Cu−Cr−O and Cu−Ce−O Regenerable Oxide Sorbents for Hot Gas Desulfurization

Binary Cu−Cr−O and Cu−Ce−O oxides were studied in this work as regenerable sorbents for high-temperature fuel gas desulfurization. CuO−Cr 2 O 3 and CuO−CeO 2 sorbents can remove H 2 S from simulated coal-derived fuel gas to less than 5−10 ppmv in the temperature range of 650−850 °C. The presence of stable CuCr 2 O 4 in CuO−Cr 2 O 3 solids retains some copper in the Cu 2+ or Cu 1+ oxidation state, which can account for the high H 2 S removal efficiency. In CuO−CeO 2 sorbents, however, CuO is easily reduced to copper metal. Participation of reduced cerium oxide in sulfidation can explain the observed high desulfurization efficiency. TGA tests and XRD analysis indicate that sulfidation proceeds through partial initial reduction of the CuO−Cr 2 O 3 sorbents: CuO → Cu/Cu 2 O → Cu x S ( x < 2). Reduction kinetics were studied in the TGA over temperature ranges of 550−850 and 350−850 °C, respectively, for the CuO−Cr 2 O 3 and CuO−CeO 2 materials. The sulfidation kinetic parameters were measured in the temperature range of 450−850 °C after prereduction of both sorbents. The sulfidation of metal copper in Cr 2 O 3 and CeO 2- x matrices is a fast reaction with low activation energy, 19.8 and 16.6 kJ/mol, respectively. Both types of sorbents can be fully regenerated with diluted air. The regeneration temperature affects the reaction pathway and the regenerability of the solid composition.