(231c) Promoted Zno Sorbents for Low Temperature H2S Removal: Influence of Temperature, Support Surface Area, Pore Volume and Pore Size

Promoted ZnO sorbents with formulation Zn_0.95M_0.05O (M = Mn, Fe, Co, Ni, Cu) were supported on silica gels, MCM-41 and MCM-48. H₂S adsorption was conducted from room temperature to 400 ^oC in flowing 1 vol.% H₂S/H₂ at various levels of relative humidity. Cu-doped ZnO (15wt %)/MCM-41 provided the highest sulfur capacity at room temperature [0.90 mmol S/mmol (Zn+Cu)O]. At low temperatures, the utilization of the reactant (Zn+M) towards H₂S removal depended on the support employed in the order MCM-41 > MCM-48 > silica gels. This dependence was investigated in terms of the support: surface area, pore volume, and pore size; using N₂ adsorption-desorption isotherms. At equivalent levels of support surface area and pore size, higher pore volumes provided greater low temperature H₂S capacities presumably due to diminution in Zn_0.95M_0.05O crystallite size resulting from the lower Zn (NO₃)₂.6H₂O concentrations used during impregnation. Estimates of crystallite size were assessed from XRD line broadening (where feasible) as well as pulse oxygen chemisorption. The sulfided sorbents were tested for their regeneration and repeated use in multiple adsorption-desorption cycles.