on the carrier.

Suitable inert carrier supports are, for example, metal oxides such as alumina, silica, TiO ₂ , MgO, clays, zeolites, polymer supports, resins, graphite and carbon. Preferred carriers are TiO ₂ , alumina or silica.

The supported catalyst is usually used in an amount of 10 ^-3 to 20 mol%, based on the amount of amine used.

Polyamines and organic carbonates can be reacted in stoichiometric amounts. However, preference is given to using excess organic carbonate.

Reaction conditions will generally depend on the type of reactant used.

The method can be carried out at atmospheric pressure or at pressures above atmospheric pressure. Preferably a pressure of 20 bar or less is preferred.

The reaction time depends on the temperature and the type and amount of carbamate compound, but will typically be 0.5 to 6 hours. The reaction time is conventionally less than 3 hours, and even at reaction times of less than 2.5 hours, no problem has been achieved.

In general, the reaction temperature will be between 50 and 300 ° C. Preferably, the process of the invention is carried out at a temperature of 100 to 250 ° C.

The solvent need not be present, but may be added as long as it does not adversely affect the reaction.

Any solvent or mixture of solvents which are inert to the reactants under the reaction conditions may be used.

Suitable solvents that can be used are, for example, aromatic hydrocarbons such as benzene, halogenated aromatic hydrocarbons such as monochlorobenzene, ortho-dichlorobenzene, trichlorobenzene or 1-chloronaphthalene, toluene, xylene, ethylbenzene, cumene or tetrahydro Alkylated aromatic hydrocarbons such as naphthalene, other functionalized aromatic hydrocarbons such as anisole, diphenylether, ethoxybenzene, benzonitrile, 2-fluoroanisole, 2,3-dimethylanisole or trifluorotoluene, n Alkanes such as pentane, n-hexane, n-heptane or higher or branched alkanes, cyclic alkanes such as cyclopentane, cyclohexane or derivatives thereof, halogenated alkanes such as chloroform, dichloromethane, carbotetrachloride, and diethyl Alkanes having other functional groups such as ether, acetonitrile, dioxane or mixtures thereof. Inert aromatic solvents are preferred.

The method can be carried out in any apparatus that can be equipped with agitation means and heating and / or cooling means to maintain a temperature within the desired range, if necessary.

The process of the invention can be carried out in a batch or semi-continuous or continuous process.

One type of continuous process is a fluidized bed reactor in which the catalyst is introduced into the reactor as a slurry in one or more reactants. Another method of working continuously is to use a moving bed reactor in which the catalyst bed and reactants pass together or countercurrently to one another. However, a preferred type of continuous process is a fixed bed reactor where the reactants pass through the catalyst bed.

During the process, reaction alcohols are produced as by-products. They can be removed from the reaction mixture, for example, by distillation or continuously after the end of the reaction.

The invention is illustrated by, but not limited to, the following examples.

<Example 1>

To a suspension of 2 g TiO2 in 100 ml of acetone, 0.308 g of zinc octoate (6% by weight Zn in terpentine mineral oil) was added and the mixture was pulsed with Ar gas for 5 minutes. The flask was placed in a water containing ultrasonic bath (frequency: 20 MHz) at room temperature for 1 hour. After sonication, the solvent was removed under reduced pressure and finally the solid was dried under reduced pressure at 70 ° C. for 1 hour. The solid thus obtained was used for the production of carbamate and the like. Isolated yield: 2.2 g.

In a 100 ml steel autoclave, 2.Og (10 mmol) of 4,4'-diamino diphenyl methane, 42.7g (0.47 mol) of dimethyl carbonate and 0.18g of TiO2 supported zinc octanoate (Ti0 ₂₎ 20 wt% zinc salt of 2-ethyl hexanoic acid supported on the phase) was added. The mixture was pulsed with nitrogen. The reaction mixture was heated at 180 ° C for 2 h.

After completion of the reaction, the autoclave was cooled to room temperature, the crude product was evaporated to dryness, redissolved in dichloromethane and finally the catalyst was filtered off. The filtrate thus obtained was evaporated to dryness under reduced pressure to obtain a crystalline solid. The conversion of amines was 100% based on the starting material. Selectivity to urethane was 96.3% based on quantitative HPLC.

<Example 2>

2.Og (10 mmol) of 4,4'-diamino diphenyl methane, 25.5g (0.28 mol) of dimethyl carbonate, 16ml of toluene and 0.18g of TiO2 supported octo in a 100 ml steel autoclave Zinc acid (20% by weight zinc salt of 2-ethyl hexanoic acid supported on Ti0 ₂ ) was added. The mixture was pulsed with nitrogen. Thereafter, the reaction mixture was heated at 180 ° C. for 2 hours.

After completion of the reaction, the autoclave was cooled to room temperature, the crude product was evaporated to dryness, redissolved in dichloromethane and finally the catalyst was filtered off. The filtrate thus obtained was evaporated to dryness under reduced pressure to obtain a crystalline solid. The conversion of amines was 100% based on the starting material. Selectivity to urethane was 98% based on quantitative HPLC.

<Example 3>

In a 100 ml steel autoclave, 2.Og (8 mmol) of polymer diamino diphenyl methane, 42.7 g (0.47 mol) dimethyl carbonate and 0.18 g of TiO2 supported zinc octanoate (Ti0 ₂ supported on phase) 20 wt% zinc salt of 2-ethyl hexanoic acid) (0.1 mmol of active catalyst) was added. The mixture was pulsed with nitrogen. Thereafter, the reaction mixture was heated at 180 ° C. for 2 hours.

After completion of the reaction, the autoclave was cooled to room temperature and the catalyst was filtered off. The filtrate obtained was evaporated to dryness under reduced pressure to obtain a solid. The conversion of amines was> 98% based on the starting material. Selectivity to urethane was determined to be 89 to 92% based on IR and ¹³ C NMR.

<Example 4>

1.22 g (10 mmol) of 2,4-diaminotoluene, 42.7 g (0.47 mol) of dimethyl carbonate and 0.18 g of TiO2 supported octosan zinc ( ₂ -ethyl hexanoic acid supported on Ti0 ₂ ) A mixture of 20% by weight salt) (0.1 mmol of active catalyst) was charged to 100 ml of steel autoclave and pulsed with nitrogen. Thereafter, the reaction mixture was heated at 180 ° C. for 2 hours.

After completion of the reaction, the autoclave was cooled to room temperature and the same amount of dichloromethane was added to dissolve the partially precipitated 2,4-bis (methoxycarbonylamino) toluene. The mixture was then filtered off to separate the catalyst. The filtrate thus obtained was evaporated to dryness under reduced pressure to obtain 2,4-bis (methoxycarbonylamino) toluene solid as yellow crystals. The conversion of amines and selectivity to urethanes were found to be 100% and 92%, respectively, from quantitative HPLC techniques.

<Example 5>

To a suspension of Al ₂ O ₃ 2 g in 40 ml of acetone was added 1.2 g of zinc octoate (6% by weight Zn in terpentin mineral oil) and the mixture was pulsed with Ar gas for 5 minutes. The flask was placed in an ultrasonic bath containing water at room temperature (frequency: 20 MHz) for 1 hour. After sonication, the solvent was removed under reduced pressure and finally the solid was dried under reduced pressure at 70 ° C. for 1 hour. The solid thus obtained was used for the production of carbamate and the like. Isolated yield: 2.8 g.

A stainless steel autoclave of 100 ml of dimethyl carbonate and Al ₂ 0 ₃ supported loam acid zinc of 0.212g of the polymer-diaminodiphenyl methane, 42.7g (0.47 mol) of _{2.Og (10 mmol) (Al 2} 0 20 wt% of zinc salt of 2-ethyl hexanoic acid supported on phase ₃ ) was added. The mixture was pulsed with nitrogen. Thereafter, the reaction mixture was heated at 180 ° C. for 2 hours.

After completion of the reaction, the autoclave was cooled to room temperature, the crude product was evaporated to dryness, redissolved in dichloromethane and finally the catalyst was filtered off. The filtrate thus obtained was evaporated to dryness under reduced pressure to obtain a crystalline solid. The conversion of amines was 100% based on the starting material. Selectivity to urethane was 91% based on quantitative HPLC.

<Example 5>

A stainless steel autoclave of 100 ml of dimethyl carbonate and Al ₂ 0 ₃ supported loam acid zinc of 0.212g of the polymer-diaminodiphenyl methane, 42.7g (0.47 mol) of _{2.Og (8 mmol) (Al 2} 0 20 wt% of zinc salt of 2-ethyl hexanoic acid (0.12 mmol of active catalyst) supported on phase ₃ was added. The mixture was pulsed with nitrogen. Thereafter, the reaction mixture was heated at 180 ° C. for 2 hours.

After completion of the reaction, the autoclave was cooled to room temperature, the crude product was evaporated to dryness and the catalyst was filtered off. The filtrate thus obtained was evaporated to dryness under reduced pressure to obtain a crystalline solid. The conversion of amines was 98% based on the starting material. Selectivity to urethanes was 84-92% based on IR and ¹³ C NMR.

<Example 7>

To a suspension of 2 g of silica (silica gel for column chromatography, 200 to 300 mesh) in 40 ml of acetone, 1.2 g of zinc octoate (6% by weight Zn in terpentine mineral oil) was added and the mixture was poured into Ar gas for 5 minutes. Pulsed. The flask was placed in an ultrasonic bath containing water at room temperature (frequency: 20 MHz) for 1 hour. After sonication, the solvent was removed under reduced pressure and finally the solid was dried under reduced pressure at 70 ° C. for 1 hour. The solid thus obtained was used for the production of carbamate and the like. Isolated yield: 2.4 g.

2.Og (10 mmol) of 4,4'-diamino diphenyl methane, 42.8g (0.47 mol) dimethyl carbonate, 0.216g silica supported octosan zinc on silica 20% by weight of a zinc salt of 2-ethyl hexanoic acid) was added thereto. The mixture was pulsed with nitrogen for 5-10 minutes. Thereafter, the reaction mixture was heated at 180 ° C. for 2 hours.

After completion of the reaction, the autoclave was cooled to room temperature, the crude product was evaporated to dryness, redissolved in dichloromethane and finally the catalyst was filtered off. The filtrate thus obtained was evaporated to dryness under reduced pressure to obtain a crystalline solid. The conversion of amines was 100% based on the starting material. Selectivity to urethane was 81.8% based on quantitative HPLC.

<Example 8>

2.Og (8 mmol) of polymer diamino diphenyl methane, 42.7 g (0.47 mol) of dimethyl carbonate and 0.216 g of acidic silica supported octosanate (supported on silica gel) in a 100 ml steel autoclave 20 wt% zinc salt of 2-ethyl hexanoic acid) was added. The mixture was pulsed with nitrogen. Thereafter, the reaction mixture was heated at 180 ° C. for 2 hours.

After completion of the reaction, the autoclave was cooled to room temperature and the crude product was filtered off to separate the catalyst. The filtrate thus obtained was evaporated to dryness under reduced pressure to obtain a crystalline solid. The conversion of amines was 97% based on the starting material. Selectivity to urethane was 81-83% based on IR and ¹³ C NMR.

Claims (13)

A process for preparing carbamate by reacting an aromatic amine with an organic carbonate in the presence of a metal based catalyst on an inert carrier support. The method of claim 1 wherein the catalyst comprises a metal selected from the group consisting of Ti, Zr, Zn, Sn and Pb. The process of claim 1 or 2, wherein the catalyst comprises alkanoates having 1 to 15 carbon atoms. The method of claim 1, wherein the carrier support comprises TiO ₂ alumina or silica. The process according to claim 1, wherein the reaction is carried out at a temperature of 100 to 250 ° C. 6. The process according to any one of claims 1 to 5, wherein the aromatic amine is selected from the group consisting of toluenediamine, diaminodiphenylmethane or polyaminopolyphenylmethane or mixtures thereof. The process according to claim 1, wherein the reaction is carried out at a pressure of up to 20 bar. 8. Process according to any one of the preceding claims, carried out in the presence of an inert aromatic solvent. The method according to claim 1, wherein the reaction time is less than 2.5 hours. A catalyst comprising an organometallic salt on an inert carrier support. The catalyst of claim 10 wherein the metal is selected from the group consisting of Ti, Zr, Zn, Sn and Pb. The catalyst according to claim 10 or 11, wherein the organic salt is an alkanoate having 1 to 15 carbon atoms. The catalyst according to claim 10, wherein the carrier support comprises TiO ₂ , alumina or silica.