HU199406B - Process for the continuous production of n,n'-diisopropylurea - Google Patents

Abstract

N,N'-di-isopropyl-urea is prepd. by batchwise or continuous reductive hydrogenation of urea in the presence of acetone in a ternary solvent mixt. using pure hydrogen or hydrogen mixed with an inert gas at 120-200 deg.C and a pressure of 5-14 MPa on a carrier supported catalyst. - Catalyst is pref. palladium, platinum, rhodium or nickel supported on a meta-oxide from the 8B gp. of the periodic table, pref. aluminum-oxide, or on an inert carrier. - Ternary solvent mixt. consists of 7-85 vol.% alcohol with 2-4 carbons, 10-20 vol.% acetone and 2-4 vol.% water.

Description

The present invention relates to a process for the continuous preparation of Ν, Ν'-diisopropylurea in a solvent medium by catalytic reductive alkylation.

N, N'-diisopropylurea is an important ingredient in post-emergence herbicidal formulations widely used in agriculture, characterized by: - a solid, crystalline substance, - melting point 191-192 ° C, - soluble in alcohol, - water, insoluble in ether.

One of the basic requirements for N, N'-diisopropylurea that can be used for further processing is a purity of at least 98%.

Relatively few publications have been published on the preparation of dialkyl ureas and N, N'-diisopropyl urea. The published publications mainly contain traditional information, such as the publication No. 1,111,162. According to a German patent, N, N'-dialkylureas were prepared by treating a mixture of biuret and urea with alkylamines at high temperature. The crude product was prepared at 160 ° C for 6-10 hours in a tank reactor in 90-95% yield.

Given that the reaction can only be carried out by batch technology and under very strong conditions, the process generates a large amount of contaminating by-products, which are eliminated with considerable loss. No. I 111 162. Indeed, N, N'-diisopropylurea was obtained in 92% yield, but the product was yellow, m.p. 165-170 ° C. containing 19% impurity by HPLC (column RP-18, eluent: acetonitrile). The crude product was recrystallized from ethanol, using activated charcoal purification, to give a purity of 90.5%, m.p. 183-187 ° C. Recrystallization gave a white solid, m.p. 190-192 ° C, 96% purity; however, this recrystallization reduced the overall process yield to 48%. The required purity of 98% was achieved only by a third recrystallization with ethanol; the product of the required quality was obtained with a total yield of 37%.

No. 163/1960. According to Japanese patent symmetric dialkylureas were synthesized by heating urea, methylamine hydrochloride in decalin at 140-150 ° C for 5 hours with vigorous stirring. After cooling to room temperature, the crude product precipitated from the separating bottom layer was separated, then extracted with ethanol and, after evaporation of most of the solvent, the crystalline product was filtered off. In this way, the dialkyl ureas were obtained in medium yield.

The preparation of urea derivatives is also described in U.S. Patent No. 1,361,768. French patent. According to this process, dialkyl ureas were prepared from carbon oxide sulfide and alkyl amines of the formula R-NH _{2 in a} special solvent medium, such as i-pro10 pylamine and carbon oxide sulfide in the presence of toluene or decalin solvent, under low pressure, The product was obtained at a temperature of 100-105 ° C in a yield of 60-65%. The disadvantage of this process is that the by-product is a pollutant-contaminating hydrogen sulfide.

The reaction of alkyl dichloramines with nickel tetracarbonyl (H. Bock and

K. L. Kompa, Angew. Chem. Intern. Ed. Engl.

5/1/123, 1966) which provides the desired end product in only a few steps. No guidance is given for the recovery of the catalyst.

N.N'-Dialkylcarbamidoate and alkylisocyanates were prepared from alkyl halides and alkali metal dANates by W. Gerhard (J. Prakt. Chem. 38 / 1-21, pp. 77-78, 1966). Only long-chain dialkyl ureas can be produced by this method, but the secondary alkyl halides are produced in low yields only.

3q can be converted to N, N'-dialkylurea.

It is also known that N, N'-diisopropylurea can be prepared from i-propyl isocyanate by heating with water (Curtius, J. Prakt. Chem. (2), 125, 187 (1980)).

By heating an ethereal solution of isobutyric acid azide in water in the presence of a small amount of isobutyric acid amide, Ν, Ν'-diisopropylurea was also prepared (Curtius, Bull. Chem. Soc. Jpn. 29, 54 (1956)).

F. Applegath et al., U.S. Patent No. 818,864. N, N'-disubstituted ureas were prepared from carbon monoxide and sulfur with ammonia (or amine derivatives).

By this method, N.N'-diisopropyl ^45- urea was obtained in only 51% yield. Another disadvantage of the process is that large amounts of corrosive by-products are formed.

5 ₀ also known a solution according to which thioglycolic acid and urea dialkyl ureas can be obtained at room temperature (P. Monforte (Atti Soc. Peloritana Sci. Fos Mat., Nature. 11/4, 457- 72 (1965)).

gg of diisopropylurea was also prepared from isopropylcarbodiimide with ethyl chloroic acid ester, but the yield was only 31% (Paul and Hartke, Rev. Ac. Acad. Cienc. Exacts. Fis. Nat. Madrid 62/1, 155-182). . She.

no ^(1θ68)) · ^w There is also known a process for the reductive alkylation of urea with acetone in the presence of little water to produce N, N'-diisopropylurea on a Raney nickel catalyst (U.S. Pat. No. 2,477,872). .

-2HU 199406 Β

Alkylated urea derivatives have also been prepared from urea and aldehydes or ketones in accordance with U.S. Patent No. 2,673,859. according to a patent in the United States of America. According to this process, Ν, Ν'-diisopropylurea was prepared from urea and ten times excess acetone, on a Raney nickel catalyst at 150-160 ° C and a pressure of 68 bar. In addition to N.N'-diisopropylurea, N-isopropylurea was also formed in significant amounts in addition to the tar by-product. From the by-product only tiszt, Ν'-diisopropylurea could be separated from the by-product only in 32% yield.

The main disadvantages of each of the processes described are the use of state-of-the-art batch technology, which requires long operating times, many of which generate sulfur-containing compounds or cause serious environmental problems with the reagent used, such as carbon monoxide sulfide. the damage is also great. The production of a pure final product is also hindered by the fact that the reaction results in a variety of by-products which require complex separation operations.

In addition to the operational hazards, batch reductive alkylation technology, with its highly unfavorable species members, large amounts of by-products, high labor effort, and many technological operations, only yields the desired urea derivatives.

It is an object of the present invention to provide a process that addresses the above shortcomings and provides state-of-the-art technology for the preparation of Ν, Ν'-diisopropylurea.

In our work, we have investigated the reductive alkylation reaction of urea and acetone and found that Raney nickel, which has been used as a catalyst so far, is not well suited to provide the desired target product in a good yield and economically and to make the process continuous.

Therefore, as a first step, we sought a catalyst with appropriate activity and selectivity. In our experiments we found that the periodic table 8.B. Groups of metals of groups I to II are most suitable for this purpose when applied to a support. Gamma-alumina and activated carbon have proved to be the best catalysts.

It has now been found that the reductive alkylation of the urea-acetone reaction mixture must be carried out in a solvent mixture which preferably contains a suitable amount of water in addition to a suitable quality and amount of organic cosolvent. C 2 to C 4 alcohols or mixtures thereof are preferably used as organic co-solvents in the formation of the special ternary solvent (acetone, alcohol, water). In the ternary solvent mixture of the process according to the present invention, the reaction proceeds at a rate which permits the development of state-of-the-art continuous technology and with such high selectivity that the product precipitated from the solvent mixture can be used without further purification. Advantageously, the selectivity and activity during reductive alkylation may be influenced by the concentration of hydrogen ion in the suitably chosen alkaline range. Without this, the rate of formation of the activated intermediate from the starting materials is low and by-products can be detected by high performance liquid chromatography, which not only reduces the yield but also causes discoloration. At an appropriately chosen pH, the formation of by-products was successfully eliminated in the presence of suitable anions and cations. Alkalines having a pH of 7.5 to 10 and salts which are capable of providing a pH of 7.5 to 11 during dissociation and hydrolysis in a particular medium are very suitable for adjusting the pH of the reaction mixture. These include carbonates, acetates, phenolates, benzoates, or formates of ammonia, alkaline hydroxides, alkaline or alkaline earth metals.

According to the invention, the process is carried out in a pure or max. Urea containing 10% by weight of biuret, in the presence of a palladium, platinum, rhodium or nickel catalyst in the presence of palladium, platinum, rhodium or nickel on a ternary solvent mixture adjusted to pH 7,5 to 11 at 5 to 14 MPa; hydrogen is diluted continuously or intermittently with hydrogen gas diluted with an inert gas. As a catalyst support, γ-allurium oxide was found to be most suitable. The solvent used is a ternary mixture of 76-85% by weight of C2-C4 alcohol, 10-20% by weight of acetone and 2-4% by weight of water.

In addition to pure hydrogen, the reductive alkylation can be carried out with a gas mixture containing up to 60% nitrogen gas or C 1-4 hydrocarbons.

The advantage of our process is that under the experimental conditions the reaction proceeds at high speed, allowing the technology to be continuous and to obtain a product which eliminates the need for complicated costly product purification operations and further increases the product yield. Of course, our process can be carried out in batch mode, with excellent results.

Without limiting the scope of the invention, the following embodiments are illustrated by the following examples:

1. p «ldb

In a fixed bed system for 2 liters of catalyst bed of 0.5 wt% Pt / Al ₂ Oj - at a rate of m ³ / nr h - continuously 2 m ³ / h of 6 parts of urea,

-3HU 199406 Β 9 parts by weight of acetone, 2.5 parts by weight of 25% ammonium hydroxide solution and 76 parts by weight of isopropyl alcohol in proportion to 800 1 to 400 m ³ / m ^{3 of} gas-liquid, . The reaction temperature was maintained at 160 ° C, pressure was 10 MPa and after expansion

A 1.98 m ³ / h product solution was recovered. Subsequently, the solvent was distilled off, and the solid crystalline Ν, di'-diisopropylurea, after dilution with water, was filtered off and dried. (The resulting solvent mixture, unconverted urea and hydrogen-containing gases were optionally recycled.) The NN-diisopropylurea was recovered in a 50% yield from the reactor leaving the reactor in 50% yield. 40% by weight of the unreacted urea containing 5.5 wt% biuret formed during the reaction was recovered after evaporation of the solvent and used for repeated product preparation.

Example 2

The procedure of Example 1 was followed except that 5% by weight of Pd / Al ₂ O _{3 was} used as catalyst. Ν, Ν'-diisopropylurea was obtained in 46% yield and 99.5% purity.

Example 3

All were prepared in the same manner as in Example 1, but using ethyl alcohol as the alcohol, 1% Rh / Al ₂ O ₃ as catalyst and 77% hydrogen and 23% C 1-4 hydrocarbons as reducing gas. The reaction yielded N, N'-diisopropylurea in 53% yield and 99.5% purity.

Example 4

The procedure of Example 1 was followed, but the reaction was carried out on a catalyst bed of 18% Ni / Al ₂ O ₃ at 180 ° C and 12 MPa. From the reaction mixture leaving the reactor, Ν, Ν'-diisopropylurea was obtained in 56% yield and 99% purity.

Example 5

Example 2 was performed starting with urea containing 3% biuret. Instead of ammonium hydroxide, a 2% sodium carbonate solution was used, the reducing gas was hydrogen nitrogen (2/3: 1/3), the catalyst was 5% activated carbon Pd, and the reaction temperature was 180 ° C. and the pressure was maintained at 12 MPa. The Ν, Ν'-diisopropylurea was recovered in 45% yield and 97.5% purity from the reaction mixture leaving the re6 actor. 40% of the starting urea containing biuret was recovered and used for re-production.

Example 6

All were carried out as in Example 2, but no basic additives were used. From the reaction mixture leaving the reactor, Ν, Ν'-diisopropylurea was obtained in 11% yield (14.5 g) and 97% purity.

Example 7

The urethane recovered urethane from Example 1 was also used in the preparation of the solution and further worked up as in Example 1 below. Thus, N, N'25-diisopropylurea was obtained in a yield of 76% based on the amount of the original urea in the first recirculation batch, and finally 98% yield and 98% purity after a lot of re-feeding.

Example 8

The procedure was as in Example 1, but the catalyst (18% Ni / Al ₂ O ₃ ) was used in powder form at a concentration of 5% under suspension conditions. From the reaction mixture leaving the reactor, the catalyst was filtered off under an inert gas stream. Ν, Ν'-Diisopropylurea was obtained in 59% yield and 99.8% purity 35.

Claims (2)

A process for the continuous production of N, N'-diisopropyl urea by alkylation of pure urea or biuret urea with acetone, characterized in that the pure urea containing from 1 to 10, preferably from 2 to 7% by weight of urethane is gamma-alumina or ^{In the presence of 45} palladium on carbon, platinum, radium or nickel on carbon, 66 to 85% by weight of C2 to C4 alcohol, 10 to 20% by weight of acetone 5q and 2-4% by weight of water, adjusted to pH 7.5-11, is continuously alkylated at 120 to 200 ° C, at 5 to 14 MPa, with pure or up to 60% by volume of nitrogen or gg of hydrogen having from 1 to 4 carbon atoms. The process of claim 1, wherein the pH of the solvent mixture is adjusted with an ammonium hydroxide solution, an alkali metal hydroxide solution, or a solution of an alkaline hydrolyzing salt of an alkali metal.