Rpc, Inc.

Twenty-first Century Research Corporation

Douglas J Dudgeon

Eustathios Vassiliou

Mark W Dassel

David C DeCoster

Ader M Rostami

This invention relates to methods of controlling the oxidation of cyclohexane to adipic acid in the presence of a monobasic acid solvent, by extracting the catalyst from the reaction mixture, outside the reaction zone. Substantially all the unreacted cyclohexane, the majority of adipic acid, and preferably substantially all the monobasic acid solvent are removed from the reaction product. In the case that substantially all the monobasic acid solvent is removed, protic solvent, is added intermittently or continuously in the reaction mixture during the removal of the monobasic acid solvent, preferably by distillation, thus preventing solids precipitation. Dipolar aprotic solvent is then added in the presence of an adequate amount of the protic solvent (the total of dipolar aprotic solvent and the protic solvent constituting a novel combination solvent) to maintain a single liquid phase, followed by a step of extracting substantially all the catalyst in protic solvent. The catalyst extract is preferably recycled to the reaction zone, where the cyclohexane is oxidized to adipic acid. Thus, the novel combination solvent, which is preferably a combination of cyclohexanone with water, allows the dissolution of the reaction product, preferably after removal of the majority of the adipic acid, followed by a substantially complete extraction of the catalyst in water. No catalyst precipitation takes place, and all disadvantages and costs of solids handling are prevented.

Methods of extracting catalyst from a reaction mixture in the oxidation of cyclohexane to adipic acid

This invention relates to methods of controlling the oxidation of cyclohexane to adipic acid in the presence of a monobasic acid solvent, by separating the catalyst from the reaction mixture, outside the reaction zone. Substantially all the unreacted cyclohexane, the majority of adipic acid, and substantially all the monobasic acid solvent are preferably removed. A protic solvent, may be added intermittently or continuously in the reaction mixture during the removal of the monobasic acid solvent, preferably by distillation, for preventing solids precipitation. A dipolar aprotic solvent is then added in the presence of an adequate amount of the protic solvent to maintain a single liquid phase, followed by a step of formation of two liquid phases, a solids-free protic liquid phase containing substantially all the catalyst, and a solids-free aprotic liquid phase containing at least the majority of ingredients of the reaction mixture. The formation of the two phases is performed by a process selected from a group consisting of lowering the first temperature to a second temperature, adding additional protic solvent, adding an apolar aprotic solvent, and a combination thereof.

Methods of separating catalyst in solution from a reaction mixture produced by oxidation of cyclohexane to adipic acid

This invention relates to methods of replacing water and cyclohexanone with acetic acid in an aqueous solution of catalyst, preferably a cobalt compound. Such an aqueous solution is produced by extracting catalyst with water from a cyclohexanone/water solution of reaction products made by the direct oxidation of cyclohexane to adipic acid. The replacement of both water and cyclohexanone are conducted in a solvent exchange column, wherein acetic acid dissolves the catalyst, while water vapors force the cyclohexanone into a condenser, followed by a decanter wherein two liquid phases may be formed and separated; an upper liquid phase containing a majority of cyclohexanone and a lower liquid phase containing a majority of water. The cyclohexanone may be removed in a pretreatment zone, wherein also part of the water may be removed, before the concentrated catalyst extract enters the solvent exchange column.

Methods and replacing water and cyclohexanone with acetic acid in aqueous solutions of catalyst

This invention relates to methods and reactor devices for controlling the oxidation of hydrocarbons to dibasic acids, in the presence of a cobalt catalyst and a monobasic acid, such as acetic acid, by treating the catalyst from the reaction mixture, outside the oxidation zone, after the oxidation has taken place at least partially. In one preferred embodiment, the catalyst is reduced to contain, preferably predominantly and more preferably substantially, cobalt ions in valence II, and at least partially precipitated by de-watering and/or thermal treatment. In a different preferred embodiment, the catalyst in the reaction mixture is first oxidized or maintained, preferably predominantly and more preferably substantially, at valence III, the reaction mixture is de-watered, the catalyst is reduced preferably predominantly and more preferably substantially, to valence II, causing precipitation either spontaneously at a predetermined temperature or after further thermal treatment. The precipitated catalyst is preferably recycled directly or indirectly.

Methods for treating cobalt catalyst in oxidation mixtures resulting from oxidation of hydrocarbons to dibasic acids

This invention relates to methods and reactor devices for controlling the oxidation of hydrocarbons to dibasic acids, in the presence of a cobalt catalyst and a monobasic acid, such as acetic acid, by treating the catalyst from the reaction mixture, outside the oxidation zone, after the oxidation has taken place at least partially. In one preferred embodiment, the catalyst is reduced to contain, preferably predominantly and more preferably substantially, cobalt ions in valence II, and at least partially precipitated by de-watering and/or thermal treatment. In a different preferred embodiment, the catalyst in the reaction mixture is first oxidized or maintained, preferably predominantly and more preferably substantially, at valence III, the reaction mixture is de-watered, the catalyst is reduced, preferably predominantly and more preferably substantially, to valence II, causing precipitation either spontaneously at a predetermined temperature or after further thermal treatment. The precipitated catalyst is preferably recycled directly or indirectly.

This invention relates to methods of controlling the oxidation of cyclohexane to adipic acid in the presence of a monobasic acid solvent, by removing the catalyst from the reaction mixture, outside the reaction zone. Substantially all the unreacted cyclohexane along with at least the majority of the monobasic acid solvent are removed. A substantially non-solvent for the catalyst (first constituent), and water are added into the resulting mixture, in such amounts as to maintain one solids-free single liquid phase. This process is highly facilitated in the presence of considerable amounts of adipic acid. The catalyst may then be extracted with water from the solids-free single liquid phase. A water phase containing dissolved catalyst may also be formed by addition of small amounts of a solvent which is substantially non-solvent for the catalyst and substantially non-solvent for the dibasic acids (second constituent), and/or dropping the temperature. Adipic acid may be precipitated after catalyst removal with further addition of second constituent and/or dropping the temperature.

Methods of recovering catalyst in solution in the oxidation of cyclohexane to adipic acid

This invention relates to methods for controlling the oxidation of hydrocarbons to dibasic acids, in the presence of a catalyst and a monobasic acid, by removing the catalyst from the reaction mixture, outside the oxidation zone, after the oxidation has taken place at least partially. Initially, the catalyst is partially precipitated and removed by reducing the water level in the reaction mixture and/or subjecting the reaction mixture to a temperature, at which or over which catalyst precipitates. After the initial partial precipitation of the catalyst, the remaining catalyst is subjected to a thermal treatment, during which at least part of the monobasic acid is removed leaving behind molten dibasic acids, in which, at least a major part of the remaining catalyst is precipitated, and it is removed. A minor part of remaining catalyst is removed by methods, which include but are not limited to ion exchange, precipitation with a base or appropriate salt, and electrodialysis. The precipitated catalyst in the three removal stages may be recycled in miscellaneous ways. The dibasic acid(s) may be removed at least partially before or after any catalyst precipitation stage.

Process of separating catalyst from oxidation mixtures

This invention relates to methods and reactor devices for controlling the oxidation of hydrocarbons to dibasic acids, in the presence of a catalyst and a monobasic acid, by removing the catalyst from the reaction mixture, outside the oxidation zone, after the oxidation has taken place at least partially. Initially, the catalyst is partially precipitated and removed by reducing the water level in the reaction mixture and/or subjecting the reaction mixture to a temperature, at which or over which catalyst precipitates. After the initial partial precipitation of the catalyst, the mother liquor remaining is subjected to a thermal treatment during which at least the major part of the monobasic acid is removed leaving behind molten dibasic acids, in which the remaining catalyst precipitates substantially in its totality, and it is removed. The precipitated catalyst in the two precipitation stages may be recycled in miscellaneous ways. From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

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Bainbridge Island, WA, United States of America

Douglas J Dudgeon