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    Comparative studies of hydrochars and biochars produced from lignocellulosic biomass via hydrothermal carbonization, torrefaction and pyrolysis
    (Elsevier Sci Ltd, 2023) Ercan, Betul; Alper, Koray; Ucar, Suat; Karagoz, Selhan
    In this study, hydrothermal carbonization, torrefaction, and pyrolysis of hornbeam wood chips were performed. Different runs were conducted at varying temperatures ranging from 225 to 575 & DEG;C, and the resulting biochars and hydrochars were analyzed. Biochars obtained from torrefaction runs had high yields, but no significant structural changes compared to raw material. Biochars produced from pyrolysis runs had high fixed carbon content that increased with temperature. Hydrochars obtained from hydrothermal carbonization had higher degree of carbonization than biochars produced from torrefaction under identical conditions. The order of carbonization degree, from highest to lowest, was: biochars obtained from the pyrolysis process, hydrochars produced from the hydrothermal carbonization process, and biochars obtained from the torrefaction process. The highest heating value of the biochar was 32.51 MJ kg-1, produced from the pyrolysis run at 575 & DEG;C.
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    Effect of a water-tolerant Lewis acid catalyst on the yields and properties of hydrochars from hydrothermal carbonization of walnut wood
    (Springer, 2023) Ercan, Betul; Ajagbe, Yusuf O.; Ucar, Suat; Tekin, Kubilay; Karagoz, Selhan
    The hydrothermal carbonization of walnut wood chips was conducted at 200-250 & DEG;C for 1-8 h. Increasing the hydrothermal carbonization temperature or the residence time decreased the volatile products and increased the fixed carbon content of the hydrochars. The hydrochars produced from the non-catalytic experiments at 250 & DEG;C for 6 and 8 h were in the lignite class. The lowest O/C and H/C atomic ratios were obtained after carbonization at 250 & DEG;C for 8 h. The catalytic hydrothermal carbonization experiments were carried out in the absence and presence of InCl3 using 1, 2, and 4 mmol of InCl3 at 200, 225, and 250 & DEG;C for 4 h. The highest heating value of hydrochar from the catalytic experiment was 24.73 MJ/kg and was obtained at 250 & DEG;C for 4 h using 1 mmol InCl3. Process water reuse resulted in increased heating values of the hydrochars in both the non-catalytic and catalytic experiments. The use of InCl3 promoted the coalification degree of the hydrochars. These results demonstrate that InCl3 is a suitable catalyst for producing hydrochars via the hydrothermal carbonization of walnut wood chips, which can be used as a solid biofuel.
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    Effects of Metal Chlorides on the Hydrothermal Carbonization of Grape Seeds
    (Amer Chemical Soc, 2021) Hasan, Rebaz O.; Ercan, Betul; Acikkapi, Ayse N.; Ucar, Suat; Karagoz, Selhan
    In this study, hydrothermal carbonization (HTC) of grape seeds, a lignocellulosic biomass, was carried out at various temperatures (200, 225, and 250 degrees C), different reaction times (6, 12, and 24 h), and different biomass:water ratios (0.025, 0.05, and 0.1). The most important parameter affecting the yields and characteristics of hydrochars was found to be temperature. The HTC of grape seeds was then conducted in the presence of metal chlorides (i.e., CsCl, ZnCl2, and SnCl2) at temperatures of 200, 225, and 250 degrees C for 12 h. SnCl2 behaved very differently in the HTC process than the other catalysts (or no catalyst). A major difference among these catalysts was the extent to which they were incorporated within the hydrochar structure. SnCl2 was much more readily incorporated than was CsCI or ZnCl2. Carbon microspheres were observed in hydrochars from obtained biomass without a catalyst and with CsCl and ZnCl2 catalysts; agglomerated carbon nanospheres were observed in hydrochars produced with SnCl2. Hydrochars obtained at 225 and 250 degrees C by using SnCl2 and ZnCl2 catalysts were in the lignite class, while hydrochars obtained from biomass without a catalyst, and using CsCI, were in the peat coal class.
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    Hydrothermal carbon spheres produced from glucose, cyclodextrin, and starch
    (Taylor & Francis Inc, 2024) Iqbal, Mehboob; Ercan, Betul; Karagoz, Selhan
    The production of hydrothermal carbons from glucose, cyclodextrin, and starch was reported at 180 degrees C and 200 degrees C for 24 hr, both with and without 2-chloro propionic acid. The yields of hydrothermal carbons varied depending on the feedstock and temperature. At the lowest temperature, glucose gave the highest yield of hydrochar, while at 200 degrees C, the yields did not differ significantly among the three feedstocks, with the highest yield obtained for cyclodextrin-derived hydrochars. The use of a catalyst not only decreased the yield of hydrothermal carbons but also resulted in an increase in the diameter of hydrochars for all saccharides. When compared to raw saccharides, the O/C and H/C ratios of hydrothermal carbons were significantly lower, suggesting that significant deoxygenation and dehydration occurred after the HTC processing. In the non-catalytic runs, hydrochars for each feedstock showed an increase in aromatic content when the temperature was increased from 180 degrees C to 200 degrees C. The size of the carbon spheres was significantly influenced by various factors including the operating conditions, the type of saccharide used, and the pH of the aqueous solutions. The diameters of carbon spheres produced in runs with catalysts were larger when compared to their corresponding hydrothermal carbons from the non-catalyst runs.
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    A Polystyrene supported Scandium (III) microencapsulated Lewis acid catalyst for hydrothermal carbonization of glucose
    (Pergamon-Elsevier Science Ltd, 2023) Ercan, Betul; Auersvald, Milos; Kejla, Lukas; Tekin, Kubilay; Simacek, Pavel; Karagoz, Selhan
    Hydrothermal carbonization of glucose in the absence and presence of recoverable solid polystyrene-supported microencapsulated Lewis acid catalyst has been carried out at 180 and 200 degrees C for 6, 12, and 24 h using either 0.25 g or 0.5 g of catalyst. The effects of temperature, residence time, and catalyst loading on the resulting hydrochars were investigated. At the lowest temperature (180 degrees C) and the shortest residence time (6 h) without the presence of a catalyst, the glucose conversion was the lowest as expected. No hydrochar was formed at 180 degrees C for 6 h without using any catalyst. In catalytic runs, the formation of hydrochar was observed under identical conditions although the yields of hydrochar were low. The use of the catalyst increased the yield of acid com-pounds (acetic, glycolic, lactic and levulinic) at the expense of 5-hydroxymethylfurfural under identical condi-tions. Except for 180 degrees C for 6 and 12 h, the use of the catalyst decreased the yield of hydrochar. The use of the catalyst led to increasing the diameter of carbon sphere particles under identical conditions. The presence of the catalyst resulted in the production of a notable amount, approximately 20 wt% of levulinic acid as a by-product.
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    Production of Hydrochars from Lignocellulosic Biomass with and without Boric Acid
    (Wiley-V C H Verlag Gmbh, 2022) Ercan, Betul; Ajagbe, Yusuf O.; Ucar, Suat; Tekin, Kubilay; Karagoz, Selhan
    Hydrothermal carbonization (HTC) is an important thermochemical process where biomass is converted into coal-like solid products known as hydrochars. The HTC process is performed in hot-compressed water under self-generated pressures. In this work, the HTC of acorn shells was conducted at various temperatures and reaction times with and without boric acid (H3BO3). A high degree of carbonization occurred at 250 degrees C in non-catalytic and catalytic 4-h runs. Hydrochars obtained from non-catalytic and catalytic runs at 250 degrees C consisted of spherically carbon particles with diameters ranging from 303 nm to 3.27 mu m. Carbon spheres at 200 and 225 degrees C for 2 h were not observed. The yield and carbon content of the hydrochars were slightly increased by reuse of the process water in thermal runs without catalysts.
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    Reference material development process for tensile test method
    (Pamukkale Univ, 2022) Incesu, Alper; Ercan, Betul; Cevik, Engin; Akgul, Yasin
    Reference materials (RMs) are one of the basic materials used by the laboratories to prove the reliability of their test results. In this research, preliminary studies have been carried out to develop RM to use in tensile tests according to ISO 6892-1. For this purpose, bone shape flat specimens were prepared from EN 10130:2006 quality 1 mm thick sheet steel related to the given standard. Homogeneity tests and inter-laboratory comparison tests were performed for calculation of measurement uncertainty and value assignment of proposed RM. Results were compared with commercial certified reference materials (CRMs). It was found that relative uncertainty values of the proposed RM were coherent with commercial CRMs. Therefore, these produced RM can be used in quality control studies for laboratories, also by the production route proposed in this study, every laboratory can be produced RM related to their needs.
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    Sulfonic Acid-Catalyzed Biocoal Production from Lignocellulosic Biomass
    (Amer Chemical Soc, 2024) Alper, Koray; Auersvald, Milos; Kejla, Lukas; Ercan, Betul; Ucar, Suat; Tekin, Kubilay; Simacek, Pavel
    In this study, hydrothermal carbonization (HTC) of spruce wood was studied at different temperatures (200-260 degrees C) and residence times (2-48 h). An increase in the temperature and residence time resulted in higher heating values of hydrochars. The effect of temperature on the hydrochar yield and carbon content was more pronounced than the residence time. Two sulfonic acid catalysts were explored for the first time in the HTC of spruce wood at 240 degrees C for 24 h. The impact of sulfonic acid type and concentration on hydrochar yields and characteristics was investigated. Among the tested acids, methanesulfonic acid (MSA) had a significant effect on HTC, producing hydrochar with increased fixed carbon content and a higher heating value compared to noncatalytic runs and runs with dodecyl benzenesulfonic acid (DBSA) under identical conditions. The highest fuel ratio obtained was 1.47 with MSA at a concentration of 0.01 M. A detailed quantitative analysis of the aqueous phase from HTC processing using gas chromatography helped to elucidate the differences between the tested acids and demonstrated promoted lignin depolymerization with increasing MSA concentration. The use of sulfonic acid significantly increased the yield of levulinic acid in the aqueous phase. Overall, these findings highlight the potential of sulfonic acid catalysts in enhancing the efficiency and product quality of HTC processes, providing insights into optimizing biomass conversion for sustainable energy production and biocoal synthesis.