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Öğe ATIK ZEYTİN KÜSPESİNİN DEĞERLİ ÜRÜNLERE DÖNÜŞTÜRÜLMESİ(2022-01) Evcil, TolgahanYenilenebilir enerji kaynaklarından olan biyokütle hidrotermal sıvılaştırma yöntemi ile değerli kimyasallara ya da sıvı yakıtlara dönüştürülebilmektedir. Bu tez çalışmasında zeytinyağı endüstrisinin bir atığı olan zeytin küspesinin farklı sıcaklıklarda (250, 270, 300 ve 330 °C) ve bekleme sürelerinde (5, 15, 30 ve 60 dk) hidrotermal sıvılaştırılması gerçekleştirilmiştir. Kullanılan metal klorürlerin (AlCl3 ve SnCl2) ürün verimlerine ve bileşimlerine etkisi optimum koşullarda (300 °C ve 15 dk) araştırılmıştır. Katalitik olmayan deneylerden elde edilen biyo-yağ ve biyo-çar verimleri ağırlıkça % 30,8 ve % 31,8 olarak bulunmuştur. Metal klorürlerin kullanımı biyo-yağ veriminin düşmesine ve biyo-çar veriminin artmasına neden olmuştur. Deneyler katalizörlü ve katalizörsüz olarak aynı koşullarda çözgen olarak metanol kullanılarak da gerçekleştirilmiştir. Katalitik olmayan süperkritik metanol sıvılaştırılmasında (SCMEL) biyo-yağ verimi ağ. % 33,5 olarak bulunmuştur. AlCl3 kullanıldığında verim ağ. % 40,3’e yükselmiş ancak SnCl2 kullanıldığında ise biyo-yağ verimi üzerinde neredeyse hiçbir etki gözlenmemiştir. HTL deneylerinde elde edilen biyo-yağların ısıl değerleri, buna karşılık gelen SCMEL deneylerinde elde edilenlerden daha yüksek hesaplanmıştır, en yüksek ısıl değeri ise 34 MJ/kg olarak AlCl3 ile elde edilmiştir. HTL deneylerinde başlıca biyo-yağ bileşenlerini fenoller ve ketonlar oluştururken, SCMEL deneylerinde esterler biyo-yağlarda en fazla bulunan bileşikler olarak karşımıza çıkmaktadır.Öğe Effects of hydrothermal carbonization on products from fast pyrolysis of cellulose(Elsevier Sci Ltd, 2021) Guducu, Isa; Alper, Koray; Evcil, Tolgahan; Tekin, Kubilay; Ohtani, Hajime; Karago, SelhanIn the first step of this study, the hydrothermal carbonization (HTC) of cellulose was performed at 225 and 250 degrees C for 4, 8 and 12 h. The effect of temperature and residence time on hydrochar (HC) yields and characteristics was investigated, and the highest hydrochar yield had a heating value of 21.06 MJ/kg. In the second step, cellulose and hydrochar-derived cellulose was subjected to fast online pyrolysis at 500, 600 and 700 degrees C, using a pyrolysis-gas chromatography-mass spectrometry system. The HTC process significantly affected the pyrolysis products. The major decomposition product resulting from the fast pyrolysis of cellulose was levoglucosan, but at all tested temperatures, 2-methylfuran was the major product from hydrochars. Increasing the pyrolysis temperature caused a decrease in the relative yield of 2-methylfuran. Another prominent compound observed in pyrolyzates was 2,5-dimethylfuran. The relative yields of these two compounds decreased when the residence time of the HTC process was increased. The highest 2-methylfuran selectivity was 67.4%, while the highest 2,5-dimethylfuran selectivity among the furanic compounds was 24.0%. This study demonstrated that, by combining HTC and pyrolysis processes, fine chemicals can be produced from cellulose.Öğe Hydrothermal carbonization of lignocellulosic biomass and effects of combined Lewis and Bronsted acid catalysts(Elsevier Sci Ltd, 2020) Evcil, Tolgahan; Simsir, Hamza; Ucar, Suat; Tekin, Kubilay; Karagoz, SelhanThis study is the first to investigate the effect of combined Lewis and Bronsted acid catalysts on the hydrothermal carbonization of fir wood samples; here, hydrothermal carbonization of fir wood-with and without catalyst-was performed. In non-catalytic runs, the effects of temperature and residence time on hydrochar yields were investigated; temperature significantly affected hydrochar yields, whereas residence time had very little effect. A gradual increase in temperature resulted in a decrease in hydrochar yields while increasing the carbon content of hydrochars. At all tested temperatures, the use of a catalyst led to a decrease in hydrochar yields. The highest heating value of 29.12 MJ kg(-1) was obtained at the highest temperature (275 degrees C) and the longest residence time (24 h). The use of catalysts slightly decreased the heating values. The hydrochars were mainly in the class of lignite coal; hydrochar obtained at 275 degrees C and a residence time of 12 h-either with or without catalysts-was classified as bituminous coal. Irregular carbon sphere formation was observed at all temperatures tested in the catalytic runs; however, no carbon spheres were observed in the non-catalytic runs. XRD patterns of hydrochars from the non-catalytic runs were similar for temperatures of 225, 250 and 275 degrees C; the peak observed at 2 theta of 22 degrees broadened after HTC processing. In the catalytic runs, two new peaks at 2 theta of 38 degrees and 49 degrees were observed, in addition to broadened peaks (2 theta = 22 degrees). The use of catalysts led to the formation of the secondary char.Öğe Hydrothermal liquefaction of olive oil residues(Elsevier, 2021) Evcil, Tolgahan; Tekin, Kubilay; Ucar, Suat; Karagoz, SelhanHydrothermal liquefaction (HTL) of olive oil residues was conducted at various temperatures (250, 270, 300 and 330 degrees C) and residence times (5, 15, 30, and 60 min). The effect of metal chlorides (AlCl3 and SnCl2) on product yields and compositions was investigated under optimum conditions (300 degrees C for 15 min). Bio-oil and solid residue yields from the non-catalytic run were 30.8 and 31.8 wt%, respectively. Use of metal chlorides led to decreased bio-oil yields and increased solid residue yields. Experiments were also carried out using methanol, with and without catalysts, and under identical conditions. The bio-oil yield from the non-catalytic supercritical methanol liquefaction (SCMEL) was 33.5 wt%, increasing to 40.3 wt% with AlCl3, however, SnCl2 had almost no effect on bio-oil yield. The heating values of bio-oils from HTL runs were higher than those of corresponding SCMEL runs, and the highest heating value of bio-oil (34 MJ/kg) was obtained with AlCl3. Phenols and ketones were major bio-oil constituents in the HTL runs, whereas esters were the most abundant compounds in bio-oils from SCMEL runs.
