Organic compounds -- part of the class 532-570 series – Organic compounds – Fatty compounds having an acid moiety which contains the...
Reexamination Certificate
1999-01-05
2001-06-12
Carr, Deborah D. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Fatty compounds having an acid moiety which contains the...
C562S605000, C423S179000
Reexamination Certificate
active
06245923
ABSTRACT:
DESCRIPTION
German Patent 195 27 276 (Patent Specification published on Aug. 08, 1996) relates to a process for the recovery of highly fluorinated carboxylic acids from off-gas streams, wherein the off-gas is brought into contact with an alkaline washing solution of density >1.15 g/cm
3
so that the salt of the highly fluorinated carboxylic acid settles out as a separate phase.
As a further development of this inventive conception, it has now been found that the alkaline washing solution used is advantageously a potassium carbonate solution. The invention thus relates to a process for the recovery of highly fluorinated carboxylic acids from off-gas streams, in which the off-gas is brought into contact with an alkaline washing solution of density >1.15 g/cm
3
so that the salt of the highly fluorinated carboxylic acid settles out as a separate phase, wherein the alkaline washing solution used is a potassium carbonate solution.
When the alkaline washing solution in the process of German Patent 195 27 276 is an alkali metal hydroxide solution, the corresponding carbonate is formed if the off-gas stream to be purified contains carbon dioxide. It has now been found that, when using sodium hydroxide solution, this sodium carbonate leads to encrustation in the scrubbing column. This formation of carbonate is furthermore associated with an undesirable consumption of sodium hydroxide. The use of potassium carbonate as the alkaline agent avoids these disadvantages.
If sodium carbonate is used instead of potassium carbonate, no sodium hydroxide is consumed but there is a considerable increase in encrustation. Moreover, sodium carbonate has a less favorable solubility behavior. This is shown by the fact that the cooling of sodium carbonate solutions of the density required for the process results in precipitation due to super-saturation. This is not the case with potassium carbonate, so it is not necessary to heat pipelines and vessels.
It has further been found that when potassium carbonate is used as the alkaline agent, the potassium salt of the highly fluorinated carboxylic acid is deposited in a form which is easier to filter off than when potassium hydroxide solution is used. This is coupled with the abovementioned advantage that when potassium carbonate is used, there is no consumption of alkaline agent by absorbed carbon dioxide.
The density of the alkaline washing solution is advantageously 1.2 to 1.4 g/cm
3
.
Reference is made to the main patent for further details.
The invention will now be illustrated further by means of the following example.
REFERENCES:
patent: 4060535 (1977-11-01), Cinco
patent: 24 32 473 (1974-07-01), None
patent: 195 27 276 (1995-07-01), None
Brandenburg Rik A.
Grasberger Rainer
Sulzbach Reinhard Albert
Carr Deborah D.
Dyneon GmbH
Lilly James V.
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