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Öğe A new mathematical approach to the bleaching process of edible oils(Wiley, 2020) Deniz, Celal Utku; Bilici, İbrahim; Tuncer, MehmetBACKGROUND As energy costs are constantly increasing, industries need to consider efficiency in all processes. Vegetable oils, which are among the daily staple foods, have large energy-consuming processes during refining. Bleaching, one of the most important of these processes, is a process in which energy is used abundantly. In this study, system parameters of bleaching earths were experimentally investigated for a factory that processes soybean and sunflower oil. RESULTS The bleaching earth used was characterized using X-ray diffraction and Brunauer-Emmett-Teller (BET) techniques, while the oils at the process outlet were analyzed according to ASTM standards. The amount of bleaching earth used and bleaching time were used as independent parameters, and color, acid and peroxide number values were determined. Furthermore, through the use of gathered experimental data, a model was developed to predict the color of products under different operating conditions. Two different approaches were used to estimate the color values of oils. According to the polynomial and thin plate spline approaches, 2-2.5 wt% bleaching earth and 60-80 min bleaching time were determined as optimum conditions. CONCLUSION It was determined that the ratio of bleaching earth and the bleaching time had a serious effect on the color, but their effects on acid and peroxide numbers were limited in comparison. There was no linear relationship between the bleaching time and the color change, and the excess time had a negative effect on the bleaching process depending on the amount of the bleaching earth. (c) 2020 Society of Chemical IndustryÖğe Adsorptive separation of CH4, H2, CO2, and N2 using fullerene pillared graphene nanocomposites: Insights from molecular simulations(SPRINGER, 2023) Mert Balaban, Hümeyra; Deniz, Celal Utku; Baykasoğlu, CengizContext The adsorptive separation performances of fullerene pillared graphene nanocomposites (FPGNs) with tunable micro and meso porous morphology are investigated for the binary mixtures of CH4, H2, CO2 and N2 by using grand canonical Monte Carlo (GCMC) simulations. Diferent fullerene types are considered in designs as pillar to investigate the efects of porosity on the gas separation performances of FPGNs, and the GCMC simulations are performed for an equimolar binary mixture of CO2/H2, CO2/CH4, CO2/N2 and CH4/H2 inspired by industrial gas mixtures. It is found that CO2/N2, CO2/H2 and CH4/H2 selectivity of FPGNs are about 72, 410 and 145 at 298 K and 1 bar, which are higher than those for several adsorbent materials reported. Methods Five diferent FPGN models which contain covalently bonded periodical fullerene and graphene units were constructed using C60, C180, C320, C540 and C720 fullerenes, followed by geometry optimization using Open Babel. All GCMC simulations of adsorption were performed in the RASPA. The adsorption isotherms of FPGNs for pure gases are comparatively examined, and their performances are discussed based on the pore structure and isosteric heat of adsorption. Then, the separation factors of FPGNs for equimolar binary mixtures of these gases are elucidated from the diference in the heat of adsorption and the adsorption selectivityÖğe Computational screening of zeolite templated carbons for hydrogen storage(Elsevier B.V., 2022) Deniz, Celal UtkuGrand Canonical Monte Carlo (GCMC) simulations were used to evaluate the hydrogen storage performance of the 68 stable ZTCs which were recently identified. The relationship between the hydrogen storage capacities and densities, accessible pore volume, specific surface area, and helium void fraction of the 68 ZTC structures at 77 K and 298 K up to100 bar pressure has been investigated. The simulation results revealed that RHO has the highest gravimetric H2 uptake (9.23 wt%) under 77 K and 100 bar condition. The RHO structure also showed better deliverable capacity than other ZTCs under room temperature (1.25 wt%) and cryogenic conditions (8.83 wt%). These results show the high potential of the ZTCs for the future ultra-lightweight hydrogen storage media. The relationship between excess hydrogen capacity and specific surface area was investigated, and it was found that 10.3 mmol/g excess hydrogen capacity per 1000 m2/g specific surface area at 77 K. It was determined that the most effective parameters on the maximum excess hydrogen capacity at 77 K were accessible pore volume and specific surface area. A multiple linear regression model was also proposed to predict maximum excess hydrogen capacity at 77 K.Öğe Determination of Mechanical Properties of Composite Supports Used in Catalytic Membranes for Hydrogen Production and Separation(Wiley-V C H Verlag Gmbh, 2020) Deniz, Celal Utku; Tuzun, Fatma NihalThis study includes the determination of mechanical properties involving equibiaxial flexural strength, elastic modulus, strain and hardness for composite supports developed to be used in catalytic membranes in order to produce and separate hydrogen. Composite supports are fabricated by mixing acidic, neutral and basic activated alumina types and sodium silicate binder. Three different Si/Al ratios are employed in the study. After preparing the support samples, they are calcined at the temperatures of 600 degrees C and 1200 degrees C for 11 hours and 22 hours respectively. At the end of calcination, equibiaxial flexural strength, elastic modulus, strain, hardness and solid density of supports are tested for both temperatures. Generally, higher mechanical properties and solid density results are obtained at 600 degrees C and it is found that neutral alumina gives the best mechanical properties and solid density for Si/Al ratio of 0.648 at 600 degrees C.Öğe Effect of boiling point and density prediction methods on stochastic reconstruction(American Chemical Society, 2018) Deniz, Celal Utku; Özören Yaşar, S. Hande; Yaşar, Muzaffer; Klein, Michael T.Stochastic reconstruction (SR) methods are used to generate a series of molecules that mimic the properties of complex mixtures using partial analytical data. Determining a quantitative composition using these methods is limited by the property prediction methods used. This paper addresses the use of two key measurements in the characterization of petroleum fractions, namely density and boiling point distributions. It is known that the different methods used in estimating these two basic properties have varying error rates. Boiling point prediction performances of the various group contribution methods were tested via the molecular library established for molecules that can be found present in the petroleum fractions. It has been observed that the combined use of these methods results in close to a 50% reduction in sum of squared errors than any single method. The predictive performances of the density calculation methods were similarly tested. The best-calculated density results were found via the Yen-Woods method with support from the linear mixing rule based on molar fractions. © 2018 American Chemical Society.Öğe Fabrication of novel neutron shielding materials: Polypropylene composites containing colemanite, tincal and ulexite(Pergamon-Elsevier Science Ltd, 2021) Bilici, İbrahim; Aygün, Bünyamin; Deniz, Celal Utku; Öz, Beytullah; Sayyed, M. I.; Karabulut, AbdulhalikExposure to neutron radiation can cause serious health problems, especially in nuclear power plants and their surroundings, high-flying aircrafts, and healthcare facilities. Conventionally, many neutron-shielding materials are used for protection, but their mechanical and thermal properties limit the use of these materials. Low density, low cost, and flexible neutron shields are becoming increasingly important for these uses, in particular where the weight factor, such as in the aerospace sector, is highly important. For this reason, polypropylene (PP) based composite materials were prepared and their neutron shielding features, such as effective removal cross-sections, half value layer, and mean free path were determined using GEANT4 code. The absorbed dose-measuring experiments were carried out using a241Am-9Be neutron source. Boron minerals such as colemanite, tincal, and ulexite were used in the production of the materials to reduce costs and increase neutron absorption capacity. All the results were compared with the shielding abilities of paraffin and conventional concrete. It was determined that these composites absorb neutron radiation much better than the referenced materials. Colemanite was characterized by X-ray diffraction (XRD) while PP was characterized by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). These composites prove to be valuable shielding materials for protection against neutron radiation in nuclear medicine, storage or transportation of radioactive waste, and other nuclear applications.Öğe Grand canonical Monte Carlo simulations of methane adsorption in fullerene pillared graphene nanocomposites(Elsevier Science Inc, 2021) Baykasoğlu, Cengiz; Mert Balaban, Hümeyra; Deniz, Celal UtkuThe objective of this study is to investigate the methane adsorption performance of fullerene pillared graphene nanocomposites (FPGNs) with adjustable micro and meso porous morphology and high surface/weight ratios. Different types of fullerenes are considered as pillar units to adjust the porosity of FPGNs. The gravimetric, volumetric and deliverable methane storage capacities of FPGNs are examined using grand canonical Monte Carlo (GCMC) simulations. The lithium doping strategy is also employed to further improve the methane adsorption performance of FPGNs. GCMC simulations revealed that FPGNs have promising potential for methane storage applications with the appropriate selection of design parameters. In particular, the simulation results demonstrated that the gravimetric absolute methane uptake of FPGNs could reach 12.5 mmol/g at 298 K and 40 bars and, this value could be increased up to 19.7 mmol/g with appropriate doping ratio under the same conditions. (c) 2021 Elsevier Inc. All rights reserved.Öğe Investigation of reaction pathways and kinetics of turkish asphaltenes(Italian Association of Chemical Engineering - AIDIC, 2013) Akmaz, Solmaz; Deniz, Celal Utku; Yaşar, MuzafferIn this study, reaction kinetics of asphaltene fractions of petroleum feedstocks from field in southeastern part of Turkey were investigated. Asphaltene was fractionated from atmospheric residue of petroleum feedstock. Atmospheric petroleum residue was obtained by removing the distillates boiling up to 350 °C using atmospheric distillation. Asphaltenes were subjected to pyrolysis reactions at 350, 375 and 400 °C for holding times ranging from 10 and 120 min. Product fractions were separated as gas, maltene, remaining asphaltene and coke. The time and temperature dependence of product distributions were determined. Four-lump model was proposed to explain the reaction pathways. This kinetic model was described as a system of ordinary differential equations. In order to estimate the rate constants in these ODEs, a Matlab code has been developed. Order of reaction is another important subject for fitting, first-order for all reactions and second-order for all reactions were analyzed. Copyright © 2013, AIDIC Servizi S.r.l.Öğe Li-doped fullerene pillared graphene nanocomposites for enhancing hydrogen storage: A computational study(Elsevier, 2021) Deniz, Celal Utku; Mert Balaban, Hümeyra; Baykasoğlu, CengizHydrogen physisorption in lithium doped fullerene pillared graphene nanocomposites (Li-FPGNs) having tunable pore structures were examined under different temperature and pressure conditions via grand canonical Monte Carlo (GCMC) simulations. Different forms of fullerenes and Li doping ratios, which have considerable effects on the pore structures and surface properties of FPGNs, were considered to optimize the gravimetric, volumetric and deliverable hydrogen adsorption performances of FPGNs. The GCMC simulations confirmed that the hydrogen adsorption performances of undoped FPGNs could be significantly enhanced with the appropriate selection of the doping ratio and types of fullerenes especially at ambient temperature or low-pressure conditions. Particularly, the GCMC simulations showed that the total gravimetric adsorption capacity of Li-FPGNs with doping ratio of Li:C = 15:100 could reach 9.1 wt% at 77 K and 1 bar, which corresponds to about two times increment in the hydrogen storage performance of undoped FPGNs. Moreover, the GCMC simulations demonstrated that Li doping could enhance the excess hydrogen storage capacity of FPGNs up to three times at ambient temperature. These results revealed that Li-FPGNs are promising candidates in the field of hydrogen storage.Öğe Monte Carlo simulations of hydrogen adsorption in fullerene pillared graphene nanocomposites(Taylor & Francis Ltd, 2020) Mert Balaban, Hümeyra; Deniz, Celal Utku; Baykasoğlu, CengizThe objective of this study is to investigate the hydrogen storage performances of three-dimensional periodic fullerene pillared graphene nanocomposites (FPGNs) consisting of covalently bonded fullerene units between graphene layers. Different forms of fullerenes were used as pillars to adjust porosity and enhance the hydrogen storage capacities of the proposed structures. The gravimetric and volumetric hydrogen uptakes of FPGNs were investigated via grand canonical Monte Carlo calculations under both low- and high -pressure (i.e. 0.01-100 bars) and different thermal (i.e. 77 and 298 K) loading conditions. The simulation results showed that a considerable enhancement in hydrogen adsorption performance could be achieved with the appropriate selection of fullerene size and loading conditions. The simulation results revealed that the FPGNs could uptake 10.3 wt.% hydrogen at 77 K. In addition, the deliverable hydrogen storage capacity of FPGNs could overpass 7.8 wt.% for the charge at 77 K, 100 bar and discharge at 160 K, 5 bar conditions which emphasises the potential of the proposed structures as future ultra-lightweight hydrogen storage media.Öğe The effect of TiO2 contained within a titanium silicalite (TS-1) catalyst and on the selective oxidation of ammonia(Berkeley Electronic Press, 2013) Deniz, Celal Utku; Akmaz, Solmaz; Yaşar, MuzafferThe selective oxidation of ammonia to hydroxylamine using titaniumsilicalite-1 as a catalyst with an increasing content range of 1-2.5 wt% TiO2 was systematically investigated in a batch reactor. The hydroxylamine yielded 33, 43, 52 and 62% at reaction temperatures of 50, 60, 70 and 80°C, respectively, for 8 min using a TS-1a catalyst, which contained 2.5% TiO2. The molar ratio of 15 NH3/H2O 2 was kept during these reactions. Experiments were also conducted with different amounts of NH3/H2O2 in molar ratios, which were between 7 and 60 to investigate the effect of NH 3/H2O2 molar ratio on the reactions. Reactions with higher ratios of NH3/H2O2 were seen to have a higher yield at the end of the reaction performance time.Öğe Thermal and mechanical characterization of composite produced from recycled PE and flue gas desulfurization gypsum(SAGE Publications Ltd, 2019) Bilici, İbrahim; Deniz, Celal Utku; Öz, BeytullahVarying ratios of industrial byproduct of flue gas desulfurization gypsum and recycled polyethylene were used to prepare composite matrices in order to develop an eco-friendly material. Small ratios of maleic anhydride grafted polyethylene were used as a compatibilizer. Surface morphologies and microstructures were examined by scanning electron microscopy images. Thermal behavior of the prepared composite materials was then investigated through thermogravimetry techniques. Hardness and tensile strength of the composite were evaluated through variations made to the contribution of individual components. The resulting composites exhibit increasing melt flow rate values, while hardness decreases with increasing maleic anhydride grafted polyethylene ratios. Amount of torque required to blend mixture also increases with maleic anhydride grafted polyethylene content. © The Author(s) 2019.
