In this study, a hollow zeolite nanoreactor is used to promote uniform nanoparticle formation and inhibit sintering of active nanoparticles during Fischer Tropsch synthesis. Cobalt oxide nanoparticles are selectively placed in the hollow zeolite cage. The confinement effect of a hollow zeolite cage results in the formation of uniformly sized cobalt oxide nanoparticles. In addition, the nanoreactor seems to inhibit the sintering of the nanoparticles located in the cavity during Fischer Tropsch synthesis. Similar Fischer Tropsch synthesis activity and durability of sintered and nonsintered catalysts indicate that other mechanisms than sintering pertain to the deactivation of this specific cobalt Fischer Tropsch synthesis catalyst.