Abstract: A fluidized-bed reactor for ammo-oxidation or oxidation and an ammo-oxidation or oxidation process using the reactor. The reactor comprises a vessel, a sparger for supplying and dispersing a gas containing an organic material, and a distributor for supplying and dispersing an oxygen-containing gas, the sparger comprising a header and a plurality of dispersion pipes connected laterally to the header, the dispersion pipes each having a plurality of orifices, wherein the hole size of an orifice farthest from the header is larger than the hole size of an orifice nearest the header, and the hole size of one orifice is larger than or equal to the hole size of adjacent orifice that is nearer the header than the one orifice.

Abstract: A process for producing an .alpha.,.beta.-unsaturated nitrile, the process comprising the step of: reacting (1) a hydrocarbon selected from an olefin selected from propylene and isobutylene, a paraffin selected from propane and butane, and tertiary butyl alcohol, (2) ammonia, and (3) an oxygen-containing gas, in a reactor at a high temperature in a gas phase over a fluidized bed, so as to prepare an .alpha.,.beta.-unsaturated nitrile having the same number of carbon atoms as the hydrocarbon as a starting material, the reactor comprising a reactor vessel having therein, from a bottom of the reactor vessel, an oxygen-containing gas dispersing plate or pipe and a mixed gas dispersing pipe for dispersing a mixed gas of the hydrocarbon and the ammonia, a pressure loss in the oxygen-containing gas dispersing plate or pipe is controlled to the range of from 0.6 to 3.0 times a pressure loss in the fluidized bed.