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.