Claims
- 1. In a process for the continuous chlorination of diketene, the improvement of continuously nebulizing said diketene within a reactor, continously contacting the diketene spray with chlorine gas in a reaction zone consisting essentially of the chlorine gas, diketene and reaction product, at a temperature of from 80.degree. C. to about 210.degree. C., directing the resultant reaction system and product against a condensation surface, and continuously removing liquid product from said reactor.
- 2. The process of claim 1 wherein the molar ratio of diketene feed to chlorine is from about 0.5 to about 1.5.
- 3. The process of claim 2 wherein the chlorinated product is fed directly to an esterification unit wherein the temperature is maintained within the range of from about 15.degree. C. to about 40.degree. C.
- 4. The process of claim 1 wherein the temperature within said reaction zone is from about 100.degree. C. to about 170.degree. C.
- 5. The process of claim 1 wherein the temperature within said reaction zone is from about 120.degree. C. to about 160.degree. C.
- 6. The process of claim 1 wherein the temperature of said condensation surface is between about 15.degree. C. and about 50.degree. C.
DESCRIPTION
This is a continuation-in-part application of Ser. No. 254,248, filed Apr. 15, 1981, now abandoned.
This invention concerns the chlorination of diketene, and in the preferred embodiment concerns a relatively high rate, non-solvent, non-refrigerated continuous process and apparatus for carrying out the chlorination.
Heretofore, the recommended chlorination procedures in the art specify, in the case of diketene, that the highly exothermic chlorination be done at moderate to high dilution, usually in an inert, chlorinated solvent, and sometimes with an inert gas diluent for the chlorine, and that both the chlorination and subsequent esterification to the 4-chloroacetoacetic acid ester be done at low temperatures. See for example, U.S. Pat. 3,666,793 wherein in order to maximize selectivity to the desired 4-chloroacetoacetyl chloride intermediate (4-CAAC) rather than, for example, 2,4-dichloroacetoacetyl chloride or 2-chloroacetoacetyl chloride, it is taught that chlorine gas should be added slowly to a batch of diketene diluted with an inert, low boiling solvent such as methylene chloride, carbon tetrachloride, dichloroethane, or liquid sulfur dioxide, and that the heat of both chlorination and esterification be removed by refrigeration to maintain the batch temperature within -10.degree. C. to -30.degree. C. In an alternative process of Japanese Pat. No. 76,113,824 employing a continuous, descending stream, wetted-wall column reactor, diketene in dichloroethane and chlorine diluted with nitrogen were reacted at 10.degree. C. and the product esterified at -5.degree. C. With such prior processes, the need for refrigeration and diluents and the separation thereof from the product and their disposal or recovery impose onerous economic penalties on the production of the desired 4-chloroacetoacetic acid ester.
In accordance with the present invention, however, it has been discovered that 4-chloroacetoacetyl chloride from diketene, can be produced continuously in high yield without the use of diluents and refrigeration by carrying out the chlorination in a certain way in a special apparatus shown in detail in the accompanying drawing. The invention, in its broad sense, is defined as a process for the continuous chlorination of diketene, comprising continuously nebulizing said diketene within a reactor, continuously contacting the spray with chlorine gas in an essentially uncooled reaction zone, directing the resultant reaction system against a cooled reactor wall, and continuously removing liquid product from said reactor. It is noted that in this process at least a major portion of the reaction, and usually essentially all of the reaction has taken place before the spray contacts the reactor wall. The cooled wall in the present process acts only to provide a condensing and run-off surface for the chlorinated product which in the absence of a limited size spray reaction zone might degrade, polymerize or become overchlorinated due to the very high temperatures within the reaction zone and the continued intimate contact of the 4-CAAC product and Cl.sub.2 gas. It is noted that the yields of desired product produced according to the present invention are significantly improved over that obtained with wetted wall reactors wherein overchlorination and degradation or polymerization occurs.
US Referenced Citations (5)
Continuation in Parts (1)
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Number |
Date |
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254248 |
Apr 1981 |
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Patent Grant
4468356
