Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
2000-12-29
2003-02-11
Siegel, Alan (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S172000, C570S159000
Reexamination Certificate
active
06518467
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to new methods for making hydrofluorocarbons and hydrochlorofluorocarbons.
BACKGROUND OF THE INVENTION
Hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) are of interest as potential replacements for highly useful chlorofluorocarbons (CFCs). In particular, HFCs are of interest because they do not contain chlorine and therefore do not decompose to form chlorine-containing chemical species, which are suspected of causing depletion of the ozone layer. Both HFCs and HCFCs have been used successfully in place of CFCs as heat transfer agents, blowing agents, and propellants. Thus, HFCs and HCFCs are desirable targets of chemical synthesis.
Applicants believe that known methods for making HFCs and HCFCs, especially methods for making 1,1,1,3,3-pentafluorobutane (“HFC-365”), are highly inefficient, often using disfavored reaction ingredients and/or reaction conditions. For example, U.S. Pat. No. 5,917,098, issued to Bertocchio et al., discloses a process for forming HFC-365 comprising the steps of (a) reacting tetrachloromethane and 2-chloropropene in the presence of a catalyst comprising an amine and a copper salt; and (b) fluorinating with hydrogen fluoride.
The present inventors have come to appreciate that such prior processes are disadvantageous for several reasons. For example, one such disadvantage is that the availability of many halogenated compounds, such as tetrachloromethane and 2-chloropropene, is limited and their use as starting materials tends to be very expensive.
Recognizing this and other drawbacks of the prior art, the present inventors have perceived a need for a new, efficient and more desirable method for producing a wide range of HFCs and HCFCs. These and other objects are achieved by the present invention as described below.
DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
The present invention is directed to a method of producing hydrofluorocarbons (HFCs) and/or hydrochlorofluorocarbons (HCFCs) using as a reactant halogenated alkanes, more preferably C
2
-C
6
halogenated alkanes, and even more preferably halogenated alkanes of Formula I, shown below. Formula I:
H
3
C—CX
3
(I)
wherein X is independently fluorine or chlorine. As used herein with respect to X, the term “independently” means that one X substituent on a compound may differ from another X substituent on the same compound. Accordingly, the X substituents on a compound of Formula I may be all chlorine, all fluorine, or combinations of chlorine and fluorine. Preferably, at least one X is chlorine. Applicants have discovered that halogenated alkanes, and preferably halogenated alkanes in accordance with Formula I, can be used with great advantage in a process which comprises converting the halogenated alkane to an HFC or HCFC.
Applicants have discovered that a process which utilizes such a conversion operation is highly advantageous in that the cost of producing HFCs and HCFCs according to the present halogenated alkane conversion operation is greatly reduced relative to conventional HFC and HCFC production techniques. This reduction in cost is due in part to the relative commercial availability of the present halogenated alkanes in comparison to the starting materials of the prior art.
According to certain preferred embodiments of the present invention, the method of converting a halogenated alkane to an HFC and/or HCFC comprises the step of: (a) reacting a starting halogenated alkane, preferably in accordance with Formula I, with a hydrohalocarbon adduct in the presence of a catalyst to form an addition-reaction product.
According to certain other preferred embodiments of the present invention, the method of converting a halogenated alkane to an HFC and/or an HCFC comprises the steps of: (a) reacting a starting halogenated alkane, preferably in accordance with Formula I, with a hydrohalocarbon adduct in the presence of a catalyst to form an addition-reaction product; and (b) fluorinating said addition-reaction product to produce an HFC and/or an HCFC.
As used herein, the term “hydrohalocarbon adduct” refers generally to alkanes, alkenes and mixtures thereof which are capable of reacting with the starting halogenated alkane to form an addition-reaction product according to the present invention. Preferred hydrohalocarbon adducts include: (1) alkenes described by the Formula (II) below:
H
2
C═CX
2
(II)
wherein X is independently chlorine or fluorine; (2) alkanes of Formula I which are capable of forming alkenes of Formula II in situ in the reaction of the present invention; and (3) mixtures thereof.
Although applicants do not wish to be bound by or to any particular theory of operation, it is believed that the methods according to certain preferred aspects of the present invention involve reaction step (a), and optionally, but preferably, reaction step (b), shown below in Scheme 1.
As used herein, the term “addition-reaction product” refers generally to a product comprising either a Formula III alkane or a Formula IV alkene alone, or a mixture of Formula III alkanes and Formula IV alkenes. In certain preferred embodiments of the present invention, the addition-reaction product formed from step (a) may be isolated as a desired end-product HFC and/or HCFC. In such embodiments, further fluorination via step (b) is unnecessary. Examples of Formula III alkanes which can be produced via step (a) include HCFCs, such as, 1-fluoro-1,1,3,3-tetrachlorobutane, 3-fluoro-1,1,1,3-tetrachlorobutane, 1,1-difluoro-3,3,3-trichlorobutane, 1,3-difluoro-1,1,3-trichlorobutane, 3,3-difluoro-1,1,1-trichlorobutane, 3,3-dichloro-1,1,1-trifluorobutane, 1,3-dichloro-1,1,3-trifluorobutane, 1,1-dichloro-1,3,3-trifluorobutane, 3-chloro-1,1,1,3-tetrafluorobutane, 1-chloro-1,1,3,3-tetrafluorobutane, and HFCs, such as, 1,1,1,3,3-pentafluorobutane. Examples of Formula IV alkenes include HCFCs, such as, 1-fluoro-1,3,3-trichlorobut-1-ene, 3-fluoro-1,1,3-trichlorobut-1-ene, 1,1-dichloro-3,3-difluorobut-1-ene, 3,3-dichloro-1,1-difluorobut-1-ene, 1,3-dichloro-1,3-difluorobut-1-ene, 3-chloro-1,1,3-trifluorobut-1-ene, 1-chloro-1,3,3-trifluorobut-1-ene, HFCs, such as, 1,1,3,3-tetrafluorobut-1-ene.
In certain other embodiments of the present invention, the addition-reaction product produced from step (a) is fluorinated via reaction step (b) to form a desired HFC and/or HCFC.
According to certain preferred embodiments of the present invention, reaction step (a) preferably comprises reacting a starting alkane of Formula I with a hydrohalocarbon adduct in the presence of a catalyst under conditions effective to achieve the formation of addition-reaction product at a yield of at least about 50% by mole.
A wide range of starting alkanes in accordance with Formula I are suitable for use in the present invention, including, for example, 1,1-dichloro-1-fluoroethane, 1-chloro-1,1-difluoroethane and 1,1,1-trichloroethane, each of which is commercially available. Furthermore, many compounds of Formula I are known in the literature and are obtainable by art-recognized procedures. Preferred Formula I alkanes include alkanes comprising at least one chlorine group, such as 1,1-dichloro-1-fluoroethane and 1,1,1-trichloroethane.
Any suitable hydrohalocarbon adduct may be used in the method of the present invention. Examples of suitable adducts include: alkenes of Formula II, such as 1-chloro-1-fluoroethene, 1,1-dichloroethene, 1,1-difluoroethene, 1-chloroethene, 1-fluoroethene; alkanes of Formula I, such as those described above; and mixtures thereof. Preferred adducts include 1-chloro-1-fluoroethene, 1,1-dichloroethane, 1,1-dichloro-1-fluoroethane, 1,1,1-trichloroethane and mixtures thereof. More preferred hydrohalocarbon adducts are 1,1-dichloro-1-fluoroethane and 1,1,1-trichloroethane.
In embodiments of the present invention wherein the hydrohalocarbon adduct comprises an alkane of Formula I, the alkane adduct may be the same as or different from the starting alkane of Formula I. In certain preferred embodiments, the hydrohalocarbon adduct comprises the same
Puy Michael Van Der
Tung Hsueh Sung
Honeywell International , Inc.
Siegel Alan
Szuch Colleen
LandOfFree
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