Nanostructured ZnO/sepiolite monolithic sorbents for H2S removal

Abstract

ZnO presents favorable thermodynamics, equilibrium constant and stability for H₂S chemisorption and sepiolite has excellent sorptive and rheological properties to be employed as a support. Four conformed ZnO/sepiolite composites are prepared, two by impregnation in zinc nitrate solution – one using activated carbon as a dispersing and pore generating agent – and two by dry mixing of the clay with dispersed or hierarchically assembled ZnO nanoparticles. The extrudates obtained with a mixture of sepiolite and nanodispersed ZnO particles are the most active for H₂S chemisorption in temperature-programmed tests performed in an inert atmosphere, which can be correlated with the higher and homogeneous ZnO dispersion. ZnO sulfidation is reversible in the presence of O₂. Thus, the activity can be regenerated, and these materials act as catalysts for H₂S to SO₂ oxidation in air.