Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-10-30
2003-05-20
Rotman, Alan L. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06566534
ABSTRACT:
TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
This invention relates to vapor-phase reaction processes and, in particular, vapor-phase processes for the preparation of aziridine compounds. More particularly, it relates to processes in which vapor-phase reactions, especially vapor-phase reactions for the preparation of aziridine compounds from alkanolamines, can be carried out with industrial advantages.
PRIOR ART
Conventionally, aziridine compounds have been prepared according to a liquid-phase process, i.e., a process wherein a sulfuric ester of monoethanolamine is treated with a concentrated alkaline solution to form ethyleneimine. However, this process has many disadvantages from an industrial point of view. For example, this process involves high production costs because large amounts of sulfuric acid and alkali are required as secondary raw materials, and this process yields inorganic salts of less utility value as by-products.
In recent years, therefore, a vapor-phase process wherein an aziridine compound is directly prepared by subjecting an alkanolamine to a vapor-phase intramolecular dehydration reaction in the presence of a catalyst (the vapor-phase intramolecular dehydration reaction in the presence of a catalyst may hereinafter be referred to briefly as the “dehydration reaction”) is being employed because it requires no secondary raw material and is hence advantageous from the viewpoint of cost. As to the preparation of aziridine compounds by a vapor-phase reaction, a variety of processes have been proposed.
For example, Japanese Patent Laid-Open No. 217659/'92 discloses a process comprising a reaction step for forming an aziridine compound by the dehydration reaction of an alkanolamine, a collection step for collecting the aziridine compound so formed by bringing the reaction mixture containing the aziridine compound into contact with the same alkanolamine as used in the reaction step (i.e., a collector), a purification step for introducing the collector liquid containing the aziridine compound (hereinafter referred to briefly as the “collector liquid”) into a purification column and purifying the aziridine compound, and a recovery step for recovering the alkanolamine by distilling the bottoms withdrawn from the purification column in the presence of water.
Japanese Patent Publication No. 55498/'93 discloses a process wherein the dehydration reaction of an alkanolamine is carried out in the absence of any diluent gas or in the presence of a small amount of a diluent gas. According to this process, an aziridine compound can be obtained by cooling the reaction gas so as to condense it, and introducing the resulting condensate directly to a distillation step, instead of subjecting the reaction gas to a collection step. Alternatively, this process may include a collection step. In this case, it is said that the amount of collector used can be reduced.
Moreover, Japanese Patent Publication No. 88353/'95 discloses a process wherein, after the dehydration reaction of an alkanolamine, the resulting aziridine compound is collected by bringing the reaction gas into contact with a collector comprising an amine compound or a solution thereof. More specifically, this process comprises cooling the reaction gas, introducing the reaction gas into a collection column where the aziridine compound is collected by contact with a collector, and then introducing the collector liquid into a distillation column where it is distilled to obtain the aziridine compound.
As described above, generally known vapor-phase processes for the preparation of aziridine compounds from alkanolamines include one comprising a reaction step for forming an aziridine compound by the dehydration reaction of an alkanolamine, a collection step for collecting the aziridine compound present in the resulting reaction gas, and a purification step for distilling the collector liquid containing the aziridine compound to obtain an aziridine compound product; and one comprising the reaction step and the purification step and requiring no collection step. Moreover, as described in the aforementioned patents, it is common practice to cool the reaction gas resulting from the reaction step by means of a heat exchanger or the like and then feed it to the collection step or the purification step. More specifically, the reaction gas is cooled to −10° C. or 100° C. and then fed to a collection column in the process of Japanese Patent Laid-Open No. 217659/'92; the reaction gas is cooled to −10° C. and then fed to a distillation column in the process of Japanese Patent Publication No. 55498/'93; and the reaction gas is cooled to 110° C. and then fed to a collection column in the process of Japanese Patent Publication No. 88353/'95.
Problems to be Solved by the Invention
However, when an aziridine compound is prepared on an industrial scale, or example, by using a reactor (or reaction column), a collection column and a distillation column, tarry matter adheres to the equipment section extending from the outlet of the catalyst bed within the reactor to the collection column, particularly to the inside of a heat exchanger installed before the collection column for the purpose of cooling, or cooling to condense, the reaction gas and to the inner wall of the pipe extending from the heat exchanger to the collection column When such tarry matter adheres to the inside of the heat exchanger and the inner wall of the piping, various problems arise. That is, (1) an increase in pressure loss is caused to increase the amount of energy required for the vaporization of the alkanolamine raw material fed to the reactor; (2) it becomes necessary to shut down the plant and wash off the tarry matter; and (3) the piping may become clogged.
The above-described problems also arise unavoidably when various vapor-phase reactions, such as vapor-phase intramolecular dehydration reactions and vapor-phase intramolecular dealcoholization reactions, are carried out.
An object of the present invention is to solve the above-described problems of the prior art by providing a process for preparing aziridine compounds with industrial advantages by effectively preventing the adhesion of tarry matter to piping and the like.
Another object of the present invention is to provide a process for carrying out various vapor-phase reactions, such as vapor-phase intramolecular dehydration reactions and vapor-phase intramolecular dealcoholization reactions, with industrial advantages by effectively preventing the adhesion of tarry matter to piping and the like.
Means for Solving the Problems
According to investigations conducted by the present inventors, it has been found that the adhesion of tarry matter can be effectively prevented (1) by maintaining at least the piping section extending from the outlet of the reactor to the inlet of the collection column at a temperature which is not lower than 200° C., or (2) by bringing the reaction gas emerging from the outlet of the catalyst bed within the reactor into contact with the same collector as used in the collection column, preferably in the neighborhood of the outlet of the catalyst bed. The present invention has been completed on the basis of this finding.
Thus, the present invention provides a process for the preparation of aziridine compounds which comprises the step of introducing an alkanolamine into a reactor and forming an aziridine compound by the vapor-phase intramolecular dehydration reaction of the alkanolamine in the presence of a catalyst, and the step of introducing the reaction gas containing the aziridine compound so formed into a collection column and collecting the aziridine compound by contact with a collector, the process being characterized in that at least the piping section extending from the outlet of the reactor to the inlet of the collection column is maintained at a temperature which is not lower than 200° C.
Moreover, the present invention also provides a process for the preparation of aziridine compounds which comprises the step of introducing an alkan
Oka Yoshihisa
Takematsu Kenichi
Nippon Shokubai Co. , Ltd.
Rotman Alan L.
Sherman & Shalloway
Small Andrea D.
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