Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
Browse
21 results
Search Results
Article Citation - WoS: 5Citation - Scopus: 5Automated Deep Learning Model Development Based on Weight Sensitivity and Model Selection Statistics(Pergamon-elsevier Science Ltd, 2025) Yalcin, Damla; Deliismail, Ozgun; Tuncer, Basak; Boy, Onur Can; Bayar, Ibrahim; Kayar, Gizem; Sildir, HasanCurrent sustainable production and consumption processes call for technological integration with the realm of computational modeling especially in the form of sophisticated data-driven architectures. Advanced mathematical formulations are essential for deep learning approach to account for revealing patterns under nonlinear and complex interactions to enable better prediction capabilities for subsequent optimization and control tasks. Bayesian Information Criterion and Akaike Information Criterion are introduced as additional constraints to a mixed-integer training problem which employs a parameter sensitivity related objective function, unlike traditional methods which minimize the training error under fixed architecture. The resulting comprehensive optimization formulation is flexible as a simultaneous approach is introduced through algorithmic differentiation to benefit from advanced solvers to handle computational challenges and theoretical issues. Proposed formulation delivers 40% reduction, in architecture with high accuracy. The performance of the approach is compared to fully connected traditional methods on two different case studies from large scale chemical plants.Article Citation - WoS: 6Citation - Scopus: 4Regenerable Nickel Catalysts Strengthened Against H2s Poisoning in Dry Reforming of Methane(Elsevier, 2025) Kesan Celik, Nazli; Yasyerli, Sena; Arbag, Huseyin; Tasdemir, H. Mehmet; Yasyerli, NailIn this study, alumina-supported bimetallic Ni-Cu and trimetallic Ni-Cu-Ce catalysts were synthesized to improve catalysts resistant to coke formation and sulfur poisoning for dry reforming of methane (DRM). The effects of parameters such as feed composition, synthesis method, and H2S concentration using the catalyst with the best activity were also investigated. To determine the physical and chemical properties of the synthesized catalysts, XRD, N2 adsorption-desorption, TGA-DTA, ICP-OES, SEM-EDX, XPS, and DRIFTS analyses were performed. XRD analysis showed that the fresh Ni-Cu catalysts have elemental nickel and gamma- alumina phases in their structures. In addition to these structures, the CeO2 crystal structure was determined for the Ni-Cu-Ce catalyst. Type IV isotherm with H1 hysteresis indicating uniform mesoporous structure was obtained with all the catalysts. The activities of the synthesized catalysts in DRM were performed in the presence of different concentrations of H2S (2 ppm, 50 ppm, and 500 ppm) in a fixed bed reactor at 750 degrees C using a gas chromatography-equipped system. The alumina-supported 8Ni-3Cu-8Ce catalyst prepared by the impregnation method exhibited a higher and more stable activity comparing the bimetallic Ni-Cu catalyst in the presence of H2S. Adding copper and cerium to the nickel catalyst has a curative effect on resistance to coke formation and sulfur poisoning. Excess CO2 in the feed stream increased the H2S poisoning resistance of the catalyst. To analyze the reactor exit stream in catalytic activity using different feed stream compositions such as H2S+He, H2S+CO2+He, and H2S+CO2+CH4+He, FTIR with a gas cell was used. The formation of carbonyl sulfide (COS) and H2O, which occurs due to the possible reaction between CO2 and H2S, was observed. Regeneration studies showed that the catalyst could undergo regeneration with a low oxygen concentration (0.3 % O2 in He). 8Ni-3Cu-8Ce@SGA, which gave 71 % CH4 conversion in the first minute of the reaction test in the presence of 50 ppm H2S, was regenerated after completely losing its activity at the end of 5 h. 66 % CH4 conversion was achieved when tested again in the absence of H2S (CH4/CO2/Ar:1/1/1). The 8Ni-3Cu-8Ce@SGA catalyst was deemed worthy of investigation for industrial applications.Article Simultaneous Topology Design and Optimization of Pde Constrained Processes Based on Mixed Integer Formulations(Elsevier, 2024) Ertürk, Emrullah; Deliismail, Özgün; Şıldır, HasanSimultaneous topological design and optimization of complex processes that are described by partial differential equations is a challenging but promising research area. Widely adopted nested and sequential approaches are mostly applicable based on heuristic solutions, hindering the theoretical improvement potential due to decentralized decision-making in subsequent stages with a significant number of trial-and-error procedures. This study introduces a mixed integer formulation addressing the governing equations and case-dependent topological constraints at each discretization point, enabling solutions through rigorous solvers under process-related constraints and objectives. Nonlinear expressions in the formulations are further tailored using piecewise linear approximations, still representing the major nonlinear trends through a mixed-integer linear nature to favor global optimality and benefit from computational advancements, when needed. Heat and Stokes flow problems are used as case studies to demonstrate the applicability of the methodology. © 2024 Elsevier B.V.Article Citation - WoS: 2Citation - Scopus: 3A Phenomenological Kinetic Flotation Model: Distinct Time-Variant Floatability Distributions for the Pulp and Froth Materials(Elsevier, 2023) Polat, Mehmet; Polat, HürriyetA simple and easy-to-use phenomenological kinetic flotation model, strongly connected with the physics of the process, is proposed in this paper. The model explicitly contains the cell volume, aeration rate, volumetric holdup, mean bubble size, and particle density as input variables. It can be employed to characterize the floatability distributions of the particles in the pulp and the froth separately any time during the flotation process. Two new time-dependent kinetic parameters, the bubble loading factor & phi;(t) and the maximum cell mass transfer capacity Mmax(t) also appear in the model expression. & phi;(t) is a measure of the degree of crowding of the bubble surfaces and accounts for the deviations from the first-order rate equation. Mmax(t) describes the maximum amount of mass that can be transported to the froth phase by the bubble population in the cell. Screen fractionation of each froth product collected at different time intervals during a single kinetic flotation test is sufficient to generate the data required by the model for analysis. Application of the model to this data yields directly time-dependent functions for the floatability of the particles reporting to froth Kf(t) or remaining in the cell Kp(t) for each size fraction separately, without the need for any empirical parameters. The test of the model was carried out using published kinetic flotation data from the literature.Article Citation - WoS: 6Citation - Scopus: 9The Effect of Military Conflict Zone in the Middle East on Atmospheric Persistent Organic Pollutant Contamination in Its North(Elsevier, 2023) Ayrı, İlknur; Genişoğlu, Mesut; Sofuoğlu, Aysun; Kurt Karakuş, Perihan B.; Birgül, Askın; Sofuoğlu, Sait CemilThis study aimed to investigate long-range atmospheric transport of selected POPs released due to the effects of mili-tary conflicts in regions to the south of Turkey's borders. Ten locations were selected to deploy passive air samplers at varying distances to the border on a southeast-west transect of the country, proximity-grouped as close, middle, and far. Sampling campaign included winter and transition months when desert dust transport events occur. Hypothesis of the study was that a decreasing trend would be observed with increasing distance to the border. Group comparisons based on statistical testing showed that PBDE-183, E45PCB, and dieldrin in winter; PBDE-28, PBDE-99, PBDE-154, p,p '-DDE, E14PBDE, and E25OCP in the transition period; and PBDE-28, PBDE-85, PBDE-99, PBDE-154, PBDE-190, PCB-52, E45PCB, p,p '-DDE, and E25OCP over the whole campaign had a decreasing trend on the transect. An analysis of concen-tration ratio to the background showed that long-range atmospheric transport impacted the study sites, especially those of close group in comparison to the local sources. Back-trajectory analyses indicated that there was transport from the conflict areas to sites in the close-proximity group, while farther sampling locations mostly received air masses from Europe, Russia, and former Soviet Union countries, followed by North Africa, rather than the military con-flict areas. In consequence, decrease in concentrations with distance and its relation to molecular weight through pro-portions, diagnostic ratios, analysis of concentration ratio to the background, and back-trajectory analyses support the effect of transport from the military-conflict area to its north.Article Citation - WoS: 17Citation - Scopus: 20Polyoxometalate-Based Hybrid Composites in Multi-Functional Wastewater Treatment Applications(Elsevier, 2023) Recepoğlu, Yaşar Kemal; Gören, Ayşegül Yağmur; Orooji, Yasin; Vatanpour, Vahid; Kudaibergenov, Nurbolat; Khataee, AlirezaThe inorganic polyanionic clusters known as polyoxometalates (POMs) have several structural variations at the nanoscale scale. They have many uses in chemistry, materials science, medicine, and other fields. This review considers the developments in treating hazardous contaminants from wastewater using POMs-based compounds. Four main treatment methods using POM-based compounds to remove water pollutants have been developed: adsorption, photocatalytic treatment, Fenton-like treatment, and membrane separation. Moreover, we report the types of POMs, synthesis procedures, strategies performed to modify POM-based compounds, and their appli-cations in wastewater treatment. To promote the development of these compounds for large-scale production and real-scale applications, gaps in knowledge and recent research obstacles are also pointed out. Most research on metal organic complexes (MOCs) based on POM has focused on using these compounds as catalysts, with little focus on their additional uses. The adsorption and photocatalytic efficiency of modified POM-based compounds are attributed to their enhanced contaminant removal efficiency, and recovery of certain POM-based compounds by magnetic separation is presented as a promising option for their recyclability. Among the reviewed studies, the highest adsorption capacity was 1108.9 mg/g, with a removal efficiency of 100 % for acid red dye using poly-[N,N-dimethyl-dodecyl-(4-vinylbenzyl)ammonium chloride] (PIL)-POM. The studies also indicate that the POM-based adsorbents could be effectively reused to remove pollutants and sustain their activity in 3-10 cycles. This review is believed to provide an overview of recent advancements in POM-based compounds for water and wastewater treatment, offers thorough research to anyone interested in learning more about this topic, and acts as a manual for researchers working in this area.Article Citation - WoS: 4Citation - Scopus: 5Antifouling Polydopamine-Modified Poly (ether Sulfone) Membrane Immobilized With Alumina-Calcium Oxide Catalyst for Continuous Biodiesel Production(Elsevier, 2023) Güngörmüş, Elif; Şeker, Erol; Alsoy Altınkaya, SacideBiodiesel is an alternative biofuel that can be blended with conventional petroleum-derived diesel fuel to partly reduce the dependence on the imported oil. Catalytic membrane reactors are promising candidates for sustainable biodiesel production. Herein, we report a novel catalytically active polydopamine-modified poly (ether sulfone) (PES) membrane immobilized with an alumina-calcium oxide catalyst. The reaction temperature, butanol to canola oil ratio, and transmembrane pressure applied through the membrane were optimized with response surface methodology and Box-Behnken design. In contrast to all previous catalytic membrane studies for biodiesel production, we used butanol as a co-reactant to improve the winter problems of biodiesel made with methanol. FTIR and SEM-EDX analysis confirmed the successful immobilization of the catalyst. At the end of 30 days of storage in the reactant mixture, 95% of the catalyst loaded to the membrane was still on the surface, and biodiesel yield values and butanol flux of the membrane did not change. We compared the batch and flowthrough operation modes by measuring the catalytic activity of membranes under static and dynamic conditions within 24 h (8-cycle). The biodiesel yield under dynamic condition decreased in the first three cycles from 54.54 +/- 0.65% to 47.31 +/- 0.70% and then stayed constant, whereas a continuous decrease from 25.42 +/- 0.57% to 17.19 +/- 0.58% was observed under static condition. In each cycle, the equilibrium limitation for the yield was overcome only when the membrane was operated under pressure. The main reason for the decrease in catalytic activities was the fouling on the catalyst surface which was quickly removed by backwashing with butanol. It is concluded that catalytic membranes with antifouling properties and alcohol stability can make biodiesel production more cost-effective and environmentally friendly.Article Citation - WoS: 7Citation - Scopus: 7Insights Into Sustainability of Engineered Carbonaceous Material-Based Technologies for Advanced Cyanide Removal From Wastewater(Elsevier, 2023) Yoon, Yeojoon; Khataee, Alireza; Gören, Ayşegül Yağmur; Recepoğlu, Yaşar KemalCyanide (CN) is a serious concern in industrial and goldmine wastewater. Strict regula-tory standards have been established by various agencies due to the detrimental effects that CN has on human health. Therefore, before discharge to water bodies or land, it is essential to create a sus-tainable model for the safe removal of CN. Carbon-based materials are well known for their adsorption and oxidation features, which can be conducive to CN removal. This paper reviews the relevant literature on the application of modified and unmodified carbon-based materials to CN removal in water; these materials include activated carbon (AC), graphene, graphene oxide (GO), and carbon nanotubes (CNTs). Moreover, CN removal mechanisms and photocatalytic removal of CN are comprehensively discussed, with a particular emphasis on modifying carbon-based materials. It has been observed that adding various elements to carbon-based materials improves their surface area, functional groups, CN adsorption capacity, and pore volume. Impacts of operational parameters, isotherm models, kinetics, and types of carbon-based materials are also outlined. This study provides insight into the real-scale applicability of carbon-based materials for CN removal from waters. Moreover, this review indicates that essential work on CN removal using carbon-based materials is still needed. Future research should focus on developing modified carbon-based materials to encourage multidisciplinary research. The most crucial gap in the literature is that the studies have been performed on a lab scale. Therefore, further pilot and real-scale applica-tions should be conducted. Overall, the cost assessment, environmental effects, and human health risks of carbon-based materials should be studied in future research to achieve a realistic perspective on applicability on an industrial scale.(c) 2023 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).Article Citation - WoS: 56Citation - Scopus: 64Carbonaceous Materials for Removal and Recovery of Phosphate Species: Limitations, Successes and Future Improvement(Pergamon-Elsevier Science Ltd, 2022) Recepoğlu, Yaşar Kemal; Gören, Ayşegül Yağmur; Orooji, Yasin; Khataee, AlirezaThe carbonaceous materials have gained significant interest for the phosphorus species remediation and recovery in the last decade. Carbonaceous materials present many unique features, such as cost effective, availability, environmentally friendly, and high removal efficiency that make them a promising adsorbent. In this review, the recent application of carbonaceous materials including activated carbon (AC), graphene and graphene oxide (GO), lignin, carbon nanotubes (CNTs), and gC(3)N(4) for phosphate removal and recovery were comprehensively summarized. The kinetics and isotherm models, removal mechanisms, and effects of operating parameters are reported. The reusability, lifetime of carbonaceous materials, and impact of modification were also considered. The modified carbonaceous materials have significantly high phosphate adsorption capacity compared to unmodified adsorbents. Namely, MgO-functionalized lignin-based bio-charcoal exhibited a 906.8 mg g(-1) of capacity as the highest one among other reviewed materials. The modification of carbonaceous materials with various elements has been presented to improve the surface functional groups, surface area and charge, and pore volume and size. Among these loaded elements, iron has been effectively used to provide a prospect for magnetic recovery of the adsorbent as well as increase phosphate adsorption. Furthermore, the phosphate recovery methods, phosphate removal efficiency of carbonaceous materials, the limitations, important gaps in the literature, and future studies to enhance applicability of carbonaceous materials in real scale are also discussed.Article Citation - WoS: 13Citation - Scopus: 14Robust Fluorinated Siloxane Copolymers Via Initiated Chemical Vapor Deposition for Corrosion Protection(Springer, 2021) Cihanoğlu, Gizem; Ebil, ÖzgençHomopolymers of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (V4D4), 2-(perfluorohexyl)ethyl acrylate (PFHEA) and 2-(perfluoroalkyl)ethyl methacrylate (PFEMA) and their copolymers were synthesized via initiated chemical vapor deposition (iCVD). All coatings exhibited excellent adhesion to substrates. The corrosion resistance of iCVD coatings was investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. In addition, chemical durability of various organic solvents and adhesion to the substrate were also evaluated. Tafel polarization measurements in 5 wt% NaCl solution revealed that the corrosion rates as low as 0.002 mpy on zinc substrates can be reached with 250-nm-thick iCVD-synthesized polymers which is lower than previously reported polymer coatings and more than three orders of magnitude lower than bare zinc. EIS analysis coupled with equivalent electric circuits model confirmed that poly(V4D4) and poly(PFHEA) homopolymers show extremely high protection efficiencies (similar to 99%) on zinc, while poly(V4D4-co-PFHEA) copolymer with slightly lower corrosion efficiency (85-91%) provides a better anticorrosion barrier with weight loss reduction by 57 and 45% for copper and zinc, respectively, and with improved chemical and mechanical properties. The results indicate that iCVD process enables fabrication of finely tuned fluorinated siloxane copolymer conformal coatings for corrosion protection on a variety of substrates.
- «
- 1 (current)
- 2
- 3
- »