Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-02-21
2002-01-22
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S383000, C568S407000, C568S411000, C570S176000
Reexamination Certificate
active
06340776
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing 1,1,1-trifluoroacetone that is useful as an intermediate of pharmaceuticals and agricultural chemicals, or as a reagent for introducing fluorine-containing groups.
1,1,1-trifluoroacetone is known to be obtained by various methods. It is described in J. Chem. Soc. (Lond.) 1956, 835 that 1,1,1-trifluoroacetone is synthesized by a Grignard reaction between trifluoroacetic acid and magnesium methyliodide. This Grignard reaction must be conducted in an anhydrous state. In addition, it is also described in Tetrahedron, 20, 2163 (1964) that trifluoroacetone can be synthesized by decarbonating trifluoroacetoethyl acetate in sulfuric acid. It is described in Tetrahedron Lett. Vol. 24 (No. 5), 507-510, 1983 that difluoromethylketones are obtained at considerably high yield as a result of reducing chlorodifluoroketones, which are represented by CF
2
ClC(═O)R (wherein R is a group not containing halogen) by zinc and methanol in tetrahydrofuran.
Japanese Patent Publication 2000-336057A, corresponding to Japanese Patent Application 11-147670, discloses a process for producing 1,1,1-trifluoroacetone by reacting 3,3-dichloro-1,1,1-trifluoroacetone with zinc in a solvent of a proton donor. In this process, it is necessary to have a relatively large amount of zinc.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for producing 1,1,1-trifluoroacetone, which is suitable for an industrial-scale production.
According to the present invention, there is provided a process for producing 1,1,1-trifluoroacetone. This process comprises conducting a hydrogenolysis of a halogenated trifluoroacetone, which is represented by the general formula (1), by a hydrogen gas in the presence of a catalyst comprising a transition metal,
where X represents a chlorine, bromine or iodine, and n represents an integer from 1 to 3.
According to the present invention, it is possible to obtain 1,1,1-trifluoroacetone with a high yield by using the above special catalyst in hydrogenolysis of the halogenated trifluoroacetone (e.g., 3,3-dichloro-1,1,1-trifluoroacetone) by a hydrogen gas.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The hydrogenolysis can be conducted by a gas phase reaction between the halogenated trifluoroacetone (gas) and a hydrogen gas using a reactor for flow method.
The halogenated trifluoroacetone used as a starting material in the process of the present invention may be a hydrate, alcohol addition product, gem-diol, acetal or hemiacetal, or their aqueous or alcohol solutions, of a halogenated trifluoroacetone represented by the general formula (1), as indicated in the following formulas, although an aqueous solution of the hydrate is preferable due to its ease of handling:
where X and n are the same as previously defined in the general formula (1), m represents an integer, R
1
represents an alkyl group, and each R
2
independently represents a hydrogen atom or alkyl group.
The halogenated trifluoroacetone can be 3-chloro-1,1,1-trifluorocetone, 3,3-dichloro-1,1,1 -trifluoroacetone, or 3,3,3-trichloro-1,1,1-trifluoroacetone. These compounds can be synthesized by known processes. For example, they can be obtained by fluorinating pentachloroacetone by hydrogen fluoride in the presence of a transition metal or the like as a catalyst. Furthermore, decarboxylation of a trifluoroacetoacetic ester is known.
As stated above, the halogenated trifluoroacetone used as a starting material in the process of the present invention may be a hydrate in which a halogenated trifluoroacetone represented by the general formula (1) has hydrated to have an arbitrary number of water molecules. In the process, it is preferable to use the halogenated trifluoroacetone in the form of an aqueous solution, since its handling is easy and thereby the reaction procedures can be simplified. The existence of water is not an obstacle to the reaction, but the existence of unnecessary water is not preferable from the viewpoint of energy consumption.
As stated above, the catalyst used in the hydrogenolysis comprises a transition metal. This transition metal is preferably a noble metal such as ruthenium, palladium, platinum, iridium, and rhodium. Further examples of the transition metal other than noble metal are nickel, copper and iron. Of these, palladium and platinum are preferable. The transition metal is preferably supported on a support such as activated carbon, alumina, silica-alumina, and silica. Of these, activated carbon is preferable. It is particularly preferable to use a catalyst containing an activated carbon supporting thereon palladium or platinum. The way of making the transition metal to be supported on the support is not particularly limited. For example, it is possible to immerse a support in a solution of a transition metal compound or to spray this solution to a support, followed by drying and then reduction with hydrogen gas. The transition metal compound may be in the form of chloride, bromide, fluoride, oxide, nitrate, sulfate or carbonate. The transition metal may be in an amount of about 0.1-10 g, preferably 0.2-5 g, per 100 ml of the support. If it is less than 0.1 g, both conversion of the halogenated trifluoroacetone and yield of 1,1,1-trifluoroacetone may become too low. An amount of greater than 5 g may not be preferable from the economical viewpoint.
The reaction temperature may be 50° C. or higher, preferably 70° C. or higher, more preferably 90° C. or higher, still more preferably 100° C. or higher, further preferably 105° C. or higher. Furthermore, the reaction temperature may be 350° C. or lower, preferably 250° C. or lower, more preferably 200° C. or lower, still more preferably 150° C. or lower, further preferably 120° C. or lower. Therefore, the reaction temperature range may be 50-350° C., preferably 70-250° C., more preferably 90-120° C. If it is lower than 50° C., both conversion of the halogenated trifluoroacetone and yield of 1,1,1-trifluoroacetone may be lowered. If it is higher than 350° C., fluorine atom hydrogenolysis and/or hydrogenation of carbonyl group may proceed. With this, yield of 1,1,1-trifluoroacetone may be lowered.
The molar ratio of hydrogen (hydrogen gas) to the halogenated trifluoroacetone may be varied depending on the number of the halogen atoms (other than fluorine) of the halogenated trifluoroacetone. This ratio may be in a range of 1.5-50, preferably 2-10, more preferably 2.5-5. If it is less than 1.5, conversion of the halogenated trifluoroacetone may not be sufficiently high. Even if it is greater than 50, conversion of the halogenated trifluoroacetone may not improve further. Furthermore, this is not preferable from the economical viewpoint, due to the necessity of recovering the unreacted hydrogen gas. It is optional to make nitrogen gas coexistent with the other reagents in the reaction system in order to adjust the reaction and to suppress the catalyst deterioration.
It is preferable that the hydrogenolysis is conducted by using a reactor made of a material lined with a lining material selected from of borosilicate glasses, tetrafluoroethylene resins, chlorotrifluoroethylene resins, vinylidene fluoride resins, perfluoroalkyl vinyl ether (PFA) resins and carbon, when water exists in the reaction system. When water does not exist in the reaction system by using a halogenated trifluoroacetone that is not hydrated, it is possible to use iron, stainless steel, nickel and Hastelloy (trade name) for the reactor in addition to the above-mentioned lining material.
The way of conducting the hydrogenolysis is not particularly limited. For example, it can be conducted by the following flow method. At first, a reactor for flow method, which is resistant against the reaction conditions of the hydrogenolysis, is charged with a transition metal supported catalyst. Then, the reactor is heated from outside, and hydrogen gas is allowed to flow through a reaction tube. When the reaction tube's inside temperature reaches a predetermined temperature, the halogenate
Goto Yoshihiko
Nadano Ryo
Nishimiya Takayuki
Sakaya Takashi
Central Glass Company Limited
Crowell & Moring LLP
Padmanabhan Sreeni
LandOfFree
Process for producing 1,1,1-trifluoroacetone does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing 1,1,1-trifluoroacetone, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing 1,1,1-trifluoroacetone will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2852093