Process for the preparation of p-toluic acid by liquid phase oxidation of p-xylene in water
AssigneeCouncil of Scientific and Industrial Research
InventorsMahendra Pratap Saxena, Ashok Kumar Gupta, Satish Kumar Sharma, Dinesh Prasad Bangwal, Krishan Kumar
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Abstract
The present invention provides a process for the preparation of p-toluic acid by liquid phase oxidation of p-xylene using oxygen or air as oxidant in the presence of p-toluic acid, water as solvent and cobalt salt or its combinations with salts of Ce, Mn as catalyst. Oxidation is carried out at 130-190° C. and pressure sufficient to keep water in liquid state. Oxidation step is followed by filteration to obtain p-toluic acid as major product. Untreated p-xylene is recovered and recycled and the catalyst is recovered from aqueous phase and is recycled.
Claims19
A process for preparation and isolation of p-toluic acid by a single step liquid phase oxidation reaction of p-xylene in water which comprises oxidizing p-xylene or a mixture of p-xylene and p-toluic acid with oxygen, air, or an oxygen/nitrogen mixture, at a pressure of 3-25 Kg/cm2 with an exit flow rate of 60-80 ml/min, in the presence of a catalytically active bromine-free salt of a transition metal selected from the group consisting of Co, Mn, Ce and combinations thereof in the range 5-160 mmol per mole of p-xylene in water in the range of 40-85 weight % of water based on a total weight of reaction mixture, at a temperature ranging between 130-150° C., for a period of 5-10 hrs, cooling the reaction mixture, removing any un-reacted p-xylene by washing the reaction mixture with an organic solvent, and filtering the reaction mixture to obtain the p-toluic acid as a desired product in a major amount and terephthalic acid in a minor amount.
A process for the preparation and isolation of p-toluic acid, the process consisting essentially of the steps of:
- oxidizing a reaction mixture, wherein the reaction mixture is selected from the group consisting of p-xylene and a mixture of p-xylene and p-toluic acid, with an oxidant selected from the group consisting of oxygen, air, a nitrogen/oxygen mixture, and combinations thereof, wherein said oxidation occurs in the presence of a catalytically active bromine-free salt of a transition metal selected from the group consisting of Co, Mn, Ce, and combinations thereof, in the range about 5 to about 160 mmol per mole of p-xylene in the reaction mixture, said reaction mixture further including water in the range of about 40 to about 85 weight % of water, based on a total weight of the reaction mixture, wherein the oxidation occurs at a temperature ranging between about 130° C. to about 150 ° C.;
- cooling the reaction mixture;
- removing the un-reacted p-xylene by contacting the reaction mixture with an organic solvent;
- and
- filtering the reaction mixture to obtain the p-toluic acid as a desired product,
- wherein the desired product, as made, is p-toluic acid in a major amount and relatively high purity with minimum amounts of terephthalic acid, carboxybenzaldehyde, and combinations thereof.
Dependencies are inferred from the claim text.