Study of the reversible/irreversible character of the deactivation of CuO/SBA-15 SOx adsorbents in wet conditions under SO2 adsorption/regeneration cycling experiments

The effect of water vapor on the DeSOx performance of regenerable CuO/SBA-15 adsorbent was investigated for different temperatures of adsorption/regeneration cycles and CuO loadings. At 400 degrees C a significant decrease of both dynamic and total SO2 adsorption capacity compared to the ones measured without water was observed. This decrease could be related to a faster migration and aggregation of the CuO active phase, an adsorption competition between water and SO2 molecules on the active sites and/or the formation of copper based sulfate/oxysulfate/hydroxy-oxysulfate species difficult to decompose during the reductive regeneration step. On the other hand, at 450 degrees C water vapor leads to an increase of the total SO2 adsorption capacity by more than 20%, which might be due to an acceleration of the oxidation of SO2, a faster chemisorption of the sulfur species on the active sites and a more efficient regeneration step with regard to 400 degrees C. The decrease of the CuO loading from 15 to 7 wt% leads to a lower deactivation (i.e loss of SO2 adsorption capacity) at the breakthrough of the adsorbent under wet conditions. Whatever the temperature and the CuO loading, once the water vapor is removed from the gas stream, the dynamic SO2 adsorption capacities are totally or partially recovered. This behavior shows that the deactivation of the CuO/SBA-15 adsorbent induced by water vapor is a reversible or partially reversible phenomenon. It appears that during the DeSOx process a migration towards the pore mouth and an aggregation of the CuO active phase occur faster under water vapor conditions with the formation of large particles of CuO.