Reactivity evolution during sulfidation of porous zinc oxide

The sulfidation of porous zinc oxide in hydrogen sulfide—nitrogen mixtures was studied in a thermogravimetric analysis system. Experiments were carried out with particles in the range 52–350 μm, at temperatures from 300 to 600°C, and with different hydrogen sulfide concentrations. The analysis of the experimental results showed that the sulfidation reaction was of first-order with respect to the H2S concentration, and that the conversion vs time trajectories depended strongly on the particle size. The generalized pore model of Yu and Sotirchos, a detailed model for diffusion, reaction, and structure evolution in chemically reacting porous media, was used to analyze the experimental data, and good agreement between model and experiment was observed. The intraparticle diffusional limitations and their evolution with the progress of the reaction were found to be the factor influencing most the sorptive capacity of the ZnO sorbet for H2S removal.