Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Biolubricant Production Over Sulfated Ti-Sba and Tio2-Sio2 Based Mesoporous Catalysts(01. Izmir Institute of Technology, 2022) Özperçin, Tuğçe; Özperçin, Tuğçe; Yılmaz, Selahattin; Yılmaz, Selahattin; 01. Izmir Institute of Technology; 03.02. Department of Chemical Engineering; 03. Faculty of EngineeringProduction 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 Epoxidation of Soybean Oil Over Mesoporous Titanium and Niobium Incorporated Sba-15 Catalysts(Izmir Institute of Technology, 2019) Kalkandelen, Mustafa; Yılmaz, Selahattin; Yılmaz, Selahattin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologySoybean 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 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, Selahattin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe 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, Selahattin; Yılmaz, Selahattin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe 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, Selahattin; Yılmaz, Selahattin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe 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 Liquid Phase Hydrogenation of Citral on Zeolite Supported Monometallic (ni,pt) and Bimetallic (ni-Sn, Pt-Sn) Catalysts(Izmir Institute of Technology, 2005) Güleç, Hilal; Yılmaz, Selahattin; Yılmaz, Selahattin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this study the liquid phase citral hydrogenation reaction over zeolite supported monometallic and bimetallic Ni and Pt catalysts was studied. The zeolite support materials were Na-Y, Na-, Na-Mordenite, MCM-41, and Clinoptilolite. The catalysts were prepared by impregnation and co-impregnation techniques. Catalytic activity and selectivity tests were performed in a semi-batch reactor at 80°C temperature, 6 bar pressure and 600 rpm stirring speed with 0.25 g catalyst. The characterization studies showed that the structures of support materials were preserved during impregnation and co-impregnation. The Ni and Pt contents of the catalysts was around 8.5 % and 5 %, respectively while the Sn content changed between 0.46 and 4.10 %. The activity of the catalysts and product distribution were affected by type of active metal and type of support. The major product over monometallic and bimetallic catalysts was citronellal. The Ni/Na-Y catalyst gave the maximum yield of desired products, unsaturated alcohols and citronellal, (93 %) and citral conversion (>99 %) among the monometallic catalysts. The most selective monometallic Pt catalyst to desired products was Pt /MCM-41 with a yield of 40 %. Addition of Sn increased the unsaturated alcohol formation and decreased the acetal formation. The activity of the Ni catalyst was generally decreased while the activity of the Pt catalyst was improved. The amount of unsaturated alcohols increased with Sn/Sn+Ni ratio for bimetallic Ni catalysts. The highest yield of desired products was obtained with Ni/Na-Y (93 %) and with Ni-Sn/MCM (80 %) among monometallic and bimetallic catalysts.