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.