Process for producing unsaturated nitrile

A process for producing an unsaturated nitrile comprising a reaction step of subjecting hydrocarbon to a vapor phase catalytic ammoxidation reaction in a fluidized bed reactor to produce a corresponding unsaturated nitrile,

• wherein, in the reaction step, a powder is fed to a dense zone in the fluidized bed reactor using a carrier gas,
• a ratio of a linear velocity LV1 of the carrier gas at a feed opening to feed the powder to the fluidized bed reactor to a linear velocity LV2 of a gas in the dense zone (LV1/LV2) is not less than 0.01 and not more than 1200,
• the powder comprises one or more powders selected from the group consisting of a catalytic powder used for the vapor phase catalytic ammoxidation reaction, a powder containing a Mo compound to replenish the catalyst with Mo atoms, and a powder containing a W compound to add W atoms to the catalyst, and
• the inner diameter of the fluidized bed reactor at the section corresponding to the dense zone is not less than 0.5 mφ and not more than 20 mφ.