JPS6054931B2 - Method for producing 1,1,1,3,3,3-hexafluoro-2-propanol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a 1,1,1,3,3,3- Hexafluoro-2-propanol CF3CHOHCF3 (hereinafter H
FIPA (abbreviated as FIPA).

HFIPA is useful as a surfactant, emulsifier, or solvent for some polymers.

HFIPA is also valuable as an intermediate for the synthesis of various fluorine-containing compounds; for example, using HFIPA as a starting material, ethers in which hydrogen in the alcohol group of HFIPA is replaced with methyl, fluoromethyl, or ethyl groups can be used as inhalation anesthetics. Proposed. Various methods have been known for producing HFIPA, and a production method has also been proposed in which HFA is reduced with hydrogen in the presence of a catalyst. Such reduction reaction catalysts include Pt-based catalysts, Pd-based catalysts, and Cu-Cr. O. Type catalysts are known, but the conversion rate of raw material A is insufficient in all of them. However, the yield of the target HFIPA is low, high reaction temperature and pressure are required, the reaction activity is inhibited by impurities in the raw materials and reaction by-products, and the durability of the catalyst is poor. I have it too. That is, U.S. Patent 341
Although Japanese Patent No. 8337 discloses a liquid phase reaction using a Pt0 catalyst, it requires an extremely high reaction pressure of 200 to 9 beat pressure.

Additionally, U.S. Patent No. 360,795 discloses a method in which the liquid phase reaction proceeds under a lower reaction pressure using a ptO catalyst, but the desired product, HFIPA, is added to the system from the beginning of the reaction. It is necessary to keep it.

Also, according to West German Patent Publication No. 2113551, Pd
HFIPA has been obtained through a liquid phase reaction using a catalyst prepared by treating activated carbon with an alkali such as Na2CO, but the preparation of such a catalyst is complicated and cumbersome. On the other hand, H
As a catalyst for obtaining HFIPA by hydrogen reduction of FA, Cu-
Cr, Os-CaF, catalyst (Japanese Patent Publication No. 39-8210), Pd/Al2O3 catalyst (US Pat. No. 3,468,964)
Pd/C catalyst (Japanese Patent Publication No. 48-21925) is known, but it has drawbacks such as requiring a high reaction temperature and unsatisfactory catalyst activity and durability. . The present inventor has conducted various studies in order to solve these difficulties and provide an excellent catalyst for the catalytic reduction reaction of HFA to HFIPA using hydrogen, and has obtained the following new findings. Based on this, the present invention has been completed.

That is, the rhodium catalyst has high activity for this reduction reaction, and is also excellent in terms of the production rate of the target HFIPA, and is also excellent in terms of durability and resistance to impurities. Thus, the present invention provides 81P characterized in that HFA is reduced with hydrogen in the presence of a rhodium catalyst.
This provides a new method for producing A. In the present invention, it is important to use a rhodium catalyst.

Examples of the rhodium catalyst include reduced rhodium, or rhodium compounds such as rhodium oxide, rhodium hydroxide, and rhodium chloride, and may be complexes containing rhodium, and the oxidation number of rhodium is not particularly limited. Among them, O-valent rhodium is effective, and reduced rhodium is a preferable example. Further, reduced rhodium may be present from the beginning of the reaction, or may be present transiently during the reaction. When such a rhodium catalyst is used, for example, in this reduction reaction using a liquid phase reaction system, it may be used as it is by being suspended or dissolved in the reaction system, but it is usually supported on a suitable carrier and used in a gas phase reaction system or liquid phase reaction system. It is conveniently used in phase reaction systems. As the carrier, activated carbon, alumina, silica, silica-alumina, magnesia, asbestos, diatomaceous earth, other oxides, sulfates, carbonates, fluorides, etc. can be used, and activated carbon and alumina are particularly convenient. The amount of rhodium supported on the supported catalyst is not particularly limited, but it is preferably 0.1 to 2 weight percent, particularly 0.5 to 1 weight percent, based on the weight of the carrier in terms of metallic rhodium. The particle size of the carrier is not particularly limited. However, when using a liquid phase reaction system with a suspended catalyst, it is necessary to use fine powder to facilitate uniform distribution of the catalyst within the system and increase contact between the reactants and the catalyst. It is generally preferred to use a carrier of the same type. In addition, gas phase reaction systems or liquid reaction systems using fixed bed catalysts can be used. When employing a phase reaction system, it is generally preferable to use a carrier with a particle size of 1 dia or more so that the catalyst can be retained in the catalyst layer and the fluid flow resistance can be maintained within an appropriate pressure drop range. . Furthermore, a reaction using a fluidized bed method can also be employed using a catalyst with an appropriate particle size. Various known and well-known methods can be used to prepare such rhodium catalysts, including supporting methods.
Various commercially available rhodium catalysts may also be used.

The prepared catalyst may be used as it is, or may be activated as appropriate. HFA used in the present invention can be prepared by various methods, but it can be used as a raw material in the present invention even if it is contaminated with impurities associated with the preparation.

For example, it may be HF'A obtained from hexachloroacetone and therefore containing monochloropentafluoroacetone as an impurity, or directly from hexafluoropropene (hereinafter abbreviated as HFP) or hexafluoropropene epoxide. obtained via HFPl hexafluoropropene epoxide,
HFA containing pentafluoropropionyl fluoride or the like as an impurity may also be used. Furthermore, it may contain other fluorine-containing or chlorine-containing compounds as impurities. It goes without saying that products in which these impurities are reduced or removed by appropriate purification methods can also be used. The present invention may be carried out by either a liquid phase method or a gas phase method.

When carrying out the present invention by a liquid phase method, a solvent or diluent may or may not be used. Solvents or diluents that can be used include HF'IPA, . CF3CH2OHl
Alcohols such as methanol, ethanol, cyclohexanol, CF2ClCFCl2, CF2Cl2, H
Examples include halogenated hydrocarbons such as FP, hydrocarbons such as heptane and cyclohexane, and ethers such as hexafluoropropene epoxide and dioxane, but it is preferable to use HFIPA, which is also the target product, as a solvent. be. When water is used as a solvent or mixed with water, HFA reacts with water and is less susceptible to reduction (
CF3)2C(0H)2, which is rather unsuitable. Reaction conditions such as reaction temperature and reaction pressure are not particularly limited, and conventionally known or well-known conditions can be employed. For example, in a batch or semi-batch liquid phase reaction in which the entire amount of raw material 1FA is charged at the start of the reaction, the reaction pressure is 0.5 to 70 atm including hydrogen partial pressure, particularly 1 to 70 atm.
5 leakage pressure is preferable, and the reaction temperature is 0 to 200°C, especially 2
0 to 100°C is preferred. The amount of the catalyst used is preferably 0.0001 to 1 wt%, particularly 0.001 to 0.1 wt%, based on the weight of the supplied 8A in terms of metallic rhodium. Although the reaction time depends on other reaction conditions such as reaction temperature or operating conditions, it can be, for example, about 1 minute to 50 C@. Hydrogen may be supplied alone or in a mixture with an inert gas such as nitrogen. The hydrogen partial pressure is preferably 0.3 to 50 atm, particularly 0.5 to (to) atm. The total amount of hydrogen supplied is raw material H
It is sufficient if the amount is at least equimolar to FA, and there is no problem even if hydrogen is supplied in excess of this amount. In addition, by supplying a smaller number of moles of hydrogen than the number of moles of raw material HFA, HF'IP
It is also possible to keep the conversion rate to A at an appropriate value of 100% or less, or to adjust the reaction rate and reaction temperature as appropriate. The total amount of hydrogen to be supplied may be supplied to the reaction system all at once at the start of the reaction, may be supplied in multiple portions as the reaction progresses, or may be supplied continuously. When the total amount of hydrogen is supplied at once at the start of the reaction, the reaction pressure and hydrogen partial pressure are preferably within the above-mentioned pressure range immediately after hydrogen supply, but may fall below this pressure range at the end of the reaction.

This is because hydrogen is consumed as the reaction progresses, 8A having a high vapor pressure decreases, and 81PA having a low vapor pressure increases, resulting in a decrease in both the reaction pressure and the hydrogen partial pressure.

This point also applies to the case where hydrogen is divided into multiple portions and supplied intermittently. In addition, a flow type liquid phase reaction in which hydrogen, HFAl, and a solvent or diluent are continuously supplied to the reaction system as necessary, or a circulating liquid phase reaction in which part or all of the raw materials are recycled and supplied to the reaction system. etc. may be adopted as appropriate. In the above description, a liquid phase reaction is defined not only when there is a clear liquid phase in the reaction system, but also when there is a condensed liquid phase, that is, a temperature above the critical temperature where it is impossible to clearly distinguish between the gas phase and the liquid phase. It also includes the state of matter at different temperatures. When carrying out the present invention by a gas phase method, a suitable example is a gas phase flow reaction method in which hydrogen and 1(FA) are continuously passed through a fixed catalyst bed.

Reaction gases include inert gases such as nitrogen, HFP, CF2, etc.
A diluent such as ClCFCl2 may be passed simultaneously or intermittently. The reaction conditions are not particularly limited, but the reaction temperature is 50 to 400 C1, especially 150 to
3000C is preferred, and the reaction pressure is preferably 0.5 to W atm, particularly preferably 1 to 4 atm. The molar ratio of hydrogen to I(F'A) to be supplied is preferably 1 or more, particularly 1.
It is preferably in the range of 5 to 5. The contact time may be changed depending on the rhodium loading rate when a supported catalyst is used, but it is preferably 0.1 to 1000 seconds, particularly 1 to 1 (1) seconds. Additionally, since this reduction reaction is an exothermic reaction, it is often effective to prevent or suppress the catalyst temperature from rising excessively by passing an inert gas or other diluent along with it, as this can extend the life of the catalyst. However, for the same purpose, it is also possible to use a method in which a catalyst is mixed with an inert or low-activity packing. Note that the reaction method is not limited to a fixed bed reaction method, but a moving bed method or a fluidized bed method may also be adopted as appropriate. In either the liquid phase method or the gas phase method, it is also possible to reactivate the catalyst once subjected to the reaction by hydrogen treatment, vacuum degassing treatment, or other appropriate methods. Thus, according to the method of the present invention, HFIPA can be obtained with high activity and high yield under convenient reaction conditions through hydrogen reduction by dipping, and the catalyst has excellent durability.
Although the present invention has the advantage of being less susceptible to impurities, examples of the present invention will be described in detail. It goes without saying that the present invention is not limited in any way by this explanation. Example 1 A metal rhodium/activated carbon fine powder supported catalyst with a rhodium loading rate of 2 wt% (manufactured by Nippon Engelhard Co., Ltd.) was placed in a vertical cylindrical pressure-resistant container made of SUS with an internal volume of about 50 m1 and equipped with a pressure gauge, an inlet port, and a needle valve. After adding 0.25y and a Teflon 9-coated stirring bar, the inside of the system was vacuum degassed at room temperature.

Next, this pressure-resistant container was heated to 120° C. and vacuum deaeration was continued for about 30 minutes to remove water and the like adsorbed on the activated carbon carrier. ``Next, this pressure-resistant container was cooled in a dry ice/acetone bath while being closed, and connected to an HFA container to introduce 25y crude HFA.This crude HF'A has a purity of about 90% and the main impurity is 1IF'P. Next, this pressure-resistant container was connected to a hydrogen cylinder, and
The mixture was placed in an autobath and heated to approximately 65°C, and the contents of the pressure vessel were simultaneously stirred using a magnetic stirrer. The pressure showed 2 direct pressure. While maintaining the bath temperature at this temperature and continuing to stir, hydrogen was introduced to bring the pressure to 34 atmospheres. The pressure immediately rose to 35 atmospheres), and about 1 minute later (
To) Atmospheric pressure decreased to Introduce hydrogen again and increase the pressure to 35
It was taken as atmospheric pressure. After the pressure rose to 36 atmospheres, the pressure rose to about 1. After the incident, the pressure dropped to 2. In this way, hydrogen was introduced intermittently every time the pressure decreased to 29 to 3 atmospheres, and the pressure was increased to 35 to 36 atmospheres, which was repeated for a total of 11 times in one hour after the first hydrogen introduction. We were able to introduce hydrogen. As the reaction time progressed, the rate of pressure drop slowed, and therefore the interval between introductions became longer as the number of introductions increased. After 1 hour, the pressure vessel was removed from the water bath and cooled in a dry ice/acetone bath to slowly release the remaining hydrogen.

Then, the system was thawed with warm water with the system closed, and then cooled with ice water to remove dissolved hydrogen and unreacted HFA. After slowly releasing HFP and the like, the pressure container was opened and the product was recovered. Analysis by Fl9-NMR and gas chromatography revealed that the obtained product was mostly HFIPA, and the molar ratio of HFIPA based on the net HFA supplied was 95%. Comparative Example 1 A liquid phase catalytic reduction reaction using crude HFA(7)H2 was carried out in substantially the same manner as in Example 1, except that the catalyst was mainly changed. The results are shown in the following table.

In all cases, the pressure drop rate was slower than in Example 1, and except for the palladium/activated carbon catalyst, the pressure drop rate was from 1 to 1.
After introducing hydrogen twice, almost no pressure drop was observed. In addition, in the case of the palladium/activated carbon catalyst, hydrogen could only be supplied six times in one hour of reaction time. Inner diameter 8
T! Rhodium loading rate 2w in nφ U-shaped SUS reaction tube
10 ml of t% metallic rhodium/granular activated carbon (10 to 20 mesh) supported catalyst (manufactured by Nippon Enkelhard Co., Ltd.) was filled.

After purging the system with N2, the reaction tube was placed in a 180° C. salt bath and heated. After pretreatment with nitrogen and then hydrogen, the same crude HFA and hydrogen as used in Example 1 were each added for 10 to 15 ml for 11 min (calculated at room temperature, the same applies hereinafter).
, and were mixed at a flow rate of approximately 30 ml/min and supplied to the reaction system. Reaction) The tube outlet gas was discharged to the vent via a two-stage ice-water bath trap. Much of the condensate is captured in the first stage ice-water trap, and virtually all of it is HFI.
It was P.A. When the trap was replaced every hour and the condensate was analyzed, HFIPA mol.
The yield is practically 100%, and for the next l hour HF'
The IPA molar ratio was 98%.

Comparative Example 2 Rough H
A reduction reaction of FA was performed.

The HFIPA molar yield from 0 to 3 hours was 90%, and the HFIPA molar ratio during the next hour was 75%.

Also, instead of crude HFA, high-purity reagent H in a small cylinder is available.
Almost the same reduction reaction was performed using FA. The HFIPA molar ratio from 0 to 3 hours was 84-94%.

These results show that the palladium/activated carbon catalyst has considerably high activity and is relatively unaffected by impurities in 8A, but the rhodium catalyst has even better activity and durability.
It also shows that it is not affected by impurities. Comparative Example 3 The catalyst was replaced with a metal palladium/granular activated Al2O3 (10-20 mesh) supported catalyst (manufactured by Nippon Engelhard Co., Ltd.) with a palladium loading rate of 0.5 Wt%, and the reaction temperature was set at 120
The reduction reaction of crude HF'A and high purity reagent HFA was carried out in substantially the same manner as in Example 2, except that the temperature was changed to .degree.

Claims (1)

[Claims] 1, 1, 1, 3, 3, characterized in that hexafluoroacetone is reduced with hydrogen in the presence of a rhodium catalyst
Method for producing 3-hexafluoro-2-propanol.