The use of an open cell lattice as the basis of the catalyst bed enables the formation of very compact, light weight and high surface area catalyst bed with excellent gas flow-through characteristics.

The present invention also relates to a SAPO-34 microsphere catalyst prepared by the method for a circulating fluidized bed reactor.

In the invention, the olefin feed is contacted with a particle-form fluidized catalyst in a circulating-bed reactor, wherein the catalyst forms the circulating bed of the reactor.

The valence of at least a portion of the catalyst sent to an activator is changed from Cr(III) to Cr(VI). The catalyst is prepared or activated continuously using a fluidization bed catalyst activator.

The invention provides a fluidized-bed catalyst for the production of acrylonitrile which can attain high yield of acrylonitrile over a long time; and a process for the production of acrylonitrile with the catalyst.