JP2675533B2 - Method for producing 1,1,1,2-tetrafluoroethane and catalyst for its synthesis - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to 1,1,1-trifluoro-2-chloroethane (CF ₃ CH ₂ Cl, HCFC
-133a) and hydrogen fluoride (HF) 1,1,1,
2-tetrafluoroethane (CF ₃ CH ₂ F, HFC-
The invention relates to a method for producing a synthesis catalyst for producing 134a) with high selectivity and a method for producing CF ₃ CH ₂ F using the same.

[0002]

_2. Description of the Related Art Dichlorodifluoromethane (CF ₂ Cl
_{2. Since} CFC-12) is harmless to the human body and has excellent thermodynamic characteristics, it has been used as one of the typical refrigerants for various refrigeration equipment such as automobile air conditioners and refrigerators. However, many studies and studies have shown that CF ₂
It has become clear that Cl ₂ is one of the major substances that destroys the stratospheric ozone layer. The internationally recognized Montreal Protocol (1987) classifies CF ₂ Cl ₂ as one of the compounds whose production and use should ultimately be banned.

CF ₃ CH ₂ F has a refrigerant performance of CF ₂ Cl ₂
CF ₃ CH ₂ F has a ozone depletion potential (OD)
P) does not have. Further, the global warming effect (GWP) is lower than that of CF ₂ Cl ₂ . For this reason, CF ₃ CH ₂ F has been the subject of investigation and research as an alternative substance of CF ₂ Cl ₂ .

CF ₃ CH ₂ F has the following formula:
1,1-trifluoro-2-chloroethane (CF ₂ CH
₂ Cl, HCFC-133a) and hydrogen fluoride (HF).

[0005]

Embedded image CH ₃ CH ₂ C1 + HF → CF ₃ CH ₂ F + HC1

However, as is generally well known, the chlorine atom of CF ₃ CH ₂ Cl is not easily replaced by a fluorine atom. Therefore, a catalyst is required to accelerate this reaction.

Chromium oxide (Cr ₂ O ₃ ) is CF ₃ CH
_{As a 2} Cl fluorination catalyst, it is known to have better performance than other catalysts. For example, JP
-105404, U.S. Pat. No. 4,153,678
No. 1,117,145 and Canadian Patent No. 1,117,145, there is disclosed 200 chromic hydroxide obtained by treating a trivalent chromium compound (for example, chromic nitrate, chromic chloride) with ammonia. A method of making a chromic oxide catalyst that is calcined at ~ 500 ° C is disclosed. European Patent Publication No. 0313061A discloses a method for producing a chromic oxide catalyst by thermally decomposing ammonium dichromate at 500 to 600 ° C.

However, these chromic oxide catalysts have various problems in terms of catalyst life and selectivity of reaction products. Generally, the fluorination reaction is carried out at a temperature of 350 ° C. or higher, but at such a high temperature, the organic compound is easily decomposed during the reaction, and the catalytic activity is rapidly lowered due to the deposition of carbon produced.

European Patent No. 0328127 and German Patent No. 293234 disclose that a certain amount of oxygen is supplied onto the catalyst together with the reaction raw material in order to prevent the activity of the catalyst from decreasing. However, in the presence of oxygen, HCl may be oxidized in the reaction system to generate chlorine gas, which is a reaction raw material CF ₃ CH _3.
Further reaction with ₂ Cl produces various by-products, which makes it difficult to separate and purify CF ₃ CH ₂ F in the reaction product. Especially, since the boiling point of CF ₂ : CHCl (HCFC-1122) is extremely close to the boiling point of the target substance CF ₃ CH ₂ F,
This separation requires high technology and more stringent reaction conditions. Therefore, the above method is not a practical solution to decrease the catalytic activity.

In addition, in order to activate the chromium (II) oxide catalyst, it is thoroughly dried under a nitrogen atmosphere at 400 ° C. for 5 to 10 hours and then before being used in the following reaction with CF ₃ CH ₂ Cl. , At 200 to 400 ° C. for 1 to 10 hours,
Pretreatment with HF is required. This pretreatment with HF converts a part of the chromic oxide into chromium oxyfluoride (CrO _x F _y ) which is said to be effective for fluorination.
However, this pretreatment produces water as a by-product by the following reaction.

[0011]

## STR2 ## _{Cr 2 O 3 + aHF → C} r O x F y + bH 2 O

The water produced as a by-product in this way remarkably increases the corrosiveness due to HF and HCl existing in the reactor.
This severely affects the durability of the reactor and requires additional equipment to separate the reaction products. Further, when recovering and reusing the unreacted material, the activity and durability of the catalyst may be reduced unless the water content is completely removed.

US Pat. No. 4,129,603 discloses a chromium oxyfluoride catalyst obtained by treating chromic hydroxide (Cr (OH) ₃ ) with HF in the presence of water vapor to form a CF ₃ fluoride catalyst.
It is disclosed for use in the production of CH ₂ F. However, the selectivity for chromium oxide fluoride catalyst is at most 91.
˜95%, especially CF ₂ : CHCl (target CF ₃
A _second reactor is required for the removal of by-products, since a considerable amount of CH ₂ F and its boiling point are by-produced.

German Patent No. 2,932,934 discloses
The use of chromic fluoride or chromic oxide fluoride is disclosed as a catalyst for fluorinating CF ₃ CH ₂ Cl with HF. When fluorinated in the presence of this catalyst at 400 ° C. and a molar ratio of 7.7, the target CF ₃ CH ₂ F initially contained 26%.
In a yield of However, after reacting for 44 hours in the anoxic state, the catalyst activity drops to 22%.

EP 0 328 127 states that alumina supported metal catalysts are effective in the production of CF ₃ CH ₂ F. Compared to the chromic oxide catalyst, the metal catalyst has an advantage that the by-product does not increase even when oxygen is supplied, but the selectivity to CF ₃ CH ₂ F in the reaction product is 93% of that of the chromic oxide. 55.2 against 0.7%
% And low.

[0016]

Therefore, an object of the present invention is to convert CF ₃ CH ₂ Cl and HF into CF ₃ CH ₂ F.
It is an object of the present invention to provide a method for producing a catalyst, which is effective in the synthesis of the above and has a significantly low activity reduction rate.

Another object of the present invention, by using the catalyst of the present invention, a high reaction conversion and high selectivity to the desired product, produce CF ₃ CH ₂ F from CF ₃ CH ₂ Cl and HF Is to provide a way to do.

[Means for Solving the Problems]

The present invention is directed to magnesium chromate (MgC
rO ₄ ) or magnesium dichromate (MgCr ₂ O ₇ ).
The method for producing a catalyst for synthesizing CF ₃ CH ₂ F is characterized in that HF and ethanol are reacted with each other, and the resulting product is calcined.

Another aspect of the present invention is a method for producing CF ₃ CH ₂ F from CF ₃ CH ₂ Cl and HF with high conversion and selectivity using the above-mentioned catalyst of the present invention.

The catalyst of the present invention is CF ₃ CH _{2 in} comparison to conventional catalysts which require oxygen to be supplied with the reactants in order to prevent a rapid decrease in activity due to carbon deposition.
The selectivity for CF ₃ CH ₂ F in the reaction product can be improved without the need to supply oxygen during the F synthesis reaction. Therefore, the desired CF ₃ CH ₂ F is more easily separated from the reaction product.

The catalyst of the present invention is easy to operate in the reactor and does not generate water, so that it significantly reduces the corrosion of the reactor.

The catalyst of the present invention may contain unreacted magnesium chromate or magnesium dichromate. Further, MgF ₂ may be included in the catalyst composition. M
Although gF ₂ has little effect on the activation of the catalyst, it has the effect of improving the mechanical strength of the catalyst. Magnesium chromate or magnesium dichromate and MgF ₂ are 1:
Mix in a molar ratio of 0 to 1: 5.

[0023]

EXAMPLES The present invention will be specifically described below with reference to examples, but the examples are for the purpose of illustration and the present invention is not limited thereto.

The conversion of CF ₃ CH ₂ Cl and the selectivity to CF ₃ CH ₂ F used here are defined by the following equations, respectively.

[0025]

(Equation 1)

Example 1 Preparation of Catalyst 226 g of MgCrO ₄ .7H ₂ O and MgF ₂ 186
The mixture of g, 400 ml of 30% HF aqueous solution and 100 ml of 95% ethanol was reacted at room temperature for 1 hour, and the product was filtered and dried. The dried product was calcined at 400 ° C for 5 hours to form 4mm x 4mm cylindrical pellets.
This pelletized catalyst was used in the CF ₃ CH ₂ F synthesis reaction.

Example 2 Production of Catalyst A catalyst was produced in the same manner as in Example 1 except that 310 g of MgF ₂ was mixed.

Example 3 Preparation of Catalyst A catalyst was prepared in the same manner as in Example 1 except that MgF ₂ was not mixed.

Example 4: Preparation of catalyst ₂ MgCr ₂ O ₇ was used instead of MgCrO ₄ .7H ₂ O.
A catalyst was produced in the same manner as in Example 1 except that 40.3 g was used.

Example 5: Production of CF ₃ CH ₂ F 50 g of the pellet catalyst obtained in Example 1 was added to an Inconel-600 tube (diameter: 2.54 cm, length: 30 cm, Super Tube Co). ., PA, USA). Nitrogen gas heated gradually to 400 ° C. was supplied to the reactor at a rate of 50 ml / min to remove traces of water remaining in the catalyst. CF ₃ CH ₂ C
1 and HF were fed to the reactor at a molar ratio of 1: 7 and a contact time of 30 seconds, while the reactor temperature was lowered and maintained at 375 ° C. The reaction product was washed with an aqueous MgO suspension, washed with water to remove HF and HCl, dried over CaCl ₂ , and finally cooled to −60 ° C. to recover the reaction product.
The reaction product is Porapak N Column
Was analyzed by gas chromatography. As a result, C
The conversion of F ₃ CH ₂ Cl is 25.6% and CF ₃ CH ₂
It was found that the selectivity to F was 98.2%.

Examples 6 to 11: Production of CF ₃ CH ₂ F Using the catalysts obtained in Examples 1 to 4, according to the reaction temperature, HF / CF ₃ CH ₂ Cl molar ratio and contact time shown in Table 1. , CF ₃ CH ₂ F respectively according to the method of Example 5.
To produce CF ₃ CH ₂ Cl conversion and CF ₃ CH ₂
The selection rates for F are shown in the same table.

[0032]

[Table 1]

Example 12 This example confirms the catalytic activity of the catalyst of the present invention after being used for a long time without supplying oxygen. That is, using the catalyst prepared in Example 5, Example 5
Under the same conditions as above, CF ₃ CH ₂ F was produced for 720 hours. As a result, it was confirmed that the conversion rate of CF ₃ CH ₂ Cl was 24.8%. This is 96% of the initial activity of this catalyst
It shows that the above activity was maintained.

[0034]

INDUSTRIAL APPLICABILITY The CF ₃ CH ₂ F synthesis catalyst of the present invention does not require the introduction of oxygen, maintains the catalytic activity for a long time, and since there is no by-product of water, there is no corrosion of the apparatus and generation of by-products Since the amount is small, separation and purification of the target product is easy. By using this catalyst, CF ₃ CH ₂ F can be produced extremely easily.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Ken Yuu, 42, Myeongyeon-dong, Koto-ku, Seoul, Republic of Korea, No. 607, 1 apartment, Usei apartment

Claims (4)

(57) [Claims] 1. A method comprising reacting magnesium chromate (MgCrO ₄ ) or magnesium dichromate (MgCr ₂ O ₇ ) with hydrogen fluoride and ethanol, and calcining the obtained product. , 1,2-tetrafluoroethane (CF ₃ CH ₂ F) method for producing a catalyst for synthesizing. 2. A method for producing a CF ₃ CH ₂ F synthesis catalyst, wherein magnesium fluoride (MgF ₂ ) is mixed with the synthesis catalyst of claim 1. 3. The method for producing a synthesis catalyst according to claim 2, wherein the molar ratio of magnesium fluoride contained in the synthesis catalyst is less than 5 with respect to magnesium chromate or magnesium dichromate. 4. CF ₃ CH ₂ Cl and H using the synthesis catalyst obtained by the production method according to claim 1.
A method of reacting F to produce CF ₃ CH ₂ F.