Master Degree / Yüksek Lisans Tezleri
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Master Thesis Devlopment of Solid Acid Catalysts for Cellulose Acetate Production(Izmir Institute of Technology, 2022) Sönmeztürk, Begüm; Yılmaz, SelahattinCellulose acetate (CA) is one of the most commercially important cellulose derivatives with a wide range of applications in various industries. As a green approach, the development of heterogeneous solid acid catalysts for cellulose acetate production is important. The objective of the present thesis is to develop active and stable mesoporous solid acid catalysts for solventless cellulose acetate production with acetic anhydride from microcrystalline cellulose. As catalyst sulfating agents, ammonium sulfate and chlorosulfonic acid (CSA) were applied. Ammonium sulfate ((NH₄)₂SO₄) sulfated catalysts are La incorporated titania-silica (SO4/La-TiO2-SiO2), sulfated titania-silica (SO4/TiO2-SiO2), and sulfated Ti-SBA-15 (SO4/Ti-SBA-15), whereas the CSA/Ti-SBA-15 catalysts were sulfated by chlorosulfonic acid. The effect of Si/Ti mole ratios (6, 10, 20) on the stability of CSA/Ti-SBA-15 catalysts was investigated. Activity and stability of the catalysts were tested in the cellulose acetylation reaction by acetic anhydride at 80 oC with a 10:1 acetic anhydride to cellulose AGU mole ratio. The effect of reaction time (2, 4, 6, and 8 h) and amount of catalyst (0.10, 0.25, and 0.5 g) on the reaction were investigated. Synthesized cellulose acetate samples were analyzed by FT-IR, 1H-NMR, and TGA. CSA/Ti-SBA-15 (10) was found to be the most active and stable catalyst with 2.84 % leaching, 89.6 % conversion, 74.6 % yield, and DS of 2.69. The activity and stability of CSA/Ti-SBA-15 (10) catalyst were further investigated after its treatment with acetone. At the end of the 3rd cycle, A-CSA/Ti-SBA-15 (10) was found as an active and stable catalyst with 58.6% cellulose conversion, 50% CA yield, DS of 2.62, and 1.68% sulfur leaching.Master Thesis Modification of Corn Starch by Oxidation and Acetylation(Izmir Institute of Technology, 2022) Çelik, Tilbe; Yılmaz, SelahattinMore sustainable and eco-efficiency industries intend to use bio-based raw materials instead of petroleum-based raw materials. Starch is one of the most useful, easily accessible, and cheap bio-based raw materials in the industry. This study aimed to produce modified starch that had proper solution viscosity for coating and low gelling enthalpy to reduce production energy for the adhesive industry. Corn starch was modified by oxidation with sodium hypochlorite (NaOCl), acetylation with acetic anhydride (AA), and a combination of the two (dual modification). The effect of different amounts of oxidants (6.0, 12.0, and 24.0 g Cl/ kg starch) and acetylation agents 7.50, 15.0, 30.0 g AA) on the properties of corn starch was examined at room temperature. The structural characteristics of starch granules were assessed using FTIR, 1H-NMR, DSC, solution viscosity, light transmittance, and SEM microphotographs. The effectiveness values that were identified as carbonyl and carboxyl percentage and degree of substitution (DS) in modified starches were determined. The results showed that increasing oxidant concentration increased the carbonyl and carboxyl percentage to 0.0061 % and 1.33 % but acetyl groups were independent from increasing acetic anhydride concentration. Oxidation had a superior reduction effect on starch solution viscosity with 42% reduction when compared to 22% reduction with acetylation. Both processes reduced the gelling enthalpy, but double modification was more effective. Acetylation had a greater effect on light transmittance. Surface morphology of starch was only affected by active chlorine content at 24.0 g Cl/ kg starch, but all acetic anhydride amounts caused the changes.Master Thesis Biolubricant Production Over Sulfated Ti-Sba and Tio2-Sio2 Based Mesoporous Catalysts(01. Izmir Institute of Technology, 2022) Özperçin, Tuğçe; Yılmaz, SelahattinProduction of ecofriendly biodegradable lubricants from vegetable oils is an attractive alternative to petroleum derived lubricants for environmental protection. This study presents an investigation for the production of biolubricants via ring opening reaction of epoxidized soybean oil using the mesoporous solid acid catalysts. SO4/SBA- 15, SO4/Ti-SBA-15, SO4/TiO2-SiO2 and SO4/La-TiO2-SiO2 catalysts were prepared and characterized. In addition, effect of increasing titanium content on SO4/Ti-SBA-15 (Si/Ti: 10, Si/Ti: 6) and effect of sulfation source (ammonium sulfate and chlorosulfonic acid) on Ti-SBA-15 and La-TiO2-SiO2 properties, activities and stabilities were studied. Activity and stability of all the catalysts were tested in the ring opening reactions of epoxidized soybean oil with 2-propanol at 80 oC with 10/1 alcohol-epoxide mol ratio. After determination of the two most stable and active catalysts, reactions were also performed with 2-ethylhexanol at 100 oC with 6/1 alcohol-epoxide mol ratio. Products were analyzed by titration, FTIR and H-NMR. Also, thermal stability and low temperature behavior of products were determined by thermogravimetric analysis and differential scanning calorimetry. Prepared catalsysts had mesoporous structure and stronger acid sites by attachment of sulfate groups The catalysts showed a serious leaching when they were sulfated with ammonium sulfate. On the other hand, chlorosulfonic acid treatment enhanced significantly stability of catalyst. Furthermore, increasing of titanium content and sulfation with chlorosulfonic acid increased the acidity of catalysts compared to ammonium sulfate. The SO4/Ti-SBA-15-6(CS) catalyst (Si/Ti:6 mole ratios and chlorosulfonic acid sulfated) was found as the most stable and active catalyst. It provided 62 % (12 h) and 90 % (18 h) conversion in the reactions with 2-propanol and 2-ethylhexanol, respectively. All products were found as thermally stable up to 300 oC showing that ring opening reaction did not affect thermal stability. Nevertheless, it affected positively low temperature properties and better low temperature properties were obtained from the products of reactions with 2-ethylhexanol. However, its influence on the products obtained from 2-propanol was not prominent.Master Thesis Production of Butyl Glucosides by Zr-Sba & So4/Zr-sba-15 Catalysts(Izmir Institute of Technology, 2020) Aydın, Utku; Yılmaz, SelahattinThe purpose of this study was to develop mesoporous solid acid catalyst for glycosidation reaction of butanol. Therefore, Zr incorporated SBA-15 silica materials with two different amount of zirconia loadings were prepared by hydrothermal synthesis. In addition to them, sulfate modified forms (SO/Zr-SBA-15) were prepared by treating Zr-SBA-15 catalysts in 0.5 M and 1.0 M H2SO4 solutions respectively. These 6 catalysts were tested in the glycosidation of butanol and as product butyl glucosides were produced. The reaction tests were carried out in a 100 ml glass reactor at 117°C. Catalysts properties were determined by different characterization techniques. The analysis showed that mesoporous, acidic catalysts were obtained and zirconium was incorporated into SBA-15 structure. While the surface area and pore diameter decreased by higher zirconium loading and sulfonation, acidity of the catalysts increased. The highest acidity was observed in 1.0 SO/Zr-SBA-15-(1.0) catalyst. The formation of butyl glucosides was determined by HPLC analysis. Results showed that activity of the catalysts were different for the glycosidation reaction of butanol. The highest butyl glucoside yield was obtained with 1.0 SO/Zr-SBA-15-(1.0) catalyst, while the lowest yield was obtained with Zr-SBA-15-(1.0) catalyst. This was attributed to the higher acidity (2.35 mmol NH3/g cat.) and B/L ratio (1.97) of 1.0 SO/Zr-SBA-15-(1.0) catalyst with respect to the others. The reusability tests were performed up to 2 times for the catalyst with the best results. There was no major decrease (7%) in the product yields and this confirmed the stability and reusability of the catalysts.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 Soy-Based Polyol Synthesis From Expoxidised Soybean Oil With Solid Acid Catalyst(Izmir Institute of Technology, 2018) Çabuk, Nehir; Yılmaz, SelahattinIn this study, acidic mesoporous catalysts, sulfonated and non-sulfonated Zr-SBA15 (08), Zr-SBA15 (10), Ti-SBA15 (10) and Ti-SBA15 (20), were prepared for oxirane ring opening reaction of epoxidized soybean oil with methanol. Two different amounts of Zr and Ti incorporated into SBA-15. They were prepared by hydrothermal synthesis. Their sulfated forms were prepared by treating Zr-SBA15 based catalyst with H2SO4 and Ti-SBA15 based catalysts by (NH4)2SO4. The catalytic activities of all catalysts in oxirane ring opening reaction were tested in a 250 ml glass batch reactor at 60 oC. The catalysts characterisation showed that Zr was succesfully loaded into SBA-15 catalyts. Low Ti content (Ti-SBA-15(20) incorporated into SBA-15 whereas anatase was observed for high Ti content (Ti-SBA15 (20)). All the catalysts had mesopore structure and were acidic. While acidity increased with sulfation significantly, slight acidity change was observed with incoporated metal amount. Zr-SBA15 based catalysts had higher acidity than Ti-SBA15 based catalysts. The catalysts showed different activities in oxirane ring opening reaction. The activities of the catalysts affected from their acidity. Zr based catalysts showed higher catalytic activity than Ti based catalysts. Higher activities were observed over non sulfated catalysts even they had low acidity. Activity of the catalysts decreased with the acidity. The formation of soy based polyols were determined by FTIR and H-NMR analysis. The highest epoxide conversion was observed over Zr-SBA15 (08) which was 84.08%. This activity was followed by Zr-SBA15 (10) which provided 57.77 %.Master Thesis Epoxidation of Soybean Oil Over Mesoporous Moo3/Ti-sba-15 and Ti-Sba Catalysts(Izmir Institute of Technology, 2018) Taş, Canan; Yılmaz, SelahattinIn this study, it was aimed to develop heterogeneous acidic mesoporous catalysts for epoxidation of soybean oil. For this, Ti-SBA-15 catalysts were prepared by hydrothermal synthesis with two Si/Ti molar ratios (10, 20). MoO3/Ti-SBA-15 catalyst were prepared by impregnating on the prepared Ti-SBA-15 catalysts. Two different loadings (8 and 12 %) were performed. The soybean oil epoxidation tests were performed in Radley multistation glass reactor system by hydrogen peroxide in ethyl acetate at 75 °C with stirring rate of 900 rpm. For comparison purposes, homogeneous catalysts tests were also performed with H2SO4. The catalyst were found to have mesoporous structure. Titania was succesfully incorporated in to SBA-15. Increasing titania content did not change acidity significantly. Loading of MoO3 decreased the surface area of Ti-SBA-15. Molybdenum loading increased the acidity of the catalysts. The acidity of MoO3/Ti-SBA-15 with 8 % wt MoO3 loading and 10 Si/Ti mole ratio was the highest. The catalysts showed different activities in epoxidation of soybean oil. Some catalysts deactivated. Others showed that the soy bean oil conversion and selectivity to epoxides increased with the acidity of the catalysts. The most active and selective catalyst was found to be 8% MoO3/Ti-SBA-15(10) which gave 35.6 % soybean oil conversion and 35.6 % selectivity to epoxides.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, SelahattinIn 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.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.