Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Subject: search.filters.subject.Catalytic reaction

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  • Master Thesis
    Dimethyl Ether Production From Methanol Over Silica-Alumina Catalysts
    (01. Izmir Institute of Technology, 2021) Tarancı, Ecem; Şeker, Erol
    This study aims to investigate the effect of acidic properties of acidic catalysts on the activity, which is required to produce dimethyl ether from methanol. In this study, silica-alumina (SiO2/Al2O3) catalysts with different compositions which are 25/75 wt.%, 50/50 wt.%, 75/25 wt.%, and 3 different calcination temperatures which are 500°C, 700°C, and 900°C were synthesized by the sol-gel method for the methanol dehydration to dimethyl ether reaction. In the further stages of the study, some changes were made in the catalyst formulations of the most active and the least active catalysts in terms of catalytic performance to modify acidic properties. In this regard, the peptizer acid of silica-alumina catalysts was changed from HNO3 to H2SO4, or 0.1 g of ZSM-5 zeolite was added to the silica-alumina sol mixture step. The NH3-TPD analysis was used to understand the acidic properties of all synthesized SiO2/Al2O3 catalysts. The reaction temperatures were 300°C and 400°C for both 30 min. The study has shown that there was a decrease in the acidity of the catalysts calcined at 900°C is observed. The activity of 75%SiO2-25%Al2O3 catalyst decreases significantly as the calcination temperature increases. The activities of all catalysts calcined at 500°C are close to each other, whereas there is a big difference in activity between 25%SiO2-75%Al2O3 and 75%SiO2-25%Al2O3 catalysts calcined at 900°C. As evidence of the NH3-TPD results, 25/75 wt.% catalyst calcined at 900°C was the most active catalyst with approximately 97% methanol conversion, while 75/25 wt.% catalyst calcined at 900°C was the least active catalyst with 63% conversion at 400°C. The 50/50 wt.% catalyst calcined at 900°C is also a very active catalyst with over 90% conversion. While sulfuric acid and/or zeolite exchange increased the performance of the least active catalyst, it did not reveal much difference in the most active catalysts. In addition, the addition of ZSM-5 zeolite increased the acidic strength of the catalysts. All synthesized catalysts are active for methanol dehydration. The DME selectivity for all catalysts is approximately 100%.
  • Master Thesis
    Development of Tungsten Loaded and Zirconia Incorporated Mesoporous Catalysts for Esterification of Palmitic Acid With Cetyl Alcohol
    (Izmir Institute of Technology, 2014) Mutlu, Vahide Nuran; Yılmaz, Selahattin; Yilmaz, Selahattin
    In this study, it was pursued to develop acidic mesoporous catalysts for esterification of cetyl alcohol by palmitic acid. For this, Zr incorporated SBA-15 was prepared by hydrothermal synthesis. Zr-SBA-15 was used both as a catalyst support and as a catalyst itself. WO3 loading onto the Zr-SBA-15 was performed by incipient wetness impregnation. Additionally, WO3-ZrO2 catalyst was prepared by co-precipitation with two different contents of WO3 (15 wt% and 20 wt%). The reaction tests were carried out in mesitylene under reflux conditions. Zr was incorporated into SBA-15 successfully. The surface areas of Zr-SBA-15 and WO3/Zr-SBA-15 catalysts were significantly higher than that of WO3-ZrO2. Loading of WO3 decreased the surface area of Zr-SBA-15. The acidity of the WO3/Zr-SBA-15 with 15 wt% WO3 was higher than that of with 20 wt% WO3. Moreover, increasing the calcination temperature from 700 to 800 oC resulted in the increase of acidity. The activity of the catalysts differed. The only product obtained was cetyl palmitate. Under the test conditions it was found that the reaction rate was not limited by equilibrium. Zr-SBA-15 provided the highest conversion (64 %) which corresponded to cetyl palmitate yield of 63% among other mesoporous catalysts because of its high surface area (600.3 m2/g) and acidity (0.152 mmol NH3/g cat). This catalyst did not show leaching. WO3/Zr-SBA-15 based catalys tests showed that catalyst activity increased by increasing calcination temperature. This was atributed to better dispersion of W. The conversion of cetyl alcohol did not change much with more W loading.