Yazar "Saglam, Mehmet" seçeneğine göre listele
Listeleniyor 1 - 20 / 32
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Aromatic sulfonic acid-catalyzed conversion of safflower stalk into levulinic acid(Springer Heidelberg, 2022) Yuksel, Dogan Emre; Ballice, Levent; Cengiz, Nihal; Saglam, Mehmet; Yuksel, MithatSafflower stalk is a suitable lignocellulosic biomass that can replace fossil resources for the production of platform chemicals. In this study, the production of levulinic acid (LA) from safflower stalk using aromatic sulfonic acids as environmentally friendly catalysts was investigated. A Taguchi experimental design was used to determine the conditions for the highest product yield. The variations of valuable by-products such as 5-HMF, formic acid, and acetic acid, which may occur depending on the reaction conditions were also analyzed. Optimum conditions for maximum LA yield were found using para-toluenesulfonic acid (PTSA) with concentration of 0.3 M, solvent/biomass ratio as 20 at a temperature of 200 degrees C. Experiments were also carried out to verify the optimum LA yield found using analysis of variance (ANOVA). Comparison experiments were performed with sulfuric acid (H2SO4) under optimum conditions, and it was concluded that PTSA could be an alternative catalyst to H2SO4 in terms of LA yield.Öğe Biomass gasification in supercritical water: Part 1. Effect of the nature of biomass(Elsevier Sci Ltd, 2007) Yanik, Jale; Ebale, Steve; Kruse, Andrea; Saglam, Mehmet; Yueksel, MithatIn this study, biomass feedstocks, including lignocellulosic materials and the tannery wastes, were gasified in supercritical water. Gasification experiments were performed in a batch autoclave at 500 degrees C. The amount of gases, the gas compositions and the amount of water soluble compounds from gasification were determined. The hydrogen yields ranging between 4.05 and 4.65 mol H-2/kg biomass have been obtained. The results showed that the yields and composition of gases depend also on the organic materials other than cellulose and lignin in lignocellulosic material. In addition to this, it was concluded that the kind of lignin may also have an effect on gasification products. In the case of tannery wastes, the type of tarmen agent used in leather production considerably effected the gasification results. (C) 2007 Elsevier Ltd. All rights reserved.Öğe Catalytic gasification of mannose for hydrogen production in near- and super-critical water(Elsevier Science Bv, 2016) Madenoglu, Tulay Gungoren; Cengiz, Nihal Uremek; Saglam, Mehmet; Yuksel, Mithat; Ballice, LeventHydrothermal decomposition of mannose (8 wt.%) in near- and super-critical water was investigated at 500-700 degrees C and 20.0-42.5 MPa with a reaction time of 1 h in the absence and presence of alkali catalyst (K2CO3). Gaseous products, aqueous products, and residue were observed in the batch reactor. The produced gases were carbon dioxide, methane, hydrogen, carbon monoxide, and C-2-C-4 hydrocarbons. The effect of operating parameters (temperature and pressure) on the product distribution was examined in the absence and presence of potassium carbonate. The gaseous product yields were compared with the theoretical equilibrium values that are estimated by Gibbs free energy minimization. In the absence of catalyst, the hydrogen yield was 5.82 mol H-2/mol mannose at 700 degrees C and 20.0 MPa. At this condition, theoretical equilibrium yield of hydrogen was found as 5.78 mol H-2/mol mannose which was very close to the experimental value and addition of K3CO3 increased the hydrogen yield to 10.34 mol H-2/mol mannose. The hydrogen yield increased with increasing temperature and decreasing pressure. Acetic acid was the major component of the aqueous product in gasification of mannose. (C) 2015 Elsevier B.V. All rights reserved.Öğe Catalytic Treatment of Opium Alkaloid Wastewater via Hydrothermal Gasification(Springer International Publishing Ag, 2020) Cengiz, Nihal U.; Saglam, Mehmet; Yuksel, Mithat; Ballice, LeventThe wastewater from an opium processing plant should meet the standards as specified in the 'Water Pollution Control Regulation (WPCR), 2004' before being discharged safely into the receiving medium. Treatment of opium alkaloid wastewater is not sufficient using the existing combined methods of aerobic/anaerobic and chemical treatment. Hydrothermal gasification (HTG) is proposed as an alternative treatment in this study. the other aim of this study is to show the ability to manufacture CH4 and H-2 as renewable energy sources and to determine to what extent the removal of chemical oxygen demand (COD) is. Studies were carried out in batch autoclave reactor systems without catalyst, with original red mud (RM), activated RM, and nickel-impregnated (10, 20, and 30%) forms. Reduction with NaBH4 was done to the nickel-impregnated forms of RM to increase the catalytic activity. Yields of CH4 and H-2 increased from 16.8 to 28.6 mol CH4/kg C in wastewater and from 20.3 to 33.3 mol H-2/kgC in wastewater with 20% impregnated nickel and reduced red mud as the highest at 500 degrees C. the COD of the wastewater was lowered by 81-85% approximately while the TOC content decreased by 85-90%.Öğe Characterization of products evolved from supercritical water gasification of xylose (principal sugar in hemicellulose)(Taylor & Francis Inc, 2016) Gokkaya, Dilek Selvi; Saglam, Mehmet; Yuksel, Mithat; Madenoglu, Tulay Gungoren; Ballice, LeventThe catalyst decomposition of xylose (the principal sugar in hemicellulose) was examined in supercritical water for temperature from 400 to 600 degrees C. Experiments were performed in the absence and presence of three main types of catalysts [alkali catalysts (K2CO3 and KOH) and metal impregnated activated carbons (Ni/AC) and (Ru/AC)] with a reaction time of 1h. Gasification yield reaches maximum values by using K2CO3 and KOH at the highest temperature of 600 degrees C. The highest H-2 yield and the highest CH4 yield were obtained by using Ru/AC and Ni/AC, respectively. Acetic acid and 5-methyl furfural were determined as the main aqueous products and reached maximum value by using Ru/AC.Öğe Conversion of leather wastes to useful products(Elsevier Science Bv, 2007) Yilmaz, Onur; Kantarli, I. Cem; Yuksel, Mithat; Saglam, Mehmet; Yanik, JaleThe main objective of the present study is to investigate the production of useful materials from different kinds of leather waste. Three different types of tannery wastes (chromium- and vegetable-tanned shavings, and buffing dust) were pyrolyzed in a fixed bed reactor at temperatures of 450 and 600 C under NZ atmosphere. Gas, oil, ammonium carbonate and carboneous residue were obtained by pyrolysis. The effect of temperature and type of leather waste on product distribution of pyrolysis was investigated. Buffing dust gave the highest yield of oil (ca. 23%), while other wastes recorded yields of ca. 9%. Results of elemental analysis and column chromatography showed that pyrolysis oils could be used as fuel or chemical feedstock after re-treatment. The yields of carboneous residue (chars) were between 37.5% and 48.5% and their calorific value was between 4300 and 6000 kcal kg(-1), suitable for use as solid fuel. In addition, these chars were activated by CO2 to obtain the activated carbon. The activated carbon having highest surface area (799.5 m(2) g(-1)) was obtained from chromium-tanned shavings. Activated carbons prepared from chromium-tanned leather were presented as an adsorbant for the adsorption of dyes from aqueous solution. (c) 2006 Elsevier B.V. All rights reserved.Öğe Determination of Pyrolysis Kinetics of Cellulose and Lignin Fractions Isolated from Selected Turkish Biomasses(Springer Heidelberg, 2020) Ballice, Levent; Sert, Murat; Saglam, Mehmet; Yuksel, MithatThe pyrolysis behavior of Turkish biomass samples such as hazelnut shell, almond shell, and sunflower stalk residue was studied using a thermogravimetric analysis (TGA) laboratory-scale setup. Biomass samples were characterized using the standard method of the Van Soest detergent analysis, and both the virgin biomass and fractions were investigated. the reaction temperature was increased to 900 degrees C with a heating rate range between 2 and 60 degrees C min(-1) in the TGA experiments. Seven solid-state reaction models were applied to evaluate the obtained experimental TGA results. the heating rate was not the only parameter affecting the values of activation energy and the ratio of the main components such as the cellulose and lignin of the virgin biomass samples (almond shell, sunflower stalk, and hazelnut shell) also affected the value of the activated energy values. It was determined that a model fitting mechanism gives limited information to determine the exact activation energy values for the samples. the reaction order model provided straightforward and decisive results for all the biomass and lignin samples. Models of two- and three-dimensional diffusion were better suitable for the cellulose devolatilization. It was also determined that the activation energy of the lignin samples was similar regardless of the types of biomass. According to the kinetic calculations, the cellulose samples showed the highest activation energy values and the lignin samples had the lowest.Öğe Effect of Demineralization on Product Yield and Composition at Isothermal Pyrolysis of Eynez Lignites(Amer Chemical Soc, 2011) Sert, Murat; Ballice, Levent; Yuksel, Mithat; Saglam, MehmetIn this study, the effect of the mineral matter of Eynez lignite on the volatile hydrocarbon recovery, the yield of polycyclic aromatic hydrocarbons (asphaltenes, preasphaltenes), and the carbon in the solid residue was investigated. First, lignite was demineralized with HCl, HNO(3), and HF, successively. Then, the samples obtained from the demineralization step were pyrolyzed in isothermal pyrolysis reactor. The reaction temperatures are 450, 500, 550, 600, and 650 degrees C. Pyrolysis products were analyzed in capillary gas chromatography, and product evolution rate was calculated. The results show that removal of the inorganic elements in HCl decreased the volatile hydrocarbon recovery and that HNO(3) slightly affected the conversion of organic materials in the pyrolysis reactions. In contrast, removal of the inorganic elements in HF increased the conversion in pyrolysis reactions. This behavior is explained by the inhibitive effect of the silicate minerals.Öğe Effect of mineral matter on product yield in supercritical water extraction of lignite at different temperatures(Elsevier Science Bv, 2011) Sert, Murat; Ballice, Levent; Yuksel, Mithat; Saglam, MehmetThe effect of demineralization on conversion of Soma Lignite in supercritical water extraction was studied using a batch autoclave operated at 400, 450 and 500 degrees C under nitrogen atmosphere. The experiments were carried out to investigate the effect of mineral matter and temperature on gaseous, liquid, residue yield and composition of gaseous products. According to the results, main product in gaseous state is CO(2). Temperature is key factor affecting product distribution when compared the effect of minerals in lignite. As temperature was increased, yield of gas and solid residue increased, while yields of liquid decreased for raw and demineralized lignite samples. The removal of mineral matter caused to decrease the conversion for all lignite samples and to increase the carbon content of solid residue in supercritical water extraction. (C) 2011 Elsevier B.V. All rights reserved.Öğe Effect of mineral matter on the isothermal pyrolysis product of Sirnak asphaltite (Turkey)(Elsevier Sci Ltd, 2011) Sert, Murat; Ballice, Levent; Yuksel, Mithat; Saglam, MehmetIsothermal pyrolysis of raw and demineralized Sirnak asphaltite (SASP) was investigated to determine product yield and distribution of volatile products at different temperatures. First, asphaltite sample treated with HCl, HNO3 and HF to remove carbonates, pyrite and silicates from organic structure. Then, raw and these treated asphaltite samples were pyrolyzed in isothermal pyrolysis reactor at 450, 500, 550, 600 and 650 degrees C. Pyrolysis products were analyzed by capillary gas chromatography. Volatile hydrocarbon recovery (VHR) and total hydrocarbon recovery (THR) were calculated. VHR and THR were increased with increasing temperature. In contrast, solid residue decreased. Removal of carbonates and pyrite decreased the volatile product yield. However, for HF treated samples gas product evolution increased. Carbon balance established around the reactor, carbon in solid residue was determined and asphaltene and pre-asphaltene fractions were calculated. In addition, n-paraffins and 1-olefins were grouped according to the carbon number. (C) 2011 Elsevier Ltd. All rights reserved.Öğe FAST PYROLYSIS AND CO-PYROLYSIS OF GOYNUK OIL SHALE (TURKEY) AND POLYPROPYLENE IN FREE FALLING REACTOR (FFR)(Estonian Academy Publishers, 2014) Erdogan, Cem; Ballice, Levent; Saglam, Mehmet; Yuksel, MithatFast pyrolysis of Goynuk oil shale (GOS), polypropylene (PP) and the blend of GOS:PP on a 1:3 total carbon ratio basis was studied. The maximum product evolution temperature and the existence of synergistic effect were determined and the characteristics of pyrolysis products by carbon number were investigated. Pyrolysis products were analyzed by capillary gas chromatography. The volatile fraction of pyrolysis products was classified according to carbon number. Conversion to the volatile fraction of recovered hydrocarbons in fast co-pyrolysis of GOS:PP increased with increasing temperature. The effect of PP on the conversion of GOS was determined by calculating the difference between experimental and hypothetical mean values of conversion of total organic carbon into volatile products and a slight synergistic effect was observed at 600 degrees C (4.78%) and 650 degrees C (5.07%).Öğe Fast pyrolysis of agricultural wastes: Characterization of pyrolysis products(Elsevier Science Bv, 2007) Yanik, Jale; Kommayer, Christoph; Saglam, Mehmet; Yueksel, MithatThis study deals with pyrolysis of three agricultural wastes (corncob, straw and oreganum stalks) at 500 degrees C in a fluidized bed reactor. The yields of char, liquid and gas were quantified. Pyrolysis liquids produced were in two separate phases; aqueous phase and oil. Oil yields varied between 35 and 41%, depending on biomass type, whereas the yields of aqueous phases were almost similar, around 6%, for all feedstock. For characterization, oils were fractionated by water extraction into two fractions; water solubles and water unsolubles. Both aqueous phase and watersoluble fraction were analyzed by gas chromatography-mass spectrometry and high-performance liquid chromatography. In addition, water content and elemental analysis of the oils were determined. Chemical compositions of gas and char products relevant to fuel applications were determined. (c) 2007 Elsevier B.V All rights reserved.Öğe Hydrogen and methane production from tomato processing plant waste by hydrothermal gasification(Elsevier, 2022) Cengiz, Uremek Nihal; Yildirir, Eyup; Saglam, Mehmet; Yuksel, Mithat; Ballice, LeventHydrothermal gasification of tomato processing plant waste was examined in batch autoclaves at temperatures of 300-600 C and pressures of 20.0-42.5 MPa. The catalytic effects of KOH and K2CO3 at the aforementioned temperatures and pressures were also investigated. While increasing the pressure enhanced methane yield, alkali addition improved both hydrogen and methane yields. The highest yields for H2 and CH4 were recorded as 27.4 and 21.8 moles kg-1 C at 600 C and with KOH. In addition, carbon gasification efficiency (CGE) obtained was up to 86% while carbon liquefaction efficiency (CLE) was reduced to 3.5% with KOH at 600 C and 20 MPa. A product gas with a calorific value of 24.9 MJ/Nm3 was obtained during hydrothermal gasification at 500 C and 42.5 MPa, in the presence of KOH.Öğe Hydrogen production from marine biomass by hydrothermal gasification(Pergamon-Elsevier Science Ltd, 2015) Deniz, Irem; Vardar-Sukan, Fazilet; Yuksel, Mithat; Saglam, Mehmet; Ballice, Levent; Yesil-Celiktas, OzlemThe hydrothermal gasification of Posidonia oceanica was investigated in a batch reactor without adding any catalysts. The experiments were carried out in the temperature range of 300-600 degrees C with different biomass loading ranges of 0.04-0.12 (g/mL) in the reaction time of 1 h, The product gas was composed of hydrogen, methane, carbon dioxide, carbon monoxide and a small amount of C-2-C-4 compounds. The results showed that the formation of gaseous products, gasification efficiency and yield distribution of produced gases were intensively affected by biomass loading and temperature. The yields of hydrogen (1037 mol/kg) and methane (6.34 mol/kg) were attained at 600 degrees C using biomass loading of 0.08 (g/mL). The results are very promising in terms of deployment of the utilization of marine biomass for hydrogen and/or methane production to industrial scale applications, thereby proposing an alternative solution to the landfill of P. oceanica residues. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Hydrogen production from marine biomass by hydrothermal gasification(Pergamon-Elsevier Science Ltd, 2015) Deniz, Irem; Vardar-Sukan, Fazilet; Yuksel, Mithat; Saglam, Mehmet; Ballice, Levent; Yesil-Celiktas, OzlemThe hydrothermal gasification of Posidonia oceanica was investigated in a batch reactor without adding any catalysts. The experiments were carried out in the temperature range of 300-600 degrees C with different biomass loading ranges of 0.04-0.12 (g/mL) in the reaction time of 1 h, The product gas was composed of hydrogen, methane, carbon dioxide, carbon monoxide and a small amount of C-2-C-4 compounds. The results showed that the formation of gaseous products, gasification efficiency and yield distribution of produced gases were intensively affected by biomass loading and temperature. The yields of hydrogen (1037 mol/kg) and methane (6.34 mol/kg) were attained at 600 degrees C using biomass loading of 0.08 (g/mL). The results are very promising in terms of deployment of the utilization of marine biomass for hydrogen and/or methane production to industrial scale applications, thereby proposing an alternative solution to the landfill of P. oceanica residues. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Hydrogen production from marine biomass by hydrothermal gasification(Pergamon-Elsevier Science Ltd, 2015) Deniz, Irem; Vardar-Sukan, Fazilet; Yuksel, Mithat; Saglam, Mehmet; Ballice, Levent; Yesil-Celiktas, OzlemThe hydrothermal gasification of Posidonia oceanica was investigated in a batch reactor without adding any catalysts. The experiments were carried out in the temperature range of 300-600 degrees C with different biomass loading ranges of 0.04-0.12 (g/mL) in the reaction time of 1 h, The product gas was composed of hydrogen, methane, carbon dioxide, carbon monoxide and a small amount of C-2-C-4 compounds. The results showed that the formation of gaseous products, gasification efficiency and yield distribution of produced gases were intensively affected by biomass loading and temperature. The yields of hydrogen (1037 mol/kg) and methane (6.34 mol/kg) were attained at 600 degrees C using biomass loading of 0.08 (g/mL). The results are very promising in terms of deployment of the utilization of marine biomass for hydrogen and/or methane production to industrial scale applications, thereby proposing an alternative solution to the landfill of P. oceanica residues. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Hydrogen production from olive-pomace by catalytic hydrothermal gasification(Elsevier Science Bv, 2018) Sert, Murat; Gokkaya, Dilek Selvi; Cengiz, Nihal; Ballice, Levent; Yuksel, Mithat; Saglam, MehmetHydrogen as a clean energy source has great potential to reducing the dependence on fossil fuels and environmental pollution. For this reason, the production of hydrogen from renewable source will decrease this dependence and pollution. In this study, production of hydrogen from olive pomace was investigated. The experiments were performed at batch autoclave between 300 degrees C and 600 degrees C temperatures and a pressure of 200 atm-425 atm range. In addition to these parameters, the effect of catalyst (Trona, K2CO3 and KOH) was also investigated. H-2, CO2, CH4, CO and small amount of C-2-C-4 hydrocarbons were identified in gaseous products. H-2 formation increased with increasing temperature and decreased with pressure increase. Hydrogen formation has the highest value as 16.80 mol/kg biomass at 600 degrees C in the presence of KOH catalyst. Besides the effect of KOH, the presence of K2CO3 and Trona catalysts also increased the formation of hydrogen. The pressure affected the gasification yield and hydrogen composition in gaseous product. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.Öğe Hydrothermal gasification of a biodiesel by-product crude glycerol in the presence of phosphate based catalysts(Pergamon-Elsevier Science Ltd, 2015) Cengiz, Nihal Uremek; Yildiz, Guray; Sert, Murat; Gokkaya, Dilek Selvi; Saglam, Mehmet; Yuksel, Mithat; Ballice, LeventEnergy from biomass can be provided in various ways, such as burning the solid wastes, production of biogas (by anaerobic digesters), biofuels (i.e. methanol, ethanol, biodiesel, and derivatives), and methane via the utilization of landfills. Biodiesel is a widely used biofuel produced by the conversion of first-generation biomass feedstock via bio-chemical conversion platforms. Crude glycerol is the by-product of biodiesel production being 10 wt.% of the produced biodiesel. The objective of this study is to utilize this glycerol fraction by converting it to fuel gas or to chemical feedstock. In this study, the concentration of glycerol feedstock solution and the catalyst concentration were 50 g/L and 5 g/L, respectively. Crude glycerol was gasified in a sub and supercritical water medium by using a batch autoclave with an inner volume of 100 ml. A temperature range from 300 to 600 degrees C was studied. Experiments were performed with pure and crude glycerol samples in the absence and the presence of homogeneous acidic and alkali catalysts, namely H3PO4, KH2PO4, K2HPO4, and K3PO4. These were used to obtain higher gasification efficiencies and hydrogen and/or methane yields. Subsequent to each experiment liquid, solid, and gaseous products were collected and analyzed by GC, TCA (total carbon analyzer), HPLC, and GC/MS. The order of the effectiveness of the catalysts on gasification was found as: K3PO4 > K2HPO4 > H3PO4 > KH2PO4 for crude glycerol and K3PO4 > K2HPO4 > KH2PO4 > H3PO4 for pure glycerol. K2HPO4 and K3PO4 were found to be more effective in terms of hydrogen production while H3PO4 and KH2PO4 showed the best performance for the maximized methane production. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Öğe Hydrothermal gasification of biomass model compounds (cellulose and lignin alkali) and model mixtures(Elsevier Science Bv, 2016) Madenoglu, Tulay Gungoren; Saglam, Mehmet; Yuksel, Mithat; Ballice, LeventBiomass model compounds (cellulose and lignin alkali) and their mixtures were gasified at sub- and super-critical water conditions in the absence and presence of alkali catalyst (K2CO3). Hydrothermal gasification was performed in batch reactor at temperature range of 300-600 degrees C and pressure range of 90-410 bar with a reaction time of 1 h. Product yields of gaseous, aqueous and residue were investigated for model compounds (cellulose/lignin alkali) and their mixtures with weight ratios of 80/20, 60/40, 40/60 and 20/80 (wt./wt.). These mixtures were arranged to define the interaction between degradation products of model compounds of lignocellulosic biomass. In addition, gaseous and aqueous product compositions were identified to highlight prevailing reaction pathways during decomposition of model compounds. The highest hydrogen and methane yields were reached at 600 degrees C in the presence of K2CO3. (C) 2016 Elsevier B.V. All rights reserved.Öğe Hydrothermal gasification of poplar wood chips with alkali, mineral, and metal impregnated activated carbon catalysts(Elsevier, 2019) Gokkaya, Dilek Selvi; Cokkuvvetli, Tugce; Saglam, Mehmet; Yuksel, Mithat; Ballice, LeventIn this study, poplar wood chips were gasified in sub-and supercritical water as biomass feedstock. Hydrothermal gasification experiments were performed to examine how the reaction temperature and different type of catalysts influence conversion efficiency. the effectiveness of commercially available [alkali catalyst; KOH], naturally available [mineral catalysts; Trona [Na-3(CO3)(HCO3)center dot 2H(2)O], Dolomite [CaMg(CO3)(2)] and Borax [Na2B4O7 center dot 10H(2)O] and laboratory-prepared catalysts [metal-impregnated activated carbons; (Ni/AC) and (Ru/AC)] have been demonstrated so as to shift the product distribution toward more desirable compounds. Gaseous compound yield was increased from 29.7% to 79.3% with respect to increasing temperature while liquid compound yield decreased from 27.6% to 1.1% and solid residue from 38.0% to 15.6%. the highest H-2 (20.1 mol/kg C in poplar) and CH4 (12.7 mol/kg C in poplar) yields were obtained with Ru/AC catalyst. Carboxylic acids and 5-methyl furfural were determined as the main liquid compounds. (C) 2019 Elsevier B.V. All rights reserved.