Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Fen Bilimleri Enstitüsü, Türkiye
Tezin Onay Tarihi: 2011
Öğrenci: SEVAL GÜNDÜZ
Danışman: TİMUR DOĞU
Özet:The interest in hydrogen as a clean energy source has increased due to depletion of limited fossil resources and environmental impact related to CO2 emissions. Hydrogen production from bio-ethanol, which already contains large amount of water, by steam reforming reaction, has shown excellent potential with CO2 neutrality. However, steam reforming of ethanol reaction is a highly complex process including many side reactions which decrease hydrogen yield and have a negative effect on process economy. Also, thermodynamic limitations cause decrease in hydrogen yield. In the present study, a new reaction process called sorption enhanced steam reforming has been investigated to improve hydrogen yield in ethanol reforming over Ni and Co impregnated MCM-41 type mesoporous catalysts. In this process in-situ removal of CO2 by CaO was used to improve hydrogen yield significantly. Catalysts play a crucial role in both steam reforming of ethanol and sorption enhanced steam reforming of ethanol reactions. Discovery of mesoporous catalyst supports, like MCM-41, started a new pathway in catalysis research. In this study, Co and Ni incorporated MCM-41 type materials having metal/Si molar ratio of 0.1 were synthesized by impregnation method, characterized and tested in both steam reforming of ethanol and sorption enhanced steam reforming of ethanol reactions at 500oC, 550oC and 600oC. EDS and XRD results of the synthesized catalysts showed that Co and Ni were successfully incorporated and well dispersed in the MCM-41 support. The characteristic ordered pore structure of MCM-41 was partially conserved. Synthesized Co-MCM-41 and Ni-MCM-41 had surface area and pore diameter values of 303.6 m2/g – 1.98 nm and 449 m2/g – 2.2 nm, respectively. Catalytic test results obtained with both catalysts proved that hydrogen yield values were significantly enhanced in the presence of CaO during in situ capture of CO2. Catalytic performance of Ni-MCM-41 was much better than Co-MCM-41 in ethanol reforming reaction. The highest hydrogen yield obtained with Co-MCM-41 catalyst was achieved at 550oC as 3.1 with in situ capture of CO2. This value is not high enough for practical use of this catalyst. At the same temperature, the corresponding hydrogen yield value was only 1.62 in the absence of CaO. The catalytic test results obtained with Ni-MCM-41 at 600oC, gave a hydrogen yield value of 5.6 in the sorption enhanced reforming run, which is about 94% of the maximum possible hydrogen yield of six.