Fluidization quality is severely affected by a decrease in volume of the fluidizing gas in the emulsion phase. Several causes underlie this phenomenon, one of which is gas adsorption on particles. In this study, the fluidization behavior was observed by switching the fluidizing gas from Ar to CO2. This gas combination was chosen to eliminate the influence of nonequimolar diffusion due to a difference in molecular weight. Because the adsorption capacity of CO2 on porous particles was large, temporary defluidization occurred when the fluidizing gas was switched from Ar to CO2. The lower limit of the adsorption capacity was obtained using particles with different adsorptivities. Two types of defluidization were observed: channeling for smaller particles and plugging for larger particles. The type of defluidization was represented by a map constructed using the minimum fluidizing velocity and the superficial gas velocity as parameters. In addition, gradual gas replacement was explored as a method to prevent defluidization.