Method for preparing 9-fluorenone from fluorene

A method for preparing 9-fluorenone from fluorine, comprising a reaction of industrial fluorine as raw materials with an oxygen-containing gas as an oxidizing agent, using 9-fluorenone and water as solvents, a base as a catalyst, a quaternary ammonium salt as a phase transfer agent, to synthesize 9-fluorenone under the conditions of a reaction temperature of 70-83°C, wherein the raw material of fluorine is added at one time or constantly supplemented along with the reaction. In the present invention, the product, 9-fluorenone, is used as the solvent, which omits the processes of solvent separation, recycling and the like, as well as the operations of reaction liquid separation and 9-fluorenone refining and coupling, and significantly simplifies the 9-fluorenone synthetic process; the alkali, the quaternary ammonium salt and the by-product, water, are all recycled; by means of the supplementation of fluorene, the utilization efficiency of the reactor is improved.