Σύνθεση, χαρακτηρισμός και καταλυτική συμπεριφορά νανοδομημένων υλικών CeO2-ZrO2, CeO2-SiO2, CeO2-Al2O3 ; Synthesis, characterization and catalytic behavior of nanostructured materials CeO2-ZrO2, CeO2-SiO2, CeO2-Al2O3.
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| Název: | Σύνθεση, χαρακτηρισμός και καταλυτική συμπεριφορά νανοδομημένων υλικών CeO2-ZrO2, CeO2-SiO2, CeO2-Al2O3 ; Synthesis, characterization and catalytic behavior of nanostructured materials CeO2-ZrO2, CeO2-SiO2, CeO2-Al2O3. |
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| Autoři: | Iosifidis, Agathaggelos, Ιωσηφίδης, Αγαθάγγελος |
| Informace o vydavateli: | University of Ioannina Πανεπιστήμιο Ιωαννίνων |
| Rok vydání: | 2012 |
| Sbírka: | National Archive of PhD Theses (National Documentation Centre Greece) |
| Témata: | Οξείδιο, Ζιρκόνιο, Δημήτριο, Πυρίτιο, Αργίλιο, Ανώμαλη υπερδιάχυση, ΕΙΔΙΚΗ ΕΠΙΦΑΝΕΙΑ, Διάσπαση αλκοόλης, OXIDE, Zirconium, Cerium, Silicon, Aluminum, Anomalous hyper-diffusion, SPECIFIC SURFACE AREA, Alcohol dicomposition, Φυσικές Επιστήμες, Χημεία, Natural Sciences, Chemical Sciences |
| Popis: | This PhD thesis has been prepared in order to study the diffusion phenomena occurring in the decomposition of secondary alcohols. For this purpose, mixed oxides were synthesized with reference oxide of cerium oxide (CeO2) and zirconium oxide (ZrO2), silica (SiO2) and alumina (Al2O3) as additives. The synthesis was made using the hydrothermal method, and mixed oxides were also produced by mechanochemical development of appropriate quantities of the two oxides in a ball mill. After the composition of oxides they were characterized and investigated using X-ray diffraction, thermal analysis (TG-DTA), N2 adsorption-desorption, themperture programmed desorption of ammonia and scanning electron microscopy. Aiming to study the diffusion phenomena, we conducted catalytic decomposition of isopropanol and isobutanol. The study found that the presence of cerium (Ce) improves the crystal structure and the size of the crystals of oxides, reduces the specific surface areas (m2/g) and the power of acid sites on the surface of the oxides-catalysts. The porosity appears to be mixed micro and meso with increasing cerium content, while ZrO2, SiO2 and Al2O3 are purely mesoporous. We also observed that mechanochemical treatment leads to lower specific surface areas and larger crystals than the hydrothermal method. The acid sites are weak and the acidity decreases in the series CeO2-ZrO2>CeO2-SiO2>CeO2-Al2O3. During the catalytic decomposition of alcohols was found that produced exclusively alkene, suggesting that the catalysts are more acidic with low basicity as the ketone is produced in very small percentage. Materials containing aluminum exhibit greater activity, while the decopmposition of isobutanol is easier than the decomposition of isopropanol for all the studied catalysts. Using the Arrhenius lines led us to conclude that the oxides containing zirconium cause abnormal hyperdiffusion of the molecules of alcohol. This phenomenon reduces over oxides containing silicon and almost disappears over those containing aluminum. ... |
| Druh dokumentu: | doctoral or postdoctoral thesis |
| Jazyk: | Greek, Modern (1453-) |
| Relation: | https://hdl.handle.net/10442/hedi/27281 |
| DOI: | 10.12681/eadd/27281 |
| Dostupnost: | https://hdl.handle.net/10442/hedi/27281 https://doi.org/10.12681/eadd/27281 |
| Přístupové číslo: | edsbas.239BBF6F |
| Databáze: | BASE |
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