gamma-Al2O3 was chemically or heat treated to modify its behavior as a catalyst of the Claus reaction at low temperature. The treatment by P or La impregnation altered substantially the surface donor properties, as revealed by NH3 adsorption, with no significant changes in the textural properties. However, the heat treatment by calcination at temperatures above 550 degrees C mostly affected the textural properties through sintering and crystallization. Using a model described in detail in a previous study the global reaction rate was calculated and the H2S conversion curves in a fixed bed reactor were theoretically predicted. The experimental results showed that the surface treatment increased largely the catalytic activity of alumina although the effects on the H2S conversion in the reactor were small since it is a diffusion controlled process. Changes in performance due to heat treatment were much more pronounced allowing to conclude that the alumina performance could be substantially improved by optimization of the textural properties.