Role of oil derived carbonaceous phase in the performance of sewage sludge-based materials as media for desulfurizaton of digester gas

Desulfurization adsorbents for purification of digester gas were prepared by pyrolysis of sewage sludge impregnated with spent mineral oil. To evaluate the changes in the structural and chemical properties the pyrolysis time and temperature varied. The materials were characterized using adsorption of nitrogen, FTIR, XRD, ICP, SEM and thermal analysis. Their catalytic activity was tested in the removal of hydrogen sulfide from simulated mixture of digester gas. The results indicated the importance of new carbon phase from the oil precursor. It provided mesoporosity, which increased the dispersion of catalytic phase and space for storage of surface reaction products. The results indicated that the adsorbents obtained at 950 °C are much more active in the process of hydrogen sulfide oxidation than those obtained at 650 °C. Moreover, longer heat treatment is also beneficial for the development of surface catalytic properties. Extensive pyrolysis stabilizes carbon phase via increasing its degree of aromatization and provides activation agents for this phase coming from decomposition and rearrangement of inorganic phase.