Lanthanum induced lattice strain improves hydrogen sulfide capacities of copper oxide adsorbents

This work probes the effects of La on reactions involving CuO sorbents and H2S in gaseous streams. La-CuO sorbents with nominal La/Cu atomic ratios of 1:2 achieved higher capacities (27 and 36 g H2S per 100 g sorbent) compared to CuO sorbents (25 g H2S per 100 g sorbent). Comparison of the La-CuO sorbents using energy dispersive x-ray spectroscopy and La L-3-edge XAS suggested that increased capacity resulted from more uniform dispersion of La within the CuO phase (3.3 wt.% vs. 1.0 wt.% La). X-Ray absorption near edge structure analysis suggested more electron-rich Cu species in La-CuO samples, while extended X-ray absorption fine structure modeling showed an increase in single-scattering path lengths for neighboring and near-neighbor atoms. These changes suggest that La induces strain in the Cu-O lattice, thereby increasing H2S capacity by reducing energy barriers associated with surface reactions between oxygen atoms and adsorbed H2S molecules.