Preparation method of furanone acid

The invention belongs to the technical field of medical chemical industry, and particularly relates to a preparation method of furanone acid. The method comprises the following steps of: adding dropwisely a sodium nitrite aqueous solution into a concentrated sulfuric acid and long-chain alcohol aqueous solution, separating an ester layer to obtain nitrite after the dropwise addition is finished; dissolving 2-acetyl furan in a dilute hydrochloric acid solution, adding concentrated sulfuric acid and a catalyst, controlling temperature, adding dropwisely the nitrite, continuously stirring to react after the dropwise addition is finished, adjusting pH after the reaction is finished, filtering to recover the catalyst, and adding an extracting agent into filtrate to extract long-chain alcohol generated by the reaction and unreacted acetyl furan, wherein a water phase is a furanone acid aqueous solution. By the adoption of the preparation method of the furanone acid, an adopted oxidant only needs to slightly exceed