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Öğe 9.08 - Environmental Issues With Hydrogen Production(Elsevier, 2022) Baykara, Sema Z.; Figen, Halit Eren; Karaismailoglu, MeltemHydrogen, its sources, production methods and use as fuel are covered in view of its “critical role” pertaining to global warming, climate change and other possible environmental impacts. Mostly, reviews are used as references to provide a wide source of information.; Environmental impact of hydrogen production is not only considered in terms of GHGs and their long-term global warming potential, but also in terms of the wider immediate environmental impact related to accession of sources of hydrogen and processes involved. Ubiquitous nature of hydrogen generation is emphasized as an advantage for securing and sustaining climate, development, eco-health and peace globally. © 2022 Elsevier Ltd. All rights reserved.Öğe 9.11 - Environmental Issues and Social Issues With Renewable Energy(Elsevier, 2022) Baykara, Sema Z.; Figen, Halit Eren; Karaismailoglu, MeltemA brief account of possible environmental and social impacts of mature renewable energy technologies is presented in terms of benefits and disadvantages/intrusive effects, keeping in perspective the greater environmental impact of the present fossil-based energy system and the potential further impact of climate change.; The technologies covered include solar energy (thermal and photovoltaic) and its derivatives (bioenergy, hydropower, wind and wave energies) and the others (tidal energy and geothermal energy). They are mostly considered from the point of view of electricity generation in anticipation of transmission opportunity via grid connections, producing a “mix,” and powering the existing stock of electrical appliances, machinery, and transportation vehicles. © 2022 Elsevier Ltd. All rights reserved.Öğe Environmental issues and social issues with renewable energy(Elsevier Science, 2022) Baykara, Zeynep Sema; Figen, Halit Eren; Elibol, Meltem Karaismailoğlu[Özet yok]Öğe Hydrogen production by catalytic methane decomposition over yttria doped nickel based catalysts(Pergamon-Elsevier Science Ltd, 2019) Karaismailoğlu, Meltem; Figen, Halit Eren; Baykara, Sema ZeynepCatalytic methane decomposition can become a green process for hydrogen production. In the present study, yttria doped nickel based catalysts were investigated for catalytic thermal decomposition of methane. All catalysts were prepared by sol-gel citrate method and structurally characterized with X-ray powder diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Brunauer, Emmet and Teller (BET) surface analysis techniques. Activity tests of synthesized catalysts were performed in a tubular reactor at 500 ml/min total flow rate and in a temperature range between 390 degrees C and 845 degrees C. In the non-catalytic reaction, decomposition of methane did not start until 880 degrees C was reached. In the presence of the catalyst with higher nickel content, methane conversion of 14% was achieved at the temperature of 500 degrees C. Increasing the reaction temperature led to higher coke formation. Lower nickel content in the catalyst reduced the carbon formation. Consequently, with this type of catalyst methane conversion of 50% has been realized at the temperature of 800 degrees C. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe Investigation of a novel & integrated simulation model for hydrogen production from lignocellulosic biomass(2018) Ersöz, A.; Baykara, Zeynep Sema; Elibol, Meltem Karaismailoğlu; Güldal, N. Ö.; Figen, Halit Eren; Yüksel, F.; Turan, A. Z.; Sarıoğlan, A.; Durak Çetin, Y.Process simulation and modeling works are very important to determine novel design and operation conditions. In this study; hydrogen production from synthesis gas obtained by gasification of lignocellulosic biomass is investigated. The main motivation of this work is to understand how biomass is converted to hydrogen rich synthesis gas and its environmentally friendly impact. Hydrogen market development in several energy production units such as fuel cells is another motivation to realize these kinds of activities. The initial results can help to contribute to the literature and widen our experience on utilization of the CO2 neutral biomass sources and gasification technology which can develop the design of hydrogen production processes. The raw syngas is obtained via staged gasification of biomass, using bubbling fluidized bed technology with secondary agents; then it is cleaned, its hydrocarbon content is reformed, CO content is shifted (WGS) and finally H2 content is separated by the PSA (Pressure Swing Adsorption) unit. According to the preliminary results of the ASPEN HYSYS conceptual process simulation model; the composition of hydrogen rich gas (0.62% H2O, 38.83% H2, 1.65% CO, 26.13% CO2, 0.08% CH4, and 32.69% N2) has been determined. The first simulation results show that the hydrogen purity of the product gas after PSA unit is 99.999% approximately. The mass lower heating value (LHVmass) of the product gas before PSA unit is expected to be about 4500 kJ/kg and the overall fuel processor efficiency has been calculated as ?93%.Öğe Investigation of the physicochemical properties of Bi,Ca-doped BaZrO3 perovskites(Mew Journal of Chemistry, 2023) Elibol, Meltem Karaismailoğlu; Akyüz, Serra Melek; Figen, Halit ErenPerovskite oxides, primarily the ones based on BaZrO3, hold significant interest for diverse applications in a variety of disciplines, such as electrocatalysts or electrolytes in fuel cell technologies. This study outlines the synthesis of BaZrO3 perovskite powders via a sol–gel route, and explores the incorporation of bismuth and calcium cations through single doping. Extensive characterization, encompassing X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller analysis, oxygen/hydrogen temperature-programmed desorption/reduction, and scanning electron microscopy/energy-dispersive X-ray spectroscopy, reveals the impact of the metal cation incorporation on physicochemical properties, enhancing oxygen vacancies and lattice oxygen species within the BaZrO3 perovskite structure.Öğe Methane decomposition over Fe-based catalysts(Elsevier Ltd, 2020) Karaismailoğlu, Meltem; Figen, Halit Eren; Baykara, Sema Z.Catalytic approach for methane decomposition can be seriously considered as a promising process for COx free hydrogen generation. In this study, catalytic methane decomposition was performed using Fe-based catalysts, and catalytic performance tests were carried out in a CH4:N2 flow at 750 and 800 °C. The analyses of reaction products were carried out by a mass spectrometer. For the preparation of Fe-based catalysts, sol-gel method was utilized. Yttria (Y2O3) and alumina (Al2O3) were used as support materials. Theoretical molar ratios (Fe2O3/Y2O3/Al2O3) of the samples C1–C5 were 1:0:0, 1:1:0, 1:1:5, 2:1:4 and 3:1:6, respectively. The characterization analyses of fresh and spent catalysts were performed with XRD, SEM, TPR, TG-FTIR and BET surface analysis techniques. Surface basicity of catalysts was determined via CO2-TPD measurements. In the presence of Fe2O3/Y2O3 and Fe2O3/Y2O3/Al2O3 catalysts, methane conversions of 29% and 4% were achieved at 750 °C. Adding alumina into Fe2O3/Y2O3 catalyst leads to the formation of garnet type crystal structure which reduces catalytic activity. © 2020 Hydrogen Energy Publications LLCÖğe Molybdenum- and vanadium-containing perovskite electrocatalysts for dissociation of H2S(Wiley, 2020) Karaismailoğlu, Meltem; Güldal, Nafi Özgür; Figen, Halit Eren; Baykara, Sema ZeynepCatalytic operations, achieving considerable energy savings, continue getting wider application especially in clean energy systems. Perovskite materials, owing to their chemical and thermal stability, can be conveniently used as catalysts and electrode materials at wide temperature ranges. Hydrogen sulfide (H2S) offers a new and abundant source of hydrogen, the ultimate energy carrier. In the present work, change in electrical conductivity of catalysts obtained by adding molybdenum (Mo) and vanadium (V) as B to the perovskite structure with lanthanum (La) and strontium (Sr) as A and A ', respectively, has been studied within a temperature range of up to 1100 K. Samples La0.75Sr0.25MoO3 and LaSr0.5V0.5O3 demonstrated the highest values of conductivity at 1100 K. At lower temperatures, Cr-added Mo and V catalysts La0.9Sr0.1Cr0.5Mo0.5O3 and La0.9Sr0.1Cr0.5V0.5O3 had higher conductivity, closely followed by LaSr0.5V0.5O3.Öğe Physicochemical characterization of calcium-doped barium zirconate perovskites for hydrogen-induced systems and their life cycle assessment(Elsevier Ltd, 2025) Yılmaz, Enes Emre; Koşma, Elvan Burcu; Figen, Halit Eren; Elibol, Meltem KaraismailoğluBaZrO3 perovskites attract considerable attention in electrocatalytic applications. This study offers a comprehensive overview of synthesizing BaZrO3 perovskite material via the sol-gel method and investigates the impact of Ca-doping on its physicochemical properties. The hydrogen temperature-programmed reduction profiles and X-ray photoelectron spectroscopy analyses demonstrate that Ca-doping effectively enhanced the concentration of oxygen vacancies, which makes the material a candidate for hydrogen-induced electrocatalytic applications. Additionally, life cycle analysis results indicate the synthesis of Ba0.6Ca0.4ZrO3 perovskite with the most concentrated oxygen vacancies among synthesized perovskites caused the highest environmental impact, with marine and freshwater ecotoxicity being the primary environmental concern. © 2025 Hydrogen Energy Publications LLCÖğe title Fe sub2/sub O sub3/sub /Y sub2/sub O sub3/sub catalystsupported on alumina and halloysite/title(2018) Elibol, Meltem Karaismailoğlu; Figen, Halit Eren; Baykara, Zeynep Sema[Özet yok]
