Microwave heating motivated performance promotion and kinetic study of iron oxide sorbent for coal gas desulfurization

Abstract

High temperature coal gas desulfurization is an efficient and environment-friendly process for clean coal technologies. In this study, microwave heating is adopted as the energy source to prepare iron oxide desulfurization sorbents and the effect on the properties of the sorbents is investigated. Sorbent synthesized through the conventional heating method is obtained as well for comparison. Characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), scanning electron microscope (SEM) and N2 adsorption are used to evaluate the as-prepared sorbents. Results from XAS and XRD show that Fe2O3 crystal possesses smaller volume and shorter length in bonds Fe-O and Fe-Fe, suggesting that there is a better dispersion of crystallites under microwave irradiation. According to XPS results, microwave irradiation induces sorbents with higher contents of surface lattice O2−, which is contributive to increasing the absorption efficiency and desulfurization reactivity towards the removal of H2S. With the help of thermogravimetry devices, kinetic studies produce the result that both the desulfurization and regeneration processes adapt the model of unreacted shrinking core. The reaction rates are limited via surface chemical reaction at first and then controlled by internal diffusion control in the later stage. Sorbents produced by microwave heating, on the whole, show a better H2S removal performance due to their facilitated chemical reaction and mass transfer, suggesting the potential of the preparation of improved industrial sorbents.