Studies of sulfur poisoning process via ammonium sulfate on MnO2/γ-Al2O3 catalyst for catalytic combustion of toluene

MnO2/γ-Al2O3 catalysts were prepared and then quantitatively sulfur-poisoned by the pre-treatment of (NH4)2SO4 as a simulated sulfur-poisoning species. Catalytic combustion of toluene on fresh and poisoned MnO2/γ-Al2O3 catalysts was comparatively investigated. The characterization results from XRD, FT-IR, HRTEM, N2 adsorption/desorption, XPS, H2-TPR and NH3-TPD confirmed that the structure and natures of MnO2/γ-Al2O3 was stable when (NH4)2SO4 was used as the poisoning species. However, catalytic activity of the poisoned catalysts significantly decreased and quantitatively depended on the amount of (NH4)2SO4. The adsorption and occupation of the sulfur species from the decomposition of (NH4)2SO4 on active sites and the formation of inactive sulfate species via further oxidation of adsorbed sulfur species were responsible for the declined activity. This work exemplified a promising strategy for quantitatively and easily evaluating the sulfur-poisoning deactivation of catalysts for catalytic combustion of VOCs.