JPH0592141A - Method for activating and regenerating chromium type fluorinating catalyst - Google Patents

Abstract

PURPOSE:To repeatedly activate a catalyst lowered in its activity, in the activation and regeneration of a fluorinating catalyst of halogenated hydrocarbon based on chromium, by successively applying oxidizing treatment and reducing treatment whose temp. ranges are respectively specified to the used catalyst. CONSTITUTION:When a fluorinating catalyst of halogenated hydrocarbon based on chromium used as an aerosol, a refrigerant, a foaming agent or a solvent lowered in its activity is activated, at first, oxidizing treatment bringing said catalyst into contact with oxidative-gas (O2, N2O or O3) at 150-500 deg.C is performed and, subsequently, reducing treatment bringing the catalyst into contact with reductive gas (H2, CO or NO) at 100-500 deg.C is performed. In succession to these treatments, reaction may be resumed immediately but it is pref. to resume reaction after the catalyst is again treated with HF. By these treatments, the activity of the catalyst can be restored up to the initial activity level without scattering effective components.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for activating and regenerating a fluorination catalyst containing chromium as a main component, which is used in a fluorination reaction of halogenated hydrocarbons.

[0002]

2. Description of the Related Art Halogenated hydrocarbons containing fluorine are called chlorofluorocarbons, and they are aerosols, refrigerants, blowing agents,
It has a wide range of uses as a solvent. In recent years, CFCs containing chlorine may damage the ozone layer. Therefore, halogenated hydrocarbons containing hydrogen (generally abbreviated as HCFC) that do not damage the ozone layer and fluorohydrocarbons that do not contain chlorine ( (Generally abbreviated as HFC) is attracting attention as a CFC alternative to CFCs that destroy the ozone layer.

When producing halogenated hydrocarbons containing hydrogen by a gas phase catalytic reaction, chromium-based catalysts have been conventionally used because of their high activity.

[0004]

However, the above-mentioned hydrogen-containing CFCs (HCFC, H
It is recognized that when a chromium-based catalyst is used in the production of FC), the catalytic activity is reduced more rapidly than in the case of producing CFCs containing no hydrogen. Therefore, in order to use a chromium-based catalyst for the production of HCFCs and HFCs, it is necessary to develop an effective activation regeneration method or a method for maintaining the activity for a long period of time.

As a method of maintaining the activity of the chromium-based catalyst, for example, a method of entraining Cl ₂ in the raw material (Japanese Patent Publication No. 52-52).
No. 33604), a method of entraining O ₂ (Japanese Patent Publication No. 56-23407), etc., but in the production of the halogenated hydrocarbon containing hydrogen, almost no activity maintaining effect is observed. Not only that, but it also has the drawback of increasing unwanted by-products.

As a method for activating and regenerating a deteriorated catalyst, chromium fluoride treated with oxygen is added to the deteriorated catalyst in a ratio of 10 to 50% (Japanese Patent Publication No. 49-4715).
8) A method of reactivating oxygen by passing oxygen through the catalyst when a decrease in activity is observed (JP-B-62-44973, JP-A-1).
However, if the catalyst treated with oxygen is used as it is in the fluorination reaction, the active ingredient will be scattered, and if it is used for a long period of time, the activity will be decreased and the treatment of the scattered substance will be a problem. In addition, depending on the reaction, the catalyst just treated with oxygen may increase undesired by-products.

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that when reactivating a fluorinated catalyst of a halogenated hydrocarbon whose main component is chromium whose activity has been lowered, an oxidizing gas is used. It has been discovered that the catalytic activity can be recovered without scattering the active component of the catalyst by sequentially performing the oxidizing treatment for contacting and the subsequent reducing treatment for contacting with a reducing gas. Since the active ingredient of the catalyst does not scatter, the activity can be maintained for a long period of time even after the regeneration, and even if the activation regeneration is repeated, the same activity as the initial stage can be obtained. Furthermore, HCFC-133a
It was also found that in the fluorination reaction, etc., higher selectivity can be obtained with a catalyst that also uses a reduction treatment in comparison with a catalyst that has only been treated with oxygen.

The present invention has been made on the basis of the above findings, and provides a method for activating and regenerating a fluorination catalyst which can regenerate the chromium-based fluorination catalyst having a reduced activity to its original state even after repeated activation. The purpose is to do.

[0009]

In the method for activating and regenerating a fluorination catalyst for halogenated hydrocarbons containing chromium as a main component according to the present invention, first, a temperature of 150 to 500 ° C. is contacted with an oxidizing gas. The oxidation treatment and the subsequent reduction treatment of contacting with a reducing gas at a temperature of 100 to 500 [deg.] C. were successively performed, which was a means for solving the problem.

Following these oxidation treatments and reduction treatments, the reaction may be restarted immediately.
It is desirable to restart the reaction after treatment. this is,
Not only is the water generated by the reduction treatment adsorbed to the catalyst and the water generated when the excessively oxidized catalyst is re-fluorinated caused a problem on the corrosion of the equipment, but it is also removed.
This is because the treatment can change the catalyst to a more active state.

The catalyst activation regeneration method of the present invention can be applied to the production of general halogenated hydrocarbons. Ie HF
It is effective when a chromium-based catalyst is used in the fluorination reaction by OH and the halogen exchange reaction between halogenated hydrocarbons.

In the case of producing a hydrogen-containing halogenated hydrocarbon that does not or hardly destroys the ozone layer, which has been attracting attention in recent years, that is, CH ₂ Cl ₂ , CHCl ₃ , CH.
Cl = CCl ₂ , CH ₂ = CCl ₂ , CCl ₂ = CCl
₂ , CH ₃ CCl ₃ , CF ₃ CHCl ₂ , CF ₃ CH ₂
When the reaction of fluorinating Cl, CF ₂ ClCF ₂ CHCl ₂ , etc. with HF is carried out with a chromium-based catalyst, the present invention is particularly effective because the activity decreases quickly.

As the fluorination catalyst containing chromium as the main component, Cr ₂ O ₃ , CrF ₃ and chromium oxyfluoride Cr are used.
A so-called chromium simple catalyst such as O _x F _y , a supported catalyst in which these chromium compounds are supported on activated carbon, alumina, AlF ₃ , TiO _2, etc., and further Mg, Ca, Sr,
Examples thereof include multi-component catalysts containing at least one metal such as Ba, Mn, Co, Ni, Cu, Ag and Al.

Now, the hydrogen-containing halogenated hydrocarbons 1,
1,1,2-Tetrafluoroethane (HFC-134a
The method of to) abbreviated To explain the Cr-based catalyst as an example and, in JP 55-27138 CrF ₃ · 3H ₂
A catalyst in which O is calcined with air, a catalyst in which chromium hydroxide is activated by HF, and a catalyst in which Cr is supported on activated carbon are disclosed, and JP-A-2-172933 discloses Cr,
A catalyst prepared from a hydroxide obtained by a coprecipitation method from an aqueous nitric acid solution of Al and Mg is disclosed as a catalyst having excellent durability.

The following two factors can be considered as the causes of the decrease in the activity of the fluorination catalyst.

One is due to the phenomenon of so-called coking, in which the raw materials or the organic matter produced are deposited on the surface of the catalyst in a large amount and deposited on the surface to inhibit the action of active sites.

The other one is due to the phenomenon that the catalyst is excessively fluorinated by HF during the reaction and becomes inactive.

In the case of Cr-based catalysts as well, when the deteriorated catalyst is analyzed, carbon adhesion and excessive fluorination are often observed to decrease the oxygen content of the catalyst, and the above factors contribute to the activity decrease. It is estimated that

Therefore, in order to regenerate such a deteriorated catalyst, it is necessary to remove carbons adhering to the surface and supply oxygen to the catalyst having advanced fluorination until the original oxygen content is reached. As a method for this, a method of treating the catalyst with an oxidizing gas can be considered.

Oxidizing gases include O ₂ , N ₂ O, O ₃
Although like can be used, ease of handling, O ₂ is preferred for reasons such as ready availability. When the treatment temperature is 150 ° C. or lower, the oxidation reaction of the catalyst itself or the adhering carbon does not proceed, and at 500 ° C. or higher, the catalyst is excessively oxidized or the particle growth is promoted to decrease the specific surface area. It is preferable to set the temperature to ˜500 ° C., especially 250 to 450 ° C.

The oxidizing gas can be used in a concentration range of 0.1 to 100%, but it is not preferable to use a high concentration of oxidizing gas because it promotes the scattering of the active ingredient of the catalyst. On the other hand, if the concentration is too low, the processing time will be long,
It is preferable to use it after diluting it with an inert gas such as N ₂ or Ar so that the concentration of the oxidizing gas becomes 1 to 30%.

The treatment pressure is not particularly limited, but it is suitable to carry out the treatment at around atmospheric pressure in terms of operation and handling. The flow rate of the gas used is 10 to 1000 in GHSV (converted to standard state) in consideration of the time required for the treatment, the effective reaction rate of the oxidizing gas, and the like.
0Hr ^-1 is suitable.

When the oxidizing gas is supplied to the deteriorated catalyst under the above conditions, heat is generated, and gases such as CO, CO ₂ and H ₂ O are generated. It is desirable to continue the treatment until the generation of gas such as CO and CO ₂ is no longer recognized, but if it takes too long, the treatment may be terminated when the catalyst layer no longer generates heat.

When HF, which is a reaction raw material, is supplied to the catalyst which has been subjected to only the above-described oxidation treatment, scattering of the active ingredient of the catalyst is recognized, and when the catalyst is used for a long period of time, the activity is lowered and the scattered matter is treated. Also becomes a problem. Therefore, it becomes necessary to suppress the scattering of the active ingredient.

The above problems can be solved by continuously using the reduction treatment and the oxidation treatment together. That is, a reducing gas is supplied to the catalyst after the oxidation treatment under the following conditions to perform the reduction treatment. The treatment temperature is 100 to 500 ° C., preferably 250 to 100 ° C., because the reduction reaction hardly progresses at 100 ° C. or less and the unfavorable excessive reduction of the catalyst proceeds at 500 ° C. or higher.
It is carried out in a temperature range of ˜450 ° C.

[0026] As the reducing gas, H _2, CO, may be used, such as NO, reducing power, it is for reasons of easy handling and the like used and H ₂ is appropriate. The reducing gas can be used at a concentration of 0.01 to 100%, but for safety in handling, the concentration of H ₂ is 0.1 to 4%, and CO is 0.1 to 12%. It is desirable to use.
Similar to oxygen treatment, the pressure is near normal pressure and the gas flow rate is GHSV.
10 to 10000 Hr ^-1 (converted to standard state) is suitable. Since the reduction treatment is also an exothermic reaction, it is desirable to perform the treatment until the reaction rate of the reducing gas reaches 0%, but it may be determined that the catalyst layer does not generate heat as the termination criterion.

As described above, by performing the reduction treatment after the oxidation treatment, the activity can be restored to the initial activity level without scattering the active ingredient. In addition, as described in the examples, the effect of suppressing the production of undesired by-products can be expected depending on the reaction by using the reduction treatment together.

The activation regeneration treatment of the present invention can be carried out at any time, including before the reaction, and is also effective as a calcination method at the time of catalyst preparation.

[0029]

EXAMPLES The present invention will be specifically described with reference to Examples and Comparative Examples. In the description, the gas flow rate and space velocity (SV) are all values converted into the standard state.

Example 1 (Catalyst preparation) CrCl ₃ .6H ₂ O: 111 g of pure water:
It was dissolved in 77 g, and 100 g of high-purity (99.93 wt%) activated alumina: 100 g was immersed to absorb the whole amount of the catalyst liquid. This was dried at 120 ° C. for 3 hours and then under air flow (SV =
Baking was performed at 200 hr ⁻¹ ) at 400 ° C. for 3 hours, and further under H ₂ flow (SV = 200 hr ⁻¹ ) at 350 ° C. for 3 hours.

(HF treatment) Catalyst 3 obtained by the above calcination
Fill 0 ml of Inconel reaction tube and
Treated with F. Treatment conditions Temperature: 250 to 450 ° C. HF concentration: 1 to 100 mol% (however, dilution was performed with N ₂ ) SV: 400 hr ⁻¹

When the HF treatment was carried out, the outlet gas of the reaction tube was bubbled into a dilute nitric acid trap to collect and analyze the scattered components, but nothing was detected and the catalyst components were not scattered. showed that.

(Fluorination reaction) After HF treatment, the reaction temperature was continuously set at 330 ° C., 1 atm, HF: 40
0 ml / min and 1,1,1-trifluorochloroethane (HCFC-133a) 100 ml / min were supplied to start the reaction. When the reaction was continued for 300 hours, the conversion rate of HCFC-133a was 3.1% compared to the initial rate.
Fell.

(Oxidation and reduction treatment) The above-mentioned activity is lowered,
30 ml of the catalyst packed in the Inconel reactor is
Hold at 50 ° C, air: 63 ml / min, N ₂ : 18
7 ml / min was supplied and oxidation treatment was performed for 10 hours. Next, after purging the inside of the reactor with N ₂ , 350 ° C.
Kept at H _2, 3.5 ml / min, N ₂ : 172 m
l / min was supplied and reduction treatment was performed for 2 hours.

(HF treatment) After that, the reactor was set at 330 ° C., HF gas: 400 ml / min was supplied, and the catalyst was subjected to HF treatment again. Scattering of the catalyst component was not recognized even in this HF treatment.

(Restart of fluorination reaction) HF: 400
HCFC-133a was further supplied at 100 ml / min in the air flow of ml / min to restart the reaction. HCF
The conversion rate of C133a was the same as that of the 5th hour of the previous fluorination reaction, indicating that the activity was restored. Further, the selectivity of the produced HFC-134a was 98.7%, which was equivalent to the initial level.

(Repetition of activation treatment) Further, the reaction was continued under the same conditions, and an activation treatment consisting of an oxidation treatment, a reduction treatment and an HF treatment was performed every 300 hours in the reactor.
The results are shown in Table 1.

[0038]

[Table 1]

Example 2 HC was used for 300 hours under the same conditions using the same catalyst as in Example 1.
30 ml of the deteriorated catalyst used for the fluorination reaction of FC-133a was kept at 350 ° C., and N ₂ O was 10 ml / mi.
Then, 160 ml / min of n and N ₂ was supplied and oxidation treatment was performed for 8 hours. Then, after purging the inside of the reactor with N ₂ ,
The temperature was maintained at 350 ° C., 3.5 ml / min of H ₂ was supplied, reduction treatment was performed for 2 hours, HF treatment was performed, and then fluorination reaction of HCFC-133a was performed again under the same conditions. The results are shown in Table 2.

[0040]

[Table 2]

Comparative Example 1 Using the same catalyst as in Example 1, under the same conditions for 300 hours, H 2
Catalyst 30m used for CFC-133a fluorination reaction
Among the activation treatments performed in Example 1, the oxidation treatment and the HF treatment were performed on 1 and the fluorination reaction of HCFC-133a was performed again.

As a result, the conversion rate of HCFC-133a was 19.7%, which was not different from that of Example 1, but the by-product dichlorofluoroethylene (HCFC-112) was used.
1), 1,1-difluoro, 1,2-chloroethane (HC
FC-132b) and the like increased, and the selectivity of HFC-134a was 98.2%, which was lower than that of Example 1, and decreased with time, and decreased to 96.8% after 100 hours.

In addition, C contained in the catalyst in the HF treatment
2% of r was scattered. From this result, it can be seen that the reduction process is necessary.

Example 3 In the same manner as in Example 1, 30 ml of the catalyst prepared and activated was kept at 300 ° C., and HF was 210 ml / mi at 1 atm.
n, trichlorethylene (CHCl = CCl ₂ ) 42 m
l / min was supplied and the fluorination reaction was continued for 500 hours to generate HCFC-133a. After that, the activation treatment of Example 1 was performed, and the reaction was performed again under the same conditions. The results are shown in Table 3.

[0045]

[Table 3]

Example 4 50 ml of the catalyst prepared and activated in the same manner as in Example 1 was added to 3 parts.
Hold at 30 ° C, HF at 1 atm: 140 ml / min,
Perchlorethylene (CCl ₂ = CCl ₂ ): 25 ml
/ Min was supplied and the fluorination reaction was carried out for 500 hours. Then, the same activation treatment as in Example 1 was performed, and the fluorination reaction was restarted under the same conditions. The results are shown in Table 4.

[0047]

[Table 4]

Example 5 2 ml of 30 ml of catalyst prepared and activated in the same manner as in Example 1
Hold at 50 ° C., HF at 1 atm: 200 ml / min,
Dichloromethane (CH ₂ Cl ₂ ): 50 ml / min was supplied and the fluorination reaction was continued for 500 hours to obtain difluoromethane (CH ₂ F ₂ ). Then, the same activation treatment as in Example 1 was performed and the reaction was restarted under the same conditions. The results are shown in Table 5.

[0049]

[Table 5]

Example 6 Commercially available CrF ₃ .3H ₂ O was tableted into pellets and 3
0 ml was filled in an Inconel reactor and air was passed (S
V200hr ^-1 ) It baked at 500 degreeC for 2 hours. Then
After being kept at 400 ° C. and subjected to HF treatment with HF gas, the temperature was lowered to 350 ° C. under an HF gas flow, and HF at 1 atm:
180 ml / min, HCFC-133a: 45 ml /
min is supplied, the fluorination reaction is continued for 200 hours and HF
C-134a was obtained. Then, the same activation treatment as in Example 1 was performed, and the reaction was restarted under the same conditions. The results are shown in Table 6.

[0051]

[Table 6]

[0052] Example _{7 Al (NO 3) 3 ·} 9H 2 O: 440g, Cr (N
_{O 3) 3 · 9H 2 O} : 50g, Mg (NO 3) 2 · 6H
₂ O: 16 g dissolved in 1 liter of water, 28%
A precipitate obtained by adding 800 g of an aqueous ammonia solution to 1.6 l of heated water while stirring was filtered, washed with water, and dried at 120 ° C. The dried product was baked at 450 ° C. for 5 hours in an air stream (SV = 250 hr ⁻¹ ) and the resulting oxide powder was tablet-molded. 30 ml of catalyst prepared in this way
Was charged into the reactor and subjected to HF treatment. Then 330
HF: 30ml / min, HCFC at 1 ℃
-133a: 120 ml / min was supplied and the fluorination reaction was continued for 300 hours to obtain HFC-134a. Then, the activation treatment of Example 1 was performed and the reaction was restarted under the same conditions. The results are shown in Table 7.

[0053]

[Table 7]

Comparative Example 2 In the catalyst preparation operation of Example 1, after drying, only calcination with air was carried out and HF treatment was carried out without carrying out H ₂ calcination. In this treatment, 10% of Cr contained in the catalyst was scattered. From this result, it can be seen that the reduction treatment is effective as a treatment at the time of catalyst preparation.

[0055]

As described above, in the method for activating and regenerating the chromium-based fluorination catalyst according to the present invention, first, the oxidation treatment and then the reduction treatment are sequentially performed, so that the catalyst is activated without losing the active ingredient. Even if the activation regeneration is repeated, not only the initial activity level is regenerated, but also the selectivity is improved by this activation regeneration method depending on the reaction. Therefore, it is advantageously used as a method for activating and regenerating an industrial catalyst, and has an advantage that the fluorination reaction can be economically performed.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location C07C 19/08 9280-4H (72) Inventor Shuji Hirayama 5-1 Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Showa Denko KK Chemicals Laboratory (72) Inventor Hidetoshi Nakayama 5-1, Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Showa Denko Chemicals Laboratory

Claims (1)

[Claims] 1. A method for activating and regenerating a fluorination catalyst for halogenated hydrocarbons containing chromium as a main component, the method comprising:
Activation of a chromium-based fluorination catalyst, characterized in that an oxidation treatment of contacting with an oxidizing gas at a temperature of ˜500 ° C. and a reduction treatment of subsequently contacting with a reducing gas at a temperature of 100 to 500 ° C. are sequentially performed. How to play.