Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
2001-03-06
2003-10-07
Parsa, J. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S161000, C570S164000
Reexamination Certificate
active
06630610
ABSTRACT:
FIELD OF INVENTION
The present invention relates generally to the preparation of fluorinated organic compounds. More specifically, the invention relates to the preparation of fluorinated organic compounds by a liquid-phase, catalytic fluorination process.
BACKGROUND OF THE INVENTION
The production of fluorinated organic compounds, such as hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs), is well known in the art. Among the more popular fluorination methods is liquid-phase, catalytic fluorination which is of particular interest herein. In this type of fluorination, a liquid starting material is reacted with a fluorination agent in a reactor in the presence of a liquid catalyst and under conditions sufficient to form a fluorinated organic compound. The fluorinated organic compound readily vaporizes under the reaction conditions and leaves the reactor as a vapor in a product stream. The product stream then is distilled to recover the fluorinated organic compound.
Although widely used, conventional liquid-phase fluorination suffers from several shortcomings. One of the more significant shortcomings is the formation of high-boiling by-products. As used herein, “by-product” refers to any compound that is produced in the fluorination process and that is neither the desired HFC/HCFC, nor a fluorinated intermediate. The most common by-products are chlorinated by-products. Chlorinated by-products are formed at particularly high levels when chlorine is added to the reaction to regenerate the catalyst. For example, in the production of 1,1,1-trifluoroethane (HFC-143a), the use of chlorine increases substantially the formation of the by-product 1,2-dichloro-1,1-difluoroethane (HCFC-132b). Chlorinated by-products can be formed also in side reactions with the fluorination catalyst.
Chlorinated by-products tend to have higher boiling points than those of the fluorinated product; consequently, they tend not to vaporize during fluorination. Over time, the chlorinated by-products accumulate in the reactor necessitating periodic shut-downs to boil off or drain them from the reactor. Shutting down the reactor disrupts the continuous fluorination process and thereby reduces production efficiency. Additionally, once accumulation of by-products begins, the space available for fluorination decreases, thereby further reducing production efficiency. Therefore, a need exists for a more efficient approach to preparing HFCs and HCFCs, including an approach that avoids the accumulation of high-boiling by-products in the reactor. The present invention fulfills this need among others.
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Brescher Curtis A.
Cottrell Stephen A.
Riegel Clifford Scott
Swain Charles F.
Allied-Signal Inc.
Parsa J.
Szuch Colleen D.
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