An "unreacted shrinking core" model was used to describe the behavior of a fixed-bed-reactor during the reaction between gas-phase H2S and perovskite-tvpe sorbents (i.e., La2CuO4, LaMnO3, and LaCoO3). Optimization of a single adjustable parameter (i.e., the effective diffusivity of H2S through the sulfided perovskite layer) results in an excellent agreement between experimental H2S breakthrough curves and model predictions for different sorbents, temperatures, and H2S inlet concentrations. The values of effective diffusivity thus obtained are on the order of 2-10 cm(2)/h, For La2CuO4, for which data were available at different temperatures, the effective diffusivity was also found, to follow an Arrhenius-type expression with an activation energy of approximately 3 kcal/mol.