JPH0372437A - Purification of 1,1,1,2-tetrafluoroethane - Google Patents

Abstract

PURPOSE:To almost completely eliminate impurities such as fluoroalkenes and chlorofluorocarbons by a simple operation by bringing a crude material of the title substance into contact with basic active carbon or zeolite having specific pore diameter. CONSTITUTION:The title substance is brought into contact with basic active carbon or zeolite having 5-7Angstrom pore diameter preferably in a liquid phase and impurities contained are adsorbed to purify the title substance. Active carbon calcined at >=750 deg.C, especially active carbon of copra meal is preferable as the basic active carbon. The purity of the title substance used as the raw material to be purified requires >=90wt.% purity. The substance is useful as a fluorocarbon 12 substitute refrigerant or a blowing agent.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is an alternative refrigerant to CFC-12, which is widely used as a refrigerant in car air conditioners, refrigerators, etc., which has recently become a problem due to ozone layer depletion. , or 1,1.1.2 tetrafluoroethane (CF), which is attracting attention as a blowing agent.
1CF (old)).

[Conventional technology]

CFS-CFH! The method for producing 2-chloro-1,1,1-trifluoroethane (CF, .c
A method of fluorinating ntco using a chromium-based catalyst (
Special Publication No. 43-10601, Special Publication No. 53-1054
No. 04), trifluoroethylene (F, C= CF
Method of adding hydrogen fluoride to H) (Japanese Patent Publication No. 62-237
No. 28'), 2,2-dichloro-1,1,1,2
-tetrafluoroethane (CFs-CFC) or 2
-Chloro-1,1,1,2-tetrafluoroethane (C
A method of reacting F1CFHCe) with hydrogen in the presence of a palladium catalyst (Japanese Patent Publication No. 56-38131) is known.

When producing CF, -CFH* by the above method, various impurities are produced depending on the catalyst, reaction conditions, etc.

As by-product impurities, for example, fluoroalkenes such as CFt=CFCQ, CFC(=CHCQ, C
F, =CHCQSCF, =CF)lSCFH=CFH, etc., CFtCLSCFH as chlorofluorocarbons
, Cd5CF, C(-CF, CQ, CF, ・CFC
Qt, CF,・CF, C&, CF,・CI(J!t
%CF, CFHCI2. CFs・CH, C1, etc.
CFsCFJSCF as hydrofluorocarbons
Examples include JCFtH, CFs/CHs, etc.

Among these impurities, hydrofluorocarbons may be contained in small amounts, but fluoroalkenes and chlorofluorocarbons in particular should be further reduced even if their content is trace. is desired, and is removed by fractional distillation, etc. However, it is extremely difficult to remove impurities with boiling points similar to CF3 and CFH, or impurities with an azeotropic composition, by fractional distillation. remain as.

Therefore, for example, as a purification method for CFs/CFH! containing CF, -C1 (CQ as an impurity), there is a method of contacting it with permanganate or an aqueous solution of permanganate (Japanese Patent Application Laid-open No. 105404/1983), or A method previously proposed by the present applicant in which impurities contained in CF, CFHt are reacted with hydrogen in the presence of a Group Ⅰ platinum group catalyst (Patent Application No.
-94930) etc. have been proposed.

[Problem to be solved by the invention]

However, the method using permanganate requires complicated operations, and the method of reacting with hydrogen in the presence of a catalyst requires the use of flammable hydrogen gas, which also requires complicated operations. All of these methods have poor industrial practicality. In view of the above circumstances, the present inventors conducted intensive research to develop an industrially practicable purification method for CF, CF)I, and found that fluoroalkenes and chlorofluorocarbons Or, it was discovered that it was well adsorbed to a specific zeolite.

The present invention was made based on the above discovery, and includes CF,
- The purpose is to provide a method for efficiently purifying CFH to high purity through simple operations.

[Means to solve the problem]

In order to achieve the above object, in the method of the present invention,
Impurities such as fluoroalkenes and chlorofluorocarbons contained in CP, CF II e are removed with salt, (
II activated carbon or zeolite with pore diameter of 5 to 7
Remove by adsorption.

In general, activated carbon used as an adsorbent consists of a group of 10 to 30 fine pores, and its specific surface area is 1000 m''/
It is much larger than g.

The surface of the activated T'l coal is heated at the activation firing temperature (hereafter firing 14
t) is 400 to 500°C, the structural formula (1
At 800 to 1000°C, acidic surface oxides are produced as shown in Structural Formula (2) (hereinafter referred to as acidic activated carbon), and basic surface oxides are produced as shown in structural formula (2) (hereinafter referred to as basic activated carbon).

The above-mentioned acidic activated carbon and basic activated carbon have completely different n absorption performance. For example, when adsorbing acids such as IIC&, almost no adsorption occurs at a firing temperature of 400°C, and as the firing temperature increases, the adsorption amount increases. When the temperature increases and exceeds 750°C, maximum adsorption amount is reached. In addition, when an alkali such as Na01 is adsorbed, on the contrary, the highest n absorption occurs at a low firing temperature.
The mouse is J misi, and the firing temperature is J2)? The amount of adsorption decreases as the temperature rises, and almost no n is adsorbed at temperatures above 750°C.

The activated carbon used in the lees manufacturing method of the present invention is I', l? L
! Basic activated carbon calcined at a temperature of 750° C. or higher, and activated carbon made from charcoal or various other materials can be used, but coconut shell activated carbon is particularly preferred.

Fluoroalkenes and chlorofluorocarbons can be adsorbed and removed using either the method of contacting CFa/CFHv with activated carbon in the gas phase or the method of contacting it in the liquid phase. Adsorption in phase is preferred.

Zeolites include naturally occurring minerals and synthetic materials, and are crystals in which Sin, tetrahedrons and Al2O, tetrahedra share oxygen and are bonded in a three-dimensional network, and there are various types depending on the form of the bond. Because zeolites are formed with cavities and pores of various shapes, there are many types of zeolites, each with a unique crystal structure.

In addition, as a method to adjust the effective diameter of zeolite pores and improve shape selectivity, there are methods to introduce cations of appropriate size through ion exchange, and tetramethoxysilane, which has a large molecular size and cannot enter the pores. There are methods such as chemical vapor deposition to narrow the pore windows of zeolite, and it is possible to create zeolites with different adsorption properties.

The zeolite used in the present invention is a zeolite with a pore size of 5 to 7 people. Even if the pore size is less than 5 pores or more than 7 pores, the adsorption and removal effect of fluoroalkenes and chlorofluorocarbons is significantly reduced.

Even in the case of zeolite, it is preferable to adsorb in the liquid phase.

In addition, even if basic activated carbon or zeolite with a pore size of 5 to 7 is used, if the amount of impurities contained in the purified CF or CFHf is large, sufficient purification will not be carried out.
The purity of CF, CFH, used as a raw material for purification is 9
It is necessary that the content is 9wt% or more.

In order to bring CF3/CFH into contact with activated carbon or zeolite in the liquid phase, known methods such as batch, continuous, and suspended bed methods can be used. As, CF containing impurities, -
A continuous flow of CFH is advantageous. in this case,
The temperature should be as low as possible, and is usually maintained at 0 to 70°C. Further, the liquid-based space velocity (LHSV) is appropriately selected depending on the concentration of harmful impurities and the temperature of CF, CFH, to be treated, but is usually in the range of 0.5 to 10 hr. The pressure is sufficient as long as it can maintain CF, CFH, in the liquid phase.

In order to industrially purify CF, .CFtl, two adsorption towers are provided, and once the impurities are adsorbed to saturation, purification can be carried out continuously by a known method of switching between them.

〔Example〕

Raw material l CF, -CH,C& and hydrogen heptafide are reacted to produce CF,
・CFH! A crude reaction product of
CF with the composition shown in the table, CFH! I got it.

The compounds in Table 1 contain fluoroalkenes and chlorofluorocarbons as trace impurities in CF, CFH, and CFH.

Using this as a raw material, the purification method of the present invention was carried out.

Example 1 A SUS container with an internal volume of 10Q was filled with 112 pieces of basic activated carbon (manufactured by Tsurumicol Co., Ltd., HC-6) with a particle size of 3 to 511 halo, and after vacuum drying, 1 of the raw materials CF, CFH!
was filled with 8e1 liquid. It was kept at room temperature and stirred occasionally, and after 2 hours a portion of the liquid phase was sampled and analyzed. Second result
Shown in the table.

Table 2 As is clear from Table 1, trace amounts of fluoroalkenes and chlorofluorocarbons, which are inert substances in CF, CFH, are removed as is clear from Table 2, which was purified by fractional distillation. .

Example 2 In a SUS container with an internal volume of 15 ff, 1 portion of basic activated carbon (manufactured by Tsurumicol Co., Ltd., H'C6) with a particle size of 3 to 5 ms was added.
412, and 30
Continuously supplied at a flow rate of f2/hr, 3 hours later, 6 hours later,
The outlet liquid after 15 hours was collected and analyzed.

The results are shown in Table 3.

Refining is carried out.

Example 3 A SUS container with an internal volume of 500 caps was filled with the activated carbon used in Example 1, and l of raw materials CF, CFHy was passed through the packed bed at a rate of 5012/hr in a standard gas phase state to the outlet. Gas analysis was performed. The results are shown in Table 4.

As is clear from Table 3, continuous flow was successful Comparative Example 1 Two SUS containers with an internal volume of IQ were each filled with 0.2Q of different types of petroleum-based granulated coal, and after vacuum drying,
CF3-CFH* of raw material 1 used in Example 1 was dissolved in liquid form.
．． I put in 812 each. The above two types of activated carbon are neutral to acidic, and are 4GK manufactured by Kuraray Chemical Co., Ltd. and 4, GV manufactured by Tsurumicol Co., Ltd.

This was kept at room temperature with occasional stirring, and after 2 hours the liquid phase was collected and analyzed. The results are shown in Table 5.

Table 5 (blank below) As is clear from Table 5, fluoroalkenes and fluorofluorocarbons are not removed.

Example 4 Zeolite (manufactured by Union Showa Co., Ltd., Molecular Siegis 5A: 5 pore diameter) was filled tQ into a SUS container with an internal volume of 1OI2, and 1 CF,
CFI (t) was charged in the form of 872.1. It was kept at room temperature and stirred occasionally, and after 2 hours a portion of the liquid phase was collected and analyzed. The results are shown in Table 6.

The reactor was filled with 14Q of CFs/CFH2 as raw material 1 in liquid form at a flow rate of 3012/hr, and the outlet liquid was collected and analyzed after 3 hours, 6 hours, and 15 hours. 7th result
Shown in the table.

As is clear from Table 6, trace impurities such as fluoroalkenes and chlorofluorocarbons in CF and CFHz were removed.

Example 5 As is clear from Table 7, good purification can be achieved by continuous flow of zeolite (Molekiller Siegis 5A, manufactured by Union Showa Co., Ltd.) into a SUS container with an internal volume of 15 i2.

Example 6 A SUS container with an internal volume of 500 m12 was filled with zeolite (Molecular Siegis 5A, manufactured by Union Showa Co., Ltd.), and the raw material 1, CFa-CFH, was charged at 50 m2 in a standard gas phase state.
7! The gas was passed through the packed bed at a rate of /hr and the outlet gas was analyzed. The results are shown in Table 8.

Table 8 Molecular sieves, MS-13X (pore size: 10).

This was kept at room temperature with occasional stirring, and after 2 hours the liquid phase was collected and analyzed. The results are shown in Table 9.

Table 9 Comparative Example 2 Two SUS containers each having an internal volume of 1e were filled with 0.2Q of two types of zeolite, and 0.8Q each of CF, -CFH, which was the raw material l used in Example 1, was added in liquid form. Ta.

The above two types of zeolites are manufactured by Union Showa Co., Ltd.
Molecular sieves, MS-74A (pore diameter: 4
A) and Union Showa Co., Ltd. As is clear from Table 9, fluoroalkenes and chlorofluorocarbons are not removed.

Example 7 Zeolite (manufactured by Union Carbide Co., Ltd., silicalite, pore diameter: 6 people) was filled in a 5t JS container with an internal volume of 1012 tQ, and raw material 1 was filled in an 8Q liquid state. It was kept at room temperature and stirred occasionally. After 2 hours, a sample was taken from the liquid phase and analyzed. The results are shown in Table 1O.

2-chloro-1,1,1-trifluoroethane and hydrogen tunide are reacted in the gas phase to form CF3.CFH! When a reaction composition was prepared and purified by fractional distillation,
The compositions shown in Table 11 were obtained.

As is clear from Table 10, fluoroalkenes and chlorofluorocarbons were removed.

Raw material 2 Example 8 A SUS container with an internal volume of 10 g was filled with basic activated carbon (HC-6, manufactured by Tsurumicol Co., Ltd.) with a particle size of 3 to 5 square meters, and after vacuum drying, CF3/CFHt of raw material 2 Filled with 8e in liquid form and kept at room temperature, stirring occasionally, 6
After standing for a period of time, the liquid phase was collected and analyzed. Results first
It is shown in Table 2.

Table 12 [Effects of the Invention] As described above, the method for purifying CF, CFI (!) according to the present invention almost completely removes harmful impurities such as fluoroalkenes and AA fluorocarbons by simple operations. Since it can be removed quickly, it will greatly contribute to the field of manufacturing CF3 and CFH, which will be important as substitutes for Freon 12 and the like.

Claims (2)

[Claims] (1) 1,1,1 characterized in that impurities such as fluoroalkenes and chlorofluorocarbons contained in 1,1,1,2-tetrafluoroethane are adsorbed and removed using basic activated carbon. , 2-tetrafluoroethane purification method. (2) Impurities such as fluoroalkenes and chlorofluorocarbons contained in 1,1,1,2-tetrafluoroethane are adsorbed and removed using zeolite with a pore diameter of 5 to 7 Å. A method for purifying 1,1,1,2-tetrafluoroethane.