Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Epoxidation of Soybean Oil Over Mesoporous Titanium and Niobium Incorporated Sba-15 Catalysts(Izmir Institute of Technology, 2019) Kalkandelen, Mustafa; Yılmaz, SelahattinSoybean oil is an abundant, cheap and nontoxic biomass source and contains triglycerides with unsaturated fatty acids which can be easily modified by epoxidation. In this study, mesoporous Ti-SBA-15 with two different Si/Ti molar ratios, MoO3/Ti-SBA-15 with two different MoO3 mass ratios and Nb-SBA-15 with two different Si/Nb molar ratios were prepared as catalysts for soybean oil epoxidation reactions. Tertbutanol and ethyl acetate was used as solvent and H2O2 was utilized as oxidant. BET analysis indicated existence of high surface area of the catalysts which ranged between 650 and 950 m2/g. XRD analysis indicated successful incorporation of Nb and Ti into SBA-15 structure. Epoxidation reactions were carried out successfully using Ti-SBA-15 and Nb-SBA-15 catalysts in tertbutanol at 75 ºC for 6 h. Utilizing ethyl acetate as solvent was caused undesired catalyst behaviour such as precipitation, gelation and aggradation. No further investigations were carried out with ethyl acetate. Epoxidation products were analysed with H-NMR, FTIR and analytic methods. Ti-SBA-15 catalysts provided only 10 % double bond conversion and 49 % epoxide selectivity. They were not very active. Nb-SBA-15 catalysts exhibited high acidity. They provided 28 % double bond conversion and 31 % epoxide selectivity. Best yield was obtained with Nb-SBA-15 (10) catalyst as 6.49 %. Stability tests of catalysts indicated that Nb and Ti did not leach whereas severe leaching was observed with Mo. Also, homogenous epoxidation reaction with H2SO4 was carried out for comparison with heterogenous catalysts. Results indicated that, heterogenous catalysts were not competitive with homogenous catalyst.Master Thesis Effects of Methanol on Species Concentrations in N-Heptane Flames(Izmir Institute of Technology, 2019) M. Alazreg, Abdalwahab Rashed; İnal, FikretFuel oxygenate additives have been used as an alternative method to reduce the combustion emissions. The effects of methanol addition on n-heptane oxidation were investigated for one-dimensional, atmospheric pressure, laminar, premixed, fuel-rich flame at an equivalence ratio of 2.10. The Detailed Chemical Kinetic Modeling approach has been used to obtain information about the combustion characteristics of n-heptane and n-heptane/methanol flames. A detailed chemical kinetic mechanism was generated by merging two mechanisms of n-heptane (with the formation of polycyclic aromatic hydrocarbons (PAHs)) and methanol. The Master Mechanism consists of 4480 reactions and 945 species. Model validation was carried out using the experimental data available in the literature for different combustion systems. The Master Mechanism was investigated for the combustion of n-heptane and n-heptane/methanol flames using reaction sensitivity, rate of production, and reaction pathway analyses. The mole fraction profiles of low-molecular-weight stable species, single ring aromatics, and PAHs have been predicted by the model. Good agreements between the modeling and experimental results of species mole fractions for both flames have been achieved. The mole fractions of low-molecular-weight species, aromatics, and PAHs were reduced as the methanol was added to n-heptane flame. Acetylene, propargyl radical, and vinylacetylene have been found as important species for the formation of the first aromatic ring and PAH species. Model reduction was also carried out using directed relation graph method. The Reduced Mechanism consists of 1113 reactions and 156 species. The Reduced Mechanism was in a good agreement with the Master Mechanism in terms of the species mole fraction predictions of the n-heptane/methanol flame.Master Thesis Effect of Aging Electrolyte and Organic Coating Type on the Corrosion Mechanism of Tinplate(Izmir Institute of Technology, 2019) Yıldırım, Koray; Kızılkaya, Ali Can; Çağlar, BaşarMarket share of the can coating industry was 2 billion dollars in 2018 globally. A large portion of this market is focused on protecting valuable goods such as foods and cosmetics. Recent bans on the Bisphenol A(BPA) created a BPA-free coating demand due to the high portion of BPA based coatings in the industry such as epoxy. A conventional epoxy based (EP) can coating was compared with a new design of BPAfree polyester coating(PE). Atomic Force Microscopy(AFM), Scanning Electron Microscopy(SEM), Electron Dispersive Spectroscopy(EDX), Electrochemical Impedance Spectroscopy(EIS), Direct Current(DC) Polarization were used to investigate degradation. Industrial and model tinplate samples are compared with surface investigation methods. AFM results indicate the surface composition difference. To investigate bare tinplate corrosion, a mixture of acidic electrolyte was prepared and compared with other conventional aging electrolytes, containing mono acids. The electrolyte prepared from mixed acids was found to have the highest detinning abilities. Therefore, coated samples were aged with this mixed acid solution electrolyte. EIS results indicated that the type of electrolyte alters the corrosion mechanism, indicated by the observance of different time constants at different time scales. During immersion tests, EP based coatings showed better corrosion resistance as shown by higher impedance at low frequency, higher coating resistance and lower capacitance values. However, after sterilization, polyester coated samples showed better corrosion protective abilities (indicated by lower amount of corrosion products and higher impedance values) compared to the epoxy sample even though AFM measurements indicated that it had larger pore sizes after aging compared to epoxy sample. These results are attributed to the larger electrochemical area and higher diffusion properties of EP coatings, obtained after modelling of EIS data.Master Thesis Development of Polyamideimide Based Nanofiltration Membranes for Separation of Dyes and Salts in Textile Wastewater Treatment(Izmir Institute of Technology, 2019) Metecan, Ayşe; Alsoy Altınkaya, SacideThe textile wastewater contains a significant level of organic dyes and inorganic salts. Separation of a vast amount of organic dyes and inorganic salts is important not only to comply with strict regulations but also to recover dyes for reuse during the process. Nanofiltration is proposed as a cost-effective alternative solution for dye and salt separation compared to traditional techniques. The main objective of this thesis is to develop a polyamideimide based positively charged nanofiltration membranes with high permeability, and high selectivity for separation of dyes and salts in textile wastewater treatment. Polyamide-imide (PAI) is an excellent choice for membrane production because of its superior processability, good mechanical features, and high chemical and thermal resistance. Its imide groups are crosslinked with polyethyleneimine (PEI), which is a suitable material to obtain a positively charged surface. In this study, support membranes of various pore sizes were produced by changing the composition of the coagulation bath and casting solution during the phase inversion method. Then, the optimum support membrane was in-situ modified with the alginate and coordinated with the metal ions for high permeability and high selectivity. The influences of the metal concentration and reaction time on the membrane performances were examined. It has been demonstrated that resulted nanofiltration membrane has high solute permeability (>22 L / m2 h bar), high dye rejection (~ 95 %) and low salt rejection (~ 11 %). Moreover, this membrane was tested in the treatment of real textile wastewater samples. Salts in wastewater permeated, while high amounts of dye were rejected.Master Thesis Investigation of Different Uv Stabilizer Effects on Hdpe Grades(Izmir Institute of Technology, 2019) Germen, Oktay; Şeker, ErolIn this study, a performance Hindered Amin Light Stabilizer (HALS), used to prevent the structure of polymeric materials from UV and thermal degradation, was investigated using High Density Polyethylene (HDPE) injection grade. The primary goal of this study is to understand the effects of different HALS types, that consist of low molecular mass and high molecular mass, on mechanical and physical properties of HDPE using a design of experiment method. In addition, Minitab program was used to analyze the data, obtained with the experimental design, with ANOVA analyses to estimate the OIT and Loss Elongation% responses of the samples made with varying HALS amounts and types. Briefly, Elongation Lost% which is the ratio of Elongation% Before Aging to Elongation % After Aging and OIT(Oxidative Induction Time) were studied in different recipes of HDPE Injection Molding Plaque specimens in order to measure the effect of HALS1 (Tin770), HALS2(Tin622) and HALS3(Chim944) on aging. One-year of aging was simulated using a standard aging chamber. It was observed that synergetic effect of HALS1 with HALS3 was much more effective than thatof HALS2 with HALS3. Moreover, it was determined that the samples containing antioxidant which did not contain any HALS additive were completely degraded at the end of the same aging process. This study showed that OIT results of samples were affected directly by the amount of HALS3 which protected the polymer against long-term exposure to UV radiation and high temperature whereas neither HALS1 nor HALS2 showed the same protection.Master Thesis Development of Kinetic Model for Industrial Ethylene Oxide Catalyst by Using Model-Targeted Experimentation Approach(Izmir Institute of Technology, 2019) Sarrafi, Şahin; Şeker, Erol; Arkun, Ziya YamanEthylene oxide (EO) is produced via selective oxidation of ethylene with oxygen using a Ag supported on -Al2O3 catalyst. The ethylene epoxidation reaction is desired, whereas the ethylene and EO combustion reactions are not. Proposed study is aimed at developing a tailor-made kinetic model in order for making use in the industrial ethylene oxide reactors which are of paramount importance from the viewpoint of process economics and the greenhouse gas (GHG) induced various environmental exposures. With aging of the catalyst, the trade-off between selectivity and productivity becomes gradually more prominent. Along with the compensation of loss of active sites under the favor of increasing of the temperature, catalyst still provides sustainable commercial yields at the expense of excess feedstock consumption which in turns leads to boost GHG emissions by releasing more carbon dioxide (CO2) into the atmosphere. To maintain catalyst activity for a longest period possible, controlling process variables more preciously with a robust model is very demanding issue throughout the last two decades. Within the scope of this thesis, model-targeted experimentation approach was used assisting by gPROMS software in determining intrinsic kinetics of the commercial catalyst in use through integral reactor coupled with gas chromatography. During the course of the kinetic experiments, the effect of VCM used as a promoter together with inhibiting effects of product gases such as CO2 and EO were also investigated and included into the kinetic model to be derived.Master Thesis Peptide Hydrogels Containing Cell Attachment Molecules(Izmir Institute of Technology, 2019) Uysal, Berk; Top, Ayben; Top, AybenIn this study, peptides with sequences and notations as KLELKLELKLEL (KLEL), KLDVKLDVKLDV (KLDV), KLDVKLDVKLKV (KLKV1), KLKVKLDVKLKV (KLKV2), KLKVKLKVKLKV (KLKV3) were synthesized using solid phase peptide synthesis (SPPS) method based on Fmoc chemistry. Reverse phase HPLC and MALDI-TOF mass spectroscopy characterization methods were used to assess the purity of the peptides. Three different synthesis procedures were tested, and it was found that employing DMF:DMSO at 1:1 ratio as a solvent increased purity of the resultant peptide. FTIR results indicated the presence of expected β-sheet secondary structure, as well as an interference band from TFA salts for all of the peptides. All the peptides formed hydrogels at pH 7.4 with 1 wt% concentration in deionized water (DIW). AFM results of these hydrogels indicated that KLKV1 and KLKV2 had fibrous morphology with a width of 5-20 nm and 7-18 nm respectively. KLDV and KLKV3 peptide hydrogels, on the other hand, exhibited globular structures, having sizes with 15-50 nm and 8-15 nm, respectively. Storage moduli (G’) of these hydrogels in DIW were obtained as ~860 ± 150 Pa, ~260 ± 60 Pa, ~210 ± 30 Pa and ~1850 ± 200 Pa for KLDV, KLKV1, KLKV2 and KLKV3 respectively. Of these peptides, only HCl salt of KLDV and KLKV1 peptides more readily formed hydrogels in PBS but at 1.5 wt% concentration. G’ values of these KLDV and KLKV1 hydrogels were determined as ~1810 ± 850 Pa and ~700 ± 230 Pa, respectively. Cell proliferation tests (CCK-8 assay) of KLDV and KLKV1 hydrogels were performed by using L929 mouse fibroblast cells. Empty wells (TCPS) were used as a control group. Cell proliferation was observed to be comparable for both select hydrogels and empty wells, suggesting possible applications of these hydrogels in tissue engineering.Master Thesis Development of Ultrasound Triggered Drug Delivery Systems for Cancer Treatment(Izmir Institute of Technology, 2019) Önercan, Cansu; Kılıç Özdemir, SevgiDoxorubicin (DOX) is one of the most commonly used hydrophilic anticancer drug in cancer treatment. However, when it is used in free form, it can attack not only cancer cells but also healthy cells. So as to prevent entering of DOX to the healthy cells, the encapsulation method is employed. Liposomes are suitable for encapsulation of DOX but the most important problems with the use of liposome are hand-foot syndrome and stomatitis. Encapsulation method is not enough because of these reasons, thus delivery of DOX to the desired site by targeted therapy has gained interest in recent years. In this study, DOX was encapsulated into liposomes and the DOX loaded liposomes (LipoDOX) was attached to microbubbles (MBs). MBs as ultrasound contrast agents are widely used in medical imaging. Use of MBs in combination of DOX loaded liposomes facilitates the uptake of the drug because ultrasound cavitation results in opening of transient pores in cell membrane via a process named sonoporation. Herein, MB-LipoDOX complex was engineered to optimize the size of the complex as well as the loaded DOX content. For this purpose, determination of incubation temperature and time for DOX loading into liposome and optimization of liposome formulation for maximum DOX loading were studied. Ratios of Lipid/Cholesterol/PEGylated lipid, PEG chain length and PEG molar ratio in liposome were determined. Also, determination of Strept Avidin (StAv) to Biotin ratio in LipoDOX and the amount of LipoDOX in LipoDOX-MB complex were studied. For characterization, Dynamic Light Scattering (DLS) method, Fluorescence Spectrometry method and Coulter Counter device were used. Lipoosme size was found to be associated with the pore size of polycarbonate membrane (200nm) resulting in liposomes at around 190±5 nm in size . When the PEGylated lipid with PEG chain of 2000 was used in liposome structure, particle size distribution is more monodispersed than the others. The maximum amount of DOX loaded liposomes was obtained at 32% Cholesterol, 5% DSPE-PEG2000, after 90 min. incubation at 65oC incubation. Optimum StAv to Biotin ratio in LipoDOX was determined as 1.0. The optimum molar ratio of Biotinylated lipids in LipoDOX was determined as 0.05% and the optimum molar ratio of Biotinylated lipids in MBs was determined as 8%.Master Thesis Synthesis of Ni and Zn Based Organic Frameworks as Photocatalyst(Izmir Institute of Technology, 2019) Dikmen, Merve; Çakıcıoğlu Özkan, Seher FehimeNickel (Ni) and zinc (Zn) based organic frameworks were synthesized on the synthetic zeolite (5A and 13X), natural zeolite mineral clinoptilolite, -Alumina. Initially the zeolite surface was modified or seeded with metal organic framework (MOF). MOF-zeolite composite materials were characterized with XRD, SEM and ATR-IR to understand whether surface processes was achieved successfully or not. Additionally, band gap energies were evaluated to understand these composite materials were used as photocatalyst. Surface modification with APTES was not affect surface of the zeolites. In spite of that seeding created a layer on the surface of zeolite. Nickel based organic framework was coated onto the surface of modified 5A surface. Hydrothermal ZIF8 (ZIF8(1)) and solvothermal ZIF8 (ZIF8(2)) were synthesized successfully as MOF crystals. Besides ZIF8(2) was coated onto the surface of natural zeolite. Additionally, ZIF8/CuBTC sample were synthesized, seeded and coated onto the surface of natural zeolite. Band gap energies of the MOFs and composite materials were calculated with Tauc plot. Results showed that UV light can be used as light source for photocatalytic reactions of these photocatalysts. Also increasing photocatalyst amount increased dye degredation under UV light.Master Thesis Influence of Ca2+ Ions on Freshly Precipitated Caco3 Particles(Izmir Institute of Technology, 2019) Majekodunmi, Olukayode Titus; Özdemir, EkremThe objective of this study was to develop a method to synthesize CaCO3 nanoparticles from a chemical precipitation reaction under ambient and high supersaturation conditions. Equimolar CaCl2 and Na2CO3 solutions were reacted in a tubular reactor at a constant rate. The particles growth inhibition was attempted by dispersing the reaction mixture in a continuously stirred Ca(OH)2 solution. This procedure separated the nucleation phase from the growth inhibition process, and was conducted without pH and composition control. The possibility of impeding the CaCO3 particles overgrowth was explored at different precipitants and Ca(OH)2 concentrations. Their effects on the particles morphology, colloidal stability and specific surface area were studied. Although rapidlysettling particles were produced at precipitants concentration of 100 mM, colloidally stable CaCO3 nanoparticles were obtained at concentrations ≤75 mM. Additive Ca2+ ions, provided by the Ca(OH)2 solutions, inhibited the crystals growth by adsorbing irreversibly on the growth sites. The synthesized particles were as much as 95% smaller than those obtained when pure H2O was used instead. Ca2+ ions concentration and amount of precipitated particles were observed to be important factors for monodispersity and high growth inhibition. Monodisperse and stable nanoparticles were synthesized at low reactants concentration and/or precipitates volume. Vaterite phase was observed in the particles obtained when pure H2O was used as the growth-inhibiting solution. However, the presence of additive Ca2+ ions effected the crystallization of pure calcite, regardless of Ca(OH)2 or precipitants concentration, reaction mixtures retention time in the tubular reactor, volume of precipitates, and the growth-inhibiting solutions initial pH.