JPH01203353A - Method for recovering anilines - Google Patents

Abstract

PURPOSE:To obtain anilines useful as a synthetic raw material for organic compounds at a high recovery ratio, by bringing a condensate of aniline with formaldehyde into contact with hydrogen in the presence of an iridium catalyst in an ether based solvent. CONSTITUTION:Aniline is condensed with formaldehyde in the presence of an acidic catalyst to provide a condensate, which is then reacted with hydrogen in the presence of an iridium catalyst in an ether based solvent (e.g., triethylene glycol dimethyl ether) at 150-400 deg.C under 10-100kg/cm<2> pressure to recover the aniline. Methylenedianiline is formed together with a high polymer condensate of the aniline with the formaldehyde as a by-product by condensing the aniline with the formaldehyde. Thereby, the anilines can be recovered from the 2,4'-isomer, 2,2'-isomer, etc., and high polymer condensates having low availability in the methylenedianiline in high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for recovering anilines from a condensate of aniline and formaldehyde.

[Technical background of the invention and the period].

Methylene dianiline, which is obtained by condensing aniline and formaldehyde in the presence of an acidic catalyst, is used in the synthesis of polyamides and polyurethanes. In particular, 4.4 DEG-methylene dianiline is useful as an intermediate in the synthesis of 4,4 DEG-methylene diphenyl isocyanate (referred to as the highest purity MDI), which is useful as a raw material for polyurethane.

However, when this condensation reaction between aniline and formaldehyde is carried out, not only methylene dianiline is produced, but also polymethylene polyphenylamine (PMPPA), which is a polymeric condensate of aniline and formaldehyde, is produced as a by-product. This polymer condensate cannot be used as a raw material for high-purity MDI, and in addition to the 4.4° form, methylene dianiline also has the 2,4° form and the 2,2° form.
There are various isomers such as 2,4° isomer or 2,2° isomer, and these isomers are less useful.

Therefore, if anilines can be effectively recovered by decomposing the above-mentioned condensates such as polymer condensates and less useful isomers, the recovered anilines can be reused in the condensation reaction of methylene dianiline. This is very industrially advantageous.

By the way, the conventional method for recovering aniline from a condensate of aniline and formaldehyde is to dissolve this condensate in a benzene solvent and bring this solution into contact with hydrogen in the liquid phase in the presence of a hydrogenation catalyst. It is known how to do this (Frank J, Weigert.

Ind, Eng, Chel, Prdod, Res,
Dev, Vo! 18. No, 3. p.

232, 1979).

However, among the condensates of aniline and formaldehyde, methylene dianiline has low solubility in solvents such as benzene, for example, its solubility in benzene is 3% by weight or less.

Therefore, even if methylene dianiline and hydrogen are contacted in the liquid phase using such a benzene solution, it is often possible to effectively obtain anilines. Even if the content of methylene dianiline in benzene is increased using a method such as dispersion in Must not be.

Also, polymethylene polyphenylamine (PMPPA)
Polymer condensates of aniline and polardehyde such as
Since the solubility in benzene solvent is extremely low, only traces of aniline can be recovered using the reaction in the liquid phase described in the above-mentioned literature, and therefore, this method is not industrially useful at all. There was no sex.

The present invention aims to solve the problems associated with the prior art as described above, and provides a method that can effectively recover anilines from a condensate of aniline and formaldehyde. It is intended to.

9. The method for recovering anilines according to the present invention is to collect a condensate of aniline and formaldehyde in the presence of an iridium catalyst.
It is characterized by contacting with hydrogen in an ether solvent.

According to the method for recovering anilines according to the present invention, an ether solvent is used as a reaction solvent, an iridium catalyst is used as a catalyst, and a condensate of aniline and formaldehyde is brought into contact with hydrogen. Anilines can be recovered at a high recovery rate.

In particular, according to the method for recovering anilines according to the present invention, not only can anilines be recovered from methylene regianiline, but also
Anilines can be recovered in high yield even from polymeric condensates of aniline and formaldehyde, which cannot be effectively decomposed using conventional methods.

9 匪αl Raw Fried Dried Fish 1 The method for recovering anilines according to the present invention will be specifically explained below.

The condensate of aniline and formaldehyde used in the present invention is obtained by condensing aniline and formaldehyde in the presence of an acidic catalyst. The condensate obtained by this reaction mainly contains a compound represented by the following formula [I].

... [I] In the above formula [I], the compound where n is 0 is methylene dianiline. Further, in polymethylene polyphenylamine, n is 1 or more, and polymethylene polyphenylamine in which n is 1 is contained in a relatively large amount.

In the present invention, a condensate containing the above-mentioned methylene dianiline and polymethylene polyphenylamine is usually used after necessary components have been separated from the condensate. Furthermore, in the present invention, it is also possible to separate polymethylene polyphenylamine from the above condensate and use the separated polymethylene polyphenylamine.

In the method for recovering anilines according to the present invention.

The condensate of aniline and formaldehyde as described above is brought into contact with hydrogen in an ether solvent.

In the present invention, as the ether solvent, a compound having an ether bond in the molecule can be used. Examples of the ether solvent that can be used in the present invention include alkyl ethers such as ethyl ether, tetrahydrofuran, and 1° Cyclic ethers such as 4-dioxane, alkoxybenzenes such as anisole, dimethoxybenzene and trimethoxybenzene, alkylene glycol dialkyl ethers such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and triethylene glycol dimethyl ether, and polyalkylene glycols such as tetraethylene glycol. can be mentioned. These ether solvents can be used alone or in combination.

Among these, cyclic ethers and alkylene glycol dialkyl esters are preferred.

Furthermore, by using an ether solvent having a boiling point higher than the boiling point of the aniline to be obtained, the separation M operation when separating the aniline from the solvent becomes very easy. In particular, alkylene glycol dialkyl ethers with a boiling point of 200°C or higher, such as triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether, which have a boiling point higher than that of aniline (184°C), dissolve polymethylene polyphenylamine in high concentrations. Because it can be It is the most preferred reaction solvent.

In the method for recovering anilines of the present invention, a condensate of aniline and formaldehyde is added to the above ether solvent in a range of usually 1 to 70% by weight, preferably 5-1-5% by weight.
It is added within the range of 0% by weight to dissolve or disperse the above condensate.

In the method for recovering anilines of the present invention, the above-mentioned ether solvent is used as a reaction solvent, and the above-mentioned condensate of aniline, formalde, and human is brought into contact with hydrogen in the presence of an iridium catalyst. Hydrogenate and decompose.

The above reaction is carried out in the presence of an iridium catalyst.The iridium catalyst used in the present invention is a catalyst containing iridium as the main hydrogenation catalyst component. Examples include iridium catalysts.

The main catalyst component in the iridium catalyst used in the present invention is iridium. However, the iridium catalyst used in the present invention may contain other hydrogenation catalyst components in addition to iridium as a hydrogenation catalyst component within a range that does not impair the properties of iridium as a catalyst. Hydrogenation catalyst components include Fe, Co, Ni, R
Mention may be made of Group I metals such as U, Rh, Pd, Os and pt.

Although metallic iridium can be used alone as the iridium catalyst, it is usually used by supporting it on a carrier.

Supports that can be used in the present invention include activated carbon, γ-A, 11203, TiO2, SiO・Al2
O3, zeolite, MgO1CaO1ZrO, 5i02
, activated clay, Bi2O3, M2O3, ZnO2, 5n0
2, CrO, YO, BaO, PbO1L
a 203, B e O, graphite 1,11 PO
4 and B2O3. These carriers can be used alone or in combination.

In the present invention, as the iridium catalyst, iridium-supported activated carbon using activated carbon as a carrier is particularly preferable.

When using a carrier, the iridium content in the catalyst is preferably 0.1 to 10% by weight.

In the present invention, the iridium catalyst is usually 0.1 to 4
It is used in an amount of 0% by weight, preferably in the range of 0.5 to 30% by weight.

In the present invention, the condensate of aniline and polardehyde is brought into contact with hydrogen at a pressure of normal pressure to 500 kg/aa.
This can be carried out by introducing hydrogen gas into the reaction vessel at a pressure within the range of 10 to 1.
It is preferable to set it within the range of 00k (1/cJ) and bring the two into contact under pressurized conditions.

The reaction temperature is usually in the range of 150 to 400°C, particularly preferably in the range of 200 to 350°C.

In addition, the reaction time can be set appropriately considering the reaction temperature, reaction pressure, etc., but is usually within the range of 0.1 to 20 hours, particularly within the range of 0.2 to 5 hours. It is preferable.

By bringing the condensate of aniline and formaldehyde into contact with hydrogen in this manner, the condensate is hydrogenated to produce anilines such as aniline, toluidine and xylidine. In particular, in the present invention, aniline can be recovered with high selectivity by setting the reaction conditions within a suitable range.

The aniline thus obtained can be separated from the ether solvent and iridium catalyst using methods such as distillation and filtration, and then used repeatedly in the reaction with formaldehyde.Toluidine or xylidine can also be used in the same manner. After separation using this method, it can be effectively used as a raw material for the synthesis of other organic compounds.

According to the method for recovering anilines according to the present invention, an ether solvent is selected as a reaction solvent, an iridium catalyst is selected as a catalyst, and both are combined, and the reaction solvent and catalyst are used. By bringing the condensate of aniline and formaldehyde into contact with hydrogen, anilines can be recovered from the condensate at a high recovery rate.

In particular, according to the method for recovering anilines according to the present invention, not only can anilines be recovered from methylene regianiline, but also
Anilines can be recovered in high yield from aniline, formaldehyde, and polymer condensates, which could not be effectively decomposed using conventional methods.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these Examples.

0.11 g of iridium powder activated carbon catalyst in which 5% by weight of iridium is supported on powdered activated carbon, 1.2 g of polymethylene polyphenylamine (PMPPA) (Number of moles of nitrogen: 12
mmol) and 4 ml of tetraethylene glycol dimethyl ether in a t-toclave (S
(manufactured by US 316), and the air inside was replaced by introducing nitrogen gas. Hydrogen gas was added to this autoclave at 52
To! Introduce at a pressure of J/-.

Then, it was heated to 275°C. Due to this heating, the pressure of hydrogen gas in the autoclave became 70 k(]/cd.

After reacting at this temperature for 3 hours, the reaction solution was cooled to room temperature, and after depressurizing, the iridium-supported powder activated carbon catalyst was added to ξ
Separately, a reaction solution was obtained.

Analysis of this reaction solution by gas chromatography revealed that 39% of aniline, 43% of toluidine, and 7% of xylidine were produced in a yield based on the number of moles of nitrogen in the PMPPA used.

The reaction conditions and results are listed in Table 1.

Example 1 was carried out in the same manner as in Example 1, except that the reaction conditions such as the amount of iridium catalyst, the type and composition of the solvent, the amount of PMPPA, and the reaction temperature, reaction pressure, and reaction time were changed as shown in Table 1. A reaction solution was obtained and analyzed in the same manner.

The results are also listed in Table 1.

Claims (1)

[Claims] (1) A method for recovering anilines, which comprises contacting a condensate of aniline and formaldehyde with hydrogen in an ether solvent in the presence of an iridium catalyst.