JPH08169864A - Production of methylamine - Google Patents

Abstract

PURPOSE: To profitably obtain the subject compound little in the amount of trimethylamine by performing a disproportionation reaction in the presence of a specific catalyst at a specified temperature and also performing a main reaction at a specified temperature, and subsequently distilling out methylamine at a specific pressure, when CH3 OH is reacted with NH3 and a methylamine mixture in a gaseous phase. CONSTITUTION: In this method for producing methylamine by catalytically reacting (A1 ) CH3 OH with (A2 ) a methylamine in a gaseous phase, A2 is reacted with B1 in the presence of a solid acid catalyst having an average particle diameter of <=15Å to subject B1 to a disproportionation reaction for reducing the amount of (T) trimethylamine. The obtained methylaminecontaining mixture (B2 ) is wholly or partially reacted with A1 and A2 in the presence of (C) a silylated solid acid catalyst. Therein, the main reaction is performed, while the difference between the inlet temperature of the C layer and the highest temperature in the C layer is <=50 deg.C. (B) the obtained methylamine-containing mixture (B3 ) and a part of B2 are subjected to a distillation treatment at a pressure of 10-25kg/cm<2> G to distill out the whole amount of T contained in the mixture as the azeotropic mixture with A2 from the tower top, and T is subsequently fed to a disproportionation reaction to obtain the objective compound.

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]

Methylamine is generally used in the presence of a solid acid catalyst in the gas phase of methanol and ammonia at 300 ° C to 300 ° C.
By reacting at 400 ° C, the following (1) to (3)
It is produced according to the reaction formula (1), and three kinds of mono, di, and tri are mixed and produced due to the difference in the number of substitution of methyl groups.

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 of the water-containing mixture, ammonia or a part of ammonia and methylamine is distilled, and the distillate is recycled to the main reaction step or the disproportionation step. In the second distillation column, the boiling point difference between MMA, DMA and TMA is small as described above.
Since TMA is azeotropically distilled with MMA and DMA, TMA is distilled by extractive distillation with water, the bottom liquid is supplied to a third distillation column to distill a mixture of MMA and DMA, and this distillate is removed. (4) Supply to the distillation column, and from the top of the tower, add MMA to the bottom of the tower.
Follow the process of separating the MA.

[0006]

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,
It is not possible to control it freely depending on the reaction conditions, more specifically, TMA rather than market demand.
The TMA produced in excess is required to be circulated again in the reaction step because the production ratio of MMA and DMA is high, and the extractive distillation performed in the second distillation column (not shown in the drawings after the second distillation column) is performed by MMA and DMA. Since it requires several times the amount of extracted water, it causes an increase in the amount of drainage, and since the liquid containing the large amount of extracted water is distilled in the third distillation column, enormous recovery energy is required. The point is to do.

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, steric hindrance of the catalyst used in the second step prevents the TMA having the largest molecular diameter in the product from leaving the pores, and as a result, suppresses the TMA forming reaction. , MMA and DMA can be obtained in high yield. Therefore, it is possible to improve the energy consumption rate in the DMA refining process and downsize 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.

After that, the catalyst for forming methylamine was further limited, and the TMA was more 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.

By using these catalysts, 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, the amount of TMA produced can be further reduced, but it is difficult to industrially prepare a catalyst at low cost, and in any of these methods, the reaction product can be efficiently produced from the reaction product. It did not mention the method for purifying methylamine.

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 efficiently and inexpensively producing methylamine. 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.

[0015]

[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, a solid acid catalyst having a specific pore size was used in the disproportionation step, and a silylated solid acid catalyst was used in the main reaction step, and the difference between the inlet temperature of the catalyst layer and the maximum temperature in the catalyst layer was 50%. It was found that the above object can be achieved by carrying out the reaction while suppressing the temperature to below 0 ° C and further performing the distillation operation at a specific pressure.

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 the mixture of ammonia and methylamine is 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. From the main reaction step in which the reaction is carried out in the presence of an acid catalyst and the reaction is carried out while suppressing the difference between the inlet temperature of the catalyst layer and the maximum temperature in the catalyst layer to 50 ° C. or less, 10 parts of the resulting methylamine-containing mixture or a part of the methylamine-containing mixture obtained from the main reaction step and the methylamine-containing mixture obtained from the disproportionation step is used. Was distilled at 25 kg / cm 2 ^G, substantially distill as an azeotrope with ammonia than the total amount top, coupling operation of the first distillation column to supply it to the disproportionation step of trimethylamine in the mixture And a method for producing methylamine.

The present invention will be described in detail below. The skeleton of the method for producing methylamine according to the present invention comprises a main reaction step for carrying out a synthetic 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. The bottom is composed of a first distillation column for obtaining a liquid containing substantially no TMA, and a disproportionation step of consuming the recovered TMA by a disproportionation reaction.

The term "methylamine mixture" as used herein means a mixture of MMA, DMA and TMA, and the term "methylamine-containing mixture" means a methylamine mixture containing components other than methylamine such as ammonia and methanol. It is defined as The raw material methanol is supplied to the inlet of the main reaction step, and the ammonia is supplied to the inlet of the disproportionation step and / or 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 method of treating this in a liquid phase in which alkoxide of silicon such as tetramethoxyorthosilicate or trimethylchlorosilane is dissolved in a solvent and modifying the surface 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 means that the catalyst layer in the catalyst layer can be removed under a silylated solid acid catalyst. This is achieved by carrying out the reaction while suppressing the difference between the inlet temperature and the maximum temperature in the catalyst layer to 50 ° C. or lower, and suppressing the amount of TMA produced to a predetermined amount or lower. The reason for this is that the silylation treatment controls the inlet diameter of the pores and the steric hindrance suppresses the TMA formation reaction, and the surface of the solid acid catalyst is poisoned by the silylation active sites. The effect of suppressing the TMA formation reaction on the catalyst surface is also suppressed, and by suppressing the difference between the inlet temperature of the catalyst layer and the maximum temperature in the catalyst layer to 50 ° C. or less, these effects can be sufficiently achieved. It is thought that it is due to being demonstrated.

Further, the importance of carrying out the reaction while suppressing the difference between the inlet temperature of the catalyst layer and the maximum temperature in the main reaction step to 50 ° C. or less will be described in detail. The methylamine formation reaction is an exothermic reaction as shown in the following formulas (4) to (6), and the temperature in the reactor rises due to the heat of reaction. When the present inventors calculated the adiabatic temperature rise in the reactor from the reaction heat of this methylamine formation, the amount of heat was about 80 to 120 ° C., although it varied depending on the reaction conditions.

NH ₃ + CH ₃ OH → CH ₃ NH ₂ + H ₂ O + 4.0 kcal / mol (4) CH ₃ NH ₂ + CH ₃ OH → (CH ₃ ) ₂ NH + H ₂ O + 8.1 kcal / mol (5) (CH ₃ ) ₂ NH + CH ₃ OH → (CH ₃ ) ₃ N + H ₂ O + 10.3 kcal / mol (6)

From the equilibrium value calculated thermodynamically,
The rise in temperature tends to decrease the amount of TMA produced,
According to the experiments conducted by the present inventors, as described above, TM
When a catalyst in which the production ratio of A is limited to a ratio lower than the thermodynamic equilibrium value is used, the production amount of TMA with a rise in temperature tends to increase sharply, contrary to equilibrium. is there. Further, it has been clarified that the production ratio of methylamine and the amount of by-products are dominated by the highest temperature reached in the catalyst layer rather than the inlet temperature of the catalyst layer in the main reaction step.

In a laboratory-scale reactor, the amount of heat released is extremely large, so that the temperature rise due to the heat of reaction does not pose a particular problem, but in the case of industrial production, this temperature rise due to the heat of reaction is sufficient. If not taken into consideration, the production ratio of each methylamine will be significantly different from that expected from the inlet temperature of the catalyst layer in the main reaction step. Further, if the temperature becomes higher than necessary, by-products such as formaldehyde, ethylamine, and acetonitrile are generated, and these are mixed in the product, so that it is not possible to obtain highly pure methylamine. Therefore, TM in the main reaction process
In order to suppress the production ratio of A and obtain highly pure methylamine, it is necessary to actively remove the reaction heat of the methylamine production reaction. In order to achieve the present invention, the catalyst of the main reaction step is used. The difference between the bed inlet temperature and the maximum temperature in the catalyst layer is 5
0 ° C or lower, preferably 30 ° C or lower, more preferably 2
The reaction must be carried out while suppressing the temperature to 0 ° C or lower.

The temperature referred to here is a macroscopic temperature that can be measured with a thermocouple thermometer, a resistance thermometer, or the like, and is distinguished from the so-called microscopic temperature found on the surface or pores of the catalyst. In fact, the inventors have not been able to clarify what temperature the surface of the catalyst and the inside of the pores have reached microscopically during the progress of the reaction. If the difference between the catalyst layer inlet temperature of the raw material and the maximum temperature in the catalyst layer is suppressed to 50 ° C. or less, the amount of TMA produced is suppressed to the extent that the entire amount can be distilled as an azeotropic composition with ammonia in the first distillation operation. Also, the amount of by-products is 100 p in terms of methylamine.
It has been confirmed that it can be suppressed to pm or less and the present invention can be achieved. Examples of the type of the main reactor satisfying such conditions include a fixed bed reactor having a jacket, a fluidized bed reactor having an intercooler, a multitubular reactor, and the like. It is necessary to design the reactor with due consideration of heat velocity, heat transfer area, etc.

The silylation-treated solid acid catalyst is charged into the main reactor, where the synthetic reaction of methylamine is carried out. At this time, the inlet temperature of the catalyst layer is preferably 250 ° C to 400 ° C, and the N / C ratio of the inlet raw material is preferably 1.5 to 5.0. If the inlet temperature is lower than 250 ° C, the catalyst activity is low and the conversion of methanol is insufficient, resulting in poor efficiency. Further, when the temperature exceeds 400 ° C., the production amount of TMA increases, so that it becomes impossible to recover substantially the entire amount of TMA from the top of the first distillation column, and by-products other than methylamine are produced. It is not preferable because high-purity methylamine cannot be obtained and the deterioration of the catalyst with time progresses rapidly.

The N / C ratio of the raw material at the main reactor inlet is 1.5
Below 1, TMA in the first distillation column due to lack of ammonia
Cannot be recovered as an azeotropic mixture with ammonia. On the other hand, when it exceeds 5.0, the circulation amount of ammonia is unnecessarily high and the energy for recovering ammonia increases, which is not preferable because it is not efficient.

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. The TMA is distilled off at the top as an azeotrope with substantially all of the ammonia.

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 of the raw material supplied to the first distillation column to ammonia (here, the weight ratio of TMA to ammonia). Is defined as TMA weight / ammonia weight × 100 in the mixture, and hereinafter, abbreviated as TMA / NH ₃ ratio) is 13% by weight.
Hereafter, the amount is preferably suppressed to 10% by weight or less.

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 this condition. 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 silylated solid acid catalyst is used as the catalyst in the main reaction step and the difference between the inlet temperature of the catalyst layer and the maximum temperature in the catalyst layer is controlled, the production ratio of TMA in the main reaction step is increased. It can be suppressed to 7% by weight or less, and is practically TM from the top of the first distillation column within a range in which industrial operation is possible.
The entire amount of A can be distilled off as an azeotropic mixture with ammonia.

PEP Report 138 contains 210 psig of ammonia and TMA (about 15 Kg / cm ²
In G) it is shown that 82% by weight of ammonia (TMA / NH ₃ ratio = 22% by weight) forms an azeotropic composition. However, the distillation performed in the first distillation column is a multi-component system distillation of ammonia, MMA, DMA, TMA, methanol, water, etc. In this system, substantially all of TMA is converted into an azeotropic mixture with ammonia as a column. In order to distill from the top, the TMA / NH ₃ ratio in the raw material must be 13% by weight or less, preferably 10% by weight or less.
This is the point that the present inventors experimentally confirmed.

The second condition is to select the operating pressure of the first distillation column. Generally, when distilling a low boiling point component such as ammonia, the condition under high pressure is
Although it is advantageous in operation because it can be condensed at a high temperature, the present inventors have confirmed that TMA substantially does not form an azeotropic composition with ammonia in the range of 25 to 30 Kg / cm ² G. If the operating pressure exceeds 25 Kg / cm ² G, the total amount of TMA cannot be distilled off from the top of the first distillation column, 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 will be 30 ° C. or less, which is not efficient. Therefore, it is necessary to select the condition in 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. There is. Kg used here for pressure unit
/ Cm ² G indicates a gauge pressure.

When the first distillation operation is carried out after satisfying the above conditions, substantially the whole amount of TMA can be distilled off from the top of the column as an azeotropic mixture with ammonia, and the bottom liquid is substantially removed. It is possible to recover a TMA-free methylamine-containing mixture.

Therefore, in the conventional method for producing methylamine, the extractive distillation operation required for the separation and recovery of TMA is not necessary, and the extracted water is also unnecessary, so that the energy consumption rate is improved. It is possible to obtain various effects such as reduction of wastewater and drainage. The methylamine-containing mixture obtained from the top of the first distillation column is mixed with ammonia as necessary and supplied to a disproportionation reactor filled with a solid acid catalyst. Here, the disproportionation reaction proceeds according to the following equations (7) to (9), and the amount of TMA produced in the main reaction step is consumed in a proportionate amount.

[0035]

The solid acid catalyst used here has an average pore size of less than 15Å, 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. Also,
The role of the solid acid catalyst used in the disproportionation step is to consume TMA, unlike the role of the catalyst used in the main reaction step, so that the average pore size of the catalyst does not cause steric hindrance to TMA. , Preferably 5 Å or more.

Since the disproportionation reaction is a slight endothermic reaction as opposed to the main reaction step, there is no particular limitation on the type of reactor, and similarly, a fixed bed reactor or a fluidized bed reaction can be used. A container or the like can be suitably used.

In the disproportionation reaction of the present invention, the inlet temperature of the catalyst layer is preferably in the range of 280 to 450 ° C. Inlet temperature is 2
Below 80 ° C, the activity of the catalyst is insufficient, and
When the temperature exceeds 0 ° C, side reactions become significant 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 step in terms of mass balance. That is, the reaction conditions cannot be freely selected within the above range, and a large amount of T
The formation of MA requires the consumption of that much TMA in the disproportionation process. This means that the disproportionation reaction must be carried out under higher temperature conditions. Therefore, minimizing the amount of TMA produced in the main reaction step also favors the disproportionation reaction. It will lead to advancement under certain conditions. All or part of the methylamine-containing mixture obtained from the disproportionation step is recycled to the main reaction step and used as a part of the raw material for the main reaction step.

By the series of operations as described above, a mixture of MMA not containing TMA, DMA, unreacted methanol, and water as a by-product can be recovered as a bottom product 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.

[0041]

The present invention will be described below in detail with reference to examples. Example 1 Both the main reactor (a) and the disproportionation reactor (c) are 1B reaction tubes having a 6B jacket, a reactor having a total length of 5 m is used, and a catalyst is provided inside the tubes and a jacket side is provided. A system was used in which an organic heating medium was filled and heating was performed from outside with an electric heater. The first distillation column (a) is a packed column having a length of 2 m, a total length of 5 m, and a filling height of 3 m. As shown in FIG. 1, a main reactor (a), a disproportionation reactor (c), and a first distillation column (a). Connected. All the reactors and piping used were made of stainless steel. Mordenite having an average pore diameter of 10 Å was washed with 2N hydrochloric acid by acid treatment and then conditioned to contain 10 wt% of water.
The silylation treatment was performed in a toluene solution of 1.5 mol% tetraethoxysilicate at an amount such that the ratio of tetraethoxysilicate and mordenite was 0.33 mol / kg-mordenite. This catalyst in the main reactor (a) 2.
The disproportionation reactor (c) was charged with 5 kg, and 1.5 kg of the catalyst obtained by only acid-washing the above natural mordenite with 2N hydrochloric acid was charged. Pressure in the system is 18 Kg / c
m ² G, internal heat medium internal temperature of main reactor (a) 300 to 3
05 ℃, the internal temperature of the organic heat medium of the disproportionation reactor 335-34
At 0 ° C., methanol 1 was supplied at a rate of 1000 g / h, and the reaction was continuously performed while adjusting the ammonia 2 flow rate so that the N / C ratio at the main reactor inlet was 2.5.
Waited for steady state. A steady state was reached about 40 hours after the start of the reaction, and the temperature distribution of the catalyst layer at that time was measured. The inlet temperature was 274 ° C, the maximum temperature was 311 ° C, and the difference was 37 ° C. When the fluid flow rate of each line was measured, the results shown in Table 1 were obtained. Even after 200 hours, the temperature distribution and the fluid flow rate did not significantly change, and the methylamine mixture containing no TMA could be stably recovered from the bottom liquid 6 of the first distillation column. When the composition of the bottoms was analyzed by gas chromatography, the TMA content was 100 ppm or less.

Example 2 A continuous reaction was carried out under the same conditions as in Example 1 except that the pressure in the system was changed to 13 Kg / cm ² G, and a steady state was awaited. About 55 hours after the start of the reaction, a steady state was reached, at which time the catalyst layer inlet temperature was 278 ° C. and the maximum temperature was 309.
In ° C, the difference was 31 ° C. When the fluid flow rate of each line was measured, the results shown in Table 2 were obtained. 160
There was no great change in the fluid flow rate even after the lapse of time, and the methylamine mixture containing no TMA could be stably recovered from the bottom liquid 6 of the first distillation column. When the composition of the bottom liquid was analyzed by gas chromatography, the TMA content was 100 ppm or less.

Example 3 A continuous reaction was carried out under the same conditions as in Example 1 except that the pressure in the system was changed to 23 Kg / cm ² G, and a steady state was awaited. About 70 hours after the start of the reaction, a steady state was reached, at which time the catalyst layer inlet temperature was 286 ° C and the maximum temperature was 315.
The difference was 29 ° C. When the fluid flow rate of each line was measured, the results shown in Table 3 were obtained. 240
There was no great change in the fluid flow rate even after the lapse of time, and the methylamine mixture containing no TMA could be stably recovered from the bottom liquid 6 of the first distillation column. When the composition of the bottom liquid was analyzed by gas chromatography, the TMA content was 100 ppm or less.

[0044]

[Table 1] Main reactor TMA production ratio = 4.3% First distillation column raw material TMA / NH ₃ × 100 = 8.0%

[0045]

[Table 2] Main reactor TMA production ratio = 3.9% First distillation column raw material TMA / NH ₃ × 100 = 11.4%

[0046]

[Table 3] Main reactor TMA production ratio = 4.6% First distillation column raw material TMA / NH ₃ × 100 = 8.2%

Comparative Example 1 Example 1 except that the pressure in the system was 30 Kg / cm ² G
A continuous reaction was carried out under the same conditions as above, and a steady state was awaited.
About 65 hours after the start of the reaction, a steady state was reached, at which time the catalyst layer inlet temperature was 278 ° C and the maximum temperature was 312 ° C.
The difference was 34 ° C. When the fluid flow rate of each line was measured, the results shown in Table 4 were obtained. Even after 240 hours had passed, there was no large change in the fluid flow rate, and TMA could not be eliminated from the first distillation column bottoms 6.

Comparative Example 2 As a catalyst to be charged in the main reactor, mordenite having an average pore size of 10 Å was acid-washed with 2N hydrochloric acid, and a catalyst not subjected to silylation was charged, and the same conditions as in Example 1 were used. The continuous reaction was carried out at and the steady state was awaited. About 40 hours after the start of the reaction, a steady state was reached, at which time the catalyst layer inlet temperature was 272 ° C, the maximum temperature was 308 ° C, and the difference was 36 ° C.
Met. When the fluid flow rate of each line was measured, the results shown in Table 5 were obtained. Even after 240 hours, the fluid flow rate did not significantly change, and TMA in methylamine recovered from the first distillation column bottoms liquid 6 could not be eliminated.

Comparative Example 3 As a main reactor, a 4B reaction tube having a 10B jacket and a total length of 0. The conditions were the same as in Example 1 except that a 6 m stainless steel reactor was used, and a continuous reaction was carried out to wait for a steady state. A steady state was reached about 50 hours after the start of the reaction. At that time, the catalyst layer inlet temperature was 273 ° C, the maximum temperature was 331 ° C, and the difference was 58 ° C. When the fluid flow rate of each line was measured, the results shown in Table 6 were obtained. Even after 180 hours, there is no big change in the fluid flow rate,
T in methylamine recovered from the first distillation column bottoms liquid 6
I couldn't get rid of MA.

[0050]

[Table 4] Main reactor TMA production ratio = 4.5% First distillation column raw material TMA / NH ₃ × 100 = 5.0%

[0051]

[Table 5] Main reactor TMA production ratio = 20.4% First distillation column raw material TMA / NH ₃ × 100 = 17.4%

[0052]

[Table 6] Main reactor TMA production ratio = 22.3% First distillation column raw material TMA / NH ₃ × 100 = 18.2%

[0053]

As described in detail above, according to the present invention, substantially all the amount of TMA in the methylamine-containing mixture that is the raw material of the first distillation column is azeotroped from the top of the first distillation column. Since the methylamine mixture containing substantially no TMA is recovered from the bottom liquid, it is not necessary to carry out a complicated operation as in the conventional method to separate TMA.
Therefore, it is possible to simplify the process, reduce the equipment cost by omitting the TMA separation step and the TMA tank, and reducing the size of the second distillation column (dehydration column), omitting the extracted water and the accompanying second distillation column (dehydration column). There are many advantages such as reduction of variable costs by improvement of energy consumption per unit in (1) and reduction of wastewater amount in terms of environment. As a result, MM with high demand
Since the recovery ratio of A and DMA is high and can be efficiently recovered at low cost, its effect is great.

[0054]

[Brief description of drawings]

FIG. 1 is a process diagram of the production of methylamine according to the present invention.

[Explanation of symbols]

 A Main reactor a 1st distillation tower c Disproportionation reactor 1 Methanol 2 Ammonia 3 Main reaction raw material 4 Methylamine mixture 5 1st distillation tower distillate 6 1st distillation tower bottoms 7 Disproportionation reaction raw material

Claims (6)

[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. A main reaction step in which the reaction is carried out in the presence of the catalyst and the reaction is carried out while suppressing the difference between the inlet temperature of the catalyst layer and the maximum temperature in the catalyst layer to 50 ° C. or less; 10-25 Kg / c of methylamine mixture or a part of the methylamine-containing mixture obtained from the main reaction step and the methylamine-containing mixture obtained from the disproportionation step Characterized by the combined operation of the first distillation column, which was distilled at m ² G to distill substantially all of the trimethylamine in the mixture as an azeotrope with ammonia from the top of the column and feed it to the disproportionation step. And a method for producing methylamine. 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 described. 3. The method for producing methylamine according to claim 1, wherein the inlet temperature of the catalyst layer in the main reaction step is in the range of 250 to 400 ° C. 4. The method for producing methylamine according to claim 1, wherein the inlet temperature of the catalyst layer in the disproportionation step is 280 to 450 ° C., and the nitrogen / carbon molar ratio of the inlet raw material is 5 or more. 5. The method for producing methylamine according to claim 1, wherein the silylation-treated solid acid catalyst is a zeolite treated with a silylating agent in a liquid phase. 6. The silylation-treated solid acid catalyst is mordenite treated with a silylating agent in a liquid phase.
The method for producing methylamine described.