Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

Browse

Filters

2010 - 201922020 - 20221

Settings

Access Right: Open AccessSubject: search.filters.subject.Hydrogenation

Search Results

Now showing 1 - 3 of 3
  • Master Thesis
    Synthesis of Titanium-Based Powders From Machining Waste by Using the Hydrogenation-Dehydrogenation Method
    (Izmir Institute of Technology, 2022) Genç, Aziz; Gökelma, Mertol; Gökelma, Mertol; Genç, Aziz; Gökelma, Mertol; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Sustainability and recycling activities have gained importance in almost every field all over the world. Many studies are conducted to recycle titanium and titanium alloys owing to their outstanding properties like low density, biocompatibility, corrosion resistance, and high strength-to-weight ratio. Although they offer superior properties, their usage is limited due to their high production cost and potential to generate waste, and therefore, recycling activities in this area should be expanded using an appropriate method. Cold hearth melting, vacuum arc re-melting, and hydrogenation and dehydrogenation process are widely used for recycling titanium scraps in industry. Among them, the hydrogenation and dehydrogenation (HDH) process has a significant environmental and economic impact. In this thesis, titanium powders were synthesized from additive manufacturing turnings. Ti-6Al-2Sn-4Zr-6Mo turnings were used as starting materials on which HDH characteristics were not investigated in the literature. Both hydrogenation and dehydrogenation parameters were studied to reach optimum conditions. Our results revealed that hydrogenation was accomplished at 500 °C for 120 minutes with 5 °C/minute heating rate. The optimum dehydrogenation condition was found at 600 °C for 90 minutes. Ti-6Al-2Sn-4Zr-6Mo powder with average 56 μm particle size was synthesized; however, hydrogen and oxygen concentrations in the powder were not at the desired level and non-spherical shaped powders were produced end of the process.
  • 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 Technology
    The 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
    An Investigation of Catalyt Preparation Conditions and Promoter Loading (sn) Effects on Activity and Selectivity of Pt Catalyists in Citiral Hydrogenation
    (Izmir Institute of Technology, 2010) Depboylu, Can Okan; Yılmaz, Selahattin; Yilmaz, Selahattin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this study, citral hydrogenation reaction in liquid phase over silica gel supported Pt and PtSn catalysts were studied. It was desired to hydrogenate carbonyl group (C.O) selectively to produce valuable unsaturated alcohols, namely nerol, geraniol and citronellol. Pt/SiO2 catalysts were prepared by impregnation method while PtSn/SiO2 catalysts were prepared by catalytic reduction (CR), co-impregnation (CI) and successive impregnation (SI) methods. Pt loading over silica gel support was 1 % (w/w). For bimetallic catalysts, the (Sn/Pt) loading ratios were varied as 0.3, 0.5 and 0.7. The effects of parameters investigated in the present study included catalyst activation temperature (350 °C, 450 °C), calcination temperature (400 °C, 500 °C), solvent type (ethanol, 2-pentanol), catalyst activation without calcination, washing of catalyst with 0.1 M NaOH solution, Pt precursor type (hexachloroplatinic acid, platinum II acetylacetonate (PAA)) and Sn loading ratio. For Pt/SiO2 catalysts, maximum citral conversion (89 %) was achieved at lower activation (350 °C) and calcination (500 °C) temperatures when PAA was used. Increasing the activation temperature to 450 °C decreased the citral conversion to 52 % but increased the selectivity to unsaturated alcohols (nerol and geraniol) (SNE+GE) from 8 % to 60 %. It was observed that the lower activation temperature provided higher citral conversion but lower selectivity to unsaturated alcohols. Washing of catalyst and using of 2-pentanol prevented the acetal formation. Catalyst activated without calcination step gave lower conversion (20 %) and SNE+GE of 30 %. For bimetallic catalyst (PtSn/SiO2), maximum citral conversion was observed as 91.1 % when catalyst was prepared by CR method and calcined at 500 °C. Higher citral conversion and selectivity to unsaturated alcohols were achieved at the higher calcination temperature and higher reduction temperature. CR method was the most appropriate preparation method for bimetallic catalysts compared to CI and SI. An optimum of activity (91.1 %) and selectivity (89.7 %) was found at a Sn/Pt ratio 0.5.