Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 22Citation - Scopus: 28The Effect of Zinc Stearate on Thermal Degradation of Paraffin Wax(Springer Verlag, 2008) Gönen, Mehmet; Balköse, Devrim; İnal, Fikret; Ülkü, SemraIn this research, the effects of zinc stearate addition on paraffin wax degradation were investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). The apparent activation energies of wax decomposition in nitrogen and air atmospheres were determined as 76 and 37 kJ mol-1, respectively applying Kissinger method to TG data. The degradation rate constants of paraffin containing zinc stearate (0.1-0.5%) were found to be almost two times greater than that of paraffin only in air atmosphere. However, zinc stearate did not affect the rate constants in nitrogen significantly.Article Citation - WoS: 34Citation - Scopus: 43Zinc Stearate Production by Precipitation and Fusion Processes(American Chemical Society, 2005) Gönen, Mehmet; Balköse, Devrim; İnal, Fikret; Ülkü, SemraIn this study, the production of ZnSt2 using sodium stearate and zinc sulfate in a precipitation process, and stearic acid and zinc oxide in a fusion process, was investigated with regard to product purity. In the fusion process, an increase in mixing rate decreased the induction time occurring at the beginning of the reaction. While the melting point of the zinc stearate prepared by the precipitation process was found to be about 122°C by optical microscopy, it was slightly lower than 122°C for zinc stearate produced by the fusion process. Differential scanning calorimetry (DSC) indicated onset of melting at 120°C and 118°C for samples prepared by precipitation and fusion processes, respectively. Characteristic peaks of ZnSt2 were present in XRD patterns of the products obtained by both processes. From SEM micrographs, it was seen that zinc stearate obtained by both processes had lamellar structure.Article Citation - WoS: 87Citation - Scopus: 110Effects of Oxygenate Additives on Polycyclic Aromatic Hydrocarbons (pahs) and Soot Formation(Taylor and Francis Ltd., 2002) İnal, Fikret; Senkan, Selim M.Effects of three oxygenate additives (methanol, ethanol, and MTBE) on the formation of polycyclic aromatic hydrocarbons (PAHs) and soot in laminar, premixed, atmospheric pressure, fuel-rich flames of n-heptane were studied at an equivalence ratio of 2.10. A heated quartz microprobe coupled to online gas chromatography/mass spectrometry was used to establish the identities and absolute concentrations of major, minor, and trace species by the direct analysis of samples withdrawn from the flames. Benzene was the most abundant aromatic compound identified. The largest PAH detected was the family of C18H10 (molecular weight of 226) that includes cyclopenta[cd]pyrene and benzo[ghi]fluoranthene. Soot particle diameters, number densities, and volume fractions were determined using classical light scattering and extinction measurements. All the oxygenate additives studied reduced the mole fractions of aromatic and PAH species, as well as soot formation. However, the reduction in soot formation was comparable for different oxygenates under the experimental conditions investigated.Article Citation - WoS: 21Citation - Scopus: 23Activated Carbon Adsorption of Fuel Oxygenates Mtbe and Etbe From Water(Springer Verlag, 2009) İnal, Fikret; Yetgin, Senem; Aksu, Gülsüm T.; Şimşek, Selvi; Sofuoğlu, Aysun; Sofuoğlu, Sait CemilThe aqueous phase adsorption of fuel oxygenates methyl tertiary butyl ether (MTBE) and ethyl tertiary butyl ether (ETBE) onto commercially available granular activated carbon (GAC; Norit GAC 1240) was investigated in a batch system at 27°C. The oxygenate concentrations were determined by headspace gas chromatography/mass spectrometry analyses. The experimental data were used with four two-parameter isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and two kinetic models (pseudo first-order and pseudo second-order) to determine equilibrium and kinetic parameters. Considering the correlation coefficient and root mean square error, Dubinin-Radushkevich isotherm showed better fit with the equilibrium data for MTBE. However, the performances of Langmuir and Dubinin-Radushkevich models were comparable for ETBE. The adsorption capacities were calculated as 5.50 and 6.92 mg/g for MTBE and ETBE, respectively, at an equilibrium solution concentration of 1 mg/L using Dubinin-Radushkevich isotherm. The differences between the model predictions and experimental data were similar for the pseudo first-order and pseudo second-order kinetic models. Gibbs free-energy changes of adsorption were found to be -22.59 and -28.55 kJ/mol for MTBE-GAC and ETBE-GAC systems, respectively, under the experimental conditions studied.