Process for fluorinating halogenated hydrocarbon

Abstract: A halogenated hydrocarbon is effectively fluorinated by reacting the halogenated hydrocarbon with hydrogen fluoride in the presence of a fluorination catalyst which comprises a partially fluorinated chromium oxide containing at least one metal selected from the group consisting of ruthenium and platinum.

Description: The present invention relates to a process for fluorinating a halogenated hydrocarbon. More particularly, the present invention relates to a process for preparing a hydrocarbon such as 1,1,1,2-tetrafluoroethane which is useful as a refrigerant, a blowing agent, a propellant, a cleaning agent and the like. As a fluorination catalyst, chromium oxide which may be supported on alumina is known (see Japanese Patent Publication Nos. 10310/1964, 3004/1967 and 44973/ 1987 and U.S. Patent Nos. 3,426,009, 3,755,477 and 4,158,675). Also, fluorination in the presence of a chromium salt or partially fluorinated chromium oxide which may be supported on a carrier is known (see U.S. Patent Nos. 2,745,886 and 2,885,427, DE Patent No. 1 252 182, Japanese Patent Publication No. 54503/1976, Japanese Patent Kokai Publication No. 132549/ 1978 and WO89/10341). There is also known a catalyst comprising chromium oxide and an additive such as NaF (U.S. Patent No. 3,644,545), Mg or Ba (Japanese Patent Publication No. 43922/1974), a transition metal (U.S. Patent No. 4,792,643) or AlPO₄ (Japanese Patent Publication No. 17413/1989). Further, there are known processes using a catalyst comprising chromium metal (Japanese Patent Kokai Publication Nos. 19038/1985 and 221338/1989) or a metal other than chromium (Japanese Patent Kokai Publication Nos. 186945/1987, 268651/1989, 172933/1990 and 95438/1990). U.S. Patent No. 4,766,259 discloses a fluorination reaction using partially fluorinated aluminum oxide. A liquid phase fluorination reaction using a Sb catalyst is known. In addition, a liquid phase fluorination reaction using an alkali metal fluoride as a catalyst is known (see U.S. Patent No. 4,311,863 and Japanese Patent Kokai Publication No. 228925/1989). Now, the fluorination of a halogenated hydrocarbon is explained by making reference to the preparation of 1,1,1,2-tetrafluoroethane (hereinafter referred to as "134a") by fluorination of trichloroethylene or 1,1,1-trifluorochloroethane (hereinafter referred to as "133a") in a gas phase. It is not advantageous to synthesize 134a from 133a by a liquid phase reaction in view of a low yield and the material of the reactor. When the above fluorination reaction is carried out in the gas phase, conversion of 133a to 134a is low due to equilibrium. Therefore, a catalyst to be used should catalyze this reaction at a relatively low conversion and have a sufficiently long life and a good selectivity in an industrial use. Prolongation of the catalyst life avoids frequent change of the catalyst and lowers the catalyst cost. The catalyst life can be prolonged by the addition of chlorine gas (Japanese Patent Publication No. 33604/1977) or oxygen gas (GB Patent No. 2 030 981 and Japanese Patent Kokai Publication Nos. 82206/1976 and 272535/1989) to the reaction gas mixture. When the chlorine gas is added, selection of the material of the reactor may be limited and also increase in by-products will be considered. When the oxygen gas is added, the conversion may be decreased. In view of the above, it is advantageous to provide a catalyst which has a long life as such. When such catalyst is excellent in catalytic activity, not only the catalyst cost but also a size of the reactor which is made of an high quality expensive material can be reduced advantageously. One object of the present invention is to provide an improved catalyst which can catalyze the phase fluorination of a halogenated hydrocarbon. Another object of the present invention is to provide an improved process for fluorinating a halogenated hydrocarbon in the gas phase. According to the present invention, there is provided a process for fluorinating a halogenated hydrocarbon comprising reacting a halogenated hydrocarbon with hydrogen fluoride in the presence of a fluorination catalyst which comprises a partially fluorinated chromium oxide (III) containing at least one metal selected from ruthenium and platinum. In particular, the present invention provides a process for preparing 134a by reacting 133a with hydrogen fluoride in the presence of the above catalyst according to the reaction formula: CF₃CH₂Cl + HF → CF₃CH₂F + HCl Herein, the term "halogenated hydrocarbon" intends to mean a hydrocarbon having at least one halogen atom other than fluorine atom. Examples of the halogenated hydrocarbon to be fluorinated by the process of the present invention are 133a, CCl₄, CHCl₃, CH₂Cl₂, CH₃Cl, CCl₃F, CCl₂F₂, C₂Cl₄, C₂Cl₃H, CHCl₂CF₃ and CHClFCF₃. The catalyst used according to the present invention comprises chromium oxide or chromium hydroxide carrying at least one metal selected from ruthenium and platinum. Chromium oxide or chromium hydroxide may be supported on a carrier such as aluminum oxide, fluorinated aluminum oxide or aluminum fluoride. The content of ruthenium or platinum is from 0.01 to 10 % by mole, preferably from 0.01 to 6 % by mole based on the amount of chromium oxide or chromium hydroxide. When the content of ruthenium or platinum is too large, the catalytic activity may be deteriorated. To carry ruthenium and/or platinum on the catalyst, their chloride, hydroxide, oxide, chlorometallic acid, and the like are used. Ruthenium and/or platinum can be carried on the catalyst by impregnation, precipitation or mixing. When chromium hydroxide is used, chromium hydroxide carrying ruthenium and/or platinum is sintered to convert chromium hydroxide to chromium oxide and is then fluorinated with hydrogen fluoride. When chromium oxide is used, it is fluorinated after ruthenium and/or platinum are added. While ruthenium or platinum are present in metal form, its surface is partially covered with a fluoride. Chromium oxide is partially fluorinated. The term "partially fluorinated" intends to mean that chromium oxide contains 8 to 48 % by weight, preferably 15 to 44 % by weight of fluorine. In the reaction according to the present invention, the conversion and/or the catalyst life can be adjusted by changing reaction conditions such as the molar ratio of hydrogen fluoride to the halogenated hydrocarbon, the reaction temperature, etc. When 133a is fluorinated, the molar ratio of hydrogen fluoride to the halogenated hydrocarbon is from 0.9:1 to 16:1, preferably 1:1 to 10:1, and the reaction temperature is from 290°C to 380°C. The reaction pressure is not critical. However, a pressure higher than atmospheric pressure is not preferable since the catalytic activity is reduced. The present invention will be explained further in detail by following Examples. In the Examples and Comparative Examples, common reaction conditions were employed. That is, the molar ratio of hydrogen fluoride to the raw material 1,1,1-trifluorodichloroethane was 1:1, a reaction temperature was 350°C, and the contact time (namely the ratio (g.sec/Nml) of the catalyst weight W to the flow rate F) was 0.4. The maximum conversion achieved by these conditions was about 13 % (equilibrium conversion). The reactor was a Hasteloy C made tube having an inner diameter of 15 mm, and a gas flow rate was 600 ml/min. The definitions of the activity, the catalyst life and the throughput are as follows: The activity is the achieved maximum conversion (%). The catalyst life is the time (h ) at which the conversion decreased to 60 % of the maximum value. The throughput is the amount of the reaction product (134a) produced by one gram of the catalyst during catalyst life time. Preparation of Standard Catalyst A partially fluorinated chromium oxide catalyst which contains no additional metal and is used as a standard catalyst was produced as follows: To a 5.7 % aqueous solution of chromium nitrate, 10 % aqueous ammonia in an equivalent amount was added dropwise to precipitate chromium hydroxide. The precipitate was filtered, washed with water and dried in air at 120°C for 12 hours. The catalyst at this stage is referred to as "chromium hydroxide state catalyst" This catalyst was pelletized by a pelletizer and kept in a nitrogen stream at 400°C for 2 hours (sintering), followed by fluorination with hydrogen fluoride (HF treatment). Then, the catalyst was ground to powder having a particle size of 300 to 1000 micrometers. Four grams of the ground catalyst was used in the reaction. This catalyst was used as a standard catalyst. Comparative Example 1 Using a standard catalyst produced from the same chromium hydroxide state catalyst as used in Example 1, the fluorination was carried out under the above common conditions. The results are as follows: Activity: 12.6 % Catalyst life: 78 hours Throughput: 177 g Example 1 The chromium hydroxide state catalyst was mixed with an aqueous solution of ruthenium chloride an amount of which was adjusted so that a Ru/Cr ratio was 4.7 % by mole and dried in air at 110°C for 12 hours. Thereafter, the catalyst was sintered and HF-treated in the same manner as in the preparation of the standard catalyst, and the fluorination was carried out under the above common conditions. The results are as follows: Activity: 12.2 % Catalyst life: 105 hours Throughput: 235 g In comparison with Comparative Example 1, the catalyst life and the throughput were increased without decreasing the activity. Example 2 The chromium hydroxide state catalyst was mixed with an aqueous solution of ruthenium chloride an amount of which was adjusted so that a Ru/Cr ratio was 0.87 % by mole and dried in the air at 110°C for 12 hours. Thereafter, the catalyst was sintered and HF-treated in the same manner as in the preparation of the standard catalyst, and the fluorination was carried out under the above common conditions. The results are as follows: Activity: 12.3 % Catalyst life: 155 hours Throughput: 329 g In comparison with Comparative Example 1, the catalyst life and the throughput were increased without decreasing the activity. Example 3 The chromium hydroxide state catalyst was mixed with an aqueous solution of ruthenium chloride an amount of which was adjusted so that a Ru/Cr ratio was 0.094 % by mole and dried in air at 110°C for 12 hours. Thereafter, the catalyst was sintered and HF-treated in the same manner as in the preparation of the standard catalyst, and the fluorination was carried out under the above common conditions. The results are as follows: Activity: 12.1 % Catalyst life: 115 hours Throughput: 244 g In comparison with Comparative Example 1, the catalyst life and the throughput were increased without decreasing the activity. Example 4 The chromium hydroxide state catalyst was mixed with an aqueous solution of chloroplatinic acid an amount of which was adjusted so that a Pt/Cr ratio was 0.24 % by mole and water was removed with an evaporator followed by the HF treatment in the same manner as in the preparation of the standard catalyst. Using this catalyst, the fluorination was carried out under the above common conditions. The results are as follows: Activity: 13 % Catalyst life: 63 hours Throughput: 153 g In comparison with Comparative Example 2, the catalyst life and the throughput were increased without decreasing the activity. Comparative Example 2 Using the same standard catalyst as in Example 4, the fluorination was carried out under the common conditions. The results are as follows: Activity: 13 % Catalyst life: 40 hours Throughput: 93 g

Claims: A process for fluorinating a halogenated hydrocarbon comprising reacting a halogenated hydrocarbon with hydrogen fluoride in the presence of a fluorination catalyst which comprises a partially fluorinated chromium oxide containing at least one metal selected from ruthenium and platinum. The process according to claim 1, wherein said halogenated hydrocarbon is 1,1,1-trifluorochloroethane and 1,1,1,2-tetrafluoroethane is prepared. The process according to claim 1, wherein said chromium oxide is supported on a carrier selected from aluminum oxide, partially fluorinated aluminum oxide and aluminum fluoride. The process according to claim 1, wherein said catalyst contains 0.01 to 10 % by mole of said at least one metal based on the amount of chromium oxide. The process according to claim 2, wherein the molar ratio of hydrogen fluoride to said halogenated hydrocarbon is from 0.9:1 to 16:1. The process according to claim 2, wherein the reaction temperature is from 290°C to 380°C.

Inventors: KANEMURA TAKASHI C O YODOGAWA, KOYAMA SATOSHI C O YODOGAWA WO, SHIBANUMA TAKASHI C O YODOGAWA, KANEMURA, TAKASHI, C/O YODOGAWA WORKS OF DAIKIN, KOYAMA, SATOSHI, C/O YODOGAWA WORKS OF DAIKIN, SHIBANUMA, TAKASHI, C/O YODOGAWA WORKS OF DAIKIN
Applicants: DAIKIN IND LTD, DAIKIN INDUSTRIES, LTD.
Application year: 1992
Main classification: C07C17
IPC codes: C07C17, C07B61, B01J27, B01J23, C07C19