Yazar "Ozsel, Burcak Kaya" seçeneğine göre listele

Listeleniyor 1 - 5 / 5
  • Küçük Resim Yok
    Öğe
    A DES or LTTM: Eco-friendly solvent mediums for conversion of biomass to levulinic acid as a key chemical
    (Elsevier, 2024) Nis, Berna; Ozsel, Burcak Kaya; Kaya, Yunus
    In this study, the effect of using environmentally friendly, less toxic, low cost, and easily recyclable deep eutectic solvent (DES) and low-transition temperature mixture (LTTM), which are alternatives to ionic liquids, on the conversion of biomass to levulinic acid (LA) was investigated. The reaction conditions such as temperature, the amount of feedstock, and the water ratio were optimized to ensure maximum product formation in DES (ChClEG)-water medium. The highest amount of LA (143.2 +/- 2.5 mg) under optimum reaction conditions was achieved by using glucose in a newly designed LTTM (SA:EG)-water solvent medium. Newly designed low-transition temperature mixture (SA:EG) characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and differential scanning calorimetry (DSC) analyses. A comprehensive theoretical study was also performed to provide a deep understanding of the formation mechanisms of new LTTM by density functional theory (DFT), reduced density gradient (RDG), frontier molecular orbitals (FMOs), and molecular electrostatic potential (MEP) methods. The glucose conversion ratio increased from 70.2 % to 96.1 % in SA:EG-water medium. When microcrystalline cellulose, corn straw, and sorghum were used under the same conditions, 118.9 +/- 5.4, 36.8 +/- 9.4, and 32.6 +/- 3.4 mg of LA were obtained per g of feedstock. A typical Br & oslash;nsted acid; phosphotungstic acid (H3O40PW12) showed high catalytic activity, resulting in 229.0 +/- 0.32 mg of LA per g of glucose in SA:EG-water medium. This shows that the use of SA:EG LTTM for cellulosic/lignocellulosic biomass sources can be used favorably in conversion reactions.
  • Küçük Resim Yok
    Öğe
    Comparison of Hydrolysis and Conversion of Wheat Straw and Linter to Platform Chemicals in Various Co-solvent: Water Medium
    (Mehmet Sinan Bilgili, 2020) Nis, Berna; Ozsel, Burcak Kaya
    The interest on the production of biofuels and biochemicals from lignocellulosic/cellulosic biomass is growing very fast, on account of the possibility of reducing global environmental problems. To develop a more efficient and green process, properties of the reaction solvents such as partition coefficient, viscocity boiling point, thermal stability and cost are very significant. Even though water is known as the greenest solvent for hydrolysis and conversion of biomass into value added chemicals, the use of different co-solvents become preferable to increase the percentage of hydrolysis, conversion yield and product selectivity. Studies in the literature have proved that product selectivity increases with the use of appropriate co-solvents [1, 2]. In this study, conversion of wheat straw and linter to valuable chemicals were investigated (furfural, hydroxymethylfurfural, levulinic acid) in the presence of three different types of co-solvent (organic solvent, ionic liquid and deep eutectic solvent (DES)). Reactions were carried out under appropriate conditions that previously determined for each co-solvent:water medium. The maximum amount of levulinic acid was achieved (30.79 mg/g biomass) from linter in DES:water medium and 11.99 mg LA was obtained from 1 g of wheat straw with the use of ionic liquids ([BMIM]HSO4) as co-solvent.
  • Küçük Resim Yok
    Öğe
    EFFICIENT PRETREATMENT OF CORN STRAW AND SORGHUM WITH LTTM FOR ENHANCED BIO-CONVERSION
    (Konya Teknik Univ, 2025) Cataloluk, Ahmet; Demirli, Harun; Nis, Berna; Ozsel, Burcak Kaya
    This study explores using a low transition temperature mixture (LTTM), containing sulfamic acid and ethylene glycol for the pretreatment of corn straw and sorghum biomass, aimed to improve the efficiency of converting biomass into platform chemicals. We first optimized the pretreatment conditions (solid-liquid ratio, temperature, and time) and assessed the conversion of pretreated biomass into 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) using the catalyst Amberlyst-15. Optimal pretreatment conditions were found to be a solid-liquid ratio of 1:5 (w/w), a temperature of 40 degrees C, and a duration of 4 hours, which resulted in the highest yields of sugars; xylose, glucose, and sucrose. In the catalytic conversion of sorghum and corn straw pretreated with LTTM at 200 degrees C in the presence of Amberlyst-15, 801.2 ppm glucose and 1967.3 ppm levulinic acid were obtained from sorghum, while 663.9 ppm glucose and 1936.3 ppm levulinic acid were produced from corn straw. The study demonstrates that LTTMs offer effective and sustainable biomass pretreatment, improving the accessibility of lignocellulosic structure to catalysts, leading to higher yields of desired products like glucose and levulinic acid.
  • Küçük Resim Yok
    Öğe
    Humic Acids Derived from Lignocellulosic Biomass: Characterization and Utilizing for Environmental Applications
    (Springer Int Publ Ag, 2022) Meryemoglu, Bahar; Ozsel, Burcak Kaya
    The goal of this research is to evaluate waste lignocellulosic materials for the production humic acid (HA) as a natural, low-cost, and effective adsorbent for heavy metals (Ni, Cr, and Cu) removal from aqueous medium. The fourier transform infrared (FTIR) spectroscopy, fluoresence spectroscopy, LC-ESI-TOF/MS, and stable carbon isotopes analysis were applied to compare the chemical structure of humic acids obtained from wheat straw (C3) and corn straw (C4). The adsorption efficiency of humic acids obtained from different lignocellulosic sources was investigated and compared to the commercial HA. The adsorption efficiency for Cu ions was almost 70% and the metal adsorption capacity of corn-HA is remarkably higher than commercial HA. Ni ions exhibited the lowest adsorption percentage for which the removal reached 21.0% with corn-HA. This work showed that lignocellulosic-derived humic acids are suitable adsorbent for heavy metals and can be used for cleaning of waters or other systems with low concentrations of metal ions.
  • Küçük Resim Yok
    Öğe
    Organic acids production from low-cost cellulosic substrates by fermentation
    (Springer Science and Business Media Deutschland GmbH, 2024) Meryemo?lu, Bahar; Nis, Berna; Ozsel, Burcak Kaya
    Lignocellulosics have potential to be used as raw materials in the production of a wide range of chemicals. It is important to develop a sustainable bioprocess for organic acids derived from these sources. The present study aimed to produce organic acids from wheat straw and cotton linter biomass materials by fermentation. As an initial step, the fermentation conditions (sugar, yeast concentration, and time) were optimized for the production of organic acids in a higher yield using cellulose as a feed material. Organic acids were quantified with different liquid chromatography techniques. Many organic acids were identified in biomass hydrolysates after fermentation, lactic and butyric acid were the main acids found to be in 122.6–478.9 and 121.0–482.2 mg/g biomass range, respectively. The elution profiles of organic acids were performed with an LC-TOF/MS system by using three different columns for a comparison of the results obtained with HPLC-RID. Furthermore, the use of various methods and perspectives on difficulties and opportunities in organic acid analysis was discussed. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023.