Process for producing acrylonitrile

Abstract

In a process for producing acrylonitrile by the ammoxidation of propylene, comprising bringing, in a fluidized-bed reactor, a gas containing propylene, ammonia and molecular oxygen into contact with a highly-active ammoxidation catalyst (this catalyst being one which can attain a rate constant of 2 s.sup.-1 or more for the ammoxidation reaction of propylene, assuming that the reaction is a first-order reaction) which is in a state of being fluidized by the gas, the improvement comprising carrying out the ammoxidation under the following conditions: (a) the superficial gas velocity in the fluidized-bed reactor is maintained at 1 to 10 m/s under such an operation condition that the rate constant of the ammoxidation reaction of propylene is 2 s.sup.-1 or more, assuming that the reaction is a first-order reaction; (b) an area in which the density of fluidized solid matter is 100 kg/m.sup.3 or more is kept in the fluidized-bed reactor at the upstream side thereof; and (c) a system for recycling the ammoxidation catalyst which has been supplied to the reaction is provided in the fluidized-bed reactor between the upstream side and downstream side thereof, and the recycling catalyst is introduced into the reactor at such a position that the weight ratio of the ammoxidation catalyst present in an area above the introduction position to the ammoxidation catalyst present in an area below the position will be from 2:1 to 99:1.