JPH0125729B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing fluorinated alcohol. [Prior Art] It is used as a working medium, medicines and agrochemicals, and various other intermediates. trifluoroethanol,
Several methods are conventionally known for producing fluorinated alcohols such as pentafluoropropanol. For example, a known method for producing pentafluoropropanol is to react a reaction product of tetrafluoroethylene and an alkali (earth) metal fluoride with formaldehyde to obtain a metal alcoholate, which is then hydrolyzed ( USP3415894). In addition, the method for producing trifluoroethanol is 2.
- A method for hydrolyzing chloro-1,1,1 trifluoroethane (Freon 133a) in Υ-butyllactone in the presence of a carboxylic acid salt (Japanese Patent Application Laid-open No. 1986-
134043, JP 58-140031) or by reacting with an alkali metal salt in an aprotic solvent to form an ester,
A method of hydrolyzing with caustic alkal (JP-A-Sho)
59-13742), and a method of hydrolysis in higher alcohols such as ethylene glycol in the presence of potassium acetate (USP 2868846) is known.
These production methods using 2-chloro-1,1,1-trifluoroethane as a raw material are basically rotary reactions, and are not expected to offer much advantage in terms of scale-up during large-scale production. On the other hand, a method for obtaining trifluoroethanol by reducing trifluoroacetic acid or its derivative 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.Chem443268
(1979), USP 4273947, USP 4396784), USP 4255594 is a method for reducing trifluoroacetic anhydride, and USP 3314987, USP 4072726 is a method for reducing trifluoroacetic ester.
EP36939 is disclosed. Additionally, USP3970710 and USP2982789 describe methods for producing trifluoroethanol by reducing trifluoroacetic acid chloride.
It has been known. [Problems to be Solved by the Invention] Among the above-mentioned conventional examples, according to USP No. 2,982,789, trifluoroacetic acid chloride is hydrogen-reduced using a Pd-supported activated carbon catalyst to form trifluoroacetaldehyde, and then this is converted into trifluoroacetaldehyde. A method of reducing hydrogen to trifluoroethanol using a chromium oxide catalyst is described. Column 4 of the same specification
According to the description in lines 15 to 23, in the dechlorination step in which trifluoroacetic acid chloride is hydrogen-reduced using a Pd-supported activated carbon catalyst to obtain trifluoroaldehyde, the reaction mole of hydrogen per mole of trifluoroacetic acid chloride is The number is 1 in the theoretical amount of reaction.
However, it is said that it is not preferable for the number of moles of hydrogen to react to be 1.5 moles or more, in other words, to be 1.5 times or more the theoretical amount of reaction. Furthermore, in column 4, lines 9 to 14 of the same specification, it is stated that the method of directly obtaining trifluoroethanol by the reaction of trifluoroacetic acid chloride and hydrogen in the presence of a copper chromium monoxide catalyst may cause side reactions. , it is stated that most of the acid chloride ends up unreacted. According to the research of the present inventors, despite the teachings of the above-mentioned US specification, fluorinated alcohols can be obtained in good yield by the reaction of acid halides and hydrogen according to the following formula. I gained some interesting knowledge. RfCOX+2H ₂ →RfCH ₂ OH+HX (Rf is a fluoroalkyl group that may contain C ₁ to C ₃ C atoms or H atoms, X is F, C or Br
Indicates an atom. ) According to the teaching of the above-mentioned US specification, in the presence of a Pd-supported activated carbon catalyst, the number of reaction moles at the level was reduced to the theoretical reaction amount.
When reacting with an acid halide at a concentration of 1.5 times or less, the formation of fluorinated alcohol was observed, but it was not obtained in sufficient yield, and the reaction products such as fluorinated alcohol and hydrogen halide were Poisoning of the catalyst due to adhesion was observed, and it was difficult to maintain long-term activity of the catalyst. 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 twice the volume or more while forming a hydrogen atmosphere, it was possible to obtain a fluorinated alcohol in a good yield and 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 involves reacting an acid halide containing a fluoroalkyl group represented by the following general formula () with hydrogen. In a method for obtaining a fluorinated alcohol represented by the following general formula (), the number of moles of hydrogen reacted with 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. RfCOX ... () (Rf is a fluoroalkyl group which may contain C ₁ to C ₃ C atoms or H atoms, X is F, C or
Indicates a Br atom. ) RfCH ₂ OH ... () (Rf is the same fluoroalkyl group as above) The method for preparing the palladium catalyst used in the present invention is not particularly limited and may be a normal method. For example, a method may be employed in which palladium chloride is supported on a carrier, dried, and further reduced with hydrogen. If the supported amount of palladium is 0.5 wt% or more, it can be used as an industrial catalyst, but if it is 5 wt% or more, the cost of the catalyst increases, so 0.5 to 5 wt% is preferable, and 1 to 3 wt% is particularly preferable. The activated carbon used for the carrier may be prepared from materials such as wood, charcoal, fruit shells, coconut shells, peat, lignite, and coal.Although any activated carbon may be used, vegetable materials are preferable to mineral materials, especially coconut shells. Activated carbon is best. Coconut shell activated carbon has a larger surface area than other activated carbons, contains fewer impurities such as silica, and has excellent hydrochloric acid resistance.
It is considered to be highly active and durable. The shape of the carrier can be various shapes such as briquette coal of about 2 to 5 mm, crushed coal of about 4 to 50 meshes, granulated coal, etc., but crushed coal of about 4 to 20 meshes,
Molded coal is preferred. In the present invention, the reaction molar ratio of acid halide and hydrogen is particularly important, and the number of reaction moles of hydrogen to acid halide is at least twice the theoretical reaction amount,
By preferably increasing the amount by 3 to 5 times, fluorinated alcohol can be obtained with a good yield. The reason for this is not necessarily clear, but
A large amount of hydrogen plays the role of a diluent, prevents the reaction temperature from rising more than necessary, suppresses side reactions, and performs the catalytic reaction in a sufficient hydrogen atmosphere, so that the reaction products are not deposited on the catalyst. This is thought to be because it prevents adhesion and deposition and maintains catalytic activity. The reaction temperature may be 130 to 250°C, preferably 150 to 200°C at normal pressure; temperatures below this will result in a low yield of fluorinated alcohol, and temperatures above this will place a large heat load on the catalyst. This is not preferable because it may lead to performance deterioration or side reactions such as thermal decomposition may occur more easily. The reaction pressure can be carried out without particular limitation, and the reaction usually proceeds satisfactorily at normal pressure or autogenous pressure. The contact time for the catalyst is usually 4 to 60
It may be selected from a range of seconds, preferably from 8 to 40 seconds. In addition, the reaction may be carried out by diluting with an inert gas such as chiso gas in order to further suppress excessive temperature rise. The palladium-supported activated carbon catalyst of the present invention has high durability and does not require long-term activation, but when activated, hydrogen reduction is preferably carried out at 100 to 300°C, preferably 200 to 300°C. 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. CF ₃ CH ₂ OH, CHF ₂ CH ₂ OH, CF ₂ CICH ₂ OH,
CH ₂ FCH ₂ OH, C ₂ F ₅ CH ₂ OH, CF ₃ CH ₂ CH ₂ OH,
_{C3F7CH2OH , HCF2CF2CH2CH2OH . _ _ _} [Example] Example 1 250 ml of a catalyst in which 0.5 wt% of palladium was supported on 4 to 8 meshes of crushed coconut shell activated carbon was filled into a reaction tube made of Inconel 600 with an inner diameter of 1 inch and a length of 1 m, 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. A reaction was carried out by introducing trifluoroacetic acid chloride into this reactor at a flow rate of 0.5 mol/hr and hydrogen at a flow rate of 4 mol/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 The reaction was carried out under the same conditions as in Example 1, except that a 2wt% palladium-supported crushed coconut shell activated carbon catalyst (4 to 8 meshes) was used, and the durability of the catalyst was investigated. The results are shown in Table 1 below. Table 1 also shows a comparison of the performance of 5wt% palladium-supported alumina catalysts under the same conditions. The performance is represented by the trifluoroethanol yield [%].

[Table] 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 in Example 1.

[Table] 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 mol/hr, and the flow rate of hydrogen was 1.5 mol/hr.
The reaction was carried out continuously under the same conditions as in Example 1 except that the reaction rate was changed to 3.0 mol/hr, and the change in performance over time was investigated. The results are shown in Table-3.

[Table] Examples 3 to 6 2wt% Pd supported activated carbon catalyst (10 to 20 meshes) 60
cm is a U made of Inconel 600 with an inner diameter of 1 cm and a length of 1 m.
The reactor was filled into a shaped reactor, immersed in a salt bath, heated from the outside, and maintained at 180°C.Acid halide was flowed through this at a flow rate of 30 mmol/hour and hydrogen at a flow rate of 180 mmol/hour, resulting in a continuous reaction. I went to 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. The performance was expressed as the yield [%] of the corresponding alcohol.

【table】

[Table] [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,
The durability of the catalyst and the yield of fluorinated alcohol are extremely good compared to cases where other noble metal catalysts or other carriers are used. In the reaction, the desired fluorinated alcohol can be obtained in one step by hydrogen reduction of the acid halide, and the palladium-supported activated carbon catalyst forms halides under the influence of the simultaneously generated acids such as HC and HF. There are few things,
Activation can also be carried out easily.

Claims (1)

[Scope of Claims] 1. A method for obtaining a fluorinated alcohol represented by the following general formula () by reacting an acid halide containing a fluoroalkyl group represented by the following general formula () with hydrogen. A method for producing a fluorinated alcohol, characterized in that the number of moles of hydrogen reacted with respect to the compound is at least twice the theoretical reaction amount, and the reaction is carried out in the presence of a palladium-supported activated carbon catalyst. RfCOX...() (Rf is a fluoroalkyl group which may contain a C ₁ to C ₃ C atom or a H atom. X is F, C or Br
Indicates an atom. ) RfCH ₂ OH ……() (Rf is the same fluoroalkyl group as above)