Silica-polyamine-based carbon composite adsorbents as media for effective hydrogen sulfide adsorption/oxidation

New silica - carbon adsorbents were prepared by pyrolysis of silica - polyamine composites at 600 degrees C. The heat treatment was expected to activate nitrogen for effective hydrogen sulfide oxidation. Moreover, the same pyrolysis treatment was applied on silica - polyamine adsorbents previously used to remove copper ions for aqueous solution. The performance of these materials as H2S adsorbents was tested using a home-developed dynamic breakthrough test. Samples from before and after the adsorption process were characterized by adsorption of nitrogen, surface pH, thermal analysis, elemental analysis, FTIR, optical microscopy, and solid-state CPMAS C-13 NMR. Differences in the performance were linked to the surface properties such as content of nitrogen, content of copper, surface acidity/basicity, and porous structure. It was found that the capacity for hydrogen sulfide removal/selectivity for oxidation to sulfur depends on the granulation of the silica matrix, the kind of polymer used for grafting, surface basicity, and porosity. Thermal transformation of the polymer causes the formation of new highly dispersed catalytic centers with active nitrogen atoms. The silica matrix also provides pore space for the storage of oxidation products, mainly elemental sulfur.