Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Research Project Metal organik ağ yapılarının (MOF) sentezlenmesi ve metan reformer çıkış gazının saflaştırılması için kullanılması(2015) Çakıcıoğlu Özkan, Seher Fehime; Helvacı, Şerife Şeref; Yener, Huriye Banu; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyBu projede metal organik ağ yapısına sahip çinko, titan, alüminyum ve bakır temelli tereftalatlar (sırası ile Zn-TPA, Al-TPA, Ti-TPA ve Al-TPA) başarı ile sentezlenmiştir. Karakterizasyon yöntemlerinden XRD ve yüzey alanı ölçümü sonuçlarının belirleyici olduğu MOF sentezinde, kristalizasyon basamağında Metal+TPA/çözücü veya Metal/TPA oranının, yıkama basamağında ise DMF’ nin gözeneklerde kalan TPA’ nın uzaklaştırılmasında etkili olduğu, DMF’ nin de MetOH ile yapıdan uzaklaştırılabileceği sonucuna varılmıştır. Sentezlenen MOF’ lardan en yüksek yüzey alanına sahip MOF seçilerek CO2, CO, H2 ve CH4 gazlarının tekli ve ikili adsorpsiyon çalışmaları yapılmıştır. ZLC (zero lenght column) tekniği kullanılarak 34oC, 70oC ve 100oC çalışma sıcaklıklarında belirlenen CO2, CO, H2 ve CH4 gazlarının difüzyon zaman sabitleri sıcaklıkla artarken Henry katsayıları düşmüştür. CO gazının seçilen MOF örnekleri üzerinde en yüksek Henry katsayısına ve adsorpsiyon ısısına (-13 kJ/mol) sahip olduğu görülmüştür. En küçük molekül olan H2 ise en yüksek difüzyon zaman sabitine sahiptir. Hidrojence zengin metan reformer çıkış gazının içeriğinde bulunan CO2, CO ve CH4 bileşenlerinin dolgulu kolonda eş molar CO2/H2, CO/H2, CH4/H2 ve CO2/CH4 ikili gaz karışımları ve Helyum gazının taşıyıcı olduğu saf bileşenlerinin adsorpsiyon çalışmalarından oluşmaktadır. Gazların dolgulu kolon salıverme eğrileri 1, 5, ve 10 bar basınçlarda değişen akış hızlarında (10 mL/dk 20 mL/dk ve 30 mL/dk) elde edilmiştir. Kolon basıncı ve gaz akış hızı arttıkça Cu-TPA, Ti-TPA, Zn-TPA ve Al-TPA MOF yapıları tarafından adsorplanan gaz miktarlarının arttığı gözlenmiştir. Tamamlanan çalışmalar sonucunda adsorpsiyon sistemine dayalı gaz ayırma/saflaştırma süreçlerinin iyileştirilmesinde ve geliştirilmesinde önemli faktörlerden olan adsorplanan madde miktarı ile seçicilik katsayıları hesaplanmıştır. En yüksek yüzey alanına (1270 m2/g) ve mikro gözenek hacmine (0.68 cm3/g) sahip Al-TPA’ nın en yüksek adsorpsiyon kapasitesine sahip olduğu; CO2 gazının en fazla tutulan bileşen (3.36 mmol/g Al-TPA) iken H2 gazı sentezlenen MOF yapıları tarafından tutulmadığı olduğu sonucuna varılmıştır. Kolon basıncı ve akış hızı arttıkça seçicilik artmakla beraber basıncın gaz seçiciliğinde daha önemli olduğu gözlenmiştir. Bu proje kapsamında başarı ile sentezlenen MOF yapılarının, CO2 gazını seçimli olarak adsorplarken H2 gazını adsorplamaması, metan reformer çıkış gazının saflaştırılmasında kullanımı umut vaat etmektedir.Article Citation - WoS: 3Citation - Scopus: 5Adsorption Characteristics of Lead-, Barium- and Hydrogen-Rich Clinoptilolite Mineral(SAGE Publications Inc., 2003) Çakıcıoğlu Özkan, Seher Fehime; Ülkü, Semra; Özkan, Seher Fehime; Ülkü, Semra; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe carbon dioxide and water vapour adsorption properties of local clinoptilolite-rich material, both as the original and as lead-, barium- and hydrogen-rich forms, were examined. The lead- and barium-rich forms were prepared by treatment of the original clinoptilolite with Pb(NO3)2 and BaCl2 respectively, while the hydrogen-rich form was prepared by NH4Cl and heat treatment. Water and CO2 adsorption experiments were conducted in a volumetric system under static conditions, with low-pressure adsorption data being used for the characterization of the natural, Pb-rich, Ba-rich and H-rich clinoptilolite samples. Although the existence of barium-exchange was not noted, an appreciable decrease in CO2 adsorption was observed with the Pb-rich and H-rich forms due to a decrease in the electrostatic interaction between the surface and the adsorbate. Application of the Dubinin-Astakhov equation to the water adsorption data established the existence of micropores of different sizes that exhibited different adsorption mechanisms.Article Citation - WoS: 15Citation - Scopus: 19Aqueous Interactions of Zeolitic Material in Acidic and Basic Solutions(Elsevier Ltd., 2010) Polatoğlu, İlker; Çakıcıoğlu Özkan, Seher Fehime; Özkan, Seher Fehime; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyAqueous interactions of natural zeolitic material in as-received and modified forms were studied. The zeolitic materials was interacted with acidic (hydrochloric acid, lactic acid, acetic acid) and basic (sodium hydroxide) solutions. Ion exchange, adsorption, complex formation, precipitation and cation hydrolysis were possible interaction mechanisms affected by the amount and cation content of zeolite and pH. The dominant mechanisms seemed to be ion exchange and adsorption in HCl solution when zeolite was used in the as-received form, but dissociation of outer-sphere complexes when modified zeolite was used. In lactic acid, acetic acid as well as the basic solution, cation hydrolysis and complex formation were additional mechanism in the interactions. © 2010 Elsevier Inc. All rights reserved.Article Kinetics of Proton Transfer in the Zeolitic Tuff(Central European Science Journals, 2009) Çakıcıoğlu Özkan, Seher Fehime; Özkan, Seher Fehime; Özkan, Seher Fehime; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe kinetics of a proton transfer into dilute acid solutions containing natural zeolitic tuff was studied by following the pH evolution of the liquid phase. Four different solutions with tuff contents of 9, 3, 1 and 0.5 (% wt) and three different particle size fractions (≤ 2000 μm) were studied. The proton concentration of the solution was decreased by increasing the zeolite amount and decreasing the particle size fraction. The proton transfer reaction was analyzed with chemical reactions and diffusion model equations. Analysis shows that the adsorption and/or ion exchange are possible mechanisms and are expressed by a second order reaction model.Article Citation - WoS: 11Citation - Scopus: 13Co2 Adsorption and Dehydration Behavior of Linax, Knax, Canax and Cenax Zeolites(Springer Verlag, 2008) Erten, Yasemin; Güneş Yerkesikli, Alev; Özkan, Seher Fehime; Çakıcıoğlu Özkan, Seher Fehime; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this study, NaX synthetic zeolite was modified by following the conventional cation exchange method at 70°C. 82, 81, 79 and 48% of sodium were exchanged with Li+, K+, Ca2+ and Ce3 +, respectively. Thermal analysis data obtained by TG/DSC was used to evaluate the dehydration behavior of the zeolites. The strongest interaction with water and the highest dehydration enthalpy (ΔH) value were found for Li-exchanged form and compared with the other forms. The temperature required for complete dehydration increased with decreasing cation size (cation size: K+>Ce3+>Ca2+>Na+>Li +). CO2 adsorption at 5 and 25°C was also studied and the virial model equation was used to analyze the experimental data to calculate the Henry's law constant, K o and isosteric heat of adsorption at zero loading Q st. K o values decreased with increasing temperature and the highest Qst was obtained for K rich zeolite. It was observed that both dehydration and CO2 adsorption properties are related to cation introduced into zeolite structure.Article Citation - WoS: 12Citation - Scopus: 17Diffusion Mechanism of Water Vapour in a Zeolitic Tuff Rich in Clinoptilolite(Springer Verlag, 2008) Çakıcıoğlu Özkan, Seher Fehime; Ülkü, Semra; Ülkü, Semra; Özkan, Seher Fehime; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe adsorption kinetics of H2O in a clinoptilolite rich zeolitic tuff was experimentally investigated at 18°C. In the identification of the diffusion mechanism the isothermal adsorption model equation was used. It was found out that the intraparticle mass transfer becomes more dominant over the heat transfer with increase in particle size and the adsorptive dose pressure. Although initially intraparticle mass transfer was the controlling resistance later external heat transfer also contributes to the transfer mechanism.Article Citation - WoS: 12Citation - Scopus: 17Dynamics of Water Vapor Adsorption on Humidity-Indicating Silica Gel(Elsevier Ltd., 1998) Balköse, Devrim; Ulutan, Sevgi; Ülkü, Semra; Özkan, Seher Fehime; Balköse, Devrim; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyWell-defined CoCl2-containing silica gels were prepared by impregnation of the aqueous solution of the salt to silica hydrogel, drying and aging methods. Silica gels having 392-437 m2 g-1 surface area and 0.21-0.37 cm3 g-1 pore volume and having an average particle size of 3 mm were obtained. Aging in CoCl2 solutions decreased the surface area of silica gels from 540 cm2 g-1 to 392-430 m2 g-1 and pore volume from 0.27 to 0.21-0.23 cm3 g-1 for CoCl2 concentration smaller than 0.28 mol dm-3 in silica gel. Adsorbed water desorbed from the gels absorbing 1917-2555 J g-1 energy as determined by differential scanning calorimetry. The CoCl2-containing gels were successfully used in dynamic column experiments, with linear relation between velocities of inlet air and movement of blue to pink boundary. The colour change also makes the detection of the defects in column filling which causes air channellingArticle Citation - WoS: 19Flexible Poly(vinyl Chloride)-Zeolite Composites for Dye Adsorption From Aqueous Solutions(Taylor and Francis Ltd., 1996) Balköse, Devrim; Ulutan, Sevgi; Balköse, Devrim; Ülkü, Semra; Özkan, Seher Fehime; Ülkü, Semra; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyFlexible poly(vinyl chloride) (PVC) composites having natural zeolite clinoptillolite were prepared by plastisol-plastigel technology. Adsoption of methylene blue on each raw material and on composites was studied both from an equilibrium and a rate approach. It was observed that the adsorption capacity of zeolite decreased when it was embedded in composites. The equilibrium uptake of methylene blue increased with an increasing zeolite fraction in composites. Methylene blue was adsorbed from a 0.02 g·cm-3 aqueous solution slowly, but was nearly adsorbed completely with a composite having a 0.3 volume fraction of zeolite. The effective diffusion coefficient of methylene blue in composites was of the order of 10-13 m2·s-1 and decreased with increasing filler fraction.