Distillation: processes – separatory – Addition of material to distilland to inhibit or prevent...
Patent
1995-12-04
1997-12-02
Manoharan, Virginia
Distillation: processes, separatory
Addition of material to distilland to inhibit or prevent...
203 34, 203 35, 568868, B01D 334, C07C 2980
Patent
active
056931905
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for the recovery of glycols from used antifreeze compositions by distillation.
Large amounts of used antifreeze compositions from combustion engines arise each year. Since these liquids contain considerable amounts, up to 50% by volume, of glycols, especially ethylene glycol and propylene glycol and, in addition, a number of additives such as corrosion inhibitors or antifoam agents (cf. Ullmanns Enzyklopadie der Technischen Chemie, 4th Edition, Volume 12, pages 208-209, Verlag Chemie, Weinheim 1976), these used antifreeze compositions cannot simply be tipped into the sewers but must undergo special disposal or processing. Disposal of antifreeze compositions by incineration consumes considerable energy because of their high water content, which is why this method of disposal is costly and uneconomic.
For this reason a number of methods for recovering glycols from used antifreeze compositions by distillation has been developed, for example the methods disclosed in DE-A 40 30 331 and U.S. Pat. No. 4,080,247. The problem which arises in the distillation of used antifreeze compositions is that thermal decomposition of nitrogenous additives during the distillation results in considerable amounts of gaseous nitrogen oxides NO.sub.x being liberated, and these must not be released to the air for ecological reasons. For this reason it has to date been necessary to extract the liberated nitrogen oxides, for example using a water ring pump, and to purify the effluent polluted in this way by neutralization in the treatment plant. As a consequence of the considerable and costly technical complexity of removing the liberated nitrogen oxides by this method, the recovery of glycols from used antifreeze compositions has remained uneconomic to date.
It is an object of the present invention to find an economic method for recovering glycols from used antifreeze compositions by distillation which does not have the abovementioned disadvantages.
We have found, after lengthy efforts and after testing a large number of chemical substances, that this object is achieved by a method for recovering glycols from used antifreeze compositions by distillation, wherein the used antifreeze composition is treated before and/or during its distillation with an effective amount of sulfamic acid.
We have found that the treatment, according to the invention, of the antifreeze composition with sulfamic acid of the formula I distillation of antifreeze compositions.
To treat the used antifreeze compositions with sulfamic acid, the used composition is generally treated at from 0.degree. to 150.degree. C., preferably 20.degree. to 100.degree. C. and particularly preferably 50.degree. to 80.degree. C., with, in general, from 1 to 20, preferably 5 to 15 and particularly preferably 5 to 10, g of sulfamic acid per liter of used composition. The treatment of the used composition can take place both in a separate stage preceding the distillation and during the distillation. In the latter case, the sulfamic acid is added to the antifreeze composition, which is then distilled. It is advantageous to establish the optimal amount to be added to specific batches of used antifreeze composition in a simple preliminary test.
The pretreatment, according to the invention, of the used antifreeze compositions is advantageously carried out when the composition has a low pH, in general at pH 1-6, preferably at pH 2-5.5 and particularly preferably at pH 3-4. The pH of the used antifreeze composition can be adjusted, for example, by adding an appropriate amount of sulfamic acid, while the used composition is advantageously acidified with an involatile, non-oxidizing mineral acid, eg. with phosphoric acid or sulfuric acid, to the desired pH, and subsequently the amount of sulfamic acid which is required to prevent nitrogen oxide formation is added to the used antifreeze composition.
The duration of this pretreatment depends on the temperature chosen for the treatment. The required treatment time is generally longer at low temperatures than at
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BASF - Aktiengesellschaft
Manoharan Virginia
LandOfFree
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