Method for preparing high-purity 9-fluorenone from high-purity fluorene

The invention discloses a method for preparing high-purity 9-fluorenone from high-purity fluorene. The high-purity 9-fluorenone is prepared by using high-purity fluorene as a raw material, alkali as a catalyst, an aromatic organic solvent and water as a solvent and a quaternary ammonium salt as a phase transfer agent. The preparation method disclosed by the invention comprises the steps of purifying industrial fluorene of which the purity is more than or equal to 95% at first, and then preparing the 9-fluorenone by using the high-purity fluorene, so that a purification process of the product namely 9-fluorenone which is difficult to purify is avoided, and the preparation process is simplified. Under the condition of the invention, the conversion rate of fluorene can reach 100%, and fluorenone with the purity of 100% can be obtained; after a reaction solution is cooled and crystal fluorenone is separated out, the filtrate containing the alkali, quaternary ammonium salt, fluorene and fluorenone is directly recycled, and a high-boiling-point solvent is used for absorbing the solvent in the reaction tail gas, so that the method is an energy-saving and environment-friendly chemical process.