Feeding a dispersed cloud of powder into a transport tube reactor, particularly on a laboratory scale, presents challenges. A major difficulty is dispersing the powder with minimal gas flow to maintain a long enough residence time in the reactor to achieve high conversions. In this study, two different laboratory feeders were designed and built to be mounted on top of an aerosol flow reactor incorporating different dispersion techniques: (1) a fluid bed feeder uses primarily gas flow to shear and disperse powder and (2) a spinning wheel feeder uses mechanical shear as the primary dispersion force. A factorial design was used to compare particle size distributions from both feeder types along with identifying factors that may influence the collected particle size distributions. Both Mn₂O₃ and ZnO powders were tested, because of their importance to solar-thermochemical based water splitting cycles. The feeders were mounted on an aerosol flow reactor and a 2 factor central composite design was executed to quantify how much the particle size distributions affected thermal reduction of Mn₂O₃ and ZnO. This talk will present the results from this study