Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Electrocatalytic isopropanol oxidation for direct organic fuel cells(01. Izmir Institute of Technology, 2024) Çetin, Yağmur; Çağlar, Başar; Şeker, ErolDünya üzerinde sürekli artan nüfus yoğunluğu ve buna eşlik eden enerji tüketim oranları nedeniyle, yenilenebilir enerji kaynaklarını bulma, bunları erişilebilir ve kullanıma hazır hale getirme ihtiyacı önemli konular gelmiştir. Son yıllarda, hidrojen taşıyıcıları ve yakıt hücresi sistemleri, geleneksel fosil yakıt türlerine bağlı enerji üretim sistemlerine iyi alternatifler olarak öne çıkmıştır. Bu çalışma için, hidrojen taşıyıcısı olarak izopropanol-aseton çifti seçilmiş ve reaksiyon kinetiği incelenmiştir. İzopropanolün elektrokimyasal oksidasyonu, yakıt hücresi uygulamaları ve enerji depolama cihazlarındaki önemi nedeniyle oldukça ilgi görmüştür. Bu tez içeriğinde, Pt/C, Cu/C, Pt-Cu(1:1)/C, Pt-Cu(3:1)/C ve Pt-Ru/C ticari katalizörleri kullanılarak izopropanolün elektrokimyasal oksidasyon davranışına odaklanılmıştır. Oksidasyon reaksiyonunun performansını iyileştirmeyi amaçlarken, her bir elektrokimyasal katalizörün aktivitesi, seçiciliği ve reaksiyon koşullarındaki kararlılığı farklı ortamların etkisi altında, alkali koşullarda incelenmiştir. Bu katalizörlerin elektrokimyasal performansı Döngülü Voltametri, Elektrokimyasal Empedans Spektroskopi ve Kronoamperometri analizleri ile değerlendirilmiştir. Sonuçlar, diğer Platin bazlı katalizörlere kıyasla daha yüksek katalitik aktivite ve daha düşük kinetik direnç gösteren Pt-Cu/C katalizörünün üstünlüğünü göstermektedir. Bu gelişmiş performans, Bakır'ın OH- türlerine olan güçlü afinitesine atfedilir ve bu da izopropanol oksidasyon hızını artırır ve genel elektrokimyasal aktiviteyi teşvik eder. Genel olarak, bu çalışma izopropanol elektrooksidasyonunun kinetiğine dair değerli bilgiler sağlayarak ve Pt-Cu alaşımının çeşitli elektrokimyasal sistemlerde verimli alkol oksidasyonu için umut verici bir katalizör olarak potansiyelini vurgular.Master Thesis Esterification of oleic acid with methanol on structured solid acid catalysis(01. Izmir Institute of Technology, 2024) Büyükkapancı, Yunus; Şeker, ErolBu çalışmada, Oleik Asit metanol ile birlikte Sülfonlanmış Alüminyum Silika (SAS) heterojen asidik katalizörü üzerinde gerçekleştireceği esterifikasyon reaksiyonu incelenecektir. Araştırma, farklı metanol/yağ asidi mol oranları (9/1-21/1), katalizör miktarları (%10-%20) ve reaksiyon sürelerinin (3s–9s) 105°C sıcaklıkta reaksiyon verimliliği üzerindeki etkisini Box Bhenkhen yardımı ile değerlendirmeyi amaçlamaktadır. Katalizörlerin aktivitesi iki farklı katalizör formu (toz, yapısal) ele alınarak değerlendirilecektir. Bu çalışma, varyans analizi istatistiksel sonuçlarına göre, toz katalizör varlığında gerçekleştirilen deneylerde reaksiyon süresinin dönüşüm değerleri üzerinde en büyük etkiye sahip olduğunu göstermektedir. Reaksiyon süresi uzadıkça dönüşüm oranları hızlı bir şekilde artmıştır. Ayrıca, kullanılan katalizör miktarı da doğrudan etkili olmuş ve en yüksek dönüşüm oranı, Alkol/FFA oranının 9/1 olduğu durumda elde edilmiştir. Ayrıca, yapısal katalizörlerin varlığında gerçekleşen reaksiyonun dönüşüm değerinin, toz formundaki katalizörlerin değerleriyle karşılaştırılabilir olduğu tespit edilmiştir. Ayrıca yapılandırılmış katalizörlerde toz katalizöre göre ayırma adımına gerek kalmamıştır.Master Thesis Catalytic Pyrolysis of Virgin and Waste Polyolefins(01. Izmir Institute of Technology, 2023) Çalık, Fatma Defne; Yıldız, Günay; Şeker, ErolThe fact that increasing plastic production and the mismanaged waste released to the environment put the ecosystem at risk. One of the most promising recycling methods developed within this framework has been pyrolysis. In this thesis, a model feedstock mi (No: 119N302). Thermal (batch and continuous) and catalytic pyrolysis (in-situ and ex-situ) techniques were applied to the polyolefins. Silica-alumina-based solid acid catalysts were produced with the simple sol-gel method to compete with commercial ZSM-5 (30) and ZSM-5 (50). Catalyst-to-plastic ratios between 1/100 and 1/1000 were used for in-situ, and 200 h-1 and 500 h-1 WHSVs were used for ex-situ mode. 57 wt.% pyrolysis oil was produced from the thermal pyrolysis of the virgin PO mixture in the batch system. In the ex-situ catalytic pyrolysis experiments by 500 h-1 WHSV and by ZSM-5, silica-alumina, and ZSM-5 supported silica-alumina, 36 wt.%, 56.6% wt.% and 45.2 wt.% liquid, and by 200 h-1 WHSV, 29.9 wt.%, 54.1 wt.%, and 57.9 wt.% pyrolysis oils were collected, respectively. The most successful test in terms of product composition was ES2 with 82.9% gasoline (8.8% BTEX), and 16.7% diesel-range hydrocarbons. The motivation was investigating whether it was suitable to produce liquid hydrocarbons, in the range of C5-C20, as a feedstock in the petrochemical industry. As a result, it has been proven that energy recovery was possible and sustainable by plastics recycling instead of using fossil fuels.Master Thesis Esterification of Free Fatty Acid Obtained From Waste Cooking Oil Over Solid Catalyst(Izmir Institute of Technology, 2022) Karacasulu, Cem; Şeker, Erol; Şeker, ErolThe objective of this study was to investigate effect of reaction temperature, catalyst weight percentage and composition of Al2O3/SiO2 on conversion of FFA obtained from waste cooking oil (WCO) to take place esterification reaction by using Box-Behnken design. Statistical analysis demonstrates that catalyst weight percentage and temperature were insignificant statistically. Alumina composition was found as significant parameter at certain conditions by considering statistical analysis. It was seen that conversion of Free Fatty Acid (FFA) increases as composition of Al2O3 in Alumina/Silica catalyst increases. %80 Al2O3/20% SiO2 catalyst was found as promising catalyst since conversion of FFA with the catalyst was 32% at 80°C and 15:1 alcohol to FFA ratio. Besides, it was found that alcohol to FFA ratio affected the conversion reversely. When alcohol to FFA ratio was reduced to 2:1, conversion of FFA increased to 41%. The prepared catalysts were characterized by XRD and TPD analysis. Activity of catalysts were attributed to acidic strength and Bronsted acid sites on the aluminum sulfate in the catalysts. After screening effects of catalysts and reaction conditions, optimum levels of parameters were used to investigate the esterification reaction of model WCO. This reveals that conversion of FFA was found as 11% at 80°C and 15:1 alcohol to FFA ratio. Finally, the proposed catalyst does not have catalytic activity of hydrolysis reaction of oil at applied conditions.Master Thesis Anaerobic Digester Modelling for Production of Biogas From Waste Hazelnut Husk(Izmir Institute of Technology, 2022) Demir, Ozan; Şeker, ErolAnaerobic digestion is a degradation process of complex organic matters into methane and carbon dioxide in an oxygen-free environment maintained by microorganisms. An advantage, besides energy production, is it is a waste management technique. Hazelnut husk is a valuable raw material for the anaerobic digestion process with more than 55 % cellulose and hemicellulose content. Anaerobic Digestion Model No. 1 (ADM1) developed by IWA Group was used in this study. This master thesis modeled biogas production by co-digestion of cattle manure and hazelnut husk process in MATLAB. The goal was to evaluate the methane amount of a household bioreactor. Tanks-in-series model with 3 CSTRs was chosen after residence time distribution (RTD) analysis. Ten different cases were investigated to show the effects of carbon source/manure ratio, temperature, carbon source type, total solid (TS) amount, reactor type, and RTD analysis. The carbon source/manure ratio improves the methane yield as it increases. When the ratio is 1, methane yield is 0.229 L/kgVS whilst yield is 0.224 L/kgVS if the ratio is 0.1. The temperature effect on the process is significant. In the thermophilic case, the methane production is 0.432 L/d which is the highest amount compared to mesophilic and psychrophilic cases. When food waste is used as a carbon source with a ratio of food waste/manure of 0.1, the methane production is 0.410 L/d while it is 0.403 L/d in hazelnut husk digester. When the TS amount is doubled, the methane yield goes down from 0.224 to 0.149 L/kgVS because the residence time is not long enough to digest it as well as in case with lower total organic carbon level. In unmixed, mixed, and Chinese Dome Digester types of reactors, methane productions are 0.403, 0.646, and 0.552 L/d, respectively. In the ideal case, the methane production is 1.525 L/d which indicates the necessity of RTD analysis.Master Thesis Dimethyl Ether Production From Methanol Over Silica-Alumina Catalysts(01. Izmir Institute of Technology, 2021) Tarancı, Ecem; Şeker, ErolThis 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 1-Octanol Dehydration on Al2o3-Sio2 Catalyst(01. Izmir Institute of Technology, 2021) Uçar, Beyza; Şeker, ErolBu çalışmada, heterojen asit katalizörün 1-oktanol dehidrasyonunda, ürün dağılımına etkisi araştırılmıştır. Kullanılan katalizörler sol-jel yöntemiyle sentezlenmiştir. Sentezlenen katı asit katalizörler ağırlıkça farklı oranlarda (25%-75%, 50%-50% ve 75%-25%) Al2O3-SiO2 katalizörleriydi. Ayrıca, sentezlenen Al2O3-SiO2 katalizörlerin kalsinasyon sıcaklıkları 500 ̊C, 700 ̊C ve 900 ̊C idi. Bu çalışmanın amacı, Al2O3-SiO2 katalizörlerin asidik-bazik özelliklerini ve birincil alkol dehidrasyonu üzerindeki etkisini anlamaktır. Kullanılan bütün katalizörler için dehidrasyon reaksiyonu 150 ̊C ve reaksiyon süresi 4 saat olarak devam etti. Ürünler ve var olan miktarı GC-MS analizi ile belirlenmiştir. Buna ek olarak, katalizörlerin asidik ve bazik özellikleri NH3-TPD ve CO2-TPD analizleri ile açıklanmıştır. Ayrıca katalizörlerin kristalografisi, XRD sonuçlarına göre belirtilmiştir. Bu çalışma, katalizörlerin bileşiminin ve uygulanan kalsinasyon sıcaklıklarının, reaksiyon yollarını etkileyen asidik-bazik kuvvetleri üzerinde etkili olduğunu ortaya koymuştur. Bunun sonucunda ürün dağılımı ve genel dönüşüm değerlendirilmiştir. Ana ürünler oksalik asit 2-etilheksil tetradesil ester, oktil eter, esterler (Formik asit, oktil ester, Asetik asit, oktil ester ve Heptanoik asit, oktil ester) ve oktanal idi. Ürün dağılımının esas olarak Al2O3-SiO2 katalizörlerinin asidik ve bazik güclerine bağlı olduğu gösterildi.Master Thesis Renewable natural gas production via Sabatier reaction(01. Izmir Institute of Technology, 2021) Çamlık, Cansu; Şeker, ErolThis study attempts to understand the effect of support basicity on Sabatier reaction and improve the performance of Ni based catalysts by introducing calcium which is known for its basicity. In accordance with this purpose, Ni-Al2O3-CaO catalysts were synthesized with modified sol-gel method. Effect of Ni loading, calcination temperature and calcium content were investigated. Al2O3-CaO supports were synthesized at three ratios as follows; 70-30 wt.%, 40-60 wt.%, 10-90 wt.% wherein Ni/Al2O3 catalyst was used as reference catalyst. Based on thermodynamic analysis, reaction was conducted at 400oC and 1 atm with inlet composition of CO2/H2=1/4 and total volumetric flow rate of 100 ml/min. Reference catalyst calcined at 700oC was found to be inactive at used reaction conditions due to the presence of inactive NiAl2O4 phase. Increasing Ni loading from 1 wt.% to 10 wt.% increased both CO2 conversion and methane selectivity. Over the catalysts calcined at the temperature of 900oC, maximum methane yield was obtained over 10Ni-70Al-30Ca-900 as 8%. The influence of Ni loading was more pronounced for catalysts calcined at 700oC. In 10Ni-70Al-30Ca-700 catalyst, NiO particles were smaller than 5 nm. Therefore, it is conceivable that the alumina-calcium mixed oxide support could disperse higher loadings of Ni, which could result in higher CO2 conversion. Ca modification was found to have a prominent impact on both methane selectivity and yield. With 10Ni-10Al-90Ca-700, being best performing catalyst, CO2 conversion obtained as 76% and methane yield was 60%. The promotion of catalytic performance might arise from intensifying the CO2 chemisorption supported by XRD and TGA results.Master Thesis Butyl Esters Production From Canola Oil Over Heterogeneous Base Catalysts(01. Izmir Institute of Technology, 2021) Akın, Oğuzhan; Akın, Oğuzhan; Şeker, Erol; Şeker, ErolIn this study, transesterification reaction of canola oil with butanol over calcium oxide alumina catalyst was investigated with varying butanol:lipid molar ratios, catalyst amount and reaction time. Catalysts were prepared with the single step sol-gel method, and the activity of synthesized catalysts were investigated for two different forms of catalysts as powder and structured form. In the case of powdered catalysts, at butanol:lipid molar ratios of 9 and 24 with 6 wt% of lipids as catalyst amount, leaded 32% and 45% butyl esters yield in 1 hour. On the other hand, ~70% butyl esters yield has obtained at butanol:lipid molar ratios of 48 and 60 for the reaction time of 1 hour, while 89% yield had achieved when the reaction lasted for 4 hours at butanol:lipid molar ratio of 48. The necessity of mild basic strength and high butanol:lipid molar ratio was found to obtain high butyl esters yield. At high butanol lipid ratios of 48 and 60, it was observed that glycerolysis reaction occurs and promotes reverse transesterification reactions in first 30 minutes of the experiments. In the case of structured catalysts, lower butyl esters yields than powder catalysts were obtained, yet they eliminated the need for catalysts separation step in the experiments. Reusability tests showed that catalyst activity has decreased due to calcium ion leaching in the first hour of reaction and kept its activity constant for the rest of the reaction.Master Thesis Carbon Dioxide Hydrogenation on Alumina Supported Ruthenium Catalysts(Izmir Institute of Technology, 2019) Hamza, Gökmen Oğuzcan; Şeker, ErolIn this study the effect of basicity of catalyst is investigated using different metal oxide supported Nickel and Ruthenium catalyst. The basic strength of catalysts was orchestrated with using different types of metals and different composition of supports. In this study Al2O3-CaO, Al2O3-MgO, Al2O3-BaO supports were used with nickel and ruthenium catalyst, which synthesized with sol-gel method. Different mass ratios of supports were used such as; 100%, 70%/30%, %50/50%, 20%/80% respectively. For all metal oxides Nickel loadings are 1 %, 5% and Ruthenium loading is 0.5%. Calcination temperature was 500 0C with 6 hours. All catalysts were used in methanation reaction with conditions varies between 300-600 0C, inlet ratio of CO2/H2 1/4 to 1/6 and GSHV 5000h-1/10000h-1. The products were analyzed using GC and catalysts were analyzed using XRD NH3-TPD and BET. Nickel load selected as 1%, magnesium supported catalysts' the main crystallites were aluminum oxide and magnesium oxide for 30%,50%,80; respectively. Calcium supported catalyst had had alumina and calcium oxide crystallites for 30%,50% respectively. Barium supported catalysts had had alumina and barium mix oxide crystallites for 30%,50% respectively. For 5% Nickel loaded 70-30% alumina magnesia mix oxide catalyst magnesia and alumina crystallites are found. Aluminum magnesium mix oxide catalysts had higher basicity than aluminum barium mix oxide catalysts for 1% nickel catalysts. Ruthenium based magnesium alumina mix oxide catalyst had higher basicity than nickel-based magnesium alumina catalysts. Ruthenium catalysts had higher total performance towards both of the reverse water gas shift reaction and carbon dioxide methanation than nickel-based catalysts.
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