Master Degree / Yüksek Lisans Tezleri

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

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Author: search.filters.author.Yüksel Özşen, AslıPublisher: search.filters.publisher.Izmir Institute of Technology

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Now showing 1 - 6 of 6
  • Master Thesis
    Production of Bio-Oil From Haelnut Shell Waste by Using Supercritical Ethanol, Acetone and Their Mixtur
    (Izmir Institute of Technology, 2018) Dal, Orkan; Yüksel Özşen, Aslı; Yüksel Özşen, Aslı; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The goal of this study was to investigate effect of reaction temperature, reaction time and solvent ratio (ethanol/acetone v/v%) on bio-oil yield, solid conversion and product distribution. Direct thermochemical biomass degradation to obtain bio-oil by using organic solvents is not a new process type, and it has some advantages over hydrothermal liquefaction technique. However, in literature, to our best knowledge, there is no study about hazelnut shell decomposition by using ethanol, acetone and their mixtures at sub/supercritical conditions. In this study, experiments were carried out between 220-300 °C, at three different temperatures (30, 60 & 90 min) for five different solvent ratios. Highest solid conversion achieved at 300 °C by using pure ethanol was 64.2%, whereas highest bio-oil yield was found as 44.2% at 300 °C with 50/50 (EtOH/Ac: v/v). Ethanol and acetone showed different characteristics during the experiments and their effect on the conversion and bio-oil yield were discussed. Statistical analysis showed that time, temperature, ratio and temperature-time are affecting parameters for the conversion and bio oil yield while time-ratio and temperature-ratio are not. According to GC-MS results, product distribution changed with respect to solvent type and ratio.
  • Master Thesis
    Extraction of Phenolic Compounds From Hazelnut Shell Waste
    (Izmir Institute of Technology, 2018) Şengün, Duygu; Yüksel Özşen, Aslı; Yüksel Özşen, Aslı; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The main objective of this study is to obtain phenolic compounds from hazelnut shell waste by extraction and to add value to hazelnut shell wastes. Soxhlet extraction, ultrasonic extraction and combined extraction (soxhlet followed by ultrasonic extraction) methods were used for the extraction of hazelnut shell to obtain phenolic and antioxidant compounds. The effect of extracting solvent (ethanol, methanol, n-hexane, acetone and chloroform), extraction time (8h, 2 cycle and 3 cycle) (1 cycle = 20 min for hexane, 25 min for chloroform, 40 min for ethanol, 45 min for methanol and 35 min for acetone), solid-liquid ratio (4, 8 and 12 g / 250 ml) and size of hazelnut shell (1 mm and 2 mm) were investigated on the phenolic content and antioxidant capacity. Gas Chromatography equipped with a Mass Spectrometry (GC-MS) was used for the analysis of liquid products obtained from the extraction of hazelnut shell. Palmitic acid and oleic acid variations were detected at high ratios. The combined extraction method, which was composed of soxhlet and ultrasonic extractions, resulted in a significant increase in the yield of extraction. Also, higher yield was obtained from methanol and ethanol extraction because of the higher polarity of the solvents. On the other hand, it was observed that there was no significant effect of the extraction time on the extraction yield. The highest phenolic content was 0.166 mg gallic acid equivalent/ml and this value was obtained with methanol by combined extraction using 4 g hazelnut shell and 250 ml solvent.
  • Master Thesis
    Mineralization of Olive Mill Wastewater Under Hydrothermal Conditions
    (Izmir Institute of Technology, 2017) Ersanlı, Çağlar; Yüksel Özşen, Aslı; Yüksel Özşen, Aslı; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The purpose of this study is to reduce the total organic carbon (TOC) and chemical oxygen demand (COD) concentrations, color, the concentration of total phenolic compounds of olive mill wastewater (OMW) by hydrothermal degradation in subcritical water medium with and without using hydrogen peroxide (H2O2). In addition to this, investigation of effect of reaction temperature, reaction time and H2O2 concentration on the reduction of TOC, COD, color and total phenolic content; and controlling the generation of secondary pollutants during the reactions are other objectives of this study. Hydrothermal degradation reactions were performed at 150-250 ºC of reaction temperature, 30-120 minutes of reaction duration with 0-100 mM H2O2. Experimental design and statistical analysis (ANOVA) were carried out by Minitab. The main product of partial mineralization of OMW was acetic acid. Increase in the reaction temperature and time resulted in increasing TOC reduction rates significantly. On the other hand, presence of H2O2 did not affect the removal efficiency of TOC concentration significantly because of competition of hydroxyl free radicals by H2O2 and target molecule (OMW). The best yield (31.65%) of TOC reduction was achieved with a reaction at 250 ºC, 120 min and without using H2O2.
  • Master Thesis
    Conversion of Hazelnut Shell Into Value-Added Chemicals by Using Sub-Critical Water as a Reaction Medium
    (Izmir Institute of Technology, 2016) Gözaydın, Gökalp; Yüksel Özşen, Aslı; Yüksel Özşen, Aslı; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The objective of this study is to clarify the effect of reaction temperature, reaction time, acid concentration and acid type on the hydrothermal conversion of waste hazelnut shell into value-added chemicals under hot compressed water with high temperature/high pressure autoclave. The other aim is to gaining of added value and new utilization field to waste hazelnut shell. This is the first study about the degradation of waste hazelnut shell in order to produce levulinic acid under subcritical water in literature. Reactions were performed at 150-280 °C of reaction temperature, 15-120 min of reaction time with different acid (H2SO4 and H3PO4) concentrations that was varied from 0 to 125 mM. The liquid product distribution was evaluated with High Performance Liquid Chromatography (HPLC) and Gas Chromatography-Mass Spectrometry (GC-MS) and gas products were identified by Gas Chromatography with a Thermal Conductivity Detector (GC-TCD). While levulinic acid, acetic acid and furfural were identified as a major liquid compounds, the main gaseous products were carbon dioxide and carbon monoxide. Increasing reaction temperature and reaction time improved the conversion of hazelnut shell up to 65.40% at 280 °C and 120 min in the presence of 50 mM H2SO4 and 13.05% of levulinic acid yield was obtained under the similar reaction conditions. Addition of dilute H2SO4 and H3PO4 in the reaction medium enhanced different product formation. H2SO4 treatment promoted the production of levulinic acid whereas addition of H3PO4 increased the formation of furfural. Furthermore, total phenolic content, antioxidant capacity and possible reaction pathways of hydrothermal conversion of waste hazelnut shell was evaluated.
  • Master Thesis
    Modelling and Simulation of Zinc Based Batteries
    (Izmir Institute of Technology, 2016) Toptop, Evren; Ebil, Özgenç; Yüksel Özşen, Aslı; Ebil, Özgenç; Yüksel Özşen, Aslı; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Energy is the determining factor of productivity and quality of living. Electric energy is the most used energy form and lack of reserve for it hinders widespread use of renewable energy technologies. Advancements in renewable energy technologies, electric vehicles and consumer electronics are highly dependent on developments of new battery technologies. High energy density, long service life, using benign and abundant materials are few of the key requirements for next generation batteries. A model, a mathematical description of the system, is an effective tool to predict the behavior of batteries under specific conditions, thus reducing cost and time for the development. A mathematical model using finite element method was designed to simulate the discharge behavior of an experimental nickel-zinc battery that includes composite zinc and commercial nickel electrodes. The model employs thermodynamic and kinetic expressions for porous electrodes considering the concentration dependency of battery characteristics. The effects of initial zinc and nickel concentrations, anodic transfer coefficients of zinc and nickel electrode reactions on the electrochemical performance of the battery have been simulated. The discharge voltage, electrode porosities, and species concentrations in electrodes as a function of model parameters and time have been evaluated. It is observed that the model results are consistent with the experiment results considering that the battery operation is limited with zinc concentration. Initial zinc concentration is the major determining factor on discharge duration. Nickel oxyhydroxide concentration affects voltage magnitude. Transfer coefficients have only limited effects on discharge voltage and concentrations.
  • Master Thesis
    Hydrothermal Treatment of Biomass in Hot-Pressurized Water
    (Izmir Institute of Technology, 2015) Dadenov, Saken; Emrullahoğlu, Mustafa; Yüksel Özşen, Aslı; Yüksel Özşen, Aslı; Emrullahoğlu, Mustafa; 03.02. Department of Chemical Engineering; 04.04. Department of Photonics; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    The aim of this study is to observe conversion of cellulose, which is the main compound of biomass, into its building-block chemicals in hot-pressured water as reaction medium with no addition of organic solvents. Water in liquid state under temperature and pressure above boiling point and below the critical point (374. 15 ºC and 22.1 MPa) is called as hot-pressurized water (or sub-critical water). Nowadays the biomass has great attention across the World as renewable source of energy, at the background of the quickly growing energy demand, since it is widely available and cheap. This technology is totally environmentally friendly and uses water as a reaction medium. As well known, since plant biomass contains up to 50% cellulose, it was decided to use it as a model compound in this study. Decomposition of cellulose leads to formation of various compounds. Among them levulinic acid is the most attractive chemical. Moreover, this acid marked as “Top 12 Building Blocks” of most perspective chemicals and obtaining from biomass by hydrothermal treatment is not widely studied. During this study, different reaction parameters such as temperature, pressure, reaction time and external oxidizer addition were studied to clarify their effects on cellulose decomposition and product yields to achieve the highest selectivity of the desired product. Addition of H2SO4 led to increase cellulose conversion up to 73% at 200 oC with a H2SO4 concentration of 125 mM at 60 min reaction time. Under same conditions, the yield of levulinic acid was successfully achieved to 38% after 60 min.