Abstract: The present invention provides various processes for selectively removing undesirably sized catalyst particles from a catalyst synthesis system. In one embodiment, a slurry is formed containing a molecular sieve, a matrix material, a slurring agent, and optionally a binder. At least a portion of the slurry is dried to produce a first catalyst mixture. At least a portion of catalyst particles are selectively removed from the first catalyst mixture based on their size. The selective removal of particles preferably occurs in a counter-flow cyclone separator. By selectively removing undesirably-sized catalyst particles from the formulated catalyst mixture, desirable fluidization and catalytic activity characteristics can be realized in an OTO reaction system.