摘要 |
This invention relates to methods of controlling the oxidation of cyclohexan e to adipic acid in the presence of a monobasic acid solvent, by extracting th e 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, preferabl y by distillation, thus preventing solids precipitation. Dipolar aprotic solve nt is then added in the presence of an adequate amount of the protic solvent (t he total of dipolar aprotic solvent and the protic solvent constituting a novel combination solvent) to maintain a single liquid phase, followed by a step o f extracting substantially all the catalyst in protic solvent. The catalyst extract is preferably recycled to the reaction zone, where the cyclohexane i s 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.
|