Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Research Project Tuzla (Çanakkale) jeotermalinin bölgedeki akifere toprağa ve suya etkilerinin araştırılması(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2005) Baba, Alper; Özcan, Hasan; Yılmaz, Selahattin; Kavdır, Yasemin; Deniz, Ozan; Yiğini, Yusuf; Yılmaz, Sevinç; Baba, BarışTürkiye'nin sıcaklık bakımından üçüncü önemli sahası durumunda olan Tuzla jeotermal sahasındaki akışkanın yöredeki toprağa ve suya olan etkileri irdelenmiştir. Soğuk ve sıcak su kaynaklarının özelliklerini ve birbirleri ile olan ilişkilerini belirlemek amacıyla Ağustos 2003, alık 2003, Mart 2004 ve Haziran 2004 tarihlerinde su numuneleri alınmıştır. Bu su -numunelerinden major anyon, katyon, ağır metal ve çevresel izotop (18O, 2H, 3H) analizleri yapılmıştır. Ayrıca 0-30; 30-60; 60-90; 90-120 cm derinliklerinde ise toprak numunelerinde ise bazı fizikokimyasal özellikler, ağır metal ve radyoaktivite çalışmaları gerçekleştirilmiştir. Sıcak sular, denizel kökenli evaporıtik yataklardan çözünerek gelen sular olup, tatlı sular ile karışım göstermektedir. Sahadaki tüm sular meteorik kökenli olup, tatlı yeraltı suları ile connate (hapis) tuzlu suyun karışımından ibarettir. Sahasının güneydoğusundan gelen EC'si düşük (600-800 micromho/cm) yeraltı sularının jeotermal sular etkisi ile EC'sinin (1400-3200 micromho/cm) yükseldiği görülmektedir. Nitekim CaHCCVlü sular fasiyesinde yer alan yeraltı suları sıcaksularm etkisi ise CaCVlı sulara geçiş göstermektedir. Proje sahasındaki jeotermal suların Tuzla tatlı yeraltı suyu akiferine olan olumsuz etkileri iki şekilde olmaktadır: a) Jeotermal suların yeraltı sularına mevsimlik etkisi, ki buna dolaylı etki denebilir: kurak dönemde yüzeyde biriken tuz ve ağır metal bileşimlerinin, kışın yağışlar vasıtası ile yeraltına süzülmesi, b) Sahada çıkan yüksek basınca sahip jeotermal suların yukarıya doğru dikey çatlak, kırık veya faylar vasıtası ile yükselimi, yani genel anlamda yeraltı suyuna etkisi. Jeotermal suların yukarıda belirtilen her iki etkisinden ötürü yeraltı suyunun duraylı izotop değerleri beklenilenden daha pozitif değerlerdedir. Genel olarak, inceleme alanındaki sıcak suların da yukarıya doğru çıkarken soğuk yeraltı suyu akiferine karışımından ötürü 518O ve 6D değerlerinde bir azalma da söz konusu olmuştur.Research Project Bazı ilaç aktif maddelerin farmasötik preparatlarda ve insan serumu gibi biyolojik sıvılarda eletktroanalitik metotlar (Voltametrik ve polarografik teknikler ile tayini(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2005) Özkan, Sibel; Yılmaz, Selahattin; Uslu, Bengi; Dilgin, Yusuf; Yağmur, Sultan; Süren, Esin; Akgün, NurBu çalışmada, elektroaktif grup içeren bazı ilaçaktif maddelerin camsı karbon disk ve karbon pasta elektrotlarda farklı tampon ortamında voltametrik davranışları araştırıldı. Pik potansiyeline ve pik akımına, konsantrasyonun, pH 'nın tarama hızının etkisi incelendi. Alt tayin sınırı (LOD) ve Kantitatif tayin sınırı (|LOQ) belirlendi. Çalışılan bazı bileşikler için yükseltgenme veya indirgenme mekanizmaları da önerildi. Bu teknikler ile maksimum pik akımının gözlendiği ortamda ilaçaktif maddelerin farmasötik preparatlarda ve serum gibi biyolojik sıvılarda tayini yapıldı. Ayrıca kesinlik ve geri kazanım çalışmaları yapıldı. Bazı etken maddelerin önerilen elektroanalitik teknikler ile yapılan ilaçlardaki miktarı , UV-Spektrofotometrişininki ile karşılaştırıldı. Böylelikle önerilen elektroanalitik metodların doğruluğu ve üstünlüğü araştırıldı.Article Citation - WoS: 2Catalytic Activity of Heteropolytungstic Acid Encapsulated Into Mesoporous Material Structure(Walter de Gruyter GmbH, 2007) Gündüz, Gönül; Dimitrova, Rayna P.; Yılmaz, SelahattinThe paper presents a spectroscopic and catalytic study of encapsulated Keggin type heteropoly acid (12-tungstophosphoric acid, HPW) in the mesopores of MCM-41 molecular sieves. Nitrogen physisorption, FTIR, SEM, XRD and catalytic methods have been used to characterize and compare the properties of the samples. Methanol conversion, alpha-pinene isomerization and ethyl acetate oxidation have been applied as model reactions for the evaluation of acid site activity. The combined physicochemical and catalytic investigations clearly show that the introduction of 12-tungstophosphoric acid into MCM-41 causes significant changes in the properties of the sample.Article Citation - WoS: 53Citation - Scopus: 60Supercritical Deposition of Pt on Sno2-Coated Al2o3 Foams: Phase Behaviour and Catalytic Performance(Elsevier Ltd., 2008) Garrido, G. Incera; Patcas, F. C.; Upper, G.; Türk, M.; Yılmaz, Selahattin; Kraushaar-Czarnetzki, B.Deposition and reduction of an organometallic platinum complex from a supercritical Pt(COD)Me2/CO2 solution was carried out to produce Pt/SnO2 catalysts supported on Al2O3 foams for CO oxidation at moderate temperatures. The phase behaviour of the complex in supercritical carbon dioxide was investigated to find the optimum pressure and temperature conditions for the deposition. For the Pt(COD)Me2/CO2 mixture, the melting point decreased with increasing pressure from 378 K at 0.1 MPa to 360 K at 25.6 MPa. Additional investigations showed that the solubility of Pt(COD)Me2 in CO2 increases from 5.9 × 10-4 mol/mol at 11.2 MPa and 313 K to 3.4 × 10-3 mol/mol at 29.6 MPa and 353 K. The supercritical deposition yielded catalysts with highly dispersed platinum nanoparticles of approx. 3 nm having a narrow size distribution and thus, a superior activity towards oxidation of carbon monoxide in comparison to a catalyst prepared by the conventional aqueous impregnation of Pt.Article Citation - WoS: 9Citation - Scopus: 10Hydrogenation of Citral Over Ni and Ni-Sn Catalysts(TUBITAK, 2008) Aykaç, Hilal; Yılmaz, SelahattinLiquid phase citral hydrogenation over zeolite-supported monometallic Ni and bimetallic Ni-Sn catalysts was studied. The zeolite support materials were Na-Y, Na-mordenite, and clinoptilolite. Ni and Sn contents of the monometallic and bimetallic catalysts were 8.1-9.2 wt% and 0.46 wt%, respectively. The type of the zeolite support affected the activity and selectivity of the catalysts differently. The main product of the citral hydrogenation reaction was citronellal, for both monometallic (84.5% yield) and bimetallic (44.5% yield) catalysts. The addition of promoter increased the selectivity to unsaturated alcohols (geraniol+nerol), i.e. it changed from 0.9% to 6.3% over mordenite and from 0.9% to 2.1% over Na-Y-supported catalysts. Furthermore, activity of the Ni catalysts decreased while the quantity of acetal remained almost constant. Intimate contact between active metal, promoter, and support, and a catalyst with a high concentration of weak acid sites gave high selectivity to geraniol+nerol.Article Citation - WoS: 3Citation - Scopus: 3Hydrogenation of Citral Over Pt and Pt-Sn Catalysts(TUBITAK, 2008) Aykaç, Hilal; Yılmaz, SelahattinHydrogenation of citral on monometallic (Pt) and bimetallic (Pt-Sn) catalysts was investigated. It was found that the catalyst activities and product distributions were different over Na-Y and Clino supports. Among monometallic catalysts, Pt/Na-Y was more selective to citronellol (3.9%) and unsaturated alcohols, geraniol and nerol, (14.1%). Sn addition increased the catalyst activities. However, its effect on product distribution differed. Yield of geraniol+nerol changed from 5.1% to 19.7% over Clino. However, selectivity to unsaturated alcohols over Na-Y decreased when it was prepared as a bimetallic catalyst support. Unsaturated alcohol formation was favored when there was a metal support interaction over monometallic catalysts, and metal-promoter interaction over bimetallic catalyst.Article Citation - WoS: 11Citation - Scopus: 13Liquid-Phase Oxidation of Carvacrol Using Zeolite-Encapsulated Metal Complexes(American Chemical Society, 2006) Güneş, Alev; Bayraktar, Oğuz; Yılmaz, SelahattinWe report here the use of zeolite-encapsulated metal (salpn) complexes as catalysts in the oxidation reaction of the natural compound carvacrol in acetonitrile with hydrogen peroxide as the oxidant. No previous studies on the oxidation of carvacrol in the presence of metal salpn complexes have been reported. By using a general flexible ligand method, Cr(III), Fe(III), Bi(III), Ni(II), and Zn(II) complexes of N,N′-bis(salicylidene)propane1,3-diamine (H2salpn) encapsulated in NaY zeolite were prepared. All catalysts were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses to confirm the complex encapsulation. The activities of all prepared catalysts for the oxidation of carvacrol and hydrogen peroxide were tested. The performances of all catalysts were compared on the basis of the leaching test results and carvacrol conversions. Thymohydroquinone and benzoquinones were observed as byproducts at high conversions of carvacrol. No product was formed in the absence of a catalyst. Fe(salpn)-NaY catalyst exhibited the highest carvacrol conversion of 27.6% with a yield of 22.0%, followed by Cr(salpn)-NaY catalyst with 23.5% carvacrol conversion and a yield of 17.6%. Other catalysts have shown relatively lower performances in terms of carvacrol conversion and leaching. The Cr(salpn)-NaY catalyst was found to be a more efficient catalyst than others on the basis of leaching and activity tests. With the selected catalyst Cr (salpn)-NaY, the effects of temperature and carvacrol/hydrogen peroxide molar ratio on carvacrol oxidation reactions were investigated. Increasing the temperature from 40 to 60 °C caused an increase in the thymoquinone yield from 6.2% to 16.0%. An increase in carvacrol/hydrogen peroxide molar ratio from 1 to 3 resulted in a decrease in the thymoquinone yield.Article Citation - WoS: 41Citation - Scopus: 43Isomerisation of ?-Pinene Over Beta Zeolites Synthesised by Different Methods(Elsevier Ltd., 2005) Gündüz, Gönül; Dimitrova, Raina D.; Yılmaz, Selahattin; Dimitrov, Ljubomir; Spassova, MayaLiquid-phase α-pinene isomerisation at l00°C in a batch reactor is studied over Beta zeolites synthesised by different methods. It is confirmed that α-pinene forms a carbenium ion in an acidic environment, which rearranges without capture by nucleophiles, to form mainly hydrocarbons as camphene, terpinenes, terpinolenes and heavy products. The microporous Beta samples show low activity despite the high acidity most probably because of the hindered intermediate formation. The nature of the enhanced activity of Beta mesopores samples is suggested to be a result from the high accessibility of the acidic sites. The isomerisation of α-pinene was studied over Beta zeolites synthesised by different methods. The main products are camphene, terpinenes, terpinolenes and heavy products. Beta zeolites with micro-/mesopores reveal excellent activity because of the appropriate balance between acidity and bimodal pore system. The microporous Beta samples show low activity despite the good total acidity most probably because of the steric effect for the formation of the intermediate cations.Article Citation - WoS: 32Citation - Scopus: 35Liquid Phase Transformation of ?-Pinene Over Beta Zeolites Containing Aluminium or Boron, Titanium and Vanadium as Lattice Ions(Elsevier Ltd., 2005) Gündüz, Gönül; Dimitrova, Raina D.; Yılmaz, Selahattin; Dimitrov, LjubomirBeta zeolites with different modules (SiO2/Al2 O3) and containing B, Ti or V in lattice positions were synthesised by different methods and tested as catalysts in liquid phase transformation of α-pinene at 100 °C in a batch reactor. It was established that the hydrogen forms of Beta samples with a SiO2/Al2O3 module of about 55-66 and containing both micro- and mesopores displayed high catalytic activity in liquid phase isomerization of α-pinene. Samples with boron, titanium or vanadium, as lattice ions possess insignificant catalytic activity.Article Citation - WoS: 36Citation - Scopus: 40The Kinetics of Citral Hydrogenation Over Pd Supported on Clinoptilolite Rich Natural Zeolite(Elsevier Ltd., 2005) Yılmaz, Selahattin; Uçar, Şule; Artok, Levent; Güleç, HilalThe liquid phase hydrogenation of citral has been investigated over Pd (2.42%) supported on clinoptilolite rich natural zeolite catalyst for different reaction conditions. The zeolite support did not affect the active metal properties. This was attributed to the large size of Pd particles on the support. High selectivity (90%) to citronellal was obtained at complete conversion of citral. The catalytic activity increased with reaction temperature (80, 100, 120°C) following an Arrhenius behaviour, while selectivity remained constant for a given conversion. Selectivity to citronellal increased from 78 to 90% with increase in the amount of catalyst in the reaction solution (Citral/Pd mole ratio 293, 176 and 105). The spent catalyst regained its fresh activity and selectivity upon regeneration.