In the present work, commercial-grade activated carbon was modified by steam activation to improve its surface properties for high temperature desulfurization. The modified sample was also further upgraded by impregnating with KOH and KI to promote the chemisorption with of H2S. The H2S adsorption performance was tested under the temperature range of 30-550 degrees C using the temperature program adsorption technique to understand the effect of adsorption temperature on the material adsorption characteristic. It was found that at ambient temperature, the impregnation of activated carbon with KOH can promote the H2S adsorption capacity of activated carbon, whereas the impregnation with KI does not provide a significant beneficial effect. At high adsorption temperature (upto 550 degrees C), both KOH and KI impregnation considerably improve the H2S adsorption performance of activated carbon in terms of the adsorption capacity and breakthrough time. It was revealed from N-2 adsorption, SEM and EDS measurement that the chemical reactions between H2S and alkaline compounds (KOH and KI) are promoted at high temperature. Based on all experimental results, the equilibrium adsorption model using the linear isotherm was developed to predict the adsorption behavior of these sorbents in terms of equilibrium isotherm constant and mass transfer coefficient for later scaling-up process.