Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1995-10-12
1997-09-09
Dentz, Bernard
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
549273, 549295, 562 2, 562 3, C07C40700, C07D31304
Patent
active
056658915
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB/00440 filed Mar. 8, 1994.
This invention concerns a process for the oxidation of ketones. Specifically, this invention concerns a process for the oxidation of ketones to esters and to the oxidation of cyclic ketones to lactones.
The oxidation of ketones to produce esters, and particularly the oxidation of cyclic ketones to produce lactones can be effected by peroxygen compounds. One of the most important industrial applications of such oxidation of ketones is the oxidation of cyclohexanone to produce caprolactone, which is widely employed in the production of polymers and co-polymers.
A number of different methods have been proposed or have found industrial application for the production of lactones. One such method is to oxidise the ketone with peracetic acid as a reagent. This method, although capable of excellent conversions requires the handling of relatively large quantities of concentrated peracetic acid solutions with its attendant hazards, and often requires the construction of dedicated plant for the production of the peracetic acid consumed in the oxidation process.
An alternative oxidant that is sometimes desirable to employ in the oxidation of alcohols is an aqueous solution of hydrogen peroxide, because it is relatively cheap, easy to handle and is environmentally acceptable in that its decomposition products are water and oxygen. In order to achieve effective oxidations of ketones with hydrogen peroxide, it has often been found necessary to employ a catalyst. Such catalysts are commonly employed as homogeneous catalysts i.e. they are employed in the same phase and/or physical state as the reagents. Although the use of homogeneous catalysts commonly has the advantage of a relatively high rate of reaction compared to other forms of catalyst, one drawback of such an approach is that the reaction depends on the formation of a solution of the catalyst, which is then brought into contact with the alcohol. This means that on completion of the reaction, the catalyst often remains in solution. Such a solution can, in theory, be separated from the reaction product and recycled, but in many cases, particularly where the product is a liquid, this process can involve a distillation stage. It is widely recognised that the distillation of a solution which may contain peroxide residuals is a potentially hazardous operation because the potential concentration of peroxides can result in the formation of explosive compositions. In order to mitigate against such hazards, solutions which may contain peroxide residuals are often chemically treated, typically with a reducing agent such as sodium metabisulphite solution, to remove any peroxide residuals. Unfortunately, such a chemical treatment can alter the chemical nature of catalyst remaining in solution, and this can mean that the activity of the catalyst is lost or significantly reduced when the solution is recycled, thereby rendering the recycling ineffective.
An alternative to recycling is to dispose of such solutions to waste, but such disposal is becoming increasingly regulated and correspondingly more expensive. In addition, such a disposal also represents a significant chemical cost because of the loss of chemicals, and particularly for relatively expensive catalysts. It has therefore become expedient to recover spent catalyst if possible, notwithstanding the problems outlined hereinbefore, but where the catalyst is in solution, such recovery can involve the construction and operation of relatively expensive separation plants.
An example of a method employing a homogeneous catalyst is that proposed in U.S. Pat. No. 4,160,769 to Union Carbide Corp. in which cyclohexanone is oxidised by hydrogen peroxide in the presence of selenium dioxide catalyst, the catalysis it is believed proceeding via the formation of soluble perselenic acid. This process suffers from the drawback that selenium compounds are highly toxic, and therefore care must be exercised in the handling of the catalyst, and in the removal of traces of the cata
REFERENCES:
patent: 4171313 (1979-10-01), Mares et al.
Chemical Abstracts, vol. 114, 185237w (1991).
Brown Scott William
Johnstone Alexander
Sanderson William Ronald
Dentz Bernard
Solvay Interox Limited
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