JP3250267B2 - Method for purifying 1,1,1,2-tetrafluoroethane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is directed to reacting one or more unsaturated impurities contained in 1,1,1,2-tetrafluoroethane with hydrogen fluoride to form 1,1,1,2-tetrafluoroethane. It relates to purifying tetrafluoroethane. In recent years, 1,1,1,2-tetrafluoroethane (hereinafter, referred to as a replacement refrigerant for CFC-12, which is widely used as a refrigerant for car air conditioners, refrigerators, and the like, which has become a problem due to depletion of the ozone layer, etc. HFC-134a or CF ₃ CH ₂ F.)

[0002]

_2. Description of the Related Art As a method for producing CF ₃ CH ₂ F, 1,1,1-trifluoro-2-chloroethane (hereinafter referred to as HCFC-133a or CF ₃ CH ₂ Cl.)
Of fluorinated phenols using chromium-based catalysts
JP-A-3-10601, JP-B-53-105404), a method of adding hydrogen fluoride to trifluoroethylene (CF ₂ ＣＨCHF) (JP-B-62-23728), 2,2-dichloro-1, 1,1,2-tetrafluoroethane (CF ₃ CCl ₂ F) or 2-chloro-1,
1,1,2-tetrafluoroethane (CF ₃ CHClF)
Is known in the presence of a palladium catalyst in the reaction with hydrogen (JP-B-56-38131).

When CF ₃ CH ₂ F is produced by the above method, various impurities are produced as by-products depending on the catalyst, reaction conditions and the like. As the by-produced impurities, for example, as unsaturated impurities, CF ₂ = CCIF, CF = CHCl, CF ₂ = CH
Cl, CHF = CClF, CF ₂ = CHF, CHCl = CH
As chlorofluorocarbons such as F, CCl ₂ F ₂ ,
CH ₂ ClF, CH ₂ Cl.CCLF ₂ , CF ₃ CHCl ₂ ,
Examples of hydrofluorocarbons such as CF ₃ CHClF include CF ₃ CHF ₂ , CF ₃ CH ₃ , and CHF ₂ CHF ₂ .

Of these impurities, hydrofluorocarbons may be contained in a small amount, but unsaturated impurities and chlorofluorocarbons are
Even if the content is very small, it is desired to further reduce it, and it is removed by fractional distillation or the like. But,
It is extremely difficult to remove impurities having a boiling point close to that of CF ₃ CH ₂ F and impurities having an azeotropic composition by fractional distillation. Particularly, unsaturated impurities are contained as trace impurities even by fractional distillation.

For this reason, various processes have been proposed as solutions. In a conventional HFC-134a production method, first, trichloroethylene and HF as raw materials are introduced into a first reactor, and a product gas is HCFC-133a, hydrogen chloride and unreacted HF.
Is the majority. Even if this gas is introduced into the second reactor as it is, since it contains a large amount of hydrogen chloride, a disadvantageous equilibrium as shown in the formula (1) is attained, and HFC-134a as a target substance is hardly generated.

(Equation 1) Therefore, this gas is separated from hydrogen chloride using a purifier,
Removed.

[0006] The remaining gas is introduced into the second reactor as it is or with an insufficient amount of HF added thereto, and the produced gas is unreacted HCFC-133a and HF, and the target product is HFC.
-134a, a mixture of by-products mainly composed of unsaturated impurities and hydrogen chloride.

This gas is supplied as it is to a third reactor, where an HF addition reaction is performed on the unsaturated impurities, and the produced gas is sent to a purification device for separating hydrogen chloride, where hydrogen chloride is separated and removed. You. The remainder is further sent to a separation and purification device, where HFC-134a as a target substance is separated, and HC
FC-133a and HF are recycled to the second reactor.

[0008] In this process, since the hydrogen gas contained in the outlet gas of the second reactor is introduced into the third reactor, the reaction efficiency of the target unsaturated impurities decreases. Further, since the target HFC-134a contains a large amount of HF and HCFC-133a, it has a disadvantage that the reactor must be enlarged. It is necessary to provide a purification device between the reactor and the third reactor, and the device is expensive.

On the other hand, as another process, E
P Patent 0 446 8691 A1, EP 0 449 614
A2 and EP0 449 617A2 have been proposed. In these production methods, the HCFC-
133a and HF are supplied, and the product of the reaction is unreacted HC
FC-133a and HF, target HFC-134a, H
It is a mixture of CFC-1122 (CF ₂ = CHCl) and other by-products and hydrogen chloride.

This mixed gas is supplied to the first reactor as it is. At the same time, the raw materials trichlorethylene and HF
Is also supplied. Trichlorethylene reacts with HF to form H
CFC-133a and hydrogen chloride are generated, and HCFC-11
22 reacts with HF to form HCFC-133a.

Therefore, the gas produced in the first reactor is HC
FC-133a, HFC-134a, HF, hydrogen chloride and a mixture of small amounts of trichlorethylene and other by-products. The product gas is sent to a purifier for hydrogen chloride separation, where hydrogen chloride is separated and removed, and then HFC-134a
Are separated. The remaining HCFC-133a and HF are returned to the second reactor.

This method is characterized in that the reaction between trichloroethylene and HF involves a large exothermic reaction, and the reaction is carried out by dilution, but has the following drawbacks. (A) Compared to the conventional method, since all of the product gas containing hydrogen chloride in the second reactor is introduced into the first reactor, the concentration of hydrogen chloride in the first reactor further increases than in the conventional method,
The reaction efficiency of the target unsaturated impurities decreases.

(B) Further, since all the generated gas of the second reactor is introduced into the first reactor, the amount of gas in the first reactor becomes larger than that of the conventional method, and the size of the reactor becomes larger. There is.

[0014]

An object of the present invention is to provide a novel method for purifying 1,1,1,2-tetrafluoroethane which does not have the above-mentioned disadvantages of the prior art. Is what you do.

[0015]

In view of the above circumstances, the present inventors have developed an industrially practical and economical HFC-134.
As a result of diligent studies to develop a purification method for a, HFC-134 was reacted with trichlorethylene and hydrogen fluoride.
In the method for producing a, hydrogen chloride is
H containing one or more unsaturated impurities removed to less than mole%
The HFC-134a is reacted with a catalyst in the gas phase, preferably without adding new hydrogen fluoride, and in a gaseous state with HFC-134a containing hydrogen fluoride in an equimolar amount or more with respect to unsaturated impurities. When 134a was recovered, it was found that high-purity HFC-134a containing no unsaturated impurities could be economically and easily purified with high yield, and the present invention was completed.

Conventionally, to produce HFC-134a,
A method of reacting trichlene with HF is known.
This reaction cannot be achieved in one step, but is carried out by two steps under different reaction conditions. First, the first-stage reaction of the formula (2) for reacting trichlorethylene with HF to produce HCFC-133a, CCl ₂ = CHCl + 3HF → CF ₃ CH ₂ Cl + 2HCl Formula (2) and HCFC-133a and HF And react with HFC-
The second stage reaction of formula (1) described above that produces 134a is used. The second stage reaction of reacting HCFC-133a with HF to produce HFC-134a is an equilibrium reaction, and the target product HFC is contained in the reaction product.
Since there is an unsaturated impurity having an azeotropic relationship with -134a, it is difficult to separate it from HFC-134a, and various processes as described above have been proposed.

The present inventors have proposed the HFC-13 proposed above.
4a (Japanese Patent Application Nos. 4-19249 and 4-1)
No. 99827), the combined products of the first and second-stage reactions are introduced into a crude purification step to remove by-product hydrochloric acid,
By a method of concentrating C-134a, a process is proposed in which the distillation step is simplified by simplified equipment and the energy consumption is reduced.

The present invention relates to economically and easily purifying one or more unsaturated impurities contained in HFC-134a concentrated through this crude purification step with good yield. The method will be described. According to the process proposed by the present inventors, hydrogen chloride contained in HFC-134a concentrated through a crude purification step is 2 mol%.
The following are essential, and it is more preferable not to contain them.

If it is more than 2 mol%, HF to unsaturated impurities
This tendency becomes remarkable as the addition reaction inhibition progresses and the concentration becomes higher, and the reaction efficiency is remarkably reduced. As a result, it is necessary to raise the reaction temperature. This is because HFC-134a and HCFC-133a represented by formulas (3) and (4)
Reaction and decomposition occur, and at the same time as the intended loss of HFC-134a, the decomposition product reduces the activity of the catalyst. CF ₃ CH ₂ F + HCl → CF ₃ CH ₂ Cl + HF Formula (3) CF ₃ CH ₂ Cl → CF ₂ = CHCl + HF Formula (4) Therefore, hydrogen chloride is not more than 2 mol%. It is essential and preferably not contained.

In the method of the present invention, HF which has undergone a crude purification step
Since C-134a contains HF in an azeotropic composition, it is not necessary to newly add HF. If the molar ratio between HF and unsaturated impurities is equal to or greater than the molar ratio, the desired reaction proceeds efficiently. Unreacted HF is recovered after the reaction and can be used without waste.

Further, HC contained in HFC-134a
The concentration of FC-133a is desirably 10 mol% or less, and if it is more than 10 mol%, the reaction efficiency is reduced, and the size of the reaction apparatus is increased, which is not economical. The HFC-134a concentration is also preferably at least 70 mol%, and if it is lower than this, the same disadvantages as HCFC-133a occur, which is not preferable. The concentrated HFC-134a having the above composition is reacted with the catalyst in a gas phase.

The catalyst used in the method of the present invention is
Any catalyst may be used as long as it has a catalytic action on the fluorination reaction, and examples of the catalyst include Group 1B, 2A, 2B,
Group 4B, 5A, 5B, 6A, 7A and 8 group metal compounds such as Cu, Mg, Zn, Pb, V, Bi, C
A fluorination catalyst containing at least one element selected from the group consisting of r, Mn, Fe, Co and Ni, which may be supported using alumina, aluminum fluoride or activated carbon as a carrier.

As a method for producing the present catalyst, a usual method can be applied. In one example, the catalyst can be produced by impregnating an aqueous solution of cobalt chloride with alumina, drying and calcining the mixture under air flow. The catalyst thus prepared is desirably activated with hydrogen fluoride or the like before the stage of use in the reaction.

The reaction temperature is from 130 to 280 ° C., preferably from 150 to 250 ° C. At a lower temperature, the reaction rate of the unsaturated impurities becomes slower, and at a higher temperature, the reaction of HFC-134a and HCFC-133a as described above occurs. It is not preferable because a problem due to the reaction and decomposition occurs.

After the reaction, unreacted HF is recovered and concentrated HF
A small amount of HCFC-133 contained in C-134a
a) Since other chlorofluorocarbons do not contain HF, there is no azeotropic relationship between the components, and the components can be separated and purified by distillation.
4a can be economically and easily purified with good yield. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0026]

EXAMPLES Preparation Example 1 3.6 g of cobalt chloride (CoCl ₂ ) was dissolved in 52 ml of pure water, and activated alumina (Nikki Universal Co., Ltd. NS) was added thereto.
T-3) 100 ml of the catalyst liquid is immersed, and the entire amount of the catalyst solution is absorbed in alumina. Next, the alumina wet with the catalyst liquid is dried on a hot water bath at 90 ° C. and dried. The dried catalyst is dried at 110 ° C. for 10 hours in a hot air dryer of an air circulation type. The dried catalyst was filled in a glass firing tube, air was flowed at a space velocity (SVo) of 500 Hr ^-1 and the temperature was raised to 400 ° C. to obtain a catalyst.

Preparation Example 2 Instead of cobalt chloride (CoCl ₂ ), nickel chloride (N
but using iCl ₂ · 6H ₂ O) 6.67g was obtained a catalyst in the same manner as in Preparation Example 1.

Raw Material Example 1 A crude product obtained by reacting trichloroethylene (CCl ₂ ＣＨCHCl) with hydrogen fluoride in the gas phase in the presence of a chromium catalyst in the presence of a chromium catalyst had the following composition. . CF ₃ CH ₂ F 81.4350, CF ₃ CH ₃ 0.5360, CHCl = CHF 0.0020 CF ₃ CH ₂ Cl 6.2400, CF ₃ CHClF 0.5310, HF (hydrogen fluoride) 9.5060 CHF ₂ CHF ₂ 0.1600, CF ₃ CClF ₂ 0.0540, HCl ( 0.5620 CF ₃ CHF ₂ 0.5320, CF ₂ = CHCl 0.4420, unit mol%

Starting Material Example 2 The recovered material in the crude purification step obtained by the same reaction as in Starting Material Example 1 had the following composition. CF ₃ CH ₂ F 71.4527, CF ₃ CH ₃ 0.6420, CHCl = CHF 0.0032 CF ₃ CH ₂ Cl 12.2160, CF ₃ CHClF 0.5880, HF (hydrogen fluoride) 8.3031 CHF ₂ CHF ₂ 0.1820, CF ₃ CClF ₂ 0.0570, HCl ( 5.4120 CF ₃ CHF ₂ 0.5620, CF ₂ = CHCl 0.5820, unit mol%

Example 1 An Inconel 600 type reactor having an inner diameter of 1 inch and a length of 1 m was charged with 80 ml of the catalyst of Preparation Example 1. At the stage before the reaction, the catalyst was partially fluorinated using hydrofluoric anhydride diluted with nitrogen and 100% hydrofluoric anhydride to activate the catalyst. The conditions for treating the catalyst with hydrofluoric anhydride are shown below. Hydrofluoric anhydride concentration: 25-100% Treatment temperature: 250-350 ° C Treatment time: about 10 hours

Using the catalyst thus obtained, Material Example 1 was supplied as a raw material at a reaction temperature of 200 ° C. at a space velocity (SVo) of 1000 Hr ⁻¹ with respect to the catalyst. Was analyzed by gas chromatography and found to have the following composition. CF ₃ CH ₂ F 90.5407, CF ₃ CHF ₂ 0.5916, CF ₃ CClF ₂ 0.060 CF ₃ CH ₂ Cl 7.4412, CF ₃ CH ₃ 0.5960, CH ₂ ClCHF ₂ 0.0021 CHF ₂ CHF ₂ 0.1779, CF ₃ CHClF 0.5904, unit mol% CF ₃ CH ₂ unsaturated impurities in F is not detected, it can be substantially 100% removal, CF ₃ is further desired product
Little loss of CH ₂ F was observed, and there was no increase or decrease in other by-products.

The reaction was continued under these conditions for 1000 hours, but no decrease in the removal rate of the unsaturated impurities was observed, and almost no loss of the target product, CF ₃ CH ₂ F, was observed. The exhaust gas from which the acid content had been removed was recovered, purified by fractional distillation, and analyzed. The result was the following composition. CF ₃ CH ₂ F 99.9976, CF ₃ CH ₃ 0.0001, CF ₃ CHClF 0.0001 CHF ₂ CHF ₂ 0.0020, CF ₃ CHF ₂ 0.0002 High purity HFC-13 containing no unsaturated impurities at all
4a was obtained.

[0033] except for using the catalyst prepared as in Example 2 Preparation Example 2 Reactions were carried out in the same manner as in Example 1, and the gas composition was acid content removed exhaust gas was analyzed using gas chromatography. As a result, as in Example 1, no unsaturated impurities in CF ₃ CH ₂ F were detected, and substantially 100% of the impurities could be removed. Further, the loss in CF ₃ CH ₂ F, which was the target substance, was reduced. Few were recognized.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1 except that the raw material example 2 was used as a raw material. The exhaust gas was removed by acid and the gas composition was analyzed using a gas chromatograph. Met. CF ₃ CH ₂ F 81.8828, CF ₃ CH ₃ 0.7446, CHCl = CHF 0.0020 CF ₃ CH ₂ Cl 15.5915, CF ₃ CHClF 0.6808, CH ₂ ClCHF ₂ 0.0017 CHF ₂ CHF ₂ 0.2101, CF ₃ CCl ₂ F 0.0658, CClF ₂ CH ₂ Cl 0.0212 CF ₃ CHF ₂ 0.6511, CF ₂ = CHCl 0.1484, unit mol% Since the concentration of hydrogen chloride in CF ₃ CH ₂ F is high, the removal rate of unsaturated impurities is reduced to about 77.8%. The loss of CF ₃ CH ₂ F is about 1.1%, which is not economical.

Next, the reaction temperature was raised to 280 ° C., the exhaust gas was removed from the acid content, and the gas composition was analyzed using a gas chromatograph. As a result, the removal rate of unsaturated impurities increased to about 92%, but could not be completely removed as in Examples 1 and 2, and the loss of CF ₃ CH ₂ F, which was the target, was about 4.1%. Increased and not economical. When the reaction was continued at the reaction temperature of 280 ° C. for 500 hours, the removal rate of unsaturated impurities was reduced to about 80%. When the catalyst was further taken out, adhesion of carbon was recognized.

Comparative Example 2 The conventional process and the above-described method were performed. Activated alumina is immersed in an aqueous solution of chromium chloride, absorbed in its entirety, and then dried,
It was calcined to obtain a fluorination catalyst. 80 ml of this was filled into an Inconel 600 type reactor having an inner diameter of 1 inch and a length of 1 m, and was used as a second reactor.

Next, Preparation Example 1 was prepared in the same reactor as the second reactor.
A third reactor was filled with 80 ml of the catalyst shown in the above. Prior to the reaction in both the second and third reactors, the catalyst was partially fluorinated with hydrofluoric anhydride under the conditions shown in Example 1 to activate the catalyst.

First, the second reactor was passed through a nitrogen stream at 350
C. Then, the supply of nitrogen was stopped, and hydrogen fluoride and HCFC-133a were supplied at flow rates of 1060 ml / min and 260 ml / min, respectively. After analyzing the exhaust gas for acid content, the gas composition was analyzed using a gas chromatograph. The composition of the exhaust gas was as follows. CF ₃ CH ₂ F 3.88, CF ₂ = CHCl 0.024, HCl 4.0 CF ₃ CH ₂ Cl 15.95, other by-products 0.106, HF 76.04 unit mol%

Next, as in the second reactor, the temperature of the third reactor was raised to 240 ° C. under nitrogen flow, and then the supply of nitrogen was stopped, and the exhaust gas of the second reactor (the above composition) Was introduced into the third reactor as it was, the exhaust gas was removed of acid content, and the gas composition was analyzed using a gas chromatograph. The following results were obtained.

CF ₃ CH ₂ F 19.3248, CF ₂ = CHCl 0.0072 CF ₃ CH ₂ Cl 80.1352, other by-products 0.5328, unit mol% The removal rate of unsaturated impurities in CF ₃ CH ₂ F is about 94%, and the removal efficiency is about 94%. Is bad. Furthermore, the throughput of CF ₃ CH ₂ F, which is the object, is clearly lower than that of Examples 1 and 2, and is not economical.

[0041]

According to the present invention, unsaturated impurities in CF ₃ CH ₂ F, which has been very difficult in the past, can be efficiently and easily removed.
And it can be economically removed and high purity CF ₃ CH ₂ F can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Kazuo Muramaki 5-1 Ogimachi, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Showa Denko KK Kawasaki Plant (56) References JP-A-6-184015 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) C07C 17/38 C07C 19/08

Claims (4)

(57) [Claims] 1. A method for producing 1,1,1,2-tetrafluoroethane by reacting trichloroethylene with hydrogen fluoride, wherein hydrogen chloride is contained in a crude purification step in an amount of 2 mol% or less.
(However, excluding the condition that does not contain hydrogen chloride)
1,1,1,2-tetrafluoroethane, which contains one or more unsaturated impurities and contains hydrogen fluoride in an equimolar amount or more with respect to the unsaturated impurities without newly adding hydrogen fluoride, 1,1,1,2,1 which is brought into contact with a catalyst in a phase state to reduce the content of the unsaturated impurities.
-A method for purifying tetrafluoroethane. 2. The method according to claim 1, wherein the concentration of 1,1,1,2-tetrafluoroethane is at least 70 mol% and the concentration of 1,1,1-trifluoro-2-chloroethane is at most 10 mol%. Purification method. 3. The method of claim 1, wherein the azeotropic composition contains hydrogen fluoride.
2. The method according to claim 1, wherein 1,1,2-tetrafluoroethane is purified.
Or the purification method of 2. 4. A catalyst comprising Cu, Mg, Zn, Pb, V, B
a fluorination catalyst comprising at least one element selected from the group consisting of i, Cr, Mn, Fe, Co and Ni;
The purification method according to claim 1, wherein the reaction temperature is 130 to 280C.