JP2003026619A - Method for purifying tetrachloroethylene and method for producing tetrachloroethylene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industrially and easily operable method for purifying pentafluoroethane by which a stabilizer included in the tetrafluoroethane can be removed, and to provide a method for producing pentafluoroethane by using the purification method. SOLUTION: The tetrafluoroethane including the stabilizer is contacted with a zeolite having 3.4-11 Å average pore diameter and/or a carbonaceous absorbent having 3.4-11 Å average pore diameter in a liquid phase.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying tetrachloroethylene and a method for producing pentafluoroethane using the method.

[0002]

2. Description of the Related Art Tetrachlorethylene (hereinafter referred to as "CCl
₂ = CCl ₂ "or" PCE ". )
Examples of the production method of (1) are: pyrolysis of carbon tetrachloride, (2) simultaneous chlorination and dehydrochlorination of chlorinated olefins, (3) hydrocarbons such as natural gas or LPG and chlorine. A method of using the raw material is known. In the manufacturing process, a stabilizer is added in order to ensure the stability of tetrachloroethylene, and the stabilizer is generally added in the range of several hundred to several thousand p.
pm is added. Further, tetrachloroethylene is used as a dry cleaning solvent, a raw material for producing CFCs, a solvent and the like.

On the other hand, pentafluoroethane (hereinafter referred to as "C
F ₃ CHF ₂ ”. ), For example, (1) a method of fluorinating tetrachloroethylene or a fluorinated product thereof with hydrogen fluoride (Table 9
No. 511515, etc.), (2) Method of hydrocracking chloropentafluoroethane (CClF ₂ CF ₃ ) (Patent No. 2540409, etc.), (3) Method of reacting halogen-containing ethylene with fluorine gas (special Kaihei 1-38
No. 034 publication).

For example, a method for producing pentafluoroethane by reacting tetrachloroethylene and hydrogen fluoride in the gas phase in the presence of a fluorination catalyst is carried out by a two-step reaction under different reaction conditions. That is, tetrachloroethylene and hydrogen fluoride (hereinafter sometimes referred to as “HF”) are reacted in the gas phase in the presence of a fluorination catalyst,
Mainly 1,1-dichloro-2,2,2-trifluoroethane (hereinafter sometimes referred to as “CHCl ₂ CF ₃ ”) and 1-chloro-1,2,2,2-tetrafluoroethane (hereinafter, may be referred to as "CHClFCF _3".) the first and the reaction allowed to generate, generated in the first reaction, primarily CHCl ₂ CF ₃ and CHClFCF
Second reaction of ₃ and HF in the gas phase in the presence of a fluorination catalyst to produce mainly pentafluoroethane
It is produced by the reaction of.

In this production method, tetrachloroethylene, which is one of the first reaction raw materials, usually contains about tens to hundreds of ppm by mass of a stabilizer in order to suppress acid generation due to decomposition. ing. For example, when an aromatic compound having a hydroxyl group such as phenol or cresol is contained and the stabilizer is not contained in tetrachloroethylene, the tetrachlorethylene lacks stability and side reactions such as generation of acid components proceed.

However, the stabilizer contained in tetrachloroethylene causes deterioration of the activity of the catalyst used in the production of pentafluoroethane, for example, and it is preferable that the stabilizer is not contained. Therefore, for example, the stabilizer may be removed before the first reaction, but the conventional removal method by fractional distillation or the like has a problem that the operation is complicated and a large amount of money is required for an actual device.

[0007]

The present invention has been made under such a background, and the present invention is capable of removing the stabilizer contained in tetrachloroethylene, is easy to operate and is industrially useful. It is an object of the present invention to provide a method for purifying tetrachloroethylene that can be carried out, and a method for producing pentafluoroethane using the method.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that tetrachloroethylene containing a stabilizer is used as a zeolite and / or an average pore size of 3.4 to 11Å. It has been found that the stabilizer can be reduced by bringing it into contact with a carbonaceous adsorbent having a pore size of 3.4 to 11Å in a liquid phase. Further, they have found that it is possible to efficiently produce pentafluoroethane by using tetrachloroethylene with reduced stabilizer as a raw material, and have completed the present invention. The present invention is a method for purifying tetrachloroethylene shown in the following [1] to [10] and a method for producing pentafluoroethane using the method.

[1] Tetrachloroethylene containing an aromatic compound having a hydroxyl group as a stabilizer is a zeolite having an average pore diameter of 3.4 to 11Å and / or a carbonaceous adsorbent having an average pore diameter of 3.4 to 11Å. A method for purifying tetrachloroethylene, characterized in that the stabilizer is reduced by bringing it into contact with a liquid phase in a liquid phase. [2] The method for purifying tetrachloroethylene according to the above [1], wherein the zeolite has a Si / Al ratio of 2 or less. [3] The zeolite is molecular sieves 4A,
Molecular sieves 5A, molecular sieves 10
The method for purifying tetrachloroethylene according to the above [1] or [2], which is at least one zeolite selected from the group consisting of X and molecular sieves 13X. [4] The method for purifying tetrachloroethylene according to the above [1], wherein the carbonaceous adsorbent is molecular sieving carbon 4A and / or molecular sieving carbon 5A. [5] The temperature at which tetrachloroethylene containing an aromatic compound having a hydroxyl group as a stabilizer is brought into contact with the zeolite and / or the carbonaceous adsorbent is −20 to 80 ° C.
The method for purifying tetrachloroethylene according to any one of the above [1] to [4].

[6] The pressure for contacting tetrachloroethylene containing an aromatic compound having a hydroxyl group as a stabilizer with the zeolite and / or the carbonaceous adsorbent is 0.
The method for purifying tetrachloroethylene according to any one of the above [1] to [5], which is ˜3 MPa. [7] A method for producing tetrachloroethylene in which the aromatic compound having a hydroxyl group contained as a stabilizer is reduced by using the purification method according to any one of the above [1] to [6]. [8] A method for producing pentafluoroethane, which comprises the following three steps. (1) Step (2) of reducing the aromatic compound having a hydroxyl group contained in tetrachloroethylene by using the purification method according to any one of [1] to [6]. Aromatic compound-containing tetrachloroethylene and HF are reacted in the gas phase in the presence of an alumina-chromia catalyst to give 1,1.
-Dichloro-2,2,2-trifluoroethane and 1
1,3-dichloro-2 obtained in the step (3) (2) of obtaining a mixed gas containing -chloro-1,2,2,2-tetrafluoroethane,
2,2-trifluoroethane and 1-chloro-1,
Mixed gas containing 2,2,2-tetrafluoroethane and H
A step of reacting F in the gas phase in the presence of an alumina-chromia catalyst to obtain pentafluoroethane [9] The aromatic compound having a hydroxyl group obtained through the step (1) is reduced to 30 mass ppm or less. The method for producing pentafluoroethane according to the above [8], wherein the step (2) is performed using tetrachloroethylene. [10] The aromatic compound having a hydroxyl group is phenol,
Method for producing pentafluoroethane according to the above [8] or [9], which is at least one compound selected from the group consisting of cresol, 2,6-di-t-butyl-p-cresol and aminomethylphenol. .

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. As a method of producing pentafluoroethane, for example, a method of producing tetrachloroethylene and HF by a two-step reaction in a gas phase in the presence of a fluorination catalyst is known. Tetrachloroethylene, which is one of the starting materials, contains a few hundred to several thousand mass ppm of a stabilizer for the above reason, and even a small amount of the stabilizer causes deterioration of catalytic activity. It is desirable to reduce as much as possible before carrying out the reaction.

The present inventors have found that the operation is easy and inexpensive,
As a result of diligent studies to develop a method for reducing the stabilizer contained in tetrachloroethylene, which is industrially practical, tetrachloroethylene containing the stabilizer was found to be zeolite and / or having an average pore diameter of 3.4 to 11Å. It has been found that the stabilizer can be reduced by contacting the carbonaceous adsorbent having an average pore diameter of 3.4 to 11Å in the liquid phase.

The zeolite used in the method for purifying tetrachloroethylene of the present invention preferably has an average pore diameter of 3.4 to 11Å, and more preferably an average pore diameter of 3.4 to 10Å. Zeolites having an average pore size larger than 11Å are not preferable because the amount of tetrachloroethylene adsorbed is large, and zeolites having an average pore size smaller than 3.4Å are not preferable because the ability to adsorb the stabilizer is small.

The Si / Al ratio of the zeolite is preferably 2 or less, and the Si / Al ratio of the zeolite is 2 or less.
If it is larger, there is a tendency that the stabilizer is not selectively adsorbed. As zeolite, molecular sieves 4A (MS-4A), molecular sieves 5A
(MS-5A), Molecular Sieves 10X (MS-
10X) and molecular sieves 13X (MS-1)
At least one zeolite selected from the group consisting of 3X) is preferable. By using these zeolites, the water content in tetrachloroethylene can be reduced at the same time.

The carbonaceous adsorbent is preferably one having an average pore diameter of 3.4 to 11Å. A carbonaceous adsorbent having an average pore diameter of more than 11Å is not preferable because the adsorbed amount of tetrachloroethylene is large, which is not preferable. A carbonaceous adsorbent having a value of less than 3.4 Å is not preferable because the ability to adsorb the stabilizer becomes small. The carbonaceous adsorbent is preferably molecular sieving carbon 4A and / or molecular sieving carbon 5A.

It is preferable to use the zeolite and the carbonaceous adsorbent individually, in consideration of regeneration of the adsorbent, but they may be used as a mixture. The mixing ratio of the zeolite and the carbonaceous adsorbent is not particularly limited, but considering that the water content in tetrachloroethylene is also reduced, the mixing ratio is preferably a ratio rich in zeolite.

As a method of bringing tetrachloroethylene containing a stabilizer into contact with the zeolite and / or the carbonaceous adsorbent in a liquid phase, a known method such as a batch system or a continuous system can be used. Industrially, a method of continuously circulating the adsorbent in a fixed bed is preferable, and the liquid-based space velocity (LH
SV) can be appropriately selected depending on the concentration of the stabilizer and the throughput of tetrachloroethylene. Usually 1 to 50
The range of Hr ^-1 is preferred. Further, in order to industrially carry out the method of reducing the stabilizer in tetrachloroethylene, a method of providing two adsorption towers and switching between the two towers to continuously perform purification may be used.

The treatment temperature for purifying tetrachloroethylene in the liquid phase is preferably -20 to 80 ° C, more preferably 0 to 50 ° C. Processing temperature is 80 ℃
If the temperature is higher, the equipment cost will increase in terms of heating of the apparatus, pressure resistance, etc., which is not preferable. The pressure is preferably in the range of 0 to 3 MPa, more preferably 0.
The range of 1 MPa is preferable. When the pressure is higher than 3 MPa, it is not economical and not preferable in terms of pressure resistance of equipment.

As described above, the stabilizer contained in tetrachloroethylene can be reduced by using the purification method of the present invention. The purification method of the present invention is
Particularly, it is preferably used for a compound having a hydroxyl group on the benzene ring, and examples of the compound having a hydroxyl group on the benzene ring include phenol, cresol, 2,6-di-t-butyl-p-cresol, aminomethylphenol and the like. .

Tetrachloroethylene containing a stabilizer is contacted with the above zeolite and / or the above carbonaceous adsorbent in the liquid phase under the above conditions, and the stabilizer is 30 ppm by mass.
It is possible to obtain tetrachloroethylene reduced below. It is also possible to obtain tetrachloroethylene in which the stabilizer is reduced to 10 mass ppm or less, and tetrachloroethylene in which the stabilizer is reduced to 5 mass ppm or less.

Next, the method for producing pentafluoroethane of the present invention will be described. The method for producing pentafluoroethane of the present invention is characterized by including the following three steps. (1) Step (2) of reducing the aromatic compound having a hydroxyl group contained in tetrachloroethylene by using the above-mentioned purification method. Tetrachloroethylene and HF in which the aromatic compound having a hydroxyl group is reduced through the step of (1). , 1, 2, by reacting in the gas phase in the presence of an alumina-chromia catalyst.
-Dichloro-2,2,2-trifluoroethane and 1
1,3-dichloro-2 obtained in the step (3) (2) of obtaining a mixed gas containing -chloro-1,2,2,2-tetrafluoroethane,
2,2-trifluoroethane and 1-chloro-1,
Mixed gas containing 2,2,2-tetrafluoroethane and H
Step of reacting F in the gas phase in the presence of an alumina-chromia catalyst to obtain pentafluoroethane

The tetrachloroethylene obtained through the step (1) is preferably tetrachloroethylene in which the aromatic compound having a hydroxyl group is reduced to 30 mass ppm or less, and more preferably 10 aromatic compounds having a hydroxyl group. The content of the aromatic compound having a hydroxyl group is preferably reduced to 5 mass ppm or less. When pentafluoroethane is produced from tetrachloroethylene in which the amount of the aromatic compound having a hydroxyl group is reduced to 30 mass ppm or less, the catalyst used in the production process has a long life, and pentafluoroethane is produced efficiently and economically. be able to.

The method for producing pentafluoroethane of the present invention is represented by the following reaction formula. CCl ₂ = CCl ₂ + 3HF → CF ₃ CHCl ₂ + 3HCl (Formula 1) CCl ₂ = CCl ₂ + 4HF → CF ₃ CHClF + 4HCl (Formula 2) CF ₃ CHCl ₂ + 2HF → CF ₃ CHF ₂ + 2HCl (Formula 3) CF ₃ CHClF + HF → CF ₃ CHF ₂ + HCl (Formula 4)

The above reaction is carried out in the gas phase in the presence of, for example, an alumina-chromia catalyst, but the reaction conditions are different, and in the first reaction represented by the formula 1 and the formula 2,
Reaction pressure is about 0.3 MPa, reaction temperature is about 300 ° C., H
In the second reaction represented by Formula 3 and Formula 4, F / PCE is 6 (molar ratio), the reaction pressure is about 0.4 MPa, the reaction temperature is about 330 ° C., and HF / (CF ₃ CHCl ₂ + CF ₃
CHClF) can be performed under the conditions of 4-8 (molar ratio).

[0025]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. (Example of raw material) When a commercially available tetrachloroethylene was analyzed by a gas chromatograph (column: capillary type / FID method), the total amount of phenol and cresol as stabilizers was 1
The amount of water contained in tetrachloroethylene was about 50 mass ppm.

(Example 1) Into a stainless steel cylinder having an internal volume of 200 ml, zeolite [Molecular Sieves 5A (manufactured by Union Showa Co., Ltd .: average pore size 4.2Å,
Si / Al ratio = 1)]. After vacuum-drying the zeolite, 100 g of tetrachloroethylene (raw material example) was charged while cooling the cylinder, and occasionally stirred while maintaining the temperature at 20 ° C. After about 4 hours, a part of the liquid phase portion was collected and It was analyzed under gas chromatographic conditions. As a result, neither the stabilizers of phenol nor cresol were detected. In addition, when the water content in the treated tetrachloroethylene was analyzed using a Karl Fischer,
The water content was 3 mass ppm or less.

(Example 2) A stainless steel cylinder having an internal volume of 200 ml was filled with 20 g of a carbonaceous adsorbent [Molecular-Sieving Carbon 5A, manufactured by Takeda Pharmaceutical Co., Ltd .: average pore diameter 5 Å]. After vacuum-drying the carbonaceous adsorbent, 80 g of tetrachloroethylene (raw material example) was charged while cooling the cylinder, and occasionally stirred while maintaining the temperature at 20 ° C., and after about 5 hours, a part of the liquid phase part was collected. And analyzed under the gas chromatographic conditions described above. As a result, neither the stabilizers of phenol nor cresol were detected.

Example 3 Zeolite as an adsorbent [Molecular Sieves 13X (manufactured by Union Showa Co., Ltd .:
Average pore size 10Å, Si / Al ratio = 0.81)]
The same operation and conditions as in (Example 1) except that g was added were used, and the analysis was performed. As a result, neither phenol nor cresol was detected.

Comparative Example 1 Zeolite [Molecular Sieves XH-9 (manufactured by Union Showa Co., Ltd .: average pore size 3.2Å, Si / Al ratio = 1)] was used as an adsorbent.
The same operation and conditions as in (Example 1) except that g was added were used, and the analysis was performed. As a result, the stabilizers phenol and cresol were hardly adsorbed, and the total amount was 132 mass ppm. It was found that the stabilizer adsorption efficiency was low when a zeolite having an average pore size smaller than 3.4 Å was used.

Comparative Example 2 Except that 20 g of a carbonaceous adsorbent [activated carbon: granular white rabbit KL, Takeda Pharmaceutical Co., Ltd .: average pore size 35 Å] was filled as an adsorbent (Example 2).
The same operation and conditions were used and the analysis was performed. As a result, the stabilizers phenol and cresol were hardly adsorbed, and the total amount was 119 mass ppm. In addition, the heat of adsorption due to the adsorption of tetrachloroethylene was large, and new decomposition products were detected.

(Example 4) 15 g of the molecular sieves 5A described in (Example 1) and 5 g of the molecular sieving carbon 5A described in (Example 2) were mixed as an adsorbent in a stainless steel cylinder having an internal volume of 200 ml. Filled. After vacuum-drying the adsorbent, 80 g of tetrachloroethylene (raw material example) was charged while cooling the cylinder, and occasionally stirred while maintaining the temperature at 20 ° C., and after about 4 hours, a part was collected in the liquid phase part and The analysis was carried out under the gas chromatographic conditions of. As a result, neither the stabilizers of phenol nor cresol were detected. Further, when the water content in tetrachloroethylene was analyzed, the water content was 5 mass ppm.

(Example 5) 4.8 L of molecular sieves 5A (MS-5A) was filled in a stainless steel cylinder having an internal volume of 5 L, and tetrachlorethylene (raw material example) was used at room temperature (15 ° C) and a pressure of about 0.3 MPa. Liquid phase 1 under conditions
It was continuously supplied at a linear velocity of 0 L / hr ^-1 . 10 from the start of supply
The outlet liquids after 0 hours, 300 hours and 500 hours were collected and analyzed. As a result, neither phenol nor cresol, which are stabilizers, was detected, and the water content was 5 ppm by mass or less.

Next, the reactor was filled with an alumina-chromia catalyst, the reaction temperature was 300 ° C., the reaction pressure was about 0.3 MPa,
Under the conditions of HF / PCE of 6 (molar ratio) and SV750 hr ^-1 , a continuous reaction using the above-mentioned tetrachlorethylene and HF as raw materials was carried out. 24 hours after starting the reaction, PC
The E conversion was 99.6%, the PCE conversion after 500 hours was 99.4%, and no decrease in catalyst activity was observed.

(Comparative Example 3) The reactor was filled with an alumina-chromia catalyst, and the stabilizer of (Raw material example) (total amount 150 mass p
PF) containing tetrachloroethylene and HF at a reaction temperature of 300 ° C., a reaction pressure of about 0.3 MPa, and HF / PCE of 6
(Molar ratio), SV750hr ^-1 The continuous reaction was performed on conditions. After the reaction was started, the PCE conversion rate after 24 hours was 9
The PCE conversion rate after 9.5% and 500 hours was 81.2%, and a decrease in catalyst activity was observed. From this it is clear that the stabilizer is associated with a reduction in catalyst activity.

[0035]

As explained above, the stabilizer contained in tetrachloroethylene can be reduced by using the purification method of the present invention. The purification method of the present invention is particularly preferably used for tetrachloroethylene containing an aromatic compound having a hydroxyl group such as phenol or cresol, but can also be used for tetrachloroethylene containing an aromatic compound having an amine group. Further, when pentafluoroethane is produced from tetrachloroethylene having a reduced amount of aromatic compounds having a hydroxyl group as a raw material, the catalyst used in the production process has a long life, and pentafluoroethane can be produced efficiently and economically. .

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C07C 17/08 C07C 17/08 17/20 17/20 19/08 19/08 21/185 21/185 / / C07B 61/00 300 C07B 61/00 300 F term (reference) 4D017 AA03 BA04 CA01 CA02 CB01 DA01 4G066 AA04B AA61B BA23 BA50 CA51 CA52 DA10 4H006 AA02 AC30 AD17 BA09 BA14 BA30 BC10 BC11 BC18 BE01 DA15 4H039 CA51 CD

Claims (10)

[Claims] 1. Tetrachloroethylene containing an aromatic compound having a hydroxyl group as a stabilizer and having an average pore size of 3.4.
~ 11Å zeolite and / or a carbonaceous adsorbent having an average pore size of 3.4 ~ 11Å in liquid phase,
A method for purifying tetrachloroethylene, characterized in that the stabilizer is reduced. 2. The method for purifying tetrachloroethylene according to claim 1, wherein the Si / Al ratio of the zeolite is 2 or less. 3. The method for purifying tetrachloroethylene according to claim 1, wherein the zeolite is at least one zeolite selected from the group consisting of molecular sieves 4A, molecular sieves 5A, molecular sieves 10X and molecular sieves 13X. 4. The method for purifying tetrachloroethylene according to claim 1, wherein the carbonaceous adsorbent is molecular sieving carbon 4A and / or molecular sieving carbon 5A. 5. The temperature at which the zeolite and / or the carbonaceous adsorbent is brought into contact with tetrachloroethylene containing an aromatic compound having a hydroxyl group as a stabilizer is −20.
It is -80 degreeC, The purification method of the tetrachloroethylene in any one of Claims 1-4. 6. The pressure for contacting tetrachloroethylene containing an aromatic compound having a hydroxyl group as a stabilizer with the zeolite and / or the carbonaceous adsorbent is 0 to 3
The method for purifying tetrachloroethylene according to any one of claims 1 to 5, which is MPa. 7. A method for producing tetrachloroethylene in which the aromatic compound having a hydroxyl group contained as a stabilizer is reduced, which comprises using the purification method according to any one of claims 1 to 6. 8. A method for producing pentafluoroethane, which comprises the following three steps. (1) A step of reducing the aromatic compound having a hydroxyl group contained in tetrachloroethylene by using the purification method according to any one of claims 1 to (2) The aromatic compound having a hydroxyl group through the step of (1) Compounds reduced tetrachlorethylene and HF are reacted in the gas phase in the presence of an alumina-chromia catalyst to give 1,1.
-Dichloro-2,2,2-trifluoroethane and 1
1,3-dichloro-2 obtained in the step (3) (2) of obtaining a mixed gas containing -chloro-1,2,2,2-tetrafluoroethane,
2,2-trifluoroethane and 1-chloro-1,
Mixed gas containing 2,2,2-tetrafluoroethane and H
Step of reacting F in the gas phase in the presence of an alumina-chromia catalyst to obtain pentafluoroethane 9. The pentafluoroethane according to claim 8, wherein the step (2) is carried out using tetrachloroethylene which has undergone the step (1) and in which the aromatic compound having a hydroxyl group is reduced to 30 mass ppm or less. Production method. 10. The aromatic compound having a hydroxyl group is at least one compound selected from the group consisting of phenol, cresol, 2,6-di-t-butyl-p-cresol and aminomethylphenol. 8. The method for producing pentafluoroethane according to 8 or 9.