WO1992010467A1

WO1992010467A1 - Method for obtaining of n-phenylcarbamic acid esters

Info

Publication number: WO1992010467A1
Application number: PCT/PL1991/000012
Authority: WO
Inventors: Wiktor Kazmierowicz; Grzegorz SMÓLKA; Janina ILMURZYN^´SKA; Jadwiga SKUPIN^´SKA; Maria BIEN^´KOWSKA; Jakub GIERMASIN^´SKI; Tadeusz Wilusz
Original assignee: Instytut Chemii Przemyslowej
Priority date: 1990-10-08
Filing date: 1991-10-02
Publication date: 1992-06-25
Also published as: PL287226A1; PL164286B1

Abstract

The object of the invention is a method for obtaining of N-phenylcarbamic acid esters in a liquid phase on the way pressure carbonylation of nitrobenzene at the presence of alcohols. The product can be a raw material basis for production of polyurethanes. According to the invention as a catalytic system there are used metallic palladium and/or its chlorides, bromides or iodides, powdered iron and elementary iodine and possibly pyridine or tertiary aliphatic amine of the molecular weight from 59 to 300.

Description

Method for Obtaining of N-Phenylcarbamic Acid Esters

The object of the invention is a method for obtaining of N-phenylcarbamic acid esters in the liquid phase on the way of nitrobenzene reduction at the presence of alcohols with application of a catalytic system. Actually the invention is designed for obtaining of urethanes (Carbamic acid esters) being an intermediate product for obtaining of di isocyanates necessary for production of polyurethanes.

There is known a method for obtaining of urethanes on the way of reductive carbonylation of nitrocompounds at the presence of alcohols with application of the catalytic system containing selenium or its compounds (Berman Federal Republic patents no 2343826; 2614101; 2623694). High toxicity of intermediate selenium compounds appearing during the reaction and the necessity to remove them applying expensive methods reduces profitability of the process.

There is also known a method for obtaining of urethanes in the reactions of nitrocompounds, carbon monoxide and alcohols at the presence of catalysts containing noble metals (mainly palladium and Lewis acids) (German Federal Republic patents 1586044 and 2603574) or combination of ferric oxides, oxychlorides and chlorides

(USA patent 4219661). It is also possible to obtain urethanes on the way of reductive carbonylation of nitrocompounds at the presence of alcohols with application of chlorideless catalysts based on ruthenium carbonyl (USA patent 4600793 and 4629804).

An important disadvantage of these catalytic systems is, however, long time of the reactions and their not very high efficiency. Besides, the above mentioned methods bring about considerable difficulties with recovery of the catalysts, especially expensive noble metals, which are in the slime together with metals oxides and chlorides. Removal of metal chlorides from the products also requires several operations because chlorides are soluble in alcohols used in excess.

Unexpectedly it has been found out that it is possible to simplify the process of nitrobenzene carbonylation and to obtain the product with high efficiency if there is applied a catalytic system according to the invention. The system includes metallic palladium and/or its halides, powdered iron and elementary iodine and possibly an additive of pyridine and/or tertiary aliphatic amine of the molecular weight 59 - 300. The process is carried out tinder the pressure of carbon monoxide 2 - 50 MPa at the temperature

120 - 300ºC in the liquid phase at the presence of aliphatic alcohol, favourably methanol and ethanol, in the mole ratio to nitrobenzene from 0.5s 1 to 100:1. In the catalytic system as a catalyst there is used palladium or its chlorides, bromides or iodides, favourably in the quantities 0.0001 - 0.01% by weight, as cocatalysts there are used elementary iodine, favourably in the quantity 0.0002 - 3% by weight and powdered iron in the quantity 0.05 10% by weight. An addition of pyridine or tertiary aliphatic amine is a possible, however not indispensible, component of the catalytic system used in the quantity 0.1 - 107. by weight.

Contrary to the other catalytic systems in the reaction system according to the invention reproduction of elementary iodine takes place, due to which concentration of iodine can be small in comparison for example to Lewis acid concentrations used for this purpose. The presence of powdered iron in the system not only guarantees quick forming of ferric iodide but also prevents iodine corrosion of the steel reactor.

An advantage of the method according to the invention of obtaining of carbamic acid esters is a high, reaching 100%, degree of nitrobenzene reacting and high selectivity and law concentration of catalysts and cocatalysts. After the recation is finished, it is possible to separate easi ly powdered iron by means of decantation and washing and metallic palladium by centrifuging of its subtle suspension. It is also possible to remove elementary iodine by its extracting with aliphatic hydrocarbons.

Example I

The solution of 10 g of nitrobenzene in 20 g of ethanol and 0.031 g of palladium black, 0.1 g of iodine, 0.5 g of powdered iron and 0.49 g of pyridine was introduced into a steel autoclave of the volume 215 cm³ previously washed with purified nitrogen. To the recator there was forced carbon monoxide at the room temperature up to the pressure of 5 MPa. Next, the reactor was closed and heated at the temperatture of 180°C. The pressutre inside the reactor first grew to 8.5 MPa and next began to drop stabilizing after two hours on the level of 7.5 MPa. After cooling of the reaction mixture to the room temperature, the reactor was decompressed by slow letting of the gas excess out. The analysis by the gas chromatography method showed the degree of nitrobenzene reacting 98% with selectivity to ethyl N-phenylcarbamate equal also to 98%.

Example II

The procedure was as in Example I, however, pyridine was not used. After two hours there was obtained 92% reacting with selectivity of 98%.

Example III

The procedure was as in Example I, however, instead of ethanol there was used 20 g of methanol. The pressure inside the reactor grew to 9.1 MPa, and after 2 hours of reaction it was stabilized on the level of 7.9 MPa. There was obtained methyl N-phenylcarbamate with the efficiency 86% in relation to nitrobenzene with the selectivity of 100%. Example IV

The procedure was as in Example I, however, instead of palladium black there was used 0.1 g of PdCl₂, and instead of pyridine there was used 1 g of triethylamine. After two hours of reaction there was obtained ethyl N-phenylcarbamate with the efficiency of 98% with the selectivity of 98%.

Example V

The solution of 70 g of nitrobenzene in 140 g of ethanol and 0.22 g of palladium black, 1.4 g of iodine; 3.5 g of powdered iron and 3.5 g of pyridine was introduced to the steel autoclave of the volume 1.5 dcm³ washed with nitrogen. The reactor was closed and heated to the temperature of 140°C.

Next, into the reactor there was forced carbon monoxide by means of a compressor up to the pressure of 11.5 MPa. The temperature in the reactor grew to 170°C. The process was conducted for 2.5 hours while keeping the stable temperature in the reactor equal to 170°C by thermostating and the pressure within the range 11.0 - 11.5 MPa by letting carbon monoxide. After cooling of the reaction mixture to the room temperature, the reactor was decompressed by letting gas excess slowly out.

The analysis performed by the gas chromatography method showed the degree of nitrobenzene reacting 99% with the selectivity to ethyl N-phenylcarbamate equal to 86%..

Claims

Patent Claims

1. The method for obtaining of N-phenylcarbamic acid esters in a liquid phase by the method of catalytic carbonylation of nitrobenzene at the presence of aliphatic alcohol specific by the fact that as a catalytic system there are used metallic palladium and/or its chlorides, bromides or iodides; powdered iron and elementary iodine and possibly pyridine or tertiary aliphatic amine of the molecular weight from 59 to 300.

2. The method according to claim 1 specific by the fact that metallic palladium or its halides are used in the quantities from 0.0001 to 0.1% by weight, elementary iodine in the quantities 0.0002 to 3% by weight and powdered iron in the quantities 0.05 to 10% by weight while pyridine and/or tertiary aliphatic amine of the molecular weight from 59 to 300 in the quantities from 0.1 to 10% by weight.

3. The method according to claim 1 specific by the fact that the reaction of reductive carbonylation of nitrobenzene is conducted under the pressure from 2 to 50 MPs. within the temperature range from 120 to 300ºC.