JPS643862B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing cyclohexylamine, which is characterized by carrying out a reductive amination reaction of phenol together with hydrogen and ammonia in a gaseous state under normal pressure through a fixed bed of nickel-based shaped catalyst, and fractionating the resulting reaction liquid. It is something. Conventionally, cyclohexylamine is produced by hydrogenation of aniline, amination of cyclohexanol, etc., and it is produced industrially by these methods. Recently, however, a method has been proposed in which cyclohexylamine is synthesized in one step by reacting phenol with hydrogen and ammonia through a so-called reductive amination reaction. For example, Brit1031169 (Japanese Patent Publication 1977)
-15103) is a pressurized liquid phase method in the presence of a rhodium catalyst, and Japanese Patent Publication No. 49-34677 is a pressurized liquid phase method in the presence of a ruthenium catalyst. Also, Japan Publication No. 55-51042 and Chemistry by Hamada et al.
Letters 1980(3) 239-240 both use palladium catalysts. That is, the reality is that it is common knowledge to use noble metal catalysts such as Rh, Ru, and Pd as a technology for reductive amination of phenol. The inventors of the present invention have examined these conventional techniques one by one and conducted detailed research. As a result, it has been found that gas phase normal pressure reductive amination of phenol is possible by using an inexpensive nickel-based shaped catalyst without using a precious metal catalyst. We discovered something and arrived at the present invention. This is a completely new discovery that could not have been conceived from the concept of conventional technology, which was thought to be impossible at low temperature and normal pressure without the use of a noble metal catalyst. The characteristics of the present invention are firstly that an inexpensive molded nickel catalyst is used as a catalyst, and secondly, the reaction is a normal pressure gas phase reaction, which eliminates the need for an expensive autoclave and may even require fractional distillation in some cases. This method can produce cyclohexylamine in a completely continuous manner, and the equipment cost is lower than that of conventional techniques, making it an industrially extremely valuable method for producing cyclohexylamine. In addition to cyclohexylamine, the reaction solution obtained by the method of the present invention contains dicyclohexylamine as a main component and some high-boiling substances such as cyclohexylaniline. This can be fractionated to collect the product cyclohexylamine. By-products mainly composed of dicyclohexylamine obtained as a high boiling point are reacted by adding an appropriate amount of phenol together with excess ammonia and hydrogen over the same nickel-based molded catalyst as described below. is converted to cyclohexylamine. Therefore, by combining this process with the above-mentioned process, only cyclohexylamine can be produced. However, it is not always necessary to carry out both of these processes separately, and by selecting the reaction conditions, it is possible to operate only one reaction column packed with a nickel-based shaped catalyst by constantly charging an appropriate amount of high-boiling substances including dicyclohexylamine into the reaction system. Cyclohexylamine can be produced via fractional distillation. In this case, the amount of phenol charged may be reduced by the amount of high-boiling substances including dicyclohexylamine added. In the nickel-based shaped catalyst used in the present invention, diatomaceous earth, pumice, alumina, silica, etc. are used as a carrier, and small amounts of other metals such as copper may be added to the nickel as a co-catalyst depending on the case. However, from the viewpoint of ease of production, handling, and cost, a nickel shaped catalyst on a diatomaceous earth carrier is most suitable.
Therefore, the method of the present invention will be described in detail using this catalyst. Generally, the nickel of such catalysts is stabilized and, when handled, is used in the form of diatomaceous earth supported stabilized nickel shaped catalysts. This catalyst is packed into a reaction tube that can be heated and cooled, and treated at 200°C for several hours while passing hydrogen through it to activate it and create a reduced nickel shaped catalyst. A fixed bed packed with phenol:hydrogen:
A mixed gas with a molar ratio of ammonia of 1:(5-30):(1-10), preferably 1:(8-20):(1-6), phenol LSV of 0.05-0.2, preferably 0.07-0.15,
The reaction is carried out at a reaction temperature of 100-250°C, preferably 130-180°C, under normal pressure. The composition of the resulting reaction solution is 30-70% cyclohexylamine, 55-25% dicyclohexylamine, and 15-5% cyclohexanol, and almost no unreacted phenol is detected by selecting the reaction conditions. High purity cyclohexylamine can be obtained by fractional distillation of this reaction solution. The fractional residue mainly contains dicyclohexylamine and contains small amounts of cyclohexylaniline and other by-products. This can be used as it is or by distillation, mixed with phenol and mixed with hydrogen and ammonia in a molar ratio (fractional residue + phenol): hydrogen: ammonia = 1: (5
-15): (2-6), gaseous state under normal pressure, reaction temperature
A reaction solution containing 60-80% cyclohexylamine is obtained by passing the reaction solution through a fixed bed of reduced nickel molded catalyst supported on diatomaceous earth carrier of the present invention at 130-180°C. This can be fractionated to obtain highly pure cyclohexylamine. Therefore, by combining both reactions, it is possible to finally obtain only cyclohexylamine from phenol, and the yield reaches 97 to 98% of theory. Next, embodiments of the present invention will be described with reference to Examples, but it is noted that the gist of the present invention is not limited by these Examples. Example 1 A 2-inch SUS304 tube was filled with 350 g (volume: 330 c.c.) of a diatomaceous earth carrier-stabilized nickel molded catalyst. The outside of this is an oil bath so that the entire catalyst layer can be heated or cooled. This fixed catalyst layer is activated by passing hydrogen through it and heating it to 200°C for 3 hours. At this time, distillation of water was completed in about 1 hour, and activation was almost completed. Check the temperature here
Lower to 160℃ Phenol:Hydrogen:Ammonia=
Molar ratio of 1:8:2, phenol LSV 0.1,
The reaction was carried out at a reaction temperature of 165°C under normal pressure for 10 hours.
The result of fractional distillation of the resulting reaction solution and gas chromatography analysis revealed that cyclohexylamine was 56.5%, dicyclohexylamine was 37.3%, cyclohexanol was 4.2%,
The content was 2% of high boiling point substances. Also, the conversion rate of phenol
100%, and the amount of cyclohexylaniline produced was very small. The purity of cyclohexylamine obtained by further fractional distillation of the above reaction solution was 99.9%. Examples 2 to 6 After carrying out reactions under various conditions using the catalytic reaction tube of Example 1, the composition of the reaction solution was analyzed by gas chromatography, and the results are shown in the table below.

[Table] Example 7 The residual liquid after cyclohexylamine was distilled off from the reaction solution of Example 1 contained dicyclohexylamine as a main component and contained cyclohexanol, cyclohexylaniline, and high-boiling components. As a recipe for recharging this residual liquid, a mixed gas with a molar ratio of (above residual liquid + 1/2 amount of phenol): hydrogen: ammonia = 1:10:6 was added to the catalytic reaction tube of Example 1 at an LSV of 0.1 and a reaction temperature. 165-175
The composition of the reaction solution obtained by reacting at ℃ for 10 hours under normal pressure was 76.2% cyclohexylamine, 18.3% dicyclohexylamine, and 3.5% high boiling point components including cyclohexylaniline, which could be easily fractionated. We were able to distill 99.9% of cyclohexylamine.

Claims (1)

[Claims] 1. A method for producing cyclohexylamine, which is characterized by carrying out a reductive amination reaction of phenol together with hydrogen and ammonia in a gaseous state under normal pressure through a fixed bed of nickel-based shaped catalyst, and fractionating the resulting reaction solution. Manufacturing method. 2. Reductive amination reaction of phenol with hydrogen and ammonia in gaseous state is carried out under normal pressure through a fixed bed of nickel-based shaped catalyst, and the resulting reaction liquid is fractionated, and the main component is dicyclohexylamine, which is produced as a by-product. It is characterized by distilling a fraction, mixing it with phenol, performing a reductive amination reaction together with hydrogen and ammonia in a gaseous state under normal pressure through a fixed bed of nickel-based shaped catalyst, and fractionating the resulting reaction liquid. A method for producing cyclohexylamine.