Breakthrough study of the adsorption and separation of sulfur dioxide from wet gas using hydrophobic zeolites

Abstract

The adsorptive and kinetic behaviour patterns of SO2 and water vapour on mordenites and pentasil zeolites were investigated using the breakthrough curve method. For all the zeolites studied, the breakthrough experimental data show a decrease in the equilibrium capacities for both SO2 and H2O with increasing SiO2/Al2O3 ratio. At the lower ratios SO2 adsorption is believed to be influenced by the basicity of the zeolite. The presence of water in the gas reduces its SO2 capacity to varying degrees, depending on the SiO2/Al2O3 ratio. In contrast, the presence of CO2 (in the wet SO2-containing gas) has very little effect. The hydrophobic indices, which were used to interpret the selectivity of SO2 adsorption, showed different trends with SiO2/Al2O3 ratios. The Langmuir-Freundlich and extended Langmuir-Freundlich equilibrium models were used to predict equilibrium properties for the single-component and binary systems, respectively. The linear driving force-based non-isothermal model was used to fit experimental breakthrough curves for the single-component systems. Overall mass transfer resistances derived from the model were compared with the values obtained for SO2 and water vapour adsorption in pelleted samples using a simplified biporous adsorbent model. Breakthrough curves for the binary systems were calculated using kinetic and equilibrium data of the single-component systems.