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Öğe A research on antioxidant activity evaluation of waste lignocellulosic biomass: optimization using response surface methodology(Sivas Cumhuriyet Üniversitesi, 2020) Meryemoğlu, Bahar; Kaya, Burçak; Niş, BernaIn the present study, lignocellulosic biomass such as corn straw and sorghum were used as raw materials for a new, abundant, low-cost and natural antioxidant source to use in foods or medicinal materials as replacements for synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The effect of extraction temperature, extraction time, solvent volume on extraction yield, total phenol content and antioxidant activity were investigated and the results obtained by response surface methodology (RSM) were evaluated. Linear and quadratic models were revealed as a result of experiments. The fit of these models with predictions results were tested and optimal condition parameters were investigated. It was seen that different results were obtained because of structural differences between corn straw and sorghum. These results showed that the extraction temperature was the main positive linear effect on extraction yield. The solvent volume and temperature were found to important model terms for total phenol content. For antioxidant activity, the solvent volume was the main linear effect for sorghum where as it has a quadratic effect for corn straw biomass.Öğe EFFICIENT PRETREATMENT OF CORN STRAW AND SORGHUM WITH LTTM FOR ENHANCED BIO-CONVERSION(2025) Çataloluk, Ahmet; Demirli, Harun; Niş, Berna; Özsel, BurcakThis 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 °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 °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.Öğe Fabrication of Carbonaceous-Modified Halloysite Nanotubes for the Removal of Metal Ions from Aqueous Solution(2023) Meryemoğlu, Bahar; Özsel, Burcak; Niş, BernaHalloysite nanotube-carbonaceous (HNT-C) composites were fabricated through one-pot hydrothermal carbonization of fructose and sodium carboxymethyl cellulose for use as an adsorbent for the removal of Pb(II), Zn(II), and Cu(II) from wastewater. The composites were chemically treated with sulfuric acid after carbonization. The acidic treatment of HNT-C structures contributed to a larger specific surface area and surface functionality, which was favorable for adsorbing more metal ions. Carbonaceous-modified HNTs were characterized by elemental analysis, FT IR, XRD, and BET analysis. Metal ion adsorption experiments were conducted with solutions containing low and high total metal ion concentrations (Cu, Zn, Pb) by mixing with HNT-C composites at a solid/liquid ratio of 1.0 and 10.0 g/L. The results indicated that the HNT C composites exhibited promising Zn(II) adsorption up to 94%, while no Zn(II) adsorbed onto unmodified HNTs. The amount of Pb(II), Zn(II), and Cu(II) ions that were taken up increased as the amount of adsorbent was increased up to 10 g/L in an aqueous solution. The HNT-C composites exhibited the highest adsorption efficiency for Pb(II) ions.Öğe FARKLI ÇÖZÜCÜ ORTAMLARINDA TUNGSTOFOSFORİK ASİT KATALİZÖRLÜĞÜNDE KİTOSANDAN LEVULİNİK ASİT ELDESİ(2023) Özdemir, Şeyma; Niş, Berna; Özsel, BurcakBu çalışmada kitosan ve glukozun farklı çözücü ortamlarında belirli sıcaklık ve sürede tungstofosforik asit katalizörlüğünde tek basamakta hidrolizi ve levulinik aside dönüşümleri incelenmiştir. Katalitik dönüşüm prosesinde kütlece 1:5 oranında (yardımcı çözücü-su) sulu ortama eklenen ?-valerolakton, kitosanın levulinik aside dönüşüm verimini değiştirmezken, glukoz dönüşüm verimini yaklaşık iki katına çıkarmıştır. Sulu ortama aynı oranda 1 butil 3 metilimidazolyum hidrojensülfat ilavesinde ise hem kitosan hem de glukoz dönüşümlerinde levulinik asit verimi sırasıyla %3,7 ve %22,7’ye ulaşmıştır. Kitosanın su/1 butil-3-metilimidazolyum hidrojensülfat ortamında dönüşümü sonrası toplam indirgen şeker miktarı ve katı atığın FT-IR spektrumu incelendiğinde iyonik sıvının asidik karakterinin hidroliz ve dönüşüm üzerinde etkili olduğu görülmektedir. Katalizörsüz sulu ortamda biyokütle dönüşümünde levulinik asit oluşmazken, tungstofosforik asit kullanıldığında kitosandan %3,1, glukozdan ise %7,0 verimle levulinik asit elde edilmiştir.Öğe Başlıksız(Elsevier Sci Ltd, 2019) Özsel Kaya, Burçak; Ozturk, Dilek; Niş, BernaThe direct hydrothermal conversion of waste biomass to 5-hydroxymethyl furfural (5-HMF) and levulinic acid was studied here in the presence of new biomass-derived sulfonated carbonaceous solid acid catalysts. Different cheap and waste lignocellulosic/cellulosic biomass materials (wheat straw, corn straw, cotton linter and industrial textile fluff) were used as feedstock to prepare bio-based chemicals in an eco-friendly and economical process. The yields of products were improved by optimization of reaction temperature, reaction time and catalyst type for various types of biomass. Under the optimum reaction conditions BT300S sulfonated solid acid carbonaceous catalyst has exhibited higher activity compared to commercial Amberlyst 15 thus 403.7 ppm 5-HMF (16.2 mg 5-HMF/g biomass) and 1624.8 ppm LA (65.6 mg LA/g biomass) have been generated from corn straw biomass in aqueous media at 200 degrees C in 1 h.Öğe Başlıksız(Wiley, 2019) Özsel Kaya, Burçak; Niş, Berna; Meryemoglu, Bahar; Hasanoglu, Arif; Irmak, SibelWaste cotton linter was evaluated for production of activated carbons (ACs) that can be used as catalyst support in aqueous-phase reforming (APR) process. Activated carbons were prepared by two different precarbonization methods (thermal and hydrothermal) and two types of chemical activating agents (H3PO4 and KOH). The catalysts prepared by deposition of platinum particles on these carbon materials were evaluated for conversion of glycerol to hydrogen gas by APR. Thermal precarbonization treated LTA and LTB samples had a higher surface area (416.7 and 775.2 m(2)/g) than hydrothermal precarbonized LHA and LHB samples (395.8 and 627.5 m(2)/g) regardless type of the activating agent. In general, KOH was more effective activating agent than H3PO4 in creating porosity in the carbon structures derived from cotton linter. The Pt/LHB catalyst (hydrothermal precarbonization-KOH activation) showed promising catalytic performance with hydrogen selectivity of 76.0% and 99.0% glycerol conversion at same APR conditions. (c) 2018 American Institute of Chemical Engineers Environ Prog, 38: 445-450, 2019Öğe Başlıksız(Elsevier Sci Ltd, 2020) Niş, Berna; Özsel Kaya, BurçakIn recent years, the utilization of biomass resources in the production of industrial chemicals and fuels become more preferable when considering low cost, renewability and environmental concerns. In this study, 5-hydroxymethylfurfural and levulinic acid obtained from catalytic one-pot reaction of different feedstocks (microcrystalline cellulose, corn straw, sorghum and waste fluff) under the specified conditions (temperature, time, solvent ratio, catalyst loading) using different cosolvents (methanol, hexane, tetrahydrofuran (THF), acetone) in reaction medium. Over the Amberlyst-15 catalyst, significant increase in levulinic acid concentration was achieved using acetone as cosolvent thus 94.34 +/- 5.25 mg levulinic acid was obtained from 1 g sorghum at 180 degrees C for 30 min. The use of polar aprotic solvents such as THF and acetone promoted further hydrolysis of raw biomass materials in reaction medium.Öğe Başlıksız(Bursa Teknik Üniversitesi, 2019) Niş, Berna; Özsel, Burçak KayaFosil yakıtlar gibi yenilenemez kaynakların, enerji üretiminin yanı sıra endüstriyel alanda da kullanılması ve hızla tükeniyor olması yenilenebilir kaynakların kullanımı üzerine yapılan çalışmaların artmasına sebep olmuştur. Son yıllarda yapılan çalışmalar ile biyokütlenin dönüşümü sonucu yakıt, çözücü, plastik gibi farklı birçok endüstriyel alanda kullanılabilecek kimyasalların üretiminin mümkün olduğu görülmüştür. Bununla birlikte fosil yakıtların kullanımına kıyasla çevreci ve temiz bir kaynak olması, kolay depolanması, hemen her koşulda ve ölçekte üretilebiliyor olması, düşük maliyetli olması, CO2 döngüsüne katkısının olması yenilenebilir kaynaklar arasında biyokütle kullanımının ön plana çıkmasına sebep olmuştur. Bu çalışma kapsamında biyokütlenin organik çözücü (metanol, aseton, THF, hegzan), iyonik sıvı ([BMIM]Cl, [BMIM]HSO4) ve derin ötektik çözücü (kolin klorür:etilen glikol) olmak üzere üç farklı çözücü ve su ortamında reaksiyonu sonucu hidroliz oranları ve elde edilen katma değeri yüksek kimyasal miktarları (5-hidroksimetilfurfural, furfural, levulinik asit, süksinik asit) belirlenmiştir. Katma değeri yüksek kimyasalların ve monosakkaritlerin belirlenmesinde HPLC, toplam indirgen şeker içeriğinin belirlenmesinde UV-VIS spektroskopisi tekniklerinden yararlanılmıştır. Her bir çözücü ortamında reaksiyon koşulları optimize edilerek uygun reaksiyon sıcaklığı, reaksiyon süresi ve çözücü oranları belirlenmiştir. Optimizasyon sonucunda tüm çözücü ortamları için en uygun reaksiyon sıcaklığının 180°C olduğu, reaksiyon süresi ve çözücü oranının ise çözücü ortamına göre değişiklik gösterdiği belirlenmiştir. Denemeler model bileşik olarak mikrokristalin selüloz, lignoselülozik biyokütle kaynağı olarak mısır samanı, buğday samanı, sorgum ve selülozik biyokütle kaynağı olarak atık hav ve linter kullanılarak gerçekleştirilmiş ve başlangıç materyalinin ürün oluşumuna etkisi incelenmiştir. Bununla birlikte denemeler ticari katalizör olan Amberlist-15 ve laboratuvar ortamında düşük maliyet ile buğday samanından elde edilen katı asit katalizör olan BT300S varlığında tekrar edilmiş ve katalizör türünün ürün oluşumuna etkisi incelenmiştir. En etkin hidroliz oranına ve en yüksek şeker içeriğine [BMIM]HSO4-su ortamında gerçekleştirilen reaksiyon sonucunda ulaşılmıştır. Organik solvent-su çözücü ortamında etkinlik sırasının polar aprotik çözücü > polar protik çözücü > apolar çözücü şeklinde olduğu görülmüştür. Biyokütle materyallerinin hidrolizi farklı çözücü ortamlarının kullanılması ile farklılık göstermesine karşın genel olarak hidroliz etkinliğinin sorgum ~ mısır samanı > buğday samanı ~ atık hav > selüloz > linter sırasını takip ettiği görülmüştür.Öğe Başlıksız(Elsevier Ltd, 2021) Niş, Berna; Özsel Kaya, BurçakIn this study, the conversion of corn straw, sorghum and cellulose into valuable chemicals (furfural, 5-hydroxymethylfurfural, levulinic acid) in different ionic liquid-water medium were investigated. Different reaction parameters such as reaction temperature, time and solvent ratio were optimized to achieve the highest conversion of biomass and selectivity of the products. Under the optimal reaction conditions (180 °C, 30 min, 1:5 ratio), 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO4) was found to display the highest efficiency which can be attributed to the acidic character of the ionic liquid. 117.4 mg levulinic acid, 11.8 mg 5-hydroxymethylfurfural and 9.4 mg furfural were obtained per g of sorghum. The results showed that 5-fold higher quantity of LA was obtained from sorghum biomass in comparison with pure cellulose. In addition, Amberlyst-15 was examined as a solid acid catalyst for conversion of cellulose in [BMIM]HSO4-water solvent system resulting in 4.6-fold increase in the quantity of levulinic acid. This study provides an alternative single step approach for production of valuable chemicals from renewable biomass.
