EXAFS and XRD characterization of palladium sorbents for high temperature mercury capture from fuel gas

Removal of pollutants such as mercury at elevated temperatures provides improvements in the overall thermal efficiency during the process of coal gasification. The two high temperature sorbents studied were 5 wt% Pd/Al2O3 and 5 wt% Pd/SiO2: materials shown to have significantly different Hg adsorption capacities. A combination of XRD and EXAFS has been used to characterize the Pd–Hg alloy formed when these Pd-based sorbents were exposed to fuel gas (CO, CO2, H2) containing Hg vapour at 204 °C. Significant differences were found in the nature of the alloy formed on the two sorbents following Hg exposure. The Pd/Al2O3 sorbent produced a single homogeneous solid solution of Pd–Hg whilst the silica-supported Pd produced an alloy of varying composition.