JPS63297356A - Production of carbamic acid ester - Google Patents

Abstract

PURPOSE:To obtain a carbamic acid ester, by reacting an amine or an amino acid with carbon monoxide, a hydroxyl-containing compound and oxygen in the presence of a catalyst and reutilizing the catalyst in the form of a solution without separating the catalyst from the reaction mother liquor as a solid. CONSTITUTION:The objective compound can be produced by reacting an amine or an amino acid with carbon monoxide, a hydroxyl-containing compound (e.g. alcohol) and oxygen in the presence of a catalyst consisting of a group VIII platinum-group transition metal of the periodic table or its salt, a complex of a cuprous salt, a Ti(III) salt or a vanadium salt and a basic compound (e.g. sulfolane). The separation efficiency of the carbamic acid ester and the solvent can be improved by leaving a proper amount of amine or amino acid in or adding the amine, etc., to the mother liquor in the separation of the product from the reaction liquid by distillation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a carbamate ester, and more particularly to a method for producing a carbamate ester in which the mother liquor is recycled and reused after separating the product.

[Conventional technology]

Carbamate esters are important as precursors for pesticides or isocyanates. Isocyanates are widely used as raw materials for urethane products such as soft and hard foams, paints, waterproofing agents, adhesives, and elastic fibers. In particular, demand for diphenylmethane diisocyanate (MDI) is rapidly increasing, with active development of new applications as insulation materials and impact-resistant and lightweight materials for automobiles.

Conventionally, carbamate esters have been synthesized from alcohols and isocyanates (reaction formula 1).

Isocyanate is then synthesized by a reaction between an amine and phosgene (reaction formula 2).

RNCO+R'0H-RNHCOOR'' (1)RN
H2+COCl2→RNCO+2HCβ (2) Phosgene is highly toxic and uses chlorine, which requires a lot of electricity. Therefore, in order to simplify the process and save energy, methods for producing carbamate esters that do not use phosgene have been investigated. Among these methods, a method of synthesizing carbamate ester in one step from nitrobenzene, CO, and alcohol (
In reaction formula 3), the reaction pressure is as high as 80 to 200 atm, and it has not been put into practical use (Japanese Patent Publication No. 52-43822,
JP-A-51-98240, JP-A-54-145601
issue). On the other hand, recently, attempts have been made to directly synthesize carbamate esters from amines, CO, alcohols, and 02 (reaction formula 4, S).

Fukuoka et al, Chem, C.

mmu, 1984.399).

This reaction was carried out using Pd black and I- as catalysts at a reaction temperature of 160
Although the reaction time was ~170°C, reaction time was 2 hours, and CO pressure was 80 kg/-, the aniline conversion was 95% lower.
Methyl N-phenylcarbamate is directly synthesized using a (Co)12 catalyst, but this method also requires a
The yield is as low as 74% at 70 atm for 4.5 hours (US Pat. No. 532,784).

Generally, when an expensive noble metal such as palladium is used as a catalyst, circulation of the reaction mother liquor is essential if the catalyst is dissolved in the reaction solution. However, it has been impossible to apply this mother liquor circulation method to conventional urethanization reactions. The reasons for this are: (1) the reaction becomes very slow and a large amount of unreacted urethane intermediate nitro compounds remain; (2) a large amount of tar-like byproducts increase, resulting in a lower yield of urethane (carbamate ester). Also, purity may decrease.

Therefore, in the conventional method, after discharging the entire amount of the reaction solution, the catalyst, solvent, and product are separated and recovered using an appropriate method, and a new solvent and catalyst are added and the reaction is carried out again. In contrast, after the reaction, most of the catalyst used once is separated and recovered from the reaction liquid as a solid substance, and recycled or reused as is or after being purified by a method such as solvent washing. A method has been proposed in which the active catalyst can be recovered in good yield and (2) the mother liquor can also be recycled many times (Japanese Patent Laid-Open No. 52-23041), but this method has the drawback of being complicated in operation.

[One problem that the invention attempts to solve]

As mentioned above, in conventional carbamate ester synthesis, it is impossible to continuously synthesize by circulating the catalyst solution, so after discharging the entire reaction solution, the catalyst, solvent, and product are In this process, it was necessary to separate and recover each product and start the reaction again using fresh solvent and catalyst. In addition, only a small percentage of the catalyst can be recovered as a solid from the reaction solution, and most of the rest is dissolved in the reaction solution, so the catalyst components (especially precious metals) can be economically recovered from there and regenerated as a new catalyst with high activity. It was difficult to do so.

On the other hand, the above-mentioned mother liquor circulation method has been proposed, but in reality, this method involves separating solids from the reaction mother liquor and then reusing them, and the operation is complicated.

An object of the present invention is to provide a method for producing a carbamate ester, which makes it possible to continuously circulate and use the catalyst component as a solution without taking it out as a solid from the reaction mother liquor.

[Means for solving problems]

The first aspect of the present invention is an amine or an amino acid, carbon monoxide,
In a method for producing a carbamate ester by reacting a hydrous acid group compound and 02 in the presence of a catalyst, the catalyst includes a transition metal or a salt thereof belonging to the platinum group of group Ⅰ of the periodic table, a monovalent copper salt, After reacting a trivalent titanium salt or vanadium salt complex with a basic compound,
The method is characterized in that the reaction mother liquor after separating unreacted substances and carbamate ester from the reaction solution by distillation is returned to the reaction system and recycled.

The second aspect of the present invention is to separate the product carbamate ester from the solvent by leaving or adding an appropriate amount of amine or amino acid in the mother liquor during distillation separation of the product from the reaction solution. It is characterized by improving performance.

[Effect]

The process of synthesizing a carbamate ester from an amine, an amino acid, or a CO1 hydrous acid group compound is as follows, using Pd as the noble metal and CuC1 as the cocatalyst.

(a) Oxidation regeneration of Pd (0) 2Pd (0)+(Cu(J)4 ・Ot+4H(J+
2L+2L'=2 Pd(J2 ・LL'+4C
u(J!-L+2H20Lf=L'or L=L'
(5) (b) Formation of Co complex and oxidative carbonylation of amine pcicz2・L−L′+CO→pd(J2・Ll・C
O+L (6) RNH2+PdCJ2・Ll・CO+
R'OH→RNHcoOR'+2Hcl+Pd (0)
↓+L' (7) RSR@ is an alkyl group or aryl group (C)02 complex formation 4CuCj! -L+02-= (CuC1)<
・02 (8) Total reaction RNH2+CO+R” OH+V10z-RNHCOO
R” + H20 (9) Here, in order to continuously circulate and use the catalyst component as a homogeneous solution without separating it as a solid, Pd (2) must be replaced by Pd (0
), it is important not to precipitate the reaction formulas (5) to (9).

1) When reaction (9) proceeds 100% (a) When pa (0) is used as Pd 2 [Aniline concentration) < (
02 complex concentration]-2(Pd (0) ) (10)
(b) When Pd (2) salt is used as Pd 2 [aniline concentration] < (02 complex concentration) + 2 (Pd (2)
(11) 2) When reaction (9) proceeds by p% (a) When pa (Q) is used as Pd -2 (Pd
(0) ) (12) (b) When Pd (2) salt is used as Pd +2 (
Pd (2) Concentration) (13) By the above operations, o
2 Absorption, Pd (2) It was confirmed that Pd does not become Pd (0) by continuously circulating the liquid between the regeneration step and the synthesis step.

Here, after the product is sufficiently concentrated, the product is separated by distillation, but the basic solvent with the highest boiling point remains in the bottom liquid of the distillation column.

Therefore, it is essential that the solubility of the CuCl1-L complex in the above solvent is high in order to continuously circulate the catalyst liquid without precipitating the catalyst components as solids. This can be achieved by choosing eg sulfolane or dimethylsulfolane as the basic solvent and by increasing the distillation temperature to 80° C. or above. In the distillation column, since the product was separated by vacuum distillation, the Co pressure was sufficiently reduced, and Pd (2) was not reduced here.

The second aspect of the present invention is to include an appropriate amount of amine or amino acid in order to increase the separation efficiency when separating the product carbamate ester and unreacted substances by distillation. When an amine or amino acid is present in an appropriate amount,
Since the product carbamate ester contains a -NH group, it forms a hydrogen bond with the N82 group of the amine or amino acid, lowering the boiling point of the carbamate itself, and
The separation efficiency between the product and the catalyst liquid is improved.

In the composite catalyst system of the present invention, the metals in the complex catalyst that oxidize and regenerate Pd (0) include Cu (1), Ti
(3), V (3) is preferable, and the anions include Cl-1Br'''''', ■-halide ion, C
N-1SCN-1CH3COO-1S042''' is preferred, and the ligands include nitriles, triphenylphosphine oxyto which is a derivative of phosphoric acid, hexamethylphosphoramide, and phosphoric acid derived from the reaction of methanol, ethanol, etc. Mono-, di-, or triester, and mono-, di-, or triester, and phenylphosphite formed by reacting dimethyl methylphosphonate, methyl dimethylphosphinate, or phosphorous acid, which is a derivative of phosphorous acid, with methanol, ethanol, etc. Organic phosphorus compounds represented by dimethylphosphinic acid ester, triethylphosphine, triphenylphosphine, etc. are preferred. Among these, benzonitrile and hmp a are particularly preferred. On the other hand, as platinum group transition metals, Pd, Pt, Rh, and Ru are preferred.

Its anion is CZ-1Br-1■-1SCN-
1NC-1N03-1CN-1SO42- is preferred,
As a ligand, acetonitrile, propionitrile,
Nitriles such as benzonitrile and the above-mentioned organic phosphorus compounds are preferred.

The amines used as main raw materials include aromatic monoamines,
The polyamines, aliphatic monoamines, polyamines, and amino acids may be either aromatic amino acids or aliphatic amino acids. For example, these include aniline, toluidines, xylidines, benzylamines,
Phenylene diamines, tolylene diamines, aminophenols, naphthylamines, oxynaphthylamines, naphthylene diamines, aminoanthracenes, aminobiphenyls, bis(aminophenyl) alkanes, bis(aminophenyl) ethers, bis Examples include (aminophenyl)thioethers, bis(aminophenyl)sulfones, aminodiphenoxyalkanes, aminophenothiazines, or heteroaromatic compounds such as 2-aminopyrimidines, aminoisoquinolines, and aminoindoles. . Specific compounds include aniline, 0-lm- and p-toluidine, 2゜3-1
2,4-12,5-12.6-13.4-xylidine,
o-1m-1p-phenylenediamine, 2.3-12.
4-12,5-12,6-13.4-diaminotrilene, benzyl atone, xylene diamine, α-1β-naphthylamine, aminobenzoic acid, aminoanthraquinone,
0-1m-1p-aminophenol, f, 2-11
．． 3-11.4-11.5-11.6-11,7-11
゜8-12.3-12.6- or 2.7-naphthylenediamine, 1-andramine, o-1m-2p-aminobiphenyl, 1-oxy-2-naphthylamine, 1-oxy-5-naphthylamine, 1-oxy-7-naphthylamine, 1-oxy-8-naphthylamine, 2-oxy-1-naphthylamine, 3-oxy-1-naphthylamine, 4-oxy-1-naphthylamine, 5-oxy-1
-naphthylamine, 6-oxy-1-naphthylamine,
7-oxy-1-naphthylamine, 8-oxy-1-naphthylamine, 2.2'-12,3'-12,4''-1
3,3'-13,4- or 4,41-diaminobifpenyl, 2,2'-12,4'-13,3'-13,41
- or 4,4°-diaminodiphenylmethane, bis(
4-aminophenyl)ether = 4.4”-diaminosulfone, bis(4-aminophenoxy)ethane, 0-1
m-1p-chloroaniline, 4chloro-1,3-phenylenediamine, p-bromoaniline, 4-fluoro-1
, 3-phenylenediamine, 0-1m-1p-aminophenyl urethane, O-1m-1p-anisidine, 2,4
-diaminophenetole, 0-1m-1p-aminobenzaldehyde, p-aminobenzoyl chloride, etc., and isomers or mixtures of these aromatic amino compounds can also be used, and homologs can also be used.

Examples of aliphatic amines include methylamine, ethylamine,
Primary amines such as amylamine, secondary amines such as dimethylamine and diethylamine, alicyclic amines such as cyclopentylamine and cyclohexylamine, diamines such as ethylenediamine, trimethylenediamine, 4,41-diaminodicyclohexylmethane and hexamethylenediamine, Examples include triamines such as 1°2.3-) riaminopropane.

Aliphatic amino acids include monoamino monocarboxylic acids such as glycine and alanine, oxyamino acids such as serine and threonine, sulfur-containing amino acids such as cysteine and methionine,
Monoaminodicarboxylic acids such as aspartic acid and glutamic acid, diaminomonocarboxylic acids such as lysine and arginine, and aromatic amino acids such as phenylalanine,
Examples of amino acids having a heterocyclic ring such as tyrosine include histidine and tryptophan.

The hydrous acid group compounds include m-alcohols or polyhydric alcohols containing primary, secondary or tertiary hydroxyl groups, and -hydric phenols and polyhydric phenols. Specifically, methyl alcohol, ethyl alcohol,
n- and 1so-butyl alcohol, n-1iso-
and aliphatic alcohols such as t-butyl alcohol, n- or 1so-amyl alcohol, hexyl alcohol, lauryl alcohol, and cetyl alcohol, cycloaliphatic alcohols such as cyclopentanol, cyclohexyl alcohol, benzyl alcohol, and chlorbenzyl. Examples include aromatic-hydric alcohols such as alcohol and methoxybenzyl alcohol, dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol, and trihydric alcohols such as glycerol and hexanetriol.

Phenols include phenol, cresol, chlorophenol, ethylphenol, n-1iso-propylphenol, higher alkylphenols, monohydric phenols such as naphthol, dihydric phenols such as catechol and resorcinol, pyrogallol, phloroglucinol, etc. Examples include trihydric phenols.

Next, the configuration of an apparatus for carrying out the present invention will be explained with reference to the drawings. FIG. 1 is a diagram showing a typical process flow of the method for producing a carbamate ester of the present invention. This equipment consists of an 02 absorption tower 1 and a carbamate ester synthesis tower 2.
and a distillation column 3. 02 absorption tower 1
In this case, the circulating catalyst liquid 10 is supplied from the upper part of the tower, comes into contact with air 4, and forms the 02 complex (CuCj2)4.02, and then is extracted from the lower part of the tower, and is supplied to the synthesis tower 2 together with the raw material 11, where it is reacts with carbon monoxide to produce carbamate ester. The product passes through line 9, a part of which is returned to the 02 absorption column 1, and the other part is sent to the distillation column 3, where purified carbamate ester 7 is separated by distillation. Unreacted feedstock and complexing agent are recycled from the top of the column through line 6 to the feedstock feed line, while bottom liquid is circulated through circulating liquid line 1.
#0 is returned to the 02 absorption tower 1 and used in the #I ring.

〔Example〕

The invention will be explained in more detail by the following examples, without being restricted thereto.

Example 1 cucj! is placed in a Teflon-treated stainless steel autoclave with an internal volume of 100ml. 2.97g (0.03m
o It ), P d Cj! 0.0532g of 2
(0.30 mmol), aniline 0.28 g (0
,003m.

11 concentration 0.015 mo It/12), 0.94 g of ethanol (0.02 mo J), 18.5 g of benzonitrile (0.18 mo it) and 2.24 g of sulfolane (0.0186 mo J). , 02 was introduced at 70°C under normal pressure, and the 02 complex concentration was 0.3.
0 m o 12/II was prepared. Next, after replacing 02 in the gas phase with N2, the reaction pressure was increased to 10 kg with CO gas.
/c4-G, the reaction was carried out at a reaction temperature of 170° C. for 1 hour. After the reaction, the reaction product was cooled to room temperature and analyzed by gas chromatography, and 0.50 g of ethyl N-phenylcarbamate was produced. At this time, pa (
0) Black indicates no precipitation and the catalyst cycle is well formed.

Comparative Example 1 The same operation as in Example 1 was performed except that the 02 complex concentration was 50 mM (mmol), and 0.210'g of ethyl N-phenylcarbamate was produced. Although 0.167 g of aniline remained, all of the consumed aniline had been converted to ethyl N-phenylcarbamate. However, after the reaction was completed, Pd(0) black was precipitated.

Comparative example 2 Pd (0) 0.0298g (0.30mM), 0
The same operation as in Example 1 was performed except that the concentration of the two complexes was 50 mM, and 0.330 g of ethyl N-phenylcarbamate was produced. Aniline is 0.931g
All of the remaining but consumed aniline had been converted to ethyl N-phenylcarbamate. After the completion of the reaction, P
d (0) Black was precipitated.

Examples 2 to 6 Experiments were conducted under the same conditions as in Example 1 using the apparatus shown in FIG. That is, after absorbing air in the 02 absorption tower, the liquid was transferred to the synthesis tower and reacted with CO set at 1 Qatm. After 1 hour of 0 reaction time, the liquid was cooled to 70°C and returned to normal pressure, and the liquid was transferred to the 02 absorption tower. Send it to the tower and perform 02 absorption again. After repeating this operation five times, the results shown in Table 1 were obtained. It can be seen that the reaction rate of the product does not change due to liquid circulation.

Table 1 Comparative Example 3 When the reaction was carried out under the same conditions as in Example 1 except for CO pressure Q, 2 atm, 150° C., and 2 hours, no N-phenylcarbamate was produced.

This shows that in the distillation column, if the CO pressure is lower than QJatm, the reaction will proceed at all and Pd (2) will not be reduced.

Example 7 L-lysine-hydrochloride instead of aniline is almost insoluble in solvents other than water and was esterified with methyl alcohol before carbamate formation. At this time, esterification was completed in 30 minutes at about 50° C. while passing 1.98% hydrogen chloride as an acid. Thereafter, the alcohol solvent was removed by heating, and it was confirmed that L-lysine methyl ester was produced with a purity of 99.9%, and the following carbamate synthesis was performed.

0.35 of the above-mentioned silica dihydrochloride as a raw material
0 g (0,0015 mo 1), methanol instead of ethanol 0.46 g (0,01 mo j)
, and the same operation as in Example 1 was performed except that the 02 complex concentration was 50 mM. After the reaction, the reaction product was cooled to room temperature and analyzed by liquid chromatography, and 0.415 g of L-lysine carbamate was produced.

At this time, Pd (0) black was not precipitated, and the catalyst cycle was well formed.

Example 8 15g of CuCl1-PhCN crystals synthesized in advance
, contents IJ15 Qml screw tube, put 1.197g of sulfolane, 0.0515g of benzonitrile (
Sulfolane molar fraction = 0.95) is added and immersed in a constant temperature bath at 120°C to completely dissolve. Next, the temperature of the constant temperature bath was lowered to 85°C, and when dissolution equilibrium was reached, a certain amount of the supernatant liquid was taken and the copper concentration was measured by EDTA titration. As a result, the copper complex concentration was 6.
It was 61M.

Example 9 CuC at various sulfolane mole fractions as in Example 8
The solubility of 42.PhCN was measured at different temperatures. Second
As shown in the figure, the solubility of the copper complex increased as the sulfolane molar fraction increased. This means that when the product is separated by distillation, if sulfolane is left behind as a residue, CuC1-
This shows that the PhCN complex does not precipitate as a solid.

Comparative Example 4 CuC/17.325g in a 250mj2 flask
(0,175 mojri, benzonitrile 232.9
4 g (2,259 mo 1), sulfolane 30.0
3g (0.29mol) and 41.29g (0.25mol) of pJ-ethyl phenylcarbamate were mixed and melted in advance.To obtain vapor-liquid equilibrium data, the above was added to the pot of an Osma type vapor-liquid balancer. Transfer the catalyst solution.

The pressure during reflux is set in the range of several tens to 760 i+mHg, and the reflux operation is repeated several dozen times until a gas-liquid equilibrium state is reached. When the temperature difference between the liquid phase and the gas phase is within ±1° C., the liquid phase and the gas phase are each sampled, and the liquid compositions of both phases are analyzed by gas chromatography. The relative volatility of ethyl N-phenylcarbamate calculated from the results of this experiment with respect to sulfolane, which also has a high boiling point in the solvent, is shown in Figure 3 (plot for a system without aniline added).

Example 10 The same operation as in Comparative Example 4 was performed except that 46.65 g (0,499 mo1) of aniline and 185.8 g (1,802 mo1) of benzonitrile were added. ) obtained the results shown below. By adding aniline, the separation of product and sulfolane was significantly improved.

From the above facts, it can be seen that the coexistence of an amine or an amino acid during distillation in the present catalyst system is effective in improving the separation ability between the product carbamate ester and the solvent.

〔Effect of the invention〕

According to the present invention, the catalyst component can be continuously circulated and used as a homogeneous solution without being separated as a solid, and by coexisting an amine or an amino acid during distillation, the product and solvent can be separated. It has the effect of increasing ability.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the conceptual flow of a method for producing a carbamate ester, which is an embodiment of the present invention, FIG. 2 is a diagram showing the solubility of the CuC1-PhCN complex with respect to the sulfolane molar fraction, and FIG. It is a figure showing the relationship between the specific volatility of N-phenyl urethane with respect to sulfolane and bubbling point during distillation. DESCRIPTION OF SYMBOLS 1...02 absorption column, 2... synthesis column, 3... distillation column, 4... air, 5... carbon monoxide, 6... unreacted raw material, complexing agent, 7... ...Purified carbamate ester, 8
...Unreacted air, 9...Product concentration line, 10.
...Circulating fluid line, 11...Raw material. Agent Patent Attorney Takenaga Kawakita Figure 3

Claims (5)

[Claims] (1) In a method for producing a carbamate ester by reacting an amine or an amino acid, carbon monoxide, a hydrous acid group compound, and O_2 in the presence of a catalyst, as a catalyst,
After reacting a transition metal belonging to the platinum group of Group VIII of the Periodic Table or its salt with a complex of a monovalent copper salt, a trivalent titanium salt, or a vanadium salt and a basic compound, from the reaction solution A method for producing a carbamate ester, which comprises returning the reaction mother liquor after separating unreacted substances and the carbamate ester to the reaction system for recycling. (2) In claim 1, the transition metals belonging to Group VIII of the periodic table include Pd, Pt, Rh, and Ru.
A method for producing a carbamate ester, the method comprising using at least one selected from the following. (3) A method for producing a carbamate ester according to claim 1, characterized in that at least one compound selected from nitriles and organic phosphorus compounds is used as a complex-forming ligand. (4) The method for producing a carbamate ester according to claim 1, characterized in that sulfolane, dimethylsulfolane, etc. are used as the basic compound. (5) In a method for producing a carbamate ester by reacting an amine or an amino acid, carbon monoxide, a hydrous acid group compound, and O_2 in the presence of a catalyst, as a catalyst,
After reacting a transition metal belonging to the platinum group of Group VIII of the Periodic Table or its salt with a complex of monovalent copper salt, trivalent titanium or vanadium salt, and a basic compound, distillation is performed from the reaction solution. The reaction mother liquor after separating unreacted substances and urethane is returned to the reaction system and recycled, and when the produced carbamate ester is distilled and separated from the reaction liquid, an appropriate amount of amine or amino acid is removed as an unreacted substance. 1. A method for producing a carbamate ester, which comprises leaving or newly adding a carbamic acid ester.