Master Degree / Yüksek Lisans Tezleri

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  • 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 Technology
    The 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
    An Investigation of Activities and Selectivities of Hzsm-5 and H-Ferrierite Zeolites Modified by Different Methods in N-Butene Isomerization
    (Izmir Institute of Technology, 2010) Kılıç, Emre; Yılmaz, Selahattin; Yilmaz, Selahattin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this study the synthesis and preparation of active and selective zeolite catalysts for the skeletal isomerization of 1-butene to iso-butene reaction were investigated. Since this reaction occurs on the acid sites, acidity of the catalyst plays important role on catalyst activity and isobutene selectivity. The acidity of synthesized HZSM-5, commercial Ferrierite (H-FER) and HZSM-5-C zeolite catalysts were modified by chemical liquid deposition (CLD) using tetraetyhyl orthosilicate (TEOS), SiCl4 and triaminopropyltriethoxysilane (3-amino), alkali, acid and ammoniumhexafluorosilicate treatment methods. Reaction tests were performed in a fixed bed reactor at 375 0C at weight hour space velocities of 22 h-1. SiCl4 deposition dramatically decreased the total acidity and surface area, both conversion and selectivity of the catalysts whereas TEOS increased selectivity. The highest selectivity (81.2 %) among CLD agents, were obtained by H-FER modified by TEOS 1 hour 1 cycle. Mild alkali treatment slightly decreased the acidity, which increased selectivity for H-ZSM5 from 57 to 60. However severe alkali treatment decreased the selectivity of the catalysts since some acid sites increased after this treatment. Acid treatment significantly decreased the surface area, acidity and caused dealumination. As a result catalyt activity decreased by 10 %. However, selectivity to isobutene changed slightly. Pre-alkali treatment before acid treatment decreased the dealumination effect, so this increased the selectivity; for H-ZSM5 from 57 to 66. AHFS treatment decreased the acidity slightly without affecting other properties. This increased the selectivity of H-ZSM5 from 58 to 87. The highest selectivity values were obtained for AHFS treatment among all modifications.