Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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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 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 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.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 Effects of Manganese Promotion on Reactants and Intermediates of Fischer Tropsch Synthesis on a Model Cobalt Surface-A Density Functional Theory Investigation(Izmir Institute of Technology, 2019) Gençoğlu, Merve; Kızılkaya, Ali Can; Sevinçli, HaldunThe effects of manganese promotion on the adsorbates and specific elementary reactions of Fischer-Tropsch Synthesis (FTS) was investigated using periodic Density-Functional Theory (DFT) calculations on a close packed cobalt surface, Co(111). In particular the effects of MnO promotion on the adsorbates of CO, HCO, CH, CH2, C2H2, OH, H2O, C, O and on the reactions of direct CO dissociation, H-assisted CO dissociation and carbon hydrogenation were studied for MnO coverages of 0.25 ML and 0.11 ML. Mn was modeled in the chemical form of MnO. MnO was modeled as a singular monomer on the Co(111) surface, based on the findings from experimental studies. The results indicate that MnO promotion increases the adsorption energies of all adsorbates, except H and C2H2. In particular, CO and H2O adsorption energies increase significantly, which indicate that the selectivity increases to long chain hydrocarbons is mainly due to an increased surface coverage of CO with respect to H. The results also indicate that the relative effect of MnO on adsorption energies are strongly dependent on MnO coverage. MnO promotion is found to decrease the activation barriers for HCO and CH formation, while increasing the activation barriers for direct CO dissociation and HCO dissociation. The results point out that MnO does not promote the direct dissociation of CO and the activity increase due to Mn promotion is most probably due to a H or OH assisted CO dissociation pathway or another rate limiting step.Master Thesis Catalytic Surface Coatings for Household Ovens(Izmir Institute of Technology, 2016) İzer, Alaz; Şeker, Erol; Şeker, ErolThe emission of harmful volatile compounds, such as aldehydes, and also carbon monoxide could occur during cooking processes at home or industry due to the combustion and cracking of spilled vegetable oil on the walls of an oven. It is known that the by-products generated during cooking could affect human health and environment if they are properly vented or removed. To eliminate the health and environmental problems related to oven emission, self-cleaning catalytic materials coated walls for ovens seem to be viable alternative to the toxic and time consuming chemical cleaning solutions. In this project, a sol-gel method and also the dip coating technique was used to produce a catalytic material coated aluminum plates. Specifically, the calcination time and the temperature were studied to better understand the relationship between the textural/chemical properties of the catalyst coated metal plates and their catalytic activities. The studied calcination temperatures were 450°C, 500°C and 550°C whereas the calcination time were 10 min, 30 min and 60 min for each type of catalyst. Aluminum oxide supported nickel and also aluminum oxide - manganese oxide supported nickel catalysts were prepared as the catalyst that were used in coating. The catalytic activities of the catalyst coated plates were determined using canola oil as a function of reaction time which were 1h at 170°C and 200°C. The results have been shown that the most convenient calcination conditions for the canola oil combustion were 500°C for 30 minutes by using aluminum oxide – manganese oxide supported nickel catalyst.Master Thesis Influence of Synthesis Parameters on the Properties of Zsm-5 & on Their Catalytic Activity for 1-Butene Isomerization(Izmir Institute of Technology, 2002) Demirkan, Korhan; Yılmaz, Selahattin; Yılmaz, SelahattinThe synthesis and preparation of active and selective zeolite catalysts (H-ZSM-5 and H-ZSM-22) for the skeletal isomerization reaction of 1-butene to iso-butene were investigated.H-ZSM-5 zeolite catalysts were synthesized by varying the synthesis time (3, 6, 12, 24, 48 and 72 h), stirring mode (static, rotational), the initial SiO2/Al2O3 ratio (15 , 30, 70) and SiO2/TPABr (Tetrapropylammonium bromide) ratio (3,3; 5,5; 12,5) of the hydrogel.A synthesis work for H-ZSM-22 type zeolite materials was also carried out both in static and rotational mode.Catalytic activity tests were performed in a constructed fixed bed tubular quartz reactor system at 440 and 375oC at weight hourly space velocities (WHSV) of 22 and 11 h-1.The X-Ray Powder Diffraction patterns and Scanning Electron Microscopy images of ZSM-5 zeolites showed that the particle size and phase purity of ZSM-5 increased with increase in synthesis time.The XRD pattern of Na-ZSM-5 zeolite synthesized by the static mode showed a higher degree of crystallization than the rotational synthesis.The sample synthesized with high Al content in the initial hydrogel (SiO2/Al2O3.15) showed less crystallization than the samples synthesized with low Al content.Increasing Si/Al ratio in the synthesis hydrogel resulted in an increase in the surface area (533 m2/g).TPABr content was found to be an important factor in the crystallization of ZSM-5 zeolites.Lowest TPABr content resulted in an amorphous phase.Increase in the organic cation content enhanced the crystallization, and larger size ZSM-5 crystals with higher phase purity and surface area were achieved. The crystal phase obtained from the hydrogel which was prepared for the synthesis of ZSM-22, were affected significantly by the synthesis mode.The catalysts prepared were tested for isomerization of 1-butene at 440oC and 22h-1 WHSV.It was found that the hydrogel composition highly influenced the catalytic properties of H-ZSM-5 giving a range of conversion and selectivity for iso-butene.Al rich zeolite (initial SiO2/Al2O3.15) showed very low selectivity (2%).This was attributed to the higher acidity of this zeolite. In contrast the samples having medium and high SiO2/Al2O3 ratios 30 and 70 gave high selectivity (52% and 56% respectively) and yield (26% and 28% respectively) under the same reaction conditions.The sample with initial SiO2/Al2O3.30, SiO2/TPABr. 3.3 gave the highest yield to iso-butene (28%) under the same reaction conditions (440oC , 22h-1). Reaction at a lower temperature (375oC) increased iso-butene yield to 32% by suppressing the byproduct formation. Decreasing the WHSV (11 h-1) increased conversion from 40% to 48% and giving yield of 32% iso-butene. The test for long time on stream (24 h) to asses catalytic deactivation, showed slight increase in the yield of iso-butene (%33).Master Thesis Effects of Metal Cation on the Skeletal Isomerization of N-Butene Over Zsm-5 and Ferrierite(Izmir Institute of Technology, 2005) Birsoy, Öniz; Yılmaz, SelahattinThe effects of metal cation on the skeletal isomerization of 1-butene to isobutene was investigated. H-ZSM-5 was sythesized with the initial SiO2/Al2O3 ratio of 30. MFI-50, MFI-90 and Ferrrierite zeolite catalysts were commercially supplied. The zeolites were ion exchanged with cobalt, nickel, zinc, cupper (magnesium and manganese only for synthesized ZSM-5) salts, impregnated with cobalt, in order to change their acidity.The H-ZSM-5 zeolite was additionally ion exchanged with cobalt using different metal loading amounts. Then, the catalysts were tested for their activity in a fixed bed tubular quartz reactor at 375°C at weight hourly space velocity (WHSV) of 22 h-1.Scanning Electron Microscopy images and X-Ray Powder Diffraction patterns of the zeolites showed that their crystallinity was not affected with ion exchange, even with the increase in the loading amount (2.68 w%). But with the impregnation method, the intensity of the characteristic peaks for zeolites were decreased. Impregnating the zeolite also resulted in a decrease in the surface area.The acidity measurements of the catalysts were made by IR spectroscopy with pyridine adsorption method. The tests showed that acidities of the catalysts were changed with ion exchange and impregnation of metal ions.The catalytic tests for H-ZSM-5 showed that different metal loadings with ion exchange lowered the yield for isobutene. H-ZSM-5 showed a conversion of 59 % and 33.2 % yield for isobutene. The lowest yield was obtained from magnesium and manganese with 12.2 % and 9.6 %, respectively. The H-ZSM-5 zeolite catalysts were also tested for Co ion exchanged with different amounts (2.68, 1.45, 0.63 and 0.23 w%).1.45 w% loaded catalyst showed the best activity for the reaction with a conversion of 59.1 %, and yield for isobutene 24.5 %. Both increased and decreased loading decreased yield 17.8 %, 2.5 % and 0.48 %, respectively. H-MFI-50 and its modified forms showed high conversions compared to H-ZSM-5. But low yields and selectivities were obtained. H-MFI-50 showed the highest conversion with 82.7 % and yield of 21.5 %. Co-MFI-50 showed similar conversion as the parent zeolite with 82.7 %, and yield of 17.9 %. The lowest conversion is obtained by Cu-MFI-50 with 76.5 % and yield for isobutene was 21 %. H-MFI-90 and its modified samples showed alike conversions around 76.1 %, but Cu loading decreased conversion as low as 65.9 %. Like MFI-50, the yield of isobutene was also affected by the metal ion exchanging. H-MFI-90 showed 24.8 % yield of isobutene. However, Co-MFI-90 had a yield of 27.6 %. The worst yield was obtained from cupper loaded catalyst with 20.4 %. As would be expected, changing the metal ion loaded to ferrierite also changed the activity of the catalyst. The highest conversion was obtained by H-FER with 57 % and a yield of 39 %. Co-FER and Ni-FER showed similar conversions 52 % and 53 %, respectively. Zn-FER and Cu-FER showed the lowest conversions with 47 % and 45 %, respectively. Yields for the metal loaded catalysts lowered to 27 %.Impregnation with Co, severely decreased the activity of the catalysts both compared to H form and ion exchanged form of the catalysts. Impregnated H-ZSM-5, H-MFI-50, H-MFI-90 and ferrierite showed conversions of 48.1 %, 66.8 %, 60.7 % and 45.4 %, respectively. The yields for isobutene were 11 %, 13.8 %, 15.5 % and 13.7 %, respectively.Master Thesis Selective Hydrogenation of Citral Over Mesoporous Ru/Tio2 Catalysts(Izmir Institute of Technology, 2013) Hassan, Hassanain Abbas; Yılmaz, SelahattinThe liquid phase citral hydrogenation was investigated over Ru/SiO2, Ru/TiO2 and Ru/TiO2/SiO2 catalysts. TiO2/SiO2 supports were prepared by sol-gel deposition, impregnation and absorption methods. The effect of the supports and catalyst reduction temperature, 300 ï‚°C (LTR) and 450 ï‚°C (HTR) on citral conversion and selectivity to unsaturated alcohols were examined. A well-defined crystalline anatase phase was only observed on the support prepared by absorption method, TiO2/SiO2-ABS. A high dispersion and interaction of Ru were observed over TiO2 for Ru/TiO2. Ru/TiO2/SiO2-ABS also displayed similar properties but to a lower extent. Ru/TiO2/SiO2-ABS catalyst showed the highest citral conversion (57.7 %) at LTR among the different Ru/TiO2/SiO2 catalysts. Its selectivity to UA was also high (70.2 %). This was attributed to a better metal support interaction and dispersion obtained by this method. However, a selectivity of 62.6 % was obtained over Ru/TiO2. Activity of the catalysts was mostly observed to decrease as reduction temperature increased from 300 ï‚°C to 450 ï‚°C. Citral conversion decreased from 57.7 % to 42.3 % over Ru/TiO2/SiO2-ABS. However, selectivities to unsaturated alcohol (nerol and geraniol) over Ru/TiO2 and Ru/TiO2/SiO2 catalysts were increased at HTR, reaching about 80 %. This was suggested to be due to more interaction of TiO2 with the Ru (strong metal support interaction). There was no significant change in the selectivity to UA obtained at HTR for Ru/SiO2. This was related to the inert nature of SiO2.Master Thesis Influence of Ni Thin Flim Structural Properties Over Graphene Growth by Cvd(Izmir Institute of Technology, 2013) Özçeri, Elif; Selamet, YusufThis thesis work focused on the effect of polycrystalline Nickel (Ni) TM thin film structure on the growth graphene by chemical vapor deposition (CVD). TM films were deposited by magnetron sputtering technique on Si/SiO2 substrates. To grow 1-2 layer graphene on Ni thin film catalyst by methane decomposition thermal CVD method was carried out using various growth parameters. To reduce the TM film surface roughness and grow larger size graphene layers on Ni film, Si/SiO2 substrates were coated by a thin Al2O3 buffer layers and Cr adhesive layers by magnetron sputtering. Ni film crystal structure and surface roughness, which affected the number of graphene layers, were examined by X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM) techniques, respectively. The thickness and columnar structure of the films were measured from Surface Profiler and Scanning Electron Microscopy (SEM) images. Ni films were annealed at 800 oC, 900 oC and 950 oC in order to improve their crystal quality and to evaluate the effect of the crystallinity on graphene growth at atmospheric pressure. Samples were studied using XRD and AFM also to assess their crystal quality after the annealing process. It was observed that the calculated grain sizes depended on the film thickness and the annealing temperature. Surface roughness of the films was increased by increasing film thickness. A sole thin Al2O3 buffer layer reduced the surface roughness significantly. However, sole Cr adhesive layer or Cr/Al2O3 buffer layers did not reduce the surface roughness, but increased the crystallinity of Ni films in (111) direction. Argon, Hydrogen or a mixture of these two gases was added to methane during graphene growth at ambient pressure by CVD. The Raman spectroscopy was utilized in order to determine the number of the layers and quality of graphene growth over the Ni catalyst film.