Distillation: processes – separatory – With measuring – testing or inspecting – Of temperature or pressure
Patent
1998-05-18
2000-09-26
Manoharan, Virginia
Distillation: processes, separatory
With measuring, testing or inspecting
Of temperature or pressure
203 6, 203 14, 203 91, 203 99, 203DIG19, 549541, B01D 334, B01D 342, C07D30132
Patent
active
061238120
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to a novel process for distilling ethylene oxide out of a mixture comprising ethylene oxide in a column by withdrawing pure ethylene oxide overhead or via a sidestream in the rectifying section of the column.
Ethylene oxide can be prepared by oxidation of ethylene with oxygen. The oxidation generally takes place in a fixed-bed reactor at from 230 to 270.degree. C. (Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed., Vol. A 10, pages 117 to 135).
The ethylene oxide production reactor effluent, which comprises ethylene oxide, ethylene, carbon dioxide, acetaldehyde and also low boilers, such as methane, is treated with water to remove ethylene oxide. Ethylene oxide can be isolated in pure form from the resulting mixture of ethylene oxide and water by distilling the mixture after removal of the low boilers.
Ethylene oxide is a significant intermediate in the chemical industry because of its high reactivity. It is used for example for the synthesis of ethylene glycol, ethylene glycol ethers, oligo- or polyethylene glycols or ethanolamines.
On the other hand, the high reactivity of ethylene oxide is a problem when it comes to distilling the ethylene oxide, since it can decompose explosively under distillation conditions when subjected to the action of a source of ignition. In addition, as mentioned, it can form glycols with the water likewise present.
It is an object of the present invention to provide a novel process for distilling ethylene oxide out of a mixture comprising ethylene oxide wherein the decomposition reaction of ethylene oxide, in particular in its initial stages, is completely suppressed or terminated.
We have found that this object is achieved by a process for distilling ethylene oxide out of a mixture comprising ethylene oxide in a column at an absolute pressure of from 2 to 10 bar and a temperature of from 20 to 180.degree. C. by withdrawing pure ethylene oxide in the liquid or gaseous state overhead or via a sidestream in the rectifying section of the column, which comprises feeding the mixture through a plurality of successive zones of structured sheet-metal packing or dumped beds of packing elements, at least one of which zones is connected to an extinguishing system via which a liquid solvent which is miscible with ethylene oxide is fed into the zone(s) from outside the column as soon as the pressure limit in the column is exceeded.
Preferably the mixture to be distilled comes from the synthesis of ethylene oxide and includes water as well as ethylene oxide. Examples of further possible ingredients in this case are ethylene glycol, oligo(ethylene glycol)s, aldehydes, such as formaldehyde or acetaldehyde, and methane.
However, it is also possible to apply the process of this invention to the distillation of mixtures which, besides ethylene oxide, include for example methanol, glycols, mono-, di- or triethanolamine or mono- or di(C.sub.1 -C.sub.4 alkyl)ethanolamines.
Preferably the mixture to be distilled comprises, in each case based on its weight, from 10 to 90% by weight, preferably 30 to 70% by weight, of ethylene oxide and from 90 to 10% weight, preferably from 70 to 30% by weight, of water. The mixture may further comprise, in each case based on its weight, from 0 to 10% by weight, preferably 0 to 5% by weight, of ethylene glycol and from 0 to 10% by weight, preferably 0 to 5% by weight, of acetaldehyde. It will be appreciated that the sum of the ingredients of the mixture is 100% by weight in each case.
According to the invention, the novel process is carried out in a column, preferably having a rectifying section. Suitable columns include customary, known distillation columns as described for example in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed., vol. B3, pages 4-82 to 4-94, or in Klaus Sattler, Thermische Trennverfahren: Grundlagen, Auslegung, Apparate, Verlag Chemie, 1988, pages 25 to 27.
The columns have on their inside a plurality of successive zones of structured sheet-metal packing or dumped beds of packing elements.
REFERENCES:
patent: 4134797 (1979-01-01), Ozero
patent: 5244604 (1993-09-01), Miller et al.
B. Bessling, U. Loeffler and A. Polt, "Ethylenoxid-Reindestillation: Durch eine ganzheitliche Betrachtungsweize zu einem integriterten Verfahrens -und Sicherheitskonzept" siehe das ganze Dokument; Dec. 12, 1995, pp. 1614-1618.
Ullmann's Encyclopedia of Industrial Chemistry, "Ethylene Oxide" Bd., 1987, 5.sup.th Ed. vol. #10, pp. 117-135.
Ullmann's Encyclopedia of Industrial Chemistry, "Distillation and Rectification", vol. B3, 5.sup.th Ed. pp. 4-82 to 4-94.
Reinhard Billet, "Packed Towers in Processing and Environmental Technology", Verlag Chemie, Weinheim, 1995, pp. 25 to 27.
Grundlagen, Auslegung, Apparate, Klaus Sattler: "Thermische Trennverfahren", Verlag Chemie, Weinheim 1988, pp. 25 to 27.
Auer Heinz
Ballenweg Rubens
Bessling Bernd
Brudi Gerhard
Gieselberg Klaus
BASF - Aktiengesellschaft
Manoharan Virginia
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