The sulfidation of cobalt oxide with H2S was proposed for the desulfurization process at low temperatures. The reaction is studied with a packed-bed reactor and TGA (thermogravimetric analysis) equipped with in situ reactor experiments in the range 300-500 degreesC. Due to larger particle size, the bulk cobalt oxide showed slower sulfidation rate having insufficient removal efficiency. Supported cobalt oxide exhibited high removal efficiency and degree of sulfidation at 300-400 degreesC primarily because of its smaller grain size. Among the three sorbents tested, extremely low values of activation energy and frequency factor were observed in Co3O4/TiO2; the rate was almost independent of temperature. The experimental data were successfully predicted by shrinking core model having a bimodal distribution in grain size. From the calculated effective diffusivity, D-e, and kinetic constant, k, the diffusion resistance controlled the overall reaction rate of bulk oxide sorbent. (C) 2004 Elsevier Ltd. All rights reserved.