JP3158720B2 - Method for purifying 1,1,1,2-tetrafluoroethane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a process for reacting 1,1,1,2-fluoroalkenes contained in 1,1,1,2-tetrafluoroethane with hydrogen fluoride in the presence of a catalyst.
It relates to purifying tetrafluoroethane. recent years,
1,1,1,2-Tetrafluoroethane (hereinafter referred to as HFC-I) has been attracting attention as an alternative refrigerant to Freon-12, which has been widely used as a refrigerant for car air conditioners and refrigerators, which has become a problem due to depletion of the ozone layer. 134a or CF ₃ CH
Abbreviated as 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 the abbreviated ₃ CH ₂ Cl.), a method (JP-B 43-10601 discloses that fluorinated using chromium-based catalysts, especially open Akira 53-10540
No. 4), trifluoroethylene (CF ₂ ＣＨCHF)
Method of adding hydrogen fluoride to water (Japanese Patent Publication No. 62-23728)
Publication), 2,2-dichloro-1,1,1,2-tetrafluoroethane (CF ₃ CCl ₂ F) or 2-chloro-1,1,1,2-tetrafluoroethane (CF ₃ C
HClF) is reacted with hydrogen in the presence of a palladium catalyst (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, fluoroalkenes such as CF ₂ ＣCHCl, CCIF ＝ CHF,
CHCl = CHF, CF ₂ = CHF, CHCl = CCl
Chlorofluorocarbons such as CCl ₂ F
₂ , CH ₂ ClF, CH ₂ Cl.CCLF ₂ , CF ₃ C
Hydrofluorocarbons such as HCl ₂ and CF ₃ CHClF, such as CF ₃ CHF ₂ , CF ₃ CH ₃ and CHF
₂ CHF _{2 and the} like.

[0004] Of these impurities, hydrofluorocarbons may be contained as long as they are in a small amount, but fluoroalkenes and chlorofluorocarbons are expected to be further reduced even if their contents are very small. It is rare and has been removed by fractional distillation and the like. However, 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, and fluoroalkenes are contained as trace impurities even by fractional distillation. .

[0005] Therefore for example, CF ₂ = as purification of CF ₃ CH ₂ F containing CHCl as impurity, a method (JP 53-105404 JP) contacting the aqueous solution of permanganate or permanganate, The impurity contained in CF ₃ CH ₂ F proposed by the applicant was changed to
A method of reacting with hydrogen in the presence of a group II platinum group metal catalyst (Japanese Patent Publication No. 2-273634), a method of removing by adsorption with synthetic zeolite and carbon molecular sieves (WO90-10612), and contacting with a metal oxide composition A method (EPO370688Al) and the like have been proposed.

[0006]

However, the above-mentioned method has a problem that the operation is complicated and extremely difficult. In the above method, the reaction proceeds smoothly, but flammable hydrogen gas must be used, which also involves a complicated operation, and thus has a problem. The method (1) has a limit in the co-adsorption phenomenon and the adsorption capacity. Although the method is simple in operation, the life of the metal oxide composition is limited. The problem to be solved by the present invention is CF ₃ CH _{2 which} does not have the above-mentioned disadvantages.
It is intended to provide a method for purifying F.

[0007]

Means for Solving the Problems In view of the above circumstances, the present inventors have conducted intensive studies to develop an industrially practicable purification method of CF ₃ CH ₂ F. Uses activated alumina having distribution and high purity, and Cu, Mg, Zn, Pb, V, Bi,
By supporting at least one metal compound selected from the group consisting of Cr, Mn, Fe, Co and Ni, and then using a partial fluoride catalyst of the metal compound obtained by hydrogen fluoride treatment in the gas phase. , High purity CF ₃ CH ₂ F
Was found with a high yield.

Heretofore, a method of reacting trichlene with HF has been known for producing HFC-134a. This reaction cannot be achieved in one stage, and is carried out by two stages under different reaction conditions. However, various by-products as described above are produced depending on the catalyst, reaction conditions and the like. Conventionally, these by-products have been separated and removed by a conventional method, for example, fractional distillation. However, separation of impurities having a boiling point close to that of the target substance, CF ₃ CH ₂ F, or impurities having an azeotropic composition is performed. Separation and removal by distillation were extremely difficult. In particular, fluoroalkenes were contained as trace impurities even by fractional distillation.

[0009] The present invention in the presence of CF ₃ CH fluoroalkenes a contained in ₂ F catalyst as described above, is reacted with hydrogen fluoride in the vapor phase, CF ₃ CH ₂ F is without reacting , CF ₃ CH ₂ F to remove fluoroalkenes
The fluoroalkenes include CF ₂ ＣCHCl, CCIF ＝ CHF, CHCl ＝ CH
F, CF ₂ = CHF and the like.

The activated alumina useful as a carrier for the catalyst used in the method of the present invention will be described in detail. The activated alumina is a hydrated alumina, which has many amorphous (amorphous) portions according to X-ray diffraction, and is also a boehmite or pseudo-boehmite whose crystallization has not progressed so much or its calcined product, κ, θ, Intermediate aluminas such as δ, γ, η, χ, ρ have been identified. Usually, what is use normal as active alumina is gamma or η- alumina in an alumina gamma, eta
When both phases exist, X-rays cannot be distinguished, and γ /
It is called η alumina.

Activated alumina is usually produced by thermal decomposition of alumina hydrate, ie, controlled heating of the hydrate to remove most of the water. As raw materials of the hydrate, alumina trihydrate, aluminum salt, alkali aluminate, aluminum alkoxide, manufactured by the Bayer method,
There is metal aluminum and the like. When expressed as hydrates, it is possible to use gibbsite, bayerite, nordstrandite (above A
l (OH) ₃ ), boehmite, diaspore (above Al
₂ O ₃ .H ₂ O or AlOOH).

An alumina gel is produced except when using the alumina hydrate according to the Bayer method.
Various alumina hydrates are produced alone or as a mixture depending on conditions such as H, time, and raw material concentration. Each of these hydrates decomposes into a different alumina phase, and the pore structure, specific surface area and physical properties differ accordingly.

The method for producing activated alumina is described in (A)
Thermal dehydration of alumina hydrates such as gibbsite and boehmite, (B) Alumina hydrate (gel) obtained by the reaction of sodium aluminate aqueous solution with aluminum sulfate aqueous solution or carbon dioxide or sodium aluminate powder and sulfurous acid gas
Dehydration of aluminum hydrate obtained by adding aqueous solution of hydroxide or carbonate of ammonia or alkali metal to aqueous solution of aluminum salt (for example, aluminum sulfate, aluminum nitrate, aluminum chloride), aluminum Dehydration of hydrated alumina obtained by the uniform precipitation method in which urea is added to a salt and heating, or addition of carbonate to aluminum sulfate to form basic aluminum sulfate (a kind of alumina hydrosol), and alumina hydrogel obtained therefrom Dehydration, (D) thermal decomposition of aluminum salt, (E) hydrolysis of aluminum isopropoxide, etc. are industrially practiced.

Among these activated aluminas, the most easily available one is synthesized from alumina trihydrate by the Bayer method. This alumina is obtained by heat-treating the obtained gibbsite at about 400 ° C. in an air stream, and is γ / η- containing a small amount of boehmite in X-ray.
Alumina. The specific surface area is about 250 m ² / g,
It has a broad pore diameter distribution with a pore diameter of 35 ° to 10μ, and there are also quite many small pores having a pore diameter of 35 ° or less.

[0015] The pores are composed of cylindrical or spherical holes. This pore size distribution is typically 50,000 psi (35 ° -1).
(Measured with a pore diameter of 77 μm). In addition, about 0.9
% Of Na ₂ O and several hundred ppm of SiO ₂ and Fe ₂ O _3, and it is difficult to reduce the content of Na ₂ O to 0.05% or less.

Activated alumina can also be obtained by rapidly activating Bayer alumina hydrate at 400 to 800 ° C. In this process, the formation of boehmite and the formation of decomposition products are significantly reduced. The pattern is weak,
Amorphous alumina can be produced. By agglomerating or rehydrating this alumina, various forms such as spheres are obtained, and those having crystallites and pore sizes smaller than the former are produced. The specific surface area is a 300~350m ² / g.

When alumina gel is used as a starting material (the above methods B and C), after the precipitate is washed with water and completely drained, the alumina X-rays are pseudo-boehmite. Industrially, this cake is dried and crushed into an extruded cylinder,
It is spray-dried and formed into spherical or pellets as spherical fine particles of about 50 °. This is heat-activated to be activated, thereby obtaining activated alumina. Γ / η-alumina which is nearly amorphous in X-ray and contains a small amount of SiO ₂ or
Contains 3% SO ₃ . In this method, gels having various structures can be synthesized, but the specific surface area is 300 to 600.
m ² / g, which is alumina having many very small pores.

The activated alumina thus obtained has a pore volume of 0.3 to 0.8 ml / g and a specific surface area of 150 to
It has pores of 350 m ² / g and an average pore diameter of about 40 to 150 °. Regarding the pore size distribution, the range is wide, and if the pore size is limited to 40 to 500 °, only about 20% is distributed.

The activated alumina used in the catalyst of the present invention has a center pore diameter of 50 to 400 ° and a center diameter of ± 5.
The pores having a distribution of 0% occupy 70% or more, and the volume of pores having a pore diameter of 0.5 to 1.6 ml / g is appropriate. Those whose distribution is concentrated at a center pore diameter of less than 50 °
It is difficult to obtain industrially, and when used as a catalyst carrier, sufficient activity cannot be obtained, and there is concern about the catalyst life. Even those whose distribution is concentrated at a location exceeding the central pore diameter of 400 ° are not preferable because sufficient catalytic activity cannot be obtained when used as a carrier.

The pore volume of activated alumina is determined by the specific surface area and the pore size distribution, and the value is 0.5 ml / g.
Below, an appropriate specific surface area and pore structure cannot be obtained,
Low catalytic activity. Therefore, in the activated alumina used in the present invention, the volume of the pores having the pore diameter is preferably 0.5 ml / g or more, particularly preferably 0.5 to 1.6 ml / g.

An example of an industrial production method of activated alumina which can be particularly preferably used in the present invention is a sol -gel / oil dropping method (similar to the above-mentioned method C). According to this method, the chemical properties of the spherical sol can be adjusted,
By changing the chemical operation of the sol-gel, it is possible to arbitrarily adjust the bulk density, specific surface area, pore volume, pore diameter and pore distribution of the produced activated alumina.

As a preferred activated alumina, a trialkyl alumina is decomposed into aluminum hydrate (similar to the method E), and then this alumina hydrate is converted into γ-hydrate.
Some are fired on alumina. When this alumina is pressed or extruded into pellets, it is possible to obtain a pellet having a higher purity than pores produced naturally and having a uniform pore diameter and a good pore diameter distribution. Activated alumina used for such a catalyst carrier is commercially available, and has a center pore diameter of 50 to 400 °, pores having a distribution of center diameter ± 50% account for 70% or more, Activated alumina having a pore volume with a pore diameter of 0.5 to 1.6 ml / g may be selected.

This activated alumina has a diameter of 20 m so that it can be conveniently used as a catalyst when charging and discharging the reactor.
m or less, preferably several mm or so, in the form of particles, beads or extruded products. Regarding impurities in the activated alumina, it is necessary that the content of sodium is 100 ppm or less, preferably as small as possible. Further, it is preferable to select an activated alumina containing less than 300 ppm of silicon, and it is preferable that the purity of the alumina is 99.9% or more. When sodium or silicon is present in the catalyst as an oxide, it exhibits an activity inhibiting effect, a reaction inhibiting effect such as generation of silicon fluoride by hydrofluoric anhydride, isomerization, and promotion of disproportionation reaction. It is preferable not to make it exist.

As a method for producing the present catalyst, a usual method can be applied. For example, the catalyst can be produced by impregnating an activated alumina with an aqueous solution of cobalt chloride, drying and calcining under an 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 fluoroalkenes is slowed, and at a higher temperature, the target compound HFC-134a and HCFC-133a is not reacted. Reaction and decomposition occur undesirably. Also, CF ₃ CH ₂
The molar ratio of hydrogen fluoride and fluoroalkenes in F the reaction if an equimolar or proceeds smoothly. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0026]

【Example】

Preparation Example 1 A catalyst was prepared using 3.2 mmφ spherical high-purity activated alumina (JST Universal Co., Ltd. product NST-3) having the following physical properties. This activated alumina is sol-gel /
It is manufactured by the oil dropping method and has the following physical properties. With a central pore diameter of 300 、, 163-444Å
Activated alumina having a pore diameter of 1.3 ml / g, a purity of 99.93% by weight, and a sodium content of 10 ppm was obtained.

0.7 g of cobalt chloride (CoCl ₂ ) was dissolved in 52 ml of pure water.
immersed in the solution to make the alumina absorb the entire amount of the catalyst solution. 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 is filled in a glass firing tube, and air is supplied at a space velocity (SV ₀ ) of 500.
The mixture was flowed at Hr ⁻¹ , heated to 400 ° C., and calcined for 8 hours to obtain a catalyst.

Preparation Examples 2 to 11 Instead of cobalt chloride (CoCl ₂ ) of Preparation Example 1, 3.30 g of NiCl ₂ .6H ₂ O (Preparation Example 2)
3.54 g of ZnCl ₂ (Preparation Example 3), 1.7 of FeCl ₃
6 g (Preparation Example 4), 1.78 g of VCl ₃ (Preparation Example 5),
1.17 g of MnCl ₂ .4H ₂ O (Preparation Example 6), Cu
(CH ₃ COO) ₂ .H ₂ O 2.24 (Preparation Example 7), B
1.82 g of iCl ₃ (Preparation Example 8), MgCl ₂ .6H ₂
3.95 g of O (Preparation Example 9), Pb (CH ₃ COO) _2.
3H ₂ O2.17 (Preparation Example 10), CrCl ₃ · 6H ₂
A catalyst was obtained in the same manner as in Preparation Example 1, except that 8.2 g of O (Preparation Example 11) was used.

Preparation Example 12 0.7 g of cobalt chloride (CoCl ₂ ) was dissolved in 52 ml of pure water, and NiCl ₂ .6H ₂ O was added thereto as a second component.
0.33 g was added and dissolved, and activated alumina (NST-
3) A catalyst was obtained in the same manner as in Preparation Example 1, except that 100 ml of the catalyst was immersed and the entire amount of the catalyst solution was absorbed in alumina.

Preparation Example 13 A catalyst was prepared by using 1.6 mmφ spherical high-purity activated alumina (NST-7 manufactured by JGC Universal Co., Ltd.) having the following physical properties. This activated alumina is also sol-gel /
It is manufactured by the oil dropping method and has the following physical properties. A pore having a central pore diameter of 80 ° and having a distribution of 50 to 100 ° occupies 94%, an activity having a pore diameter of 0.6 ml / g, a purity of 99.93% by weight, and a sodium content of 10 ppm. Alumina.

0.7 g of cobalt chloride (CoCl ₂ ) was dissolved in 30 ml of pure water.
1 was immersed, and the catalyst was obtained in the same manner as in Preparation Example 1 except that the entire amount of the catalyst solution was absorbed in alumina.

Comparative Preparation Example 1 A catalyst was prepared in the same manner as in Preparation Example 1 except that the activated alumina shown in Preparation Example 1 was replaced with activated alumina having the following physical properties (Sumitomo Chemical, KHA-24). This activated alumina shows only a broad pore distribution in the pore diameter range of 40 to 450 °, and has about 20% of pores having a diameter of 40 ° or less. The sodium content is about 1900ppm
, Purity is 98.4% by weight.

Comparative Preparation Example 2 Instead of cobalt chloride (CoCl ₂ ) of Preparation Example 1, C
A catalyst was obtained in the same manner as in Preparation Example 1, except that 1.76 g of sCl was used.

Raw Material Example 1 A crude purification process recovered from HFC-134a produced by reacting trichloroethylene (CCl ₂ ＣCHCl) with hydrogen fluoride in the gas phase in the presence of a chromium catalyst in the presence of a chromium catalyst is as follows. It was a 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 9.5060 CHF ₂ CHF ₂ 0.1600 CF ₃ CCl ₂ F 0.0540 HCl 0.5620 CF ₃ CHF ₂ 0.5320 CF ₂ = CHCl 0.4420 Unit: mol%

Example 1 An Inconel 600 reactor having an inner diameter of 1 inch and a length of 1 m was charged with 80 ml of the catalyst prepared as shown in Preparation Example 1. Before the reaction, the catalyst was partially fluorinated using hydrogen fluoride diluted with nitrogen and 100% hydrogen fluoride to activate the catalyst. Hydrogen fluoride concentration: 25 to 100% Processing temperature: 250 to 350 ° C Processing time: about 10 hours

Using the catalyst thus obtained, the raw material example 1 was supplied at a reaction temperature of 200 ° C. as a raw material at a space velocity (SV ₀ ) of 800 Hr ⁻¹ with respect to the catalyst, and the exhaust gas was removed of acid. The composition was analyzed using gas chromatography, and as a result, the following composition was obtained.

CF ₃ CH ₂ F 90.5407 CF ₃ CHF ₂ 0.5916 CF ₃ CCl ₂ F 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%

The CF ₃ CH ₂ F in the unsaturated impurities (fluoroalkenes) may be 100% removed, further CF ₃ CH ₂ F loss not be hardly recognized as the target compound, also other products There was no increase or decrease.

Examples 2 to 13 The reaction was carried out in the same manner as in Example 1 except that the catalysts prepared as shown in Preparation Examples 2 to 11 and Preparation Examples 12 and 13 were used. It was removed and the gas composition was analyzed using a gas chromatograph. Table 1 shows the results of the removal rates of the fluoroalkenes.

[0041]

[Table 1]

Example 14 The reaction was carried out in the same manner as in Example 1 except that the reaction temperature of the catalyst used in Example 6 was changed to 230 ° C., the exhaust gas was removed from the acid, and the gas composition was changed using gas chromatography. analyzed. The removal rate of fluoroalkenes was 100%.

By increasing the reaction temperature , 100% of the fluoroalkene can be removed, and the target compound, CF ₃ CH
Of ₂ F loss was hardly recognized.

Comparative Examples 1-2 The reaction was carried out in the same manner as in Example 1 except that the catalysts prepared as in Comparative Preparation Examples 1 and 2 were used. And analyzed. Table 2 shows the results of the removal ratio of fluoroalkenes.

[0045]

[Table 2]

[0046]

According to the present invention, fluoroalkenes in CF ₃ CH ₂ F, which have been very difficult in the past, can be efficiently removed, and high-purity CF ₃ CH ₂ F can be efficiently obtained.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-184015 (JP, A) JP-A-6-72912 (JP, A) JP-A-4-321632 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C07C 17/395 C07C 19/08

Claims (2)

(57) [Claims] 1. A pore having a central pore diameter of 50 to 400 °, a pore having a distribution of the central diameter ± 50% occupies 70% or more, and a volume of pores having a pore diameter of 0.5 to 1.6 ml / g. Activated alumina having a purity of 99.9% by weight or more and a sodium content of 100 ppm or less produced in the range described above is used as a catalyst carrier, and Cu, Mg, Zn, Pb, V, Bi, Cr,
Mn, Fe, at least one metal compound selected from the group consisting of Co and Ni is supported, and then subjected to hydrogen fluoride treatment in the gas phase to obtain a partial fluoride catalyst of the metal compound. 1,1,1,2-tetrafluoroalkylenes contained in 1,1,2-tetrafluoroethane are reacted with hydrogen fluoride in a gas phase to reduce the content of fluoroalkenes. A method for purifying fluoroethane. 2. The fluoroalkene contained in 1,1,1,2-tetrafluoroethane is 1,1-difluoro-2-chloroethylene, 1,2-difluoro-1-chloroethylene, 1-chloroethylene. The purification method according to claim 1, wherein one or more of -2-fluoroethylene and 1,1,2-trifluoroethylene are used.