Phd Degree / Doktora
Permanent URI for this collectionhttps://hdl.handle.net/11147/2869
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Doctoral Thesis Characterization and Catalytic Applications of Hydrothermally Synthesized Poyoxotungstate Clusters Containing Organic-Inorganic Hybrid Materials(Izmir Institute of Technology, 2019) Ece, Özlem; Eanes, Mehtap; Çağır, AliMany scientists have been interested in hydrothermal synthesis and characterization of polyoxometalate clusters containing organic-inorganic hybrid materials recently because of having different applications in lots of fields, especially, using as catalysis in chemical reactions. In this study, three novel polyoxotungstate clusters were synthesized using hydrothermal method and catalytic activities of these three novel polyoxometalates and in addition two crystals previously synthesized in our group were studied. The first compound, [(4,4’-bpyH2)3][PCuW11O39] yellow crystals, crystallize in the space group P2(1)/n of the monoclinic system with four formula units in a cell. The crystal is a Keggin polyoxometalate and includes free 4,4’-bipyridine groups between the clusters. The second compound, (4,4’-bpyH2)[H2PW12O40]2.H2O colorless crystals, crystallize in the space group Ia-3 of the cubic system with twelve formula units in a cell. The crystal is a Keggin polyoxometalate and consists of two polyoxotungstate clusters, a free 4,4’-bipyridine group and a water molecule. The third and the last novel compound, (4,4’-bpyH2)4[H2P2W18O62]2 dark yellow crystals, crystallize in the space group P-1 of the triclinic system with four formula units in a cell. The crystal is a Wells-Dawson polyoxometalate and contains two polyoxotungstate clusters and free 4,4’-bipyridine groups between clusters. The catalytic study has been carried out using starch hydrolysis reactions by using hydrothermal synthesis and five different crystals were tried and conversion results were obtained. Starch samples converted to D-glucose with glucose yields above 90 wt.%. Catalyst reusability was performed for each crystal. No appreciable loss was observed in activity after five reaction cycles for each crystal.Doctoral Thesis Hydrogen Production From Biomass on Structured Catalysts(Izmir Institute of Technology, 2012) Umdu, Emin Selahattin; Şeker, ErolThe objective of this study is to investigate crystallite-size effect for oxides of transition metals iron supported on magnesium oxide (MgO) and cerium oxide (CeO2) modified alumina (Al2O3) and the effect of the basicity and/or basic strength of support material, on activity and hydrogen selectivity in the steam reforming of glycerol. Crystallite size effect is observed for MgO and Fe on MgO/Al2O3. It is observed that larger MgO crystallites size shifts gaseous product selectivity towards CO. Further as crystallite size is becomes higher than ~5 nm for Fe for gas product selectivity decreases. Basisity has also a similar behaviour; higher basisity or presence of unidentate carbonate basic sites observed at 865 and 800 cm-1 FTIR bands for CeO2 promoted catalysts hinder CO formation and promotes CO2 formation. This also results in high activity of steam reforming. Also basisity studies shows that inorganic carboxylate catalyst site with FTIR band 1535 and 1410 cm-1 is dominantly effective for gaseous product selectivity. High total basisity do not required for high glycerol conversion, yet high total basisity results in high gaseous product selectivity. Considering studied catalysts and their catalytic activities it can be concluded that MgO and Fe modified catalysts shows better activity for syngas production due to their basic and crystalline properties. And CeO2 modified catalysts or MgO catalysts with crystallite sizes lower than 5 nm are shows better performances for CO free product