Biyokütle gazlaştırma işlemi ıçin çinko titanat esaslı H₂S adsorbentlerinin geliştirilmesi

The goal of this research study is to develop copper promoted zinc titanate based adsorbents and examine H2S elimination during biomass gasification process by combining desulfurization and reforming stages. Firstly, the effects of fluid velocity and temperature on the desulfurization of Zn2TiO4 (ZT) were investigated to determine mass transfer limitation. The tests with different gas flow rates suggested that surface-reaction controlled the mechanism; while the reaction rates at high temperatures were found greater resulting high diffusion coefficient. The relationship was supported with TEM analysis, demonstrating that high temperature enabled formation of small ZnS particles which suppressed product layer resistance. Under both steam and H2 atmospheres, the efficiency of ZT sample was reduced due to the steam poisoning of active sites, thereby the activity was decreased. In the second part, copper doped zinc titanate (Cu-ZT) adsorbents with different Cu/Zn weight ratios were prepared with co-precipitation method and the properties of the samples were investigated by XRD, XPS, BET and SEM/EDS analyses. XPS analysis revealed that the successful addition of Cu into the main lattice which was confirmed by presence of Cu2p3/2 state and oxygen peaks with high-intensity. The doping with Cu significantly affected the desulfurization efficiency especially under H2 atmosphere; which H2S removal of bare ZT was almost zero, while Cu-ZT adsorbent exhibited approximately 60% removal after 5 h. In the last part; different amounts of Cu-ZT adsorbents were incorporated with CaSiO3 based filter via ball-milling process to integrate as a protective layer for Ni/Al2O3 impregnated filter during hydrocarbon reforming. The characterization with XRD, SEM and FTIR techniques indicated that Cu-ZT grains were homogenously distributed on the host lattice of ceramic filter. The incorporation of Cu-ZT into the filter structure remarkably enhanced the sulfur resistance under reducing and gasification atmospheres which were attributed to the increasing affinity and preventing diffusion limitation. Although, the CH4 and C6H6 reforming activities of Ni/Al2O3 based catalytic filter decreased in the presence of H2S, the performance was improved by integrating with the Cu-ZT/filter sample as primarily active stage in the integrated process. The hybrid process displayed superior reforming efficiencies for CH4 and C6H6 degradation in the H2S atmosphere, which were 10 times higher for methane and 1.15 times higher for benzene than that of the single stage system. Herein, an innovative concept was found to obtain high quality synthesis gas by integrating desulfurization and reforming processes.