JPH07233125A - Production of methylamine - Google Patents

Abstract

PURPOSE:To obtain methylamine through simplified processes without the need for TMA separation. CONSTITUTION:In a method for producing methylamine by subjecting methanol, ammonia and a methylamine mixture to vapor phase catalytic reaction, the following processes are made consecutively: disproportionation process: the ammonia and methylamine are subjected to catalytic reaction in the presence of a solid acid catalyst <=15Angstrom in average fine pore diameter to decrease the amount of trimethylamine; the chief reaction process: part or the whole of the resultant methylamine-contg. mixture, the methanol and ammonia are subjected to catalytic reaction in the presence of a silylated solid acid catalyst; and the 1st distillation process: the resultant methylamine-contg. mixture, or its mixture with part of the methylamine-contg. mixture obtained from the disproportionation process is distilled under a pressure of 10-25kg/cm<2>.G to distill off virtually the whole amount of the trimethylamine in said mixture via the top of the distillation column in the form of an azeotropic mixture with the ammonia and this trimethylamin is then fed to the disproportionation process.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing methylamine by reacting methanol with ammonia.
More specifically, it relates to a method for producing methylamine that does not produce trimethylamine, which is in low demand.

[0002]

BACKGROUND OF THE INVENTION Methylamine is generally prepared by reacting methanol and ammonia in the gas phase at 300 ° C. to 400 ° C. in the presence of a solid acid catalyst. To (3), the three types of mono, di, and tri are mixed and produced depending on the difference in the number of substitutions of the methyl group.

NH ₃ + CH ₃ OH → CH ₃ NH ₂ + H ₂ O (1) CH ₃ NH ₂ + CH ₃ OH → (CH ₃ ) ₂ NH + H ₂ O (2) (CH ₃ ) ₂ NH + CH ₃ OH → (CH ₃ ) ₃ N + H ₂ O (3) CH ₃ NH ₂ : monomethylamine (hereinafter abbreviated as MMA) (CH ₃ ) ₂ NH: dimethylamine (hereinafter abbreviated as DMA) (CH ₃ ) ₃ N: trimethylamine (hereinafter TMA) Abbreviated)

The methylamine-containing mixture obtained by the reaction is
It is separated and refined in the subsequent refining process, and is widely used as a raw material for chemicals, agricultural chemicals, medicines, feeds, and the like. However, the demand for these methylamines is not uniform, and MMA and DMA occupy 95% or more of the market, and TMA accounts for only about 5%. The separation and purification of the methylamine mixture is generally carried out by distillation.
Small difference in boiling point between A and DMA and TMA, and TMA
It is not easy to efficiently separate three kinds of methylamines because they azeotrope with MMA and DMA, so it is necessary to consider these points in order to establish a rational methylamine production process. There is.

According to the conventional general method for producing methylamine, methylamine produced in the presence of a solid acid catalyst in the main reaction step, ammonia supplied in excess, unreacted methanol, and by-products. In the first distillation operation, the water-containing mixture distills off ammonia or a part of ammonia and methylamine, and the distillate is recycled to the main reaction step or the disproportionation reaction step. In the second distillation column, as described above, the boiling point difference between MMA, DMA and TMA is small, and because TMA is azeotroped with MMA and DMA, TMA is distilled by extractive distillation with water, and the bottom liquid is The process of feeding the mixture to the third distillation column to distill a mixture of MMA and DMA, feeding this distillate to the fourth distillation column, and separating MMA from the top of the column and DMA from the bottom of the column is followed.

The problem with the conventional production method is that the production ratio of each methylamine produced in the main reaction step is close to that determined thermodynamically, and can be freely controlled by the reaction conditions. However, more specifically, since the TMA production ratio is higher than the market demand, the excess TMA needs to be recycled to the reaction step, and the second distillation column Extractive distillation conducted in (not shown in the drawings after the second distillation column) requires several times the amount of extracted water with respect to MMA and DMA, which leads to an increase in the amount of waste water, and in the third distillation column, a large amount of the extracted water is required. Since the liquid containing the extracted water is distilled, a huge amount of recovery energy is required.

As mentioned above, the demand for TMA is low,
It is not a rational method to carry out a bad operation of energy intensity such as extractive distillation to separate this. Considering these, the rational methylamine production process is to suppress the production amount of TMA,
It can be said that it is a process of increasing the production ratio of and DMA, and a process of efficiently purifying and separating the reaction product. Here, the efficient purification separation means that the process is simplified, the energy consumption rate is improved, and the purification is performed at low cost. Specifically, it is a method aimed at improving the energy intensity and reducing the amount of wastewater by eliminating the TMA separation operation.

However, regarding the suppression of the amount of TMA produced, as described above, the production ratio of each methylamine is close to that which is determined thermodynamically, and for example, from ammonia and methanol to methylamine. When the production reaction is carried out, the production ratio of TMA depends on the reaction temperature and the nitrogen / carbon molar ratio of the raw material at the reactor inlet (hereinafter simply referred to as N /
It is approximately 40-
It is in the range of 60% by weight. That is, it cannot be freely controlled depending on the conditions.

On the other hand, in Japanese Patent Publication No. 62-47172, the first step of reducing the amount of TMA in the presence of a porous solid acid catalyst having an average pore diameter of 20 Å or more, and a pore having an effective pore diameter of 10 Å or less. Disclosed is a method for producing methylamine by combining with a second step of carrying out a reaction for producing methylamine in the presence of a solid acid catalyst. According to this method, the steric hindrance of the catalyst used in the second step prevents TMA, which has the largest molecular diameter in the product, from leaving the pores, and as a result, suppresses the TMA formation reaction,
And DMA can be obtained in high yield. Therefore, DMA
It is possible to improve the energy intensity of the refining process and reduce the size of the device. In addition, TMA, which is in low demand, is recycled to the first step, where it reacts with the methylamine mixture and ammonia to reduce the amount and re-apply it as a raw material to the second step. Is a method for producing each methylamine.

However, even in this method, the production ratio of TMA in the main reaction step can only be reduced to about 20 to 30% by weight, and the details of the reason will be described later, but as described in the publication. , TMA requires extractive distillation with water to separate it, and therefore problems such as deterioration of energy intensity and increase of wastewater cannot be solved. Here, the production ratio of TMA in the main reaction step means T in total methylamine increased by the reaction in the main reaction step.
It is defined as the weight ratio of MA.

Thereafter, the catalyst for the formation of methylamine was further limited, and the TMA was higher than the equilibrium value calculated thermodynamically.
Various methods have been disclosed in which MMA and DMA are obtained in a high yield by significantly reducing the production amount of. For example, a method using natural mordenite as a catalyst (Japanese Patent Publication No. 2-273).
No. 35), a method of using mordenite ion-exchanged with lanthanum ions as a catalyst (Japanese Patent Publication No. 3237/1990).
No. 8), a method of using mordenite with the content of alkali metal limited to a specific range as a catalyst (Japanese Patent Publication No. 2).
No. 16743), a method of steam-treating a zeolite catalyst (JP-B-2-2876), and a method of using an A-type zeolite substantially containing no binder as a catalyst (JP-B-3-8331). ) And the like.

If these catalysts are used, the amount of TMA produced can be reduced. However, even in these methods, the production ratio of TMA in the main reaction step can only be reduced to about 10% by weight. Further, JP-A-3-262540 discloses a method of modifying mordenite by a gas phase chemical reaction of carbon tetrachloride. According to this method, it is possible to further reduce the amount of TMA produced, but it is difficult to adjust the catalyst industrially at low cost. Furthermore, in any of these methods, it is possible to efficiently generate methyl from the reaction product. It was not even mentioned how to purify the amine.

An object of the present invention is not only to obtain MMA and DMA, which are in high demand, in high yield, but also to provide a method for producing methylamine efficiently and inexpensively. More specifically, it is an object of the present invention to provide a method for producing methylamine that simplifies the steps by omitting the TMA separation operation that causes problems such as deterioration in energy consumption rate and increase in wastewater amount.

[0014]

[Means for Solving the Problems] The inventors of the present invention reasonably reduce the amount of TMA produced in the main reaction step, omit the TMA separation operation, and improve the energy consumption rate. We have been earnestly studying to establish the amine production process. As a result, it was found that the solid acid catalyst having a specific pore size in the disproportionation step, the solid acid catalyst subjected to the silylation treatment in the main reaction step, and the distillation operation at a specific pressure can achieve the above object. It was

That is, the present invention provides a method for producing methylamine by subjecting a mixture of methanol, ammonia and methylamine to a gas phase catalytic reaction, wherein ammonia and methylamine mixture are mixed with a solid acid catalyst having an average pore diameter of 15 Å or less. In the presence of methane, a disproportionation step for reducing the amount of trimethylamine, and a solid obtained by silylating methanol or ammonia with all or part of the methylamine-containing mixture obtained from the disproportionation step. Main reaction step subjected to catalytic reaction in the presence of acid catalyst, and methylamine-containing mixture obtained from main reaction step, or methylamine-containing mixture obtained from main reaction step and methyl-containing step obtained from disproportionation step 10-25 kg / cm ² of a portion of the amine mixture
Methylated by G to distill substantially all the trimethylamine in the mixture as an azeotrope with ammonia from the top of the column, and feed it to the disproportionation step, characterized by the combination of the first distillation operation. The present invention relates to a method for producing an amine.

The present invention will be described in detail. The skeleton of the method for producing methylamine according to the present invention comprises a main reaction step for carrying out a synthesis reaction of methylamine, and ammonia and TMA in a methylamine-containing mixture obtained from the main reaction step, which are recovered from the top of a distillation operation, It is composed of a first distillation column for obtaining a liquid containing substantially no TMA from the discharged liquid, and a disproportionation step of consuming the recovered TMA by a disproportionation reaction.

The term "methylamine mixture" as used in the present invention means M
A mixture of MA, DMA and TMA is defined as a methylamine-containing mixture which is a methylamine mixture containing components other than methylamine such as ammonia and methanol.

The raw material methanol is supplied to the inlet of the main reaction step, and the ammonia is supplied to the disproportionation step and / or the inlet of the main reaction step. The synthesis reaction of methylamine is generally carried out in the presence of a solid acid catalyst, but in the present invention, the solid acid catalyst used in the main reaction step is limited to the silylated solid acid catalyst.

The silylation treatment referred to in the present invention is Japanese Patent Application No.
The method disclosed in Japanese Patent Laid-Open No. 185908 is used. That is, the solid acid catalyst treated with acid, washed and dried is once calcined at several hundreds of degrees Celsius and then conditioned to contain 3 to 40% by weight of water.
This is a treatment method in which this is treated in a liquid phase in which alkoxide of silicon such as tetramethoxy orthosilicate or trimethylchlorosilane is dissolved in a solvent and the surface is modified with silicon oxide.

The prior art has shown that the steric hindrance added to the catalyst suppresses the TMA formation reaction, but the object of the present invention is to minimize the amount of TMA formation in the main reaction step. However, in the first distillation operation, the TM
By distilling the entire amount of A as an azeotrope with ammonia from the top of the column, a complicated TMA separation operation is omitted, which is carried out in the presence of a silylated solid acid catalyst. This is achieved by suppressing the production amount to a predetermined amount or less. The reason for this is that silylation treatment controls the pore size, and steric hindrance causes TM
It is considered to be due to both the effect of suppressing the reaction of forming A and the effect of suppressing the reaction of generating TMA on the surface of the solid acid catalyst because the active sites are poisoned by the silylation treatment. To be

The silylated solid acid catalyst is charged into the main reactor, where the synthetic reaction of methylamine is carried out. At this time, the reaction temperature is preferably 250 to 400 ° C., and the N / C ratio of the starting material is preferably 1.5 to 5.0. Reaction temperature is 250 ℃
If it is less than the above range, the catalyst activity is low and the conversion of methanol is insufficient, resulting in poor efficiency. Also, if the temperature exceeds 400 ° C, TM
Due to the increase in the amount of A produced, it becomes impossible to recover substantially all of TMA from the top of the first distillation column, and by-products other than methylamine are produced, so that highly pure methylamine cannot be obtained. Further, deterioration of the catalyst with time progresses rapidly, which is not preferable.

If the N / C ratio of the inlet raw material is less than 1.5, the total amount of TMA cannot be recovered as an azeotropic mixture with ammonia in the first distillation column due to lack of ammonia. Further, if it exceeds 5.0, the circulation amount of ammonia is unnecessarily high and the energy for recovering ammonia increases, which is not efficient and is not preferable.

The reaction for producing methylamine from methanol and ammonia is an exothermic reaction. However, if the temperature of the catalyst layer rises significantly due to the heat of reaction, the above-mentioned problems occur, and therefore the heat of reaction for producing methylamine is positive. It is better to exchange heat to suppress the temperature rise. As the type of such a main reactor, a fixed bed reactor having a jacket, a fluidized bed reactor having an intercooler, and a multitubular reactor can be used, but considering the heat removal capacity and wear of the catalyst, etc. It is more effective to use a tubular reactor.

The methylamine-containing mixture obtained from the main reaction step is optionally mixed with a part of the methylamine-containing mixture obtained from the disproportionation step and supplied to the first distillation column for purification separation. Here, substantially all of TMA is distilled off as an azeotrope with ammonia from the top.

One of the conditions required here is that in order not to produce TMA, which is in low demand, as a product, the weight ratio of TMA to ammonia in the raw material supplied to the first distillation column (here, the weight of TMA to ammonia is used). The ratio is defined as TMA weight / ammonia weight in the mixture × 100, and hereinafter, abbreviated as TMA / NH ₃ ratio) is 13% by weight.
Hereafter, the amount is preferably suppressed to 10% by weight or less. However, when the production ratio of TMA in the main reaction step is high, it is necessary to circulate an excessive amount of ammonia to meet the above conditions. However, circulating excess ammonia means that the first distillation column is upsized and the energy consumption is deteriorated due to ammonia recovery, and it is practically impossible to operate industrially. Therefore, if a silylation-treated solid acid catalyst is used as the catalyst in the main reaction step, the TM in the main reaction step is
The production ratio of A can be suppressed to 7% by weight or less, and substantially the entire amount of TMA is distilled out as an azeotropic mixture with ammonia from the top of the first distillation column within a range where industrial operation is possible. It is possible.

The PEP Report 138 contains 210 psig of ammonia and TMA (about 15 Kg / cm ²
・ G) 82% by weight ammonia (TMA / NH ₃
Ratio = 22% by weight) has been shown to form an azeotropic composition. However, the distillation performed in the first distillation column is a distillation of a component system of ammonia, MMA, DMA, TMA, methanol, water, etc. In this system, substantially all the amount of TMA is azeotropically mixed with ammonia from the top of the column. It is a point experimentally confirmed by the present inventors that the TMA / NH ₃ ratio in the raw material must be 13% by weight or less, preferably 10% by weight or less for distilling.

The second is to specify the operating pressure of the first distillation column. Generally, when distilling a component having a low boiling point such as ammonia, a condition under a high pressure is advantageous in operation because it can be condensed at a high temperature, but the present inventors have found that the pressure is 25 to 30 Kg / cm. ^It has been confirmed that TMA does not substantially form an azeotropic composition with ammonia in the range of ² · G, and when the operating pressure exceeds 25 kg / cm ² · G, the TMA from the top of the first distillation column The whole amount cannot be distilled, and the present invention cannot be carried out.
If it is less than 10 kg / cm ² · G, the boiling point at the top of the column is 30 ° C.
Since the following is not efficient, it is necessary to select the conditions within the range of 10 to 25 Kg / cm ² · G in consideration of the composition of the outlet of the main reactor and the operation efficiency. Here, Kg / cm ² · G used as a pressure unit indicates a gauge pressure.

If the first distillation column is operated after satisfying the above conditions, substantially the entire amount of TMA can be distilled off from the top of the column as an azeotropic composition with ammonia. Can recover a methylamine-containing mixture that is substantially free of TMA. Therefore, in the conventional manufacturing method, the complicated extractive distillation operation required for the separation and recovery of TMA is not necessary, and the extracted water is not necessary, so that the energy consumption rate is improved and the amount of discharged water is reduced. Various effects can be obtained.

The methylamine-containing mixture obtained from the top of the first distillation column is optionally mixed with ammonia and supplied to a disproportionation reactor filled with a solid acid catalyst. here,
The disproportionation reaction proceeds according to the following equations (4) to (6), and the amount of TMA produced in the main reaction step is consumed.

[0030]

The solid acid catalyst used here has an average pore diameter of 15 Å or less, and zeolite is particularly preferable. The reason for this is that when the average pore diameter exceeds 15 Å, by-products such as ethylamine and acetonitrile are likely to be generated, and the purity of methylamine is reduced. Further, the role of the solid acid catalyst used in the disproportionation reaction step is to consume TMA, unlike the role of the catalyst used in the main reaction step. Therefore, the average pore diameter of the catalyst is sterically hindered by TMA. Those that do not undergo the treatment, preferably those that exceed 5Å are used. Contrary to the main reaction step, the disproportionation reaction is a slight endothermic reaction overall, so there is no particular limitation on the type of reactor, and similarly, a fixed bed reactor, a fluidized bed reactor, or the like can be used. It can be preferably used.

In the present invention, the disproportionation reaction is carried out at a reaction temperature of 280 to 280.
The range of 450 ° C is preferred. If the reaction temperature is lower than 280 ° C., the activity of the catalyst is insufficient, and if it exceeds 450 ° C., side reactions become remarkable and deterioration of the catalyst with time progresses rapidly, which is not preferable.

Generally, it is advantageous to operate at a temperature as low as possible in terms of by-products, catalyst deterioration and energy as described above, however, in the present invention, TM is used.
Since A is not manufactured as a product, it is necessary to consume the same amount of TMA newly generated in the main reaction step in the disproportionation reaction step in terms of mass balance. That is, the reaction conditions cannot be freely selected within the above range, and if a large amount of TMA is produced in the main reaction step, that much amount of TMA must be consumed in the disproportionation step. This means that the disproportionation reaction must be carried out under the condition of higher reaction temperature. Therefore, minimizing the production amount of TMA in the main reaction step also causes the disproportionation reaction. It will lead to favorable conditions. All or part of the methylamine-containing mixture obtained from the disproportionation reaction step is recycled to the main reaction step and used as part of the raw material for the main reaction step.

By the series of operations described above, a mixture of MMA containing no TMA, DMA, unreacted methanol and water as a by-product can be recovered from the bottoms of the first distillation column. Purification and separation of these mixtures according to a known method, a mixture of MMA and DMA is distilled from the top of the second distillation column, and methanol and water are recovered from the bottom liquid,
MMA and DMA may be separated in the third distillation column and recovered as a product.

[0035]

EXAMPLES The present invention will be specifically described below with reference to examples. In addition,% is expressed by weight unless otherwise specified. Example 1 Mordenite having an average pore diameter of 10 Å was acid-washed with 2N hydrochloric acid, and then conditioned to contain 10% of water, and 1.5 mo
In a toluene solution of 1% tetraethoxysilicate, the ratio of tetraethoxysilicate and mordenite is 0.3.
The silylation treatment was performed in an amount of 3 mol / kg-mordenite. The main reactor was charged with 2.5 kg of this catalyst, and the disproportionation reactor was charged with the catalyst obtained by only acid-washing the above-mentioned natural mordenite with 2N hydrochloric acid. The main reactor, the first distillation column, and the disproportionation reactor are connected as shown in FIG. 1, the pressure in the system is 18 kg / cm ² · G, the main reactor temperature is 300 to 305 ° C., the disproportionation reactor. Temperature 335-340 ° C
Then, methanol was supplied at a rate of 1000 g / h, the ammonia flow rate was adjusted so that the N / C ratio at the inlet of the main reactor was 2.5, the reaction was continuously performed, and a steady state was awaited. About 40 hours after starting the reaction, a steady state is reached,
When the fluid flow rate of each line at that time was measured, the results shown in Table 1 were obtained. The fluid flow rate did not change significantly even after 200 hours, and the TMA-free methylamine mixture could be stably recovered from the bottoms of the first distillation column. When the composition of the bottoms was analyzed by gas chromatography, the TMA content was 100 ppm or less. The TMA production ratio in the main reaction step is 4.3.
%Met.

Example 2 Except that the pressure in the system was changed to 13 Kg / cm ² · G,
Continuous reaction was carried out under the same conditions as in Example 1, and a steady state was awaited. A steady state was reached about 55 hours after the start of the reaction, and the fluid flow rate of each line at that time was measured. The results shown in Table 2 were obtained. Even after 160 hours, the fluid flow rate did not significantly change, and the methylamine mixture containing no TMA could be stably recovered from the bottoms of the first distillation column. When the composition of the bottoms was analyzed by gas chromatography, the TMA content was 100 ppm or less. Further, the TMA production ratio in the main reaction step is 3.9.
%Met.

Example 3 Except that the pressure in the system was changed to 23 Kg / cm ² · G,
Continuous reaction was carried out under the same conditions as in Example 1, and a steady state was awaited. A steady state was reached about 70 hours after the start of the reaction, and when the fluid flow rate of each line at that time was measured, the results shown in Table 3 were obtained. The fluid flow rate did not change significantly after 240 hours, and the TMA-free methylamine mixture could be stably recovered from the bottoms of the first distillation column. When the composition of the bottoms was analyzed by gas chromatography, the TMA content was 320 ppm. In addition, the TMA production ratio in the main reaction step was 4.6%.

Comparative Example 1 Except that the pressure in the system was changed to 30 kg / cm ² · G,
Continuous reaction was carried out under the same conditions as in Example 1, and a steady state was awaited. A steady state was reached about 65 hours after the start of the reaction, and when the fluid flow rate of each line at that time was measured, the results shown in Table 4 were obtained. The fluid flow rate did not change significantly even after 240 hours, and TMA was detected in the bottoms of the first distillation column. In addition, the TMA production ratio in the main reaction step is 4.5.
%Met.

Comparative Example 2 As a catalyst to be charged in the main reactor, mordenite having an average pore diameter of 10 Å was acid-washed with 2N hydrochloric acid, and was charged with a catalyst not to be silylated.
A continuous reaction was performed and a steady state was awaited. After starting the reaction, about 40
When the steady state was reached in time and the fluid flow rate of each line at that time was measured, the results shown in Table 5 were obtained. The fluid flow rate did not change significantly even after 240 hours, and TMA was detected in the bottoms of the first distillation column. In addition, the TMA production ratio in the main reaction step was 20.4%.

Example 4 Two natural zeolites (mordenite content of about 70%) were added.
After acid treatment and washing with N hydrochloric acid, the moisture was adjusted to contain 10% of water, and in a toluene solution of 2.4 mol% tetramethoxysilicate, the ratio of tetramethoxysilicate and zeolite was 0.5 mol / kg-zeolite. The amount of silylation treatment was performed. 2.5 kg of this catalyst in the main reactor
The catalyst was charged and the disproportionation reactor was charged with the catalyst obtained by only acid-washing the above natural zeolite with 2N hydrochloric acid. Pressure in the system is 20 Kg / cm ² · G, main reactor temperature 295 to 300 ° C, disproportionation reactor temperature 320 to 325 ° C
Then, methanol was supplied at a rate of 1000 g / h, the ammonia flow rate was adjusted so that the N / C ratio at the main reactor inlet was 2.0, and a continuous reaction was carried out in the same manner as in Example 1. Waited for steady state. A steady state was reached about 30 hours after the start of the reaction, and when the fluid flow rate of each line at that time was measured, the results shown in Table 6 were obtained. The fluid flow rate did not change significantly after 180 hours, and the TMA-free methylamine mixture could be stably recovered from the bottoms of the first distillation column. When the composition of the bottom liquid was analyzed by gas chromatography, the TMA content was 20.
It was 0 ppm or less. Also, TM in the main reaction process
The A production ratio was 3.2%.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

[0045]

[Table 5]

[0046]

[Table 6]

[0047]

As described in detail above, according to the present invention, substantially all the amount of TMA in the methylamine-containing mixture which is the raw material of the first distillation column is distilled from the top of the column as an azeotropic mixture with ammonia. Then, the methylamine mixture containing substantially no TMA can be recovered from the bottom liquid. It is not necessary to separate TMA by performing a complicated operation as in the conventional method. Therefore, the process can be simplified and the TM
Equipment cost reduction by omission of A separation step and TMA tank and reduction of the size of the second distillation column (dehydration tower), omission of extracted water and improvement of energy consumption per unit in the second distillation column (dehydration tower) There are many advantages such as reduction of variable costs and reduction of wastewater from the environmental aspect. As a result, MMA and DMA, which are in high demand, can be efficiently recovered at a high recovery ratio at a low cost, which is a great effect.

[0048]

[Brief description of drawings]

FIG. 1 Process diagram of methylamine production

[Explanation of symbols]

 A main reactor a first distillation tower c disproportionation reactor 1 methanol 2 ammonia 3 main reactor raw material 4 methylamine-containing mixture 5 first distillation tower distillate 6 first distillation tower can 7 disproportionation reaction Raw material

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Noriyuki Iwanaga 7-1, 1-1 Hikoshimasako-cho, Shimonoseki City, Yamaguchi Prefecture Mitsui Toatsu Chemicals, Inc.

Claims (7)

[Claims] 1. A method for producing methylamine by subjecting a mixture of methanol, ammonia and methylamine to a gas phase catalytic reaction, wherein the mixture of ammonia and methylamine is present in the presence of a solid acid catalyst having an average pore size of 15Å or less. Of the solid acid catalyst obtained by subjecting the disproportionation step of reducing the amount of trimethylamine to a catalytic reaction in the above step, and all or a part of the methylamine-containing mixture obtained from the disproportionation step and methanol and ammonia to silylation treatment. Of the main reaction step of subjecting to a catalytic reaction in the presence, and the methylamine-containing mixture obtained from the main reaction step, or the methylamine-containing mixture obtained from the main reaction step and the methylamine-containing mixture obtained from the disproportionation step some were distilled at 10~25Kg / cm ² · G, and substantially ammonia than the total amount the top of trimethylamine in the mixture Distill the azeotropic mixture, method for producing methylamines, wherein binding of the first distillation operation and supplies it to the disproportionation step. 2. The nitrogen / carbon molar ratio of the raw material at the inlet of the main reaction step is in the range of 1.5 to 5.0.
The method for producing methylamine according to 1. 3. The reaction temperature in the main reaction step is 250.
The method for producing methylamine according to claim 1, wherein the temperature is in the range of 400 ° C to 400 ° C. 4. The reaction temperature in the disproportionation step is 280.
The method for producing methylamine according to claim 1, wherein the inlet material has a nitrogen / carbon molar ratio in the range of from 5 to 450 ° C. 5. The method for producing methylamine according to claim 1, wherein the silylation-treated solid acid catalyst is zeolite treated with a silylating agent in a liquid phase. 6. The method for producing methylamine according to claim 1, wherein the silylation-treated solid acid catalyst is mordenite treated with a silylating agent in a liquid phase. 7. The method for producing methylamine according to claim 1, wherein a multitubular reactor is used as a reactor in the main reaction step.