JP2002363140A - Method for purifying trimethylamine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To economically obtain high-purity trimethylamine with reduced consumption energy cost by a simple distillation operation. SOLUTION: The objective method for purifying trimethylamine is characterized in comprising the 1st step of vapor phase catalytic reaction between a methylamine mixture and/or methanol and ammonia in the presence of a zeolite catalyst to obtain a methylamine reaction mixture from which unreacted ammonia is separated in an ammonia separation column followed by subjecting the resultant methylamine reaction mixture to water extractive distillation in the 1st column (trimethylamine separation column) to obtain a crude trimethylamine, and the 2nd step of subjecting only a necessary amount of the crude trimethylamine to water extractive distillation in the 2nd column (trimethylamine purification column) to obtain the objective high-purity trimethylamine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing methylamine by a gas-phase catalytic reaction between methanol and ammonia. More specifically, the present invention relates to an improvement in economic efficiency by reducing energy consumption cost in a methylamine production process, and a method for purifying high-purity trimethylamine for electronic materials and pharmaceuticals.

[0002]

2. Description of the Related Art Methylamine is generally produced by reacting methanol and ammonia in the gas phase at a high temperature (around 400 ° C.) in the presence of a solid acid catalyst having a dehydrating and aminating action such as alumina and silica alumina. Is done. Usually, this reaction produces a mixture of dimethylamine, monomethylamine, and trimethylamine. Also,
Since demand for these methylamines is extremely small except for dimethylamine, dimethylamine is separated from the reaction product and then recycled and reused in the reaction system.

In order to separate a methylamine mixture, distillation is commonly used. However, trimethylamine is
Since it forms a complex azeotropic system with ammonia, monomethylamine, and dimethylamine, its separation requires a very complicated distillation operation and a large-sized apparatus, and the energy consumption cost of the methylamine production process is very high. It will be big. The collection process is described in, for example, “Completed Completed Manufacturing Process Diagram” (April 2, 1978
5th, issued by Chemical Industry Co., Ltd.).

A method for reducing energy consumption cost in a trimethylamine separation step of a methylamine production process is as follows.
JP-A-8-169864, JP-A-8-31100
There is a method disclosed in Japanese Patent Laid-Open Publication No. 0-205, in which trimethylamine and ammonia are separated by azeotropic distillation, and the entire amount is recycled to a reaction system. Although this method does not require a new trimethylamine separation column, it has a disadvantage that it cannot cope with a case where trimethylamine is required as a product.

[0005] Trimethylamine is required to be of high purity for use in electronic materials and pharmaceutical raw materials. For the production of high-purity trimethylamine, see JP-A-10-13
No. 9737 discloses a method of adding a carboxylic acid ester, but has a drawback that the operation becomes complicated.

[0006]

As described above, since trimethylamine forms a complicated azeotropic system with ammonia, monomethylamine, and dimethylamine, it is very complicated to separate the azeotropic system from the distillation operation and to use a large-sized azeotropic system. There is a problem that an apparatus is required, and the energy consumption cost of the methylamine production process becomes very large.

An object of the present invention is to provide a method for purifying trimethylamine with high purity while reducing energy consumption cost in the trimethylamine separation step.

[0008]

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, in separating and purifying trimethylamine from a methylamine mixture, the distillation was carried out in two columns, and the distillation in the second column was carried out. The present inventors have found that by making the column smaller than the first column, the energy consumption cost can be significantly reduced and, at the same time, high-purity trimethylamine can be easily obtained.

That is, according to the present invention, a reaction mixture obtained by subjecting at least one of a methylamine mixture and methanol to ammonia in the presence of a zeolite catalyst is used to separate unreacted ammonia in an ammonia separation column. Thereafter, in a method for purifying trimethylamine, 1) an aqueous solution containing a methylamine mixture and methanol is supplied to a trimethylamine separation column, which is a water extraction distillation column, and an aqueous solution of monomethylamine, dimethylamine and methanol is recovered from the bottom of the column. Distill crude trimethylamine from the top and feed part of it to the trimethylamine purification tower,
A process of recycling the remainder to the reaction system; 2) a process of distilling product trimethylamine from the top of a trimethylamine purification tower, which is a water extraction distillation column, and discharging water from the bottom of the column. And a method for purifying the same.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reaction mixture obtained by subjecting methanol and ammonia, a mixture of methanol and methylamine and ammonia, or a mixture of methylamine and ammonia to a gas phase in the presence of a zeolite catalyst.
In this method, unreacted ammonia is separated by an ammonia separation tower, and trimethylamine is obtained with high purity and economically from an aqueous solution containing a methylamine mixture and methanol.

A feature of the method for purifying trimethylamine in the present invention is that the method is carried out using two water extraction distillation columns.
The combination of the distillation towers used here is smaller than the first one, and the first one is a trimethylamine separation tower, and the second one is a trimethylamine purification tower.

The reaction mixture obtained by gas-phase contact reaction of methanol and ammonia, methanol and methylamine mixture and ammonia, or methylamine mixture and ammonia in the presence of a zeolite catalyst is converted into unreacted ammonia in an ammonia separation column. After being separated to form an aqueous solution containing a methylamine mixture and methanol, it is supplied to the middle stage of a trimethylamine separation tower.

The trimethylamine separation column has a theoretical plate number of 20 to
Approximately 40 packed towers and tray towers are used, and the reflux ratio is
0, the top pressure is 0.4 to 0.8 MPa, and water is supplied above the raw material supply stage to perform water extraction distillation. Here, the supply amount of water is 3 to 10 times (mass ratio) the amount of trimethylamine in the trimethylamine supply liquid. By distillation under such conditions, trimethylamine in the bottom of the column is reduced to 1%.
It becomes 0 ppm or less. In addition, the purity is 90-97 from the top.
% Of trimethylamine is distilled off, a part required as a product is supplied to a trimethylamine purification tower, and the remaining part is recycled to the reaction system.

The trimethylamine purification tower has a theoretical plate number of 10 to 10.
Approximately 20 packed towers and tray towers are used, and the reflux ratio is 3 to 2
0, the top pressure is 0.4 to 0.8 MPa, and water is supplied above the raw material supply stage to perform water extraction distillation. Here, the supply amount of water is 3 to 10 times (mass ratio) the amount of trimethylamine in the trimethylamine supply liquid. By distillation under such conditions, the purity at the top of the column was 99.9% by mass.
As described above, high-purity trimethylamine with dimethylamine of 100 ppm or less as an impurity is obtained.

[0015]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples.

Example 1 A reaction product obtained by reacting methanol and ammonia in the gas phase in the presence of a zeolite catalyst was subjected to ammonia removal in an ammonia separation tower, and 11.0% by mass of monotylamine and 40.9% by mass of dimethylamine were removed. , Trimethylamine 8.5
A liquid of 100% by mass, 5.3% by mass of methanol and 34.3% by mass of water was obtained at 1000 kg / hr. This aqueous solution was distilled using the process shown in FIG. First, an aqueous solution from which ammonia has been removed is placed in a trimethylamine separation tower (column diameter 0.35).
m, a packed tower having 30 theoretical plates), water was supplied above the supply stage at 722.3 kg / hr, the top pressure was 0.7 MPa, and the reflux ratio was 9.8 (this reflux ratio was Flow rate /
(Column gas withdrawal + liquid withdrawal)). At this time, 64.6 kg / hr of the top gas was recycled to the reaction system as it was, and the remainder was condensed by a condenser, and 25.08 kg / hr required as a product was extracted. At this time, the purity of the crude trimethylamine was 94.4% by mass. In addition, 1632.64 kg of an aqueous solution containing monomethylamine, dimethylamine and methanol was added from the bottom of the column.
/ Hr. Then, the crude trimethylamine extracted with a liquid from the top of the column is converted into a trimethylamine purification column (column diameter 0.10).
m, packed column having 14 theoretical plates), water is supplied at a rate of 27.59 kg / hr above the supply stage, steam is supplied to the bottom of the column at 12.54 kg / hr, and the top pressure is 0.4 MPa. ,
Distillation was performed at a reflux ratio of 3. As a result, 21.28 kg of a product having a purity of 99.9% by mass or more from the top of the column was obtained.
/ Hr. The impurities at this time were 40% dimethylamine.
ppm. Table 1 shows the composition of each line. The vapor used for the purification of trimethylamine was 336k.
g / hr.

[0017]

[Table 1]

Comparative Example 1 A reaction product obtained by reacting methanol and ammonia in the presence of a zeolite catalyst in a gas phase was subjected to ammonia removal in an ammonia separation column, and 11.0% by mass of monotylamine and 40.9% by mass of dimethylamine were removed. , Trimethylamine 8.5
1000 kg / hr of a liquid containing 5% by mass of methanol, 5.3% by mass of methanol, and 34.3% by mass of water. This aqueous solution was distilled by the process shown in FIG. First, the aqueous solution from which ammonia has been removed is supplied to the middle stage of a trimethylamine separation column (packed column having a column diameter of 0.5 m and 46 theoretical plates), and water is supplied above the supply stage at 722.3 kg / hr. Pressure 0.7MP
a, Distillation was performed at a reflux ratio of 23.8. An aqueous solution containing monomethylamine, dimethylamine and methanol was withdrawn from the bottom of the column at 1638.04 kg / hr, and trimethylamine was withdrawn at 84.27 kg / hr from the top of the tower. Of these, 2
1.28 kg / hr was recovered as a product, and the remainder was recycled to the reaction system. At this time, the purity of trimethylamine was 98.14% by mass. Table 2 shows the composition of each line. The steam used for the purification of trimethylamine was 469 kg / hr.

[0019]

[Table 2]

[0020]

According to the method of the present invention, the energy consumption is reduced by a simple distillation operation, the cost is reduced, and the concentration is 9%.
High-purity trimethylamine of 9.9% by mass or more can be obtained.

[Brief description of the drawings]

FIG. 1 is an example of a process flow sheet for implementing the present invention.

FIG. 2 is an example of a process flow sheet for comparing the present invention.

[Explanation of symbols]

A Trimethylamine separation tower B Trimethylamine separation tower condenser C Trimethylamine separation tower reboiler D Trimethylamine purification tower E Trimethylamine purification tower condenser 1 Methylamine mixture aqueous solution 2 Water injection 3 Crude trimethylamine 4 Trimethylamine reaction system recycling 5 Monomethylamine, dimethylamine and methanol aqueous solution 6 Water injection 7 Steam 8 Trimethylamine products 9 Drainage

Claims (1)

[Claims] 1. A reaction mixture obtained by subjecting at least one of a methylamine mixture and methanol to ammonia in the presence of a zeolite catalyst in a gas phase, separating an unreacted ammonia in an ammonia separation column, and then trimethylamine 1) An aqueous solution containing a methylamine mixture and methanol is supplied to a trimethylamine separation column, which is a water extraction distillation column, and an aqueous solution of monomethylamine, dimethylamine and methanol is recovered from the bottom of the column, and crude water is collected from the top of the column. Distilling off trimethylamine, part of which is fed to a trimethylamine purification tower,
A process of recycling the remainder to the reaction system; 2) a process of distilling product trimethylamine from the top of a trimethylamine purification tower, which is a water extraction distillation column, and discharging water from the bottom of the column. Purification method.