Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
2001-01-10
2002-09-24
Siegel, Alan (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S168000
Reexamination Certificate
active
06455745
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a manufacturing method for fluorine-containing ethane to obtain 2-chloro-1,1,1,2-tetrafluoroethane (in places abbreviated to HCFC-124) and/or 2,2-dichloro-1,1,1-trifluoroethane (in places abbreviated to HCFC-123) as well as 1,1,1,2,2-pentafluoroethane (in places abbreviated to HFC-125) as the main reaction products.
PRIOR ART
HFC 125 is used as a component in an alternative refrigerant gas to 1-chloro-1,1-difluoromethane (HCFC-22), because its ozone destruction coefficient is 0. Among manufacturing methods for HFC-125 using HCFC-124 as the material, a manufacturing method using chromium oxide (Cr
2
O
3
) as the catalyst is described in publication U.S. Pat. No. 5,475,167 as a paten for controlling the generation of CFCs (which are currency banned because they cause damage to the ozone layer). In the method described in this publication, a conversion to HCFC-125 of not less than 50% is said to be necessary. Also, in the method described in the Examples, a Cr
2
O
3
catalyst with high specific surface area prepared from (N
4
)
2
Cr
2
O
7
or one which is further treated with CO, H
2
and H
2
O is used. When using these catalysts, the amount of CFCs generated is 0.3 mol % of the HFC-125.
Further, in publication U.S. Pat. No. 5,334,787, a manufacturing method for HFC-125 through a gas phase reaction from HCF -123 or HCFC-124 is described which uses Cr
2
O
3
as the catalyst. According to this description, an increase in the generation rate is necessary in order to control the generation ratio of CFCs to less than 2%. However, there is no detailed description of the actual generation ratio. Similarly in publication U.S. Pat. No. 5,399,549, a manufacturing method for HFC-125 through a gas phase reaction from the same starting material is described which uses Cr
2
O
3
as the catalyst. However, there is no detailed description of the generation ratio of CFCs.
On the other hand, in Japanese Patent Laid-Open No. 247,883/94 a manufacturing method for HFC-125 characterized by a controlled low amount of CFCs generated is disclosed which uses a catalyst of alumina fluorinated to over 70% in a fluorination reaction of HCFC-123 or HCFC-124. According to this manufacturing method, although the amount of CFCs generated in the fluorination reaction of HCFC-123 with the alumina catalyst is 0.5% at a reaction temperature of 350° C., the ratio of CFCs/HFC-125 is high at about 1.1%.
A fluorination method for tetrachloroethylene with a catalyst of fluorinated alumina is described in Japanese Patent Laid-Open No. 505,328/91 in which a method is disclosed that use a catalyst of alumina containing over 90 wt. % of AlF
3
and carrying metals such as Cr and Mn. This publication, however, includes no description of impurities such as CFCs.
With regard to other methods, although similar methods are also disclosed in Japanese Patent Laid-Open No. 247,884/9 and in Japanese Patent Laid-Open No. 97,725/93, the amount of CFCs generated is high in both of them: the amount of CFCs generated at a reaction temperature 350° C. is 1.7% in the former method and 2-3% at a reaction temperature of 360° C. in the latter method.
Further, the method is disclosed in Japanese Patent Laid-Open No. 146,832/89 as a fluorination reaction of tetrachloroethylene using a chromium catalyst. The catalyst is Cr
2
O
3
, prepared by pyrolysis of ammonium dichromate. The amount of CFCs generated, however, is not referred to at all.
In Japanese Patent Laid-Open No. 268,933/96, a fluorination method of tetrachloroethylene is disclosed that uses a mixed catalyst of MgO and Cr
2
O
3
. Tests were performed with several mixed catalysts having different ratios of the amount of MgO to Cr
2
O
3
. When using a catalyst having a Cr content which minimizes the ratio of CFCs/HFC-125, the conversion rate of tetrachloroethylene is about 93% at a reaction temperature of 320° C. and the ratio of CFCs/HFC-125 is 2.9%. The amount of CFCs generated itself is lower if the ratio of MgO is higher, whereas the conversion rate of tetrachloroethylene is lower; it is also shown that increasing the Cr content in order to obtain a higher conversion rate results in an increase in the amount of CFCs generated by two-fold at a maximum.
OBJECT OF THE INVENTION
The resent invention was carried out in consideration of the above situation. The object is to provide a manufacturing method for fluorine-containing ethane in which, when obtaining the fluorine-containing ethane having HFC-125 as the main reaction product through a fluorination reaction that uses tetrachloroethylene or HCFC-123 or HCFC-124 as the starting material, generation of CFC by-products can be controlled to be as low as possible by improving the catalyst used in the fluorination reaction.
CONSTITUTION OF THE INVENTION
The manufacturing method of the present invention for the fluorine-containing ethane that has HFC-125 as the main component by fluorination of at least one selected from the group composed of tetrachloroethylene, HCFC-123 and HCFC-124 with hydrogen fluoride, is characterized by using fluorochromium oxide that has not less than 30 wt. % of fluorine content as the catalyst.
By increasing the fluorine content of the fluorochromium oxide catalyst, fluorine-containing ethane having HFC-125 as the main component can be manufactured while controlling the generation of CFC by-products to be as low as possible when applying this catalyst to the fluorination reaction of the starting material described above. Herein, however, as the manufactured fluorine-containing ethane, HCFC-123 and/or HCFC-124 are usually included in addition to the HFC-125 as described later.
The starting material of the present invention is either a single material selected from tetrachloroethylene, HCFC-12 and HCFC-124 or a mixture of two or more of them.
The above HCFC-124 can be obtained by, for example, fluorination of HCFC-123 or reduction of CFC-114a (2, 2-dichloro-1,1,1,2-tetrafluoroethane). The above described HCFC-123 can be obtained by, for example, fluorination of tetrachloroethylene, chlorination of HCFC-133 (2-chloro-1,1,1-trifluoroethane) or reduction of CFC-113a (1,1,1-trichloro-2,2,2-trifluoroethane). In addition, the above tetrachloroethylene is manufactured by an industrially common method, e.g. chlorination of hydrocarbon or its chlorine derivatives at its own pyrolysis temperature.
Now even when carrying out a fluorination reaction by HF using these selected starting materials, the ratio of CFCs/HFC-125 cannot be kept low by conventional methods. The mechanism of the generation of CFCs as by-products is described as follows.
If the starting material is HCFC-124, the conversion rate to HFC 125 cannot reach 100% under ordinary reaction conditions and unreactive HCFC-124 exists in the reactor. This unreactive HCFC-124 will generate HCFC-123 resulting from the reaction with a by-product, HCl.
On the other hand, if the starting material is HCFC-123, the organic substances at the exit of the reactor after the fluorination reaction are mainly fluorinated HCFC-124, HFC-125 tetrachloroethylene chlorinated by HCl, which is a by-product, and unreactive HCFC-123.
Similarly, if the starting material is tetrachloroethylene, the organic substances at the exit of the reactor are mainly HCFC-123, HCFC-124 and HFC-125.
From these gases which passed through the reactor, the gas with HFC-125 as the main component is separated and the remaining gas is recycled to the reactor to improve the yield. This, whatever the starting material may be, fluorination of the mixture mainly consisting of tetrachloroethylene, HCFC-123 and HCFC-124 will proceed in the reactor although the amount of each is different. Therefore, HCFC-133a and HFC-134a (1,1,1,2-tetrafluoroethane), which are by-products if tetrachloroethylene is the starting material, and CFCs such as CFC-113a, CFC-114a and CFC-115 are generated. CFCs generated in such reactions do not convert to HFC-125 by the fluorination reaction and will be lost in production. All of the C C-113a and CFC-114a are fluorinated to CFC-115 by rec
Kono Satoru
Shibanuma Takashi
Takahashi Kazuhiro
Armstrong Westerman & Hattori, LLP
Daikin Industries Ltd.
Siegel Alan
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