JPS61268639A - Production of fluorinated alcohol - Google Patents

Abstract

PURPOSE:To obtain the titled substance useful as a hydraulic medium, intermediate for pharmaceuticals and agricultural chemicals, etc., in high yield, keeping the activity of the catalyst to a high level for a long period, by reacting an acid halide containing fluoroalkyl group with excess hydrogen in the presence of an active carbon catalyst supporting Pd. CONSTITUTION:The fluorinated alcohol of formula II can be produced by reacting the acid halide of formula I (Rf is 1-3C fluoroalkyl which may contain Cl or H; X is F, Cl or Br) with more than twice of the stoichiometric amount of H2 in the presence of a Pd-supporting activated carbon catalyst. The amount of the Pd supported by the activated carbon is preferably 1-3wt%, and the reaction is carried out at 150-200 deg.C for 8-40sec. The catalyst can be activated by reducing with hydrogen at 200-300 deg.C. EFFECT:Since the reaction is carried out in hydrogen atmosphere using hydrogen in excess, the poisoning of the catalyst caused by the deposition of reaction product can be inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing fluorinated alcohol.

[Prior Art] Several methods have been known for producing fluorinated alcohols such as trifluoroethanol and pentafluoropropanol, which are used as working media, pharmaceuticals and agricultural chemicals, and various other intermediates. For example, a known method for producing pentafluoropropanol is to react a reaction product of tetrafluoroethylene and an alkaline earth metal fluoride with formaldehyde to produce a metal alcoholate, which is then hydrolyzed. C.I.J.
S93, 415, 894).

In addition, the method for producing trifluoroethanol is 2-1)
e+ II+ -1,1,1) j) Fluoroethane (
A method of hydrolyzing Freon 113a) in γ-butyllactone in the presence of a carboxylate (Japanese Patent Application Laid-Open No. 58-1340
43, JP-A-58-140031) and a method of reacting with an alkali metal salt in an aprotic solvent to form an ester, followed by hydrolysis with a caustic alkali (JP-A-59-137).
42), and a method of hydrolysis in higher alcohols such as ethylene glycol in the presence of potassium acetate (U
SP 2,888.848) is known. These manufacturing methods, which use 2-chloro-1,1,1-)lifluoroethane as a raw material, are basically rotary reactions, and are not expected to have much advantage in scale-up during large-scale production. A method for obtaining trifluoroethanol by reducing fluoroacetic acid or a derivative thereof in the presence of a catalyst is also known. As a method for reducing trifluoroacetic acid, a method using a rhodium catalyst etc. (J, Org, Chem 44
32E18 (197!3), USP 4,273
．． 947, USP 4.398.784) Kachi 1”+
Retail et al., U as a method for reducing trifluoroacetic anhydride
SP 4,255,594. Furthermore, as a method for reducing trifluoroacetic ester, USP 3,314,987
, USP 4,072,728. EP 38,939 is disclosed. In addition, Toshite's method for producing trifluoroethanol by reducing trifluoroacetic acid chloride is from the US.
P 3,970,710, USP 2,982,789
It has been known.

[Problems to be Solved by the Invention] Among the aforementioned conventional examples, according to USP 2,982,789, trifluoroacetic acid chloride is hydrogen-reduced using a Pd-supported activated carbon catalyst to form trifluoroacetaldehyde, A method is described in which this is then subjected to hydrogen reduction using a copper-chromium oxide catalyst to produce trifluoroethanol. According to the description in lines 441115 to 23 of the same specification, in the dechlorination step in which trifluoroacetic acid chloride is hydrogen-reduced using a Pd-supported activated carbon catalyst to obtain trifluoroaldehyde, The number of reacting moles of hydrogen is 1 mole in the theoretical reaction amount, but it is considered undesirable for the reacting mole number of hydrogen to be 1.5 moles or more, in other words, 1.5 times or more the reaction theoretical amount. There is. Also, column 4 of the same specification, 9
Lines ~14 indicate that the method of directly obtaining trifluoroethanol by reacting trifluoroacetic acid chloride with hydrogen in the presence of a copper-chromium oxide catalyst may cause side reactions or most of the acid chloride may remain unreacted. It is stated that the result will be .

According to research conducted by the present inventors, despite the teachings of the above-mentioned US specification, an interesting finding has been made that fluorinated alcohols can be obtained in good yield according to the following formula by reacting acid halides with hydrogen. I got it.

RrCOX +2H2→RrCH20H+ HX(Rr
is a C1 to C3 fluoroalkyl group which may contain a CQ atom or a H atom, and X represents a F, CQ or Br atom,
) According to the teachings of the above-mentioned US specification, when the reaction with an acid halide was carried out in the presence of a Pd-supported activated carbon catalyst at a level of reaction moles of 1.5 times or less of the theoretical reaction amount, the formation of fluorinated alcohol was also observed. However, a sufficient yield could not be obtained, and poisoning of the catalyst due to adhesion of reaction products such as fluorinated alcohols and hydrogen halides was observed, making it difficult to maintain the activity of the catalyst for a long period of time. The present inventors predicted that reaction products would be difficult to adhere to the catalyst in a hydrogen atmosphere, and contrary to the teaching of the above-mentioned US specification, hydrogen was added to the stoichiometric amount of the reaction. Surprisingly, when the reaction was carried out at more than twice the temperature and a hydrogen atmosphere was formed,
In addition to obtaining fluorinated alcohol in good yield, it was also possible to maintain the activity of the catalyst for a long period of time.

[Means for Solving the Problems] The present invention has been made based on the above-mentioned novel findings, and it combines an acid halide containing a fluoroalkyl group represented by the following general formula (1) with hydrogen. In the method of reacting to obtain a fluorinated alcohol represented by the following general formula (II), the number of moles of hydrogen to be reacted with respect to the acid halide is at least twice the theoretical reaction amount, and the reaction is carried out in the presence of a palladium-supported activated carbon catalyst. The present invention relates to a method for producing a fluorinated alcohol characterized by the following.

RrCOX” (I) (Rr is at
-03, a fluoroalkyl group which may contain a CQ atom or a H atom; X represents F, C; Q or Br atom; ) RrCH20H...(II) (Rr is the same fluoroalkyl group as above) The method for preparing the palladium catalyst used in the present invention is not particularly limited, and the usual method 0 For example, palladium chloride is supported on a carrier and then dried. , Furthermore, the activated carbon used as a carrier can be wood, charcoal,
Any material prepared from raw materials such as fruit shells, coconut shells, peat, lignite or coal can be used.

Vegetable raw materials are preferable to mineral raw materials.

Coconut shell activated carbon is particularly suitable. Coconut shell activated carbon is
It has a larger surface area than other activated carbons, contains fewer impurities such as silica, and has excellent hydrochloric acid resistance, so it is thought to have high activity and excellent durability. The shape of the carrier may be various shapes, such as a compactness of about 2 to 5 mm and a granularity of crushed coal of about 4 to 50 mesh, but 4 to 20 mm.
Crushed coal before and after mesh, and briquette coal are preferred.

In the present invention, the molar ratio of the reaction between the acid halide and hydrogen is particularly important, and the number of moles of hydrogen reacted with respect to the acid halide is set to be at least twice, preferably 3 to 5 times, the theoretical reaction amount.

Fluorinated alcohols can be obtained in good yields. The reason for this is not necessarily clear, but a large amount of hydrogen plays the role of a diluent, preventing an unnecessary rise in reaction temperature and suppressing side reactions. This is believed to be because carrying out the reaction in an atmosphere prevents the reaction products from depositing on the catalyst and maintains the catalytic activity.

The reaction temperature may be 130 to 250"C1, preferably 150 to 200"C at normal pressure; below this temperature, the yield of fluorinated alcohol will be low, and above this temperature, the heat load on the catalyst will be large. The reaction pressure can be carried out without any particular limitation, and the reaction can be carried out at normal pressure or autogenous pressure, which is not preferable because it may lead to performance deterioration or side reactions such as thermal decomposition may easily occur. The contact time with the catalyst is usually selected from the range of 4 to 60 seconds, preferably 8 to 40 seconds, and the reaction is carried out by diluting with an inert gas such as nitrogen gas to further suppress excessive temperature rise. The palladium-supported activated carbon catalyst of the present invention is highly durable and does not require long-term activation. It is best to calculate based on the amount of hydrogen.

As the fluorinated alcohol that can be produced by the method of the present invention, various hydrogen reduction products of acid halides can be mentioned, and the following compounds can be suitably exemplified.

CF3CH20H, GHF2CHzOH, CF2ClC
H20H9GH2FCH20H, C2F5GH20H,
CF3Cl21CI20H.

C3FpGH2GH, HGhCF2CIhGH20H.

[Example] Example 1 A reaction tube made of Inconel 600 with an inner diameter of 1 inch and a length of 1 m was filled with catalyst 2501 in which O, 5 wt% palladium was supported on 4 to 8 meshes of crushed coconut shell activated carbon, and this was heated from the outside. The mixture was then placed in a salt bath furnace maintained at a constant temperature of 170°C. Add 0.5 m of trifluoroacetic chloride to this reactor.
The reaction was carried out by introducing hydrogen at a flow rate of 4+sol/hr. One day later, the reactor outlet gas was analyzed using a gas chromatograph. A trifluoroacetic acid chloride reaction rate of 100% and a trifluoroethanol selectivity of 99.5% were obtained.

Example 2 2 wt% palladium supported crushed coconut shell activated carbon catalyst (4
The reaction was carried out under the same conditions as in Example 1, except that a 5wt% palladium-supported alumina catalyst was used, and the durability of the catalyst was investigated. The results are shown in Table 1 below. A comparison is shown in Table 1. Performance is expressed as trifluoroethanol yield [%].

Table 1 Comparative Examples 1 to 4 Table 2 shows the results of a comparative study of the performance of other noble metal light catalysts under the same conditions as Example 1.

Table 2 Comparative Example 5 Using the same 2wt% palladium-supported crushed coconut shell activated carbon catalyst as in Example 2, the flow rate of trifluoroacetic acid chloride was 1.5 layers of/hr, and the flow rate of hydrogen was 3.0 mol/h.
The reaction was carried out continuously under the same conditions as in Example 1, except that the temperature was changed to r, and changes in performance over time were investigated. The results are shown in Table-3.

Table 3 Examples 3 to 6 2wt% Pd supported activated carbon catalyst (10 to 20 meshes) 8
A U-shaped reactor made of Inconel 600 with an internal diameter of 1 cm and a length of 1 cm was filled with 0 cm Q, immersed in a salt bath, heated from the outside, and maintained at 180°C.
The reaction was carried out continuously by flowing hydrogen at a flow rate of 0 mmol/hour and 180 mmol/hour.

The reactor outlet gas was analyzed by gas chromatography to examine the performance and durability of the catalyst. The results are shown in the table below, and the performance is expressed as the yield [%] of the corresponding alcohol.

Table 4 [Effects of the Invention] In the present invention, by using a palladium-supported activated carbon catalyst and making the number of moles of hydrogen reacted with the acid halide at least twice the theoretical reaction amount, other precious metal catalysts or
, compared to cases using other carriers, the durability of the catalyst and the yield of hydrogenated alcohol are extremely good.
The desired fluorinated alcohol can be obtained in one step by hydrogen reduction of acid halides, and the palladium-supported activated carbon catalyst is less likely to form halides due to the influence of acids such as HCQ and HF that are generated at the same time. Activation can also be carried out easily.

Claims (1)

[Claims] 1. A method for obtaining a fluorinated alcohol represented by the following general formula (II) by reacting an acid halide containing a fluoroalkyl group represented by the following general formula (I) with hydrogen, A method for producing a fluorinated alcohol, characterized in that the number of moles of hydrogen reacted with an acid halide is at least twice the theoretical reaction amount, and the reaction is carried out in the presence of a palladium-supported activated carbon catalyst. R_fCOX...(I) (R_f is a fluoroalkyl group which may contain a Cl atom or H atom of C_1 to C_3. X represents F, Cl or Br atom.) R_fCH_2OH...(II) (R_f is the same fluoroalkyl group as above)