Process for removal of hydrogen fluoride

Distillation: processes – separatory – Adding material to distilland except water or steam per se – Organic compound

Reexamination Certificate

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Details

C203S091000, C423S481000, C510S408000, C570S178000

Reexamination Certificate

active

06676809

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an azeotropic mixture consisting essentially of hydrogen fluoride (hereinafter, referred to as “HF”) and dichloromethane (hereinafter, referred to as “R-30”), an azeotropic mixture consisting essentially of HF and chlorofluoromethane (hereinafter, referred to as “R-31”) and an azeotropic mixture consisting essentially of HF and difluoromethane (hereinafter, referred to as “R-32”), and a process for the removal of HF from a mixture comprising HF and R-30, R-31 and/or R-32.
R-32 is focused on as a substitute cooling medium for chlorodifluoromethane, and R-30 and R-31 are starting materials for the production of R-32.
2. Description of the Related Art
R-30, R-31 and/or R-32 are conventionally produced by reacting a chlorinated hydrocarbon such as R-30 with HF. Hitherto, a process has been employed in which HF is removed by washing the mixture produced by the reaction and unreacted materials comprising HF, R-30, R-31 and R-32 with an aqueous phase. This process is not so effective because an large amount of an alkali is required to neutralize the washing aqueous solution, and also because a waste from the neutralization has to be treated.
SUMMARY OF THE INVENTION
The present invention provides a process to concentrate or remove HF or other components by forming an azeotropic mixture of HF and R-30, R-31 or R-32 and optionally utilizing liquid separation of a mixture of HF and R-30 and/or a mixture of HF and R-31 into an upper liquid phase and a lower liquid phase under certain conditions.


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Lee & Kim, “Vapor-Liquid Equilibria for Hydrogen Fluoride + Difluoromethane, +1, 1, 1, 2-Tetrafluoroethane, and +1-Chloro-1,2,2,2-tetrafluoroethane at 283.3 and 298.2 K”, J. Chem. Eng. Data (1996), pp. 41, 43-46.
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Amparo Galindo et al., “Predicting the Phase Equilibria of Mixtures of Hydrogen Fluoride with Water, Difluoromethane (HFC-32), and 1, 1, 1, 2-Tetrafluoroethane (HFC-134a) Using a Simplified SAFT Approach”, J. Phys. Chem. B. (1997), pp. 2082-2091.
Ela-Study on the HF/R-32 system carried out by Allied Signal Inc. in 1996.
Elb-Study on the HF/R-32 system carried out by Allied Signal Inc. in 1974.

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