Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 10Citation - Scopus: 11Liquefaction of Oak Wood Using Various Solvents for Bio-Oil Production(AMER CHEMICAL SOC, 2023) Öcal, Bulutcem; Yüksel, AslıRapidly increasing global energy demand resulting from the growing population and worldwide development has increased the consumption of limited fossil fuel. The usage causes severe environmental deterioration by CO2 emission, which has sparked interest in finding green, renewable, and sustainable alternative sources of energy. Bio-oil, derived from several biomasses via liquefaction, is a promising candidate to replace fossil fuels. Turkey's land (27%) is covered with forested areas (consisting of mostly oak trees). Therefore, it has great potential for cheap lignocellulosic feedstock forest residues from industrial applications and harvesting. In the present study, the thermal liquefaction of oak wood particles (OWP) was performed using various solvents in addition to water, namely, ethanol, 1-butanol, and 1,4-dioxane. The experiments were carried out in a batch reactor for 1 and 2 h residence times at different temperatures (210, 240, and 270 degrees C). Bio-oil samples obtained at 270 degrees C and a 1 h residence time determined as optimum conditions were analyzed with TGA, CHNS elemental analysis, FTIR, and GC-MS. 1,4-Dioxane showed the best performance in yielding the maximum bio-oil with 51.8% at those conditions. The higher heating values of the bio-oils ranged from 22.1 to 35 MJ/kg. Phenolic groups were the predominant components of bio-oil produced from OWP, while the intensity of alcohols, ketones, and acids varied based on used solvents. Based on energy recovery calculations, the enhancement of pristine OWP's energy efficiency depended on bio-oil yield, and quality was confirmed for all solvent types (1,4-dioxane > 1-butanol > water > ethanol).Article Citation - WoS: 31Citation - Scopus: 38Liquefaction of Waste Hazelnut Shell by Using Sub- and Supercritical Solvents as a Reaction Medium(Elsevier, 2019) Demirkaya, Emre; Dal, Orkan; Yüksel, AslıDirect 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, up to our best knowledge, in this study, hazelnut shell decomposition by using ethanol, acetone and their mixtures at sub/supercritical conditions was studied for the first time in literature. Experiments were carried out between 220-300 degrees C, at three different reaction times (30, 60 and 90 min) for five different solvent ratios. Highest solid conversion achieved at 300 degrees C by using pure ethanol was 64.2%, whereas highest bio-oil yield was found as 44.2% at 300 degrees C with 50/50 (EtOH/Ac: v/v). Ethanol and acetone showed different characteristics during the reactions and their effects on the conversion and bio-oil yield were discussed. Statistical analysis showed that time, temperature, ratio and synergy between temperature-time were affecting parameters for the conversion and bio-oil yield. (C) 2019 Elsevier B.V. All rights reserved.Article Citation - WoS: 36Citation - Scopus: 44Assessment of Elliptic Flame Front Propagation Characteristics of Iso-Octane, Gasoline, M85 and E85 in an Optical Engine(Elsevier Ltd., 2014) Ihracska, Balazs; Korakianitis, Theodosios P.; Ruiz, Paula; Emberson, David Robert; Crookes, Roy James; Diez, Alvaro; Wen, DongshengPremixed fuel-air flame propagation is investigated in a single-cylinder, spark-ignited, four-stroke optical test engine using high-speed imaging. Circles and ellipses are fitted onto image projections of visible light emitted by the flames. The images are subsequently analysed to statistically evaluate: flame area; flame speed; centroid; perimeter; and various flame-shape descriptors. Results are presented for gasoline, isooctane, E85 and M85. The experiments were conducted at stoichiometric conditions for each fuel, at two engine speeds of 1200. rpm (rpm) and 1500. rpm, which are at 40% and 50% of rated engine speed. Furthermore, different fuel and speed sets were investigated under two compression ratios (CR: 5.00 and 8.14). Statistical tools were used to analyse the large number of data obtained, and it was found that flame speed distribution showed agreement with the normal distribution. Comparison of results assuming spherical and non-isotropic propagation of flames indicate non-isotropic flame propagation should be considered for the description of in-cylinder processes with higher accuracy. The high temporal resolution of the sequence of images allowed observation of the spark-ignition delay process. The results indicate that gasoline and isooctane have somewhat similar flame propagation behaviour. Additional differences between these fuels and E85 and M85 were also recorded and identified.Article Citation - WoS: 20Citation - Scopus: 19The Catalytic Reforming of Bio-Ethanol Over Sio2 Supported Zno Catalysts: The Role of Zno Loading and the Steam Reforming of Acetaldehyde(Elsevier Ltd., 2008) Şeker, ErolIn this study, the activity and the product distributions of sol-gel made SiO2 supported ZnO catalysts in the steam reforming of ethanol and acetaldehyde is presented as a function of ZnO loading and temperature. We show that although highly dispersed ZnO in SiO2 (upto 50% ZnO loading) can be prepared using a single step sol-gel method, a precise control of crystallite size could not be achieved. From CO2 TPD measurements, we found that the basic site densities of ZnO/SiO2 catalysts stays < 0.05 μ mol / m2 and do not increase linearly with ZnO loading. The highest basic site density among the catalysts occurs on pure ZnO. All ZnO/SiO2 catalysts are active at 350 °C whereas pure ZnO catalyst is active at 450 °C. Iso-conversion activity tests show that ethanol steam reforming activities of the catalysts seem to be dependent on the ZnO crystallite size rather than the basic site density of the catalysts when the surface coverage of the basic site density is < 0.32 % but acetone is not formed only on catalysts with ZnO crystallite size < 5 nm regardless of their basic site densities. Interestingly, we found that ethanol was mostly dehydrogenated to acetaldehyde and hydrogen although H2O/C2H5OH molar ratio in the feed was 12. CO was not also produced in the steam reforming of ethanol over all the catalysts. Acetone and propene are produced from acetaldehyde as observed in the steam reforming of acetaldehyde. The steam reforming of acetaldehyde as compared to its decomposition was found to be more favorable over the catalysts with small ZnO crystals, such as 30% and 50% ZnO catalysts.Article Citation - WoS: 10Citation - Scopus: 11Use of Clinoptilolite in Ethanol Dehydration(Taylor and Francis Ltd., 1996) Tıhmınlıoğlu, Funda; Ülkü, SemraClinoptilolite-type natural zeolite, which exists in various regions of Turkey, has been experimentally studied. For the ethanol-water-local clinoptilolite system, uptake and breakthrough curves were determined under a nitrogen gas atmosphere. In adsorption kinetics and adsorption equilibrium studies, the effects of particle size, temperature and, amount of zeolite on the uptake rate have been investigated. The breakthrough curves for four different flow rates of ethanol and three different bed heights were determined in dynamic column studies. The results of the experiments show that intraparticle diffusion is the main resistance. The local clinoptilolite is a promising adsorbent for water adsorption from aqueous ethanol.