Distillation: processes – separatory – Plural distillations performed on same material – One a distillation under positive pressure or vacuum
Patent
1996-11-07
1998-11-10
Cain, Edward J.
Distillation: processes, separatory
Plural distillations performed on same material
One a distillation under positive pressure or vacuum
B01D 300
Patent
active
058338136
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of recovering ethylene sulfide. The present invention also relates to a method of dehydrating hydrous ethylene sulfide while suppressing polymerization of the same. Ethylene sulfide is highly reactive, and therefore, known as an advantageous compound for use as a raw material of medical supplies, agricultural chemicals, industrial chemicals, sulfur-containing polymers, etc.
BACKGROUND OF THE INVENTION
Ethylene sulfide is an oil compound having a specific gravity of approximately 1 and a boiling point of 55.degree. C. According to the prior art references and the best knowledge of the inventors of the present invention, ethylene sulfide is, in brief, characterized in that: pressure in the azeotropic composition ratio to water 95:5 in weight; with water and eventually turns into a polymer, or a white solid material having a higher melting point; and product.
Conventional example methods of synthesizing ethylene sulfide are set forth in U.S. Pat. Nos. 3,687,976 and 3,622,597, U.K. Patent No. 1,135,800, Dutch Patent Nos. 7,001,172 and 6,512,117, J. Chem. Soc. (Sect C) 1252 (1969), etc. In addition, a method subjecting 2-mercaptoethanol to contact dehydration (intramolecular dehydration) in a gaseous phase is proposed to produce ethylene sulfide for industrial use, and a useful catalyst for such a dehydration reaction is disclosed in Japanese Laid-Open Patent Application No. 202027/1993 (Tokukaihei 5-202027). Also, Japanese Laid-Open Patent Application No. 339257/1993 (Tokukaihei 5-339257) discloses a method of scavenging ethylene sulfide obtained as a result of the above dehydration reaction using a hydrophobic organic compound.
According to the above scavenging method, ethylene sulfide is scavenged in the form of a solution of the hydrophobic organic compound with 2-mercaptoethanol as a non-reacted raw material, sulfide compounds as a by-product, and a small quantity of water.
Ethylene sulfide is preserved in the form of a solution of the hydrophobic organic compound in co-existence with a known stabilizer, such as alkylmercaptan and thioamide compounds, and a small quantity of water. In general, a compound having a higher boiling point than ethylene sulfide is used as the hydrophobic organic compound because of its industrial advantages, such as readiness in handling.
The aforementioned prior art references disclose the method of producing ethylene sulfide. However, all the references remain silent about a method of isolating ethylene sulfide from a resulting reactant mixture and purifying the same in a stable manner. In short, no reference discloses a method of recovering ethylene sulfide. Besides, a method of producing ethylene sulfide for industrial use has not been fully established.
As previously mentioned, the hydrophobic organic compound has a higher boiling point than ethylene sulfide which is actually an oil product. Thus, to separate and recover ethylene sulfide from a solution of the hydrophobic organic compound, the solution of the hydrophobic organic compound is distilled continuously using a fractionating tower, so that ethylene sulfide and water form an azeotrope having the lowest boiling point in the distillation system. In other words, since ethylene sulfide and water form an azeotrope, water dissolved and/or suspended in the solution of the hydrophobic organic compound is distilled out with ethylene sulfide from the fractionating tower.
However, when the resulting distillate is cooled, ethylene sulfide in the form of liquid touches water, and eventually turns into a polymer having a high melting point. Thus, some of ethylene sulfide is lost as it undergoes the polymerization, thereby reducing a recovering percentage of ethylene sulfide. Moreover, the fractionating tower or pipes clog with deposits of the resulting polymer, which makes continuous distillation difficult.
Thus, there has been an increasing need to a method of separating and recovering ethylene sulfide from a hydrous solution containing ethylene sulfide, a hyd
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A.D.B. Sloan, "Cyclodehydration of 2-Mercaptoalkanois as a Route to Episulphides", J. Chem. Soc. (C) 1969, pp. 1252-1256.
Ishikawa Ryuichi
Ito Hirokazu
Kaziwara Teruhisa
Matsumoto Yukihiro
Yamaguchi Yoshinari
Cain Edward J.
Nippon Shokubai Co. , Ltd.
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