Insights to the microwave effect in the preparation of sorbent for H2S removal: Desulfurization kinetics and characterization

•Microwave was applied to prepare sorbents used for syngas desulfurization.•Iron oxide sorbents were prepared by microwave and conventional heating.•Microwaves lead to more porous structure and raise the surface area of sorbent.•Desulfurization performance of sorbent can be improved through microwave heating.

High temperature coal gas desulfurization is an efficient and environmental-friendly process for clean coal technologies such as the integrated coal gasification combined cycle. This study adopted microwaves as the energy source to prepare iron oxide desulfurization sorbents and investigated the effect of microwave heating on the properties of the sorbents. The desulfurization kinetics of H2S removal by the two kinds of sorbents heated using both microwave and conventional method were studied and the sorbents were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), N2-adsorption and energy dispersive spectrometry (EDS). The shrinking core model was used to describe the desulfurization reaction. The calculated activation energies of microwave-heated sorbent in the regions of chemical reaction and diffusion control were both smaller than those of the conventional-heated sorbent. The characterization data indicate that the sorbents prepared by microwave heating have higher contents of active metal elements on the surface, which improve the adsorption efficiency. Fractal dimensions were calculated based on Frenkel-Halsey-Hill theory and the results revealed that the fractal dimension of microwave-heated sorbent is 2.850 and that of conventional-heated sorbent is 2.832. The results indicate that microwave irradiation provides a more porous internal structure and irregular surface which facilitates gas transfer during the desulfurization process. Overall, the microwave heating method produced sorbents with better H2S removal performance, suggesting the potential of using this method to prepare improved industrial sorbents.