Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 123Citation - Scopus: 134Effect of Moisture on Adsorption Isotherms and Adsorption Capacities of Co2 on Coals(American Chemical Society, 2009) Özdemir, Ekrem; Schroeder, KarlThe effect of moisture on the adsorption isotherms and adsorption capacities of CO 2 on Argonne Premium coals has been investigated. In some experiments a small hysteresis was observed between the adsorption and desorption isotherms. The hysteresis was absent or negligible for high-rank and as-received coals but was discernible for lower rank and dried coals. An equation that accounted for the volumetric changes when an adsorbate alters the structure of an adsorbent was employed to interpret the data. The best-fit solutions indicate that the coal volume decreases upon drying. The microscopic shrinkage estimated using helium expansion was greater than the shrinkage reported using the bed-height technique. The microscopic shrinkage was 5-10% for low-moisture medium and high-rank coals and up to 40% for low-rank coals having higher moisture contents. The CO 2 swelling of coals during adsorption isotherm measurements was estimated to be about the same as the shrinkage that occurred during the moisture loss. The adsorption capacity, isosteric heat of adsorption, average pore size, and surface area of the as-received (moist) and dried Argonne coals were estimated after accounting for the volume changes. The isosteric heat of adsorption of CO 2 was found to be between 23 and 25 kJ/mol for as-received coals and between 25 and 27 kJ/mol for dried coals, regardless of the rank. The degree of drying was shown to affect the adsorption capacity and the calculated surface area. For dried coals, the adsorption capacity showed the typical 'U-shape' dependence on rank whereas the as-received coals displayed a more linear dependence. A relationship is proposed to quantify the effect of moisture on the adsorption capacity. The mechanism of CO 2 adsorption on moist coals and the implications of the lower adsorption capacity of wet coals to coal seam sequestration of CO 2 are presented.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; Çetin, Ali Emrah; Çakıcıoğlu Özkan, Seher FehimeIn 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: 30Citation - Scopus: 36Effects of Oxygenate Concentration on Species Mole Fractions in Premixed N-Heptane Flames(Elsevier Ltd., 2005) İnal, Fikret; Senkan, Selim M.Atmospheric pressure, laminar, premixed, fuel-rich flames of n-heptane/oxygen/argon and n-heptane/oxygenate/oxygen/argon were studied at an equivalence ratio of 1.97 to determine the effects of oxygenate concentration on species mole fractions. The oxygen weight percents in n-heptane/oxygenate mixtures were 2.7 and 3.4. Three different fuel oxygenates (i.e. MTBE, methanol, and ethanol) were tested. A heated quartz micro-probe coupled to an on-line gas chromatography/mass spectrometry has been used to establish the identities and absolute concentrations of stable major, minor, and trace species by the direct analysis of samples, withdrawn from the flames. The oxygenate addition has increased the maximum flame temperatures and reduced the mole fractions of CO, low-molecular-weight hydrocarbons, aromatics, and polycyclic aromatic hydrocarbons. The reduction in mole fractions of aromatic and polycyclic aromatic hydrocarbon species by an increase in oxygenate concentration was more significant.