Effect of Activated Carbon Supports on Removing H2S from Coal-Based Gases using Mn-Based Sorbents

A series of MnOx/AC sorbents were prepared by a sub- or supercritical water impregnation method at different temperatures using three types of active carbons (ACs) as supports. The desulfurization activities of the MnOx/AC sorbents were studied, and the physicochemical properties of fresh and used sorbents were characterized by X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, and X-ray absorption near edge structure. The results indicate that the AC composition and preparing temperature affect the desulfurization activity of prepared sorbent by changing the form and dispersion of the active component. MnOx/AC sorbent prepared at 350 degrees C and active carbon AC(Z) from walnut shell as support presents the best desulfurization activity, holding above 22 h under the desulfurization level of nearly entire removing H2S in hot coal-based gas with breakthrough sulfur capacity of 7.24 g of S/100 g of sorbent. It is found that the valence of Mn loaded on the different AC supports was various, which related directly to the activity and capacity of the H2S removal from hot coal-based gases. The species, content, and the dispersion of the manganese oxide on the surface of the supports were dominated by AC properties. In addition, Mn3O4 is the main active component for the H2S removal over MnOx/ACs sorbents.