Catalyst roller for gravity-assisted particle flow

Systems and methods are provided for controlling the flow and transport of catalyst particles within a reaction system. The flow of catalyst particles can be managed using a rotating disc or wheel that is configured within a roller volume to allow for control over the rate of catalyst flow while reducing or minimizing attrition of the catalyst particles. This can be achieved in part by maintaining a relationship between the center of the rotating disc, the inlet for catalyst particles to the roller volume, and the top wall of the roller volume so that catalyst particles are not exposed to compressive forces and/or abrasion during rotation of the disc. Additionally or alternately, the disc and roller volume surfaces can be configured to reduce or minimize the potential for catalyst particles to become trapped in "dead space" regions within the roller volume. By using a disc to provide force for transport of particles through the roller volume, the speed of catalyst movement can be controlled at relatively slow catalyst flow rates with a reduced or minimized risk for clogging or plugging within the roller volume.