(91b) Preparation Characterization and Surface Chemical Reactions of Model Cu-ZnO/Silica Sorbents Upon H2S Adsorption
AIChE Annual Meeting
Monday, November 9, 2009 - 12:55pm to 1:20pm
Metal dopants are known to play significant role in improving the performance of ZnO-based supported sorbents used for H2S removal. Lifespan of the supported doped sorbents depends on the conditions of oxidative regeneration of the sulfided (?spent?) sorbents that affect changes in oxidation, coordination states, dispersion and ion diffusion off and towards the active surface. Well-characterized model sorbents are often used in combination with surface science techniques to study the above processes. Among model sorbents, those prepared under the conditions resembling industrial ones, i.e. pressure, temperature and choice of precursors are especially useful.
Model supported sorbents have been prepared by depositing mixed Cu-Zn oxides of variable stochiometry from aqueous solutions of nitrate precursors onto oxidized silicon wafers by chemical spray pyrolysis technique under controlled atmosphere conditions (?calcined sorbents?). Further, model ?calcined? sorbents were reacted with H2S gas forming ?sulfided sorbents?. Morphology of model sorbents was studied by SEM-EDX. Oxidation states and atomic ratios of the elements were confirmed by XPS.
Regeneration of ?sulfided? sorbents by oxygen was performed in-situ by temperature-dependent XPS. Changes in oxidation states of Sulfur and metal ions present in the sorbents with respect to the temperature and partial pressure of oxygen have been analysed.