Yılmaz, Selahattin
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Yilmaz, SB
Yılmaz, Selahattin Berk
Yılmaz, SB
Yılmaz, S.
Yilmaz, Selahattin Berk
Yilmaz, Selahattin
Yılmaz, S
Yilmaz, S
Yilmaz, S.
Yılmaz, Selahattin Berk
Yılmaz, SB
Yılmaz, S.
Yilmaz, Selahattin Berk
Yilmaz, Selahattin
Yılmaz, S
Yilmaz, S
Yilmaz, S.
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selahattinyilmaz@iyte.edu.tr
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03.02. Department of Chemical Engineering
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Current Staff
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30
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60
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37
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47945/25315
Supervised MSc Theses
16
Supervised PhD Theses
4
WoS Citation Count
872
Scopus Citation Count
934
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18
WoS Citations per Publication
14.53
Scopus Citations per Publication
15.57
Open Access Source
51
Supervised Theses
20
| Journal | Count |
|---|---|
| International Journal of Chemical Reactor Engineering | 4 |
| Applied Catalysis A: General | 4 |
| Reaction Kinetics, Mechanisms and Catalysis | 3 |
| Turkish Journal of Chemistry | 3 |
| Industrial and Engineering Chemistry Research | 2 |
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Master Thesis Development of Tungsten Loaded and Zirconia Incorporated Mesoporous Catalysts for Esterification of Palmitic Acid With Cetyl Alcohol(Izmir Institute of Technology, 2014) Mutlu, Vahide Nuran; Yılmaz, Selahattin; Yilmaz, SelahattinIn this study, it was pursued to develop acidic mesoporous catalysts for esterification of cetyl alcohol by palmitic acid. For this, Zr incorporated SBA-15 was prepared by hydrothermal synthesis. Zr-SBA-15 was used both as a catalyst support and as a catalyst itself. WO3 loading onto the Zr-SBA-15 was performed by incipient wetness impregnation. Additionally, WO3-ZrO2 catalyst was prepared by co-precipitation with two different contents of WO3 (15 wt% and 20 wt%). The reaction tests were carried out in mesitylene under reflux conditions. Zr was incorporated into SBA-15 successfully. The surface areas of Zr-SBA-15 and WO3/Zr-SBA-15 catalysts were significantly higher than that of WO3-ZrO2. Loading of WO3 decreased the surface area of Zr-SBA-15. The acidity of the WO3/Zr-SBA-15 with 15 wt% WO3 was higher than that of with 20 wt% WO3. Moreover, increasing the calcination temperature from 700 to 800 oC resulted in the increase of acidity. The activity of the catalysts differed. The only product obtained was cetyl palmitate. Under the test conditions it was found that the reaction rate was not limited by equilibrium. Zr-SBA-15 provided the highest conversion (64 %) which corresponded to cetyl palmitate yield of 63% among other mesoporous catalysts because of its high surface area (600.3 m2/g) and acidity (0.152 mmol NH3/g cat). This catalyst did not show leaching. WO3/Zr-SBA-15 based catalys tests showed that catalyst activity increased by increasing calcination temperature. This was atributed to better dispersion of W. The conversion of cetyl alcohol did not change much with more W loading.Master Thesis Influence of Synthesis Parameters on the Properties of Zsm-5 & on Their Catalytic Activity for 1-Butene Isomerization(Izmir Institute of Technology, 2002) Demirkan, Korhan; Yılmaz, Selahattin; Yılmaz, SelahattinThe synthesis and preparation of active and selective zeolite catalysts (H-ZSM-5 and H-ZSM-22) for the skeletal isomerization reaction of 1-butene to iso-butene were investigated.H-ZSM-5 zeolite catalysts were synthesized by varying the synthesis time (3, 6, 12, 24, 48 and 72 h), stirring mode (static, rotational), the initial SiO2/Al2O3 ratio (15 , 30, 70) and SiO2/TPABr (Tetrapropylammonium bromide) ratio (3,3; 5,5; 12,5) of the hydrogel.A synthesis work for H-ZSM-22 type zeolite materials was also carried out both in static and rotational mode.Catalytic activity tests were performed in a constructed fixed bed tubular quartz reactor system at 440 and 375oC at weight hourly space velocities (WHSV) of 22 and 11 h-1.The X-Ray Powder Diffraction patterns and Scanning Electron Microscopy images of ZSM-5 zeolites showed that the particle size and phase purity of ZSM-5 increased with increase in synthesis time.The XRD pattern of Na-ZSM-5 zeolite synthesized by the static mode showed a higher degree of crystallization than the rotational synthesis.The sample synthesized with high Al content in the initial hydrogel (SiO2/Al2O3.15) showed less crystallization than the samples synthesized with low Al content.Increasing Si/Al ratio in the synthesis hydrogel resulted in an increase in the surface area (533 m2/g).TPABr content was found to be an important factor in the crystallization of ZSM-5 zeolites.Lowest TPABr content resulted in an amorphous phase.Increase in the organic cation content enhanced the crystallization, and larger size ZSM-5 crystals with higher phase purity and surface area were achieved. The crystal phase obtained from the hydrogel which was prepared for the synthesis of ZSM-22, were affected significantly by the synthesis mode.The catalysts prepared were tested for isomerization of 1-butene at 440oC and 22h-1 WHSV.It was found that the hydrogel composition highly influenced the catalytic properties of H-ZSM-5 giving a range of conversion and selectivity for iso-butene.Al rich zeolite (initial SiO2/Al2O3.15) showed very low selectivity (2%).This was attributed to the higher acidity of this zeolite. In contrast the samples having medium and high SiO2/Al2O3 ratios 30 and 70 gave high selectivity (52% and 56% respectively) and yield (26% and 28% respectively) under the same reaction conditions.The sample with initial SiO2/Al2O3.30, SiO2/TPABr. 3.3 gave the highest yield to iso-butene (28%) under the same reaction conditions (440oC , 22h-1). Reaction at a lower temperature (375oC) increased iso-butene yield to 32% by suppressing the byproduct formation. Decreasing the WHSV (11 h-1) increased conversion from 40% to 48% and giving yield of 32% iso-butene. The test for long time on stream (24 h) to asses catalytic deactivation, showed slight increase in the yield of iso-butene (%33).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: 4Citation - Scopus: 4Hzsm-5 and H-Ferrierite Acidity Modification by Silylation and Their Activities in N-Butene Isomerisation(Walter de Gruyter GmbH, 2010) Kılıç, Emre; Yılmaz, SelahattinH-ZSM5 and H-Ferrierite acidities were modified by chemical liquid deposition using tetraethylorthosilicate (TEOS), silicontetratchloride (SiCl4) and triaminopropyltriethoxysilane (3-APTES). All depositions were carried out at room temperature for deposition times of 0.5 and 1 h. Reaction tests were performed in a tubular quartz fixed bed reactor at 375°C for weight hour space velocities of 22 h-1. Surface area and pore volume of the catalysts were decreased upon modifications. The least modification of acidity was achieved by TEOS. However, SiCl4 and 3-APTES deposition modification strongly decreased the number of Bronsted and Lewis acid sites. As the effect of the modification increased, total acidity of the SiCl4 modified catalyst decreased. The catalysts were tested in isomerization of n-butene. Modification decreased the activity of the catalysts, but improvement in selectivity was observed with TEOS deposition. TEOS deposition increased the selectivity of the catalysts; for synthesized H-ZSM5 from 57.95 to 63.74 percent, for commercial H-ZSM5-C from 26.78 to 32.52 percent, and for H-FER from 63.06 to 81.23 percent. However, modification with SiCl4 and 3-APTES decreased both conversion and selectivity of the parent catalysts.Master Thesis Süperkapasitör Uygulamaları için Kenevir Sapı Kaynaklı Aktif Karbon Üretimi ve Performans Analizi(2025) İnan, Ece; Çağlar, Başar; Yılmaz, SelahattinBu çalışmada, kenevir sapı biyokütlesinden türetilen aktif karbon elektrotlar, sistematik bir deneysel tasarım kullanılarak süperkapasitör uygulamaları için üretilmiş ve optimize edilmiştir. Sentez süreci, kontrollü karbonizasyonu farklı sıcaklıklarda (500-600 °C), aktivasyon sürelerinde (1-3 saat) ve ZnCl2/biomass ağırlık oranlarında (0.5-1 ) gerçekleştirilen kimyasal aktivasyonla birleştirmiştir. Özgül kapasitans ve enerji yoğunluğunu maksimize etmek amacıyla Box-Behnken tasarımı ve yanıt yüzey yöntemi (RSM) uygulanmıştır. Elde edilen aktif karbonlar, BET yüzey alanı analizi, Raman spektroskopisi, FTIR, SEM–EDX ve CV, GCD, EIS gibi elektrokimyasal ölçümlerle kapsamlı bir şekilde karakterize edilmiştir. En iyi performans gösteren örnekler, iyi geliştirilmiş hiyerarşik gözeneklilik ve orta düzeyde grafitik düzenlilik (ID/IG oranı 0.96'ya kadar) sergileyerek iyon taşınımını ve çift katmanlı kapasitansı artırmıştır. Elektrotlar, 0–1 V potansiyel aralığında 0.5 A/g akım yoğunluğunda 79.5 F/g özgül kapasitansa ulaşmış, 20 A/g akım altında 5000 çevrimden sonra ilk kapasitanslarının yaklaşık %78'ini korumuş ve coulombic verimlilik %97'nin üzerinde tutulmuştur. Sonuçlar, kenevir sapının yüksek performanslı gözenekli karbon elektrotlar üretmek için verimli ve sürdürülebilir bir öncü olabileceğini göstermektedir. Çalışma, termal ve kimyasal parametrelerin ince ayarının, yapısal ve elektrokimyasal özellikleri nasıl etkili şekilde şekillendirdiğini ortaya koyarak biyokütle kaynaklı süperkapasitör malzemelerinin geliştirilmesine yönelik değerli bilgiler sunmaktadır.Article Citation - Scopus: 6Lithium Extraction From Geothermal Brine Using Γ-Mno2: a Case Study for Tuzla Geothermal Power Plant(Elsevier Ltd, 2024) Toprak, S.; Yılmaz, Selahattin; Öncel, Ç.; Baba, Alper; Yılmaz, S.; Demir, Mustafa Muammer; Baba, A.; Koç, G.A.; Demir, M.M.Geothermal brines contain high concentrations of ions and form a source of various valuable elements. The isolation of the elements from their water systems is a great challenge when the gradual depletion of ores in mining is considered. Attempts have been made for a long time to isolate valuable elements from aqueous mixtures prepared in the laboratory. However, those studies might not reflect the complexity of natural systems and might yield results that deviate significantly from the performance in real field systems. In this study, sorption is used to extract lithium ions from a representative field, Tuzla Geothermal Power Plant (TGPP) Turkey, using a mini-pilot reactor introduced to the reinjection well of the plant. Electrolytic manganese dioxide (γ-MnO2), a relatively inexpensive material widely used as the cathode material in lithium-ion batteries, was employed as a sorbent material for lithium. The sorption/desorption performance of the novel γ-MnO2 was investigated under various conditions. Sorption is performed at 360K and 2 bars. The maximum sorption performance was obtained at 1 h in Tuzla GPP. The desorption experiments were performed in acidic solutions. The concentration of Li+ in the desorption solution was found to be 25 mg/L on average when 10 g of γ-MnO2 was dispersed into 30 mL of the acidic aqueous solution. The first desorption solution was used consecutively for collecting more Li+ ions through the desorption of fresh brine-treated powder samples (cumulative desorption). By repeating this process four times consecutively, 230 mg/L of Li+ was obtained in the desorption solution. Moreover, the reusability of the γ-MnO2 sorbent was examined. The sorbent powder showed almost 40% performance efficiency compared to virgin powder under the conditions employed in this study. The use of electrolytic γ-MnO2 sorbent for lithium adsorption was found to be a promising process for practical use in the separation of lithium from geothermal brines. © 2024Article Citation - WoS: 8Citation - Scopus: 8Synthesis of Butyl Glucoside Over Sulphated Zr-Sba and Tungstophosphoric Acid Incorporated Sba-15 Catalysts(Elsevier Ltd., 2021) Mutlu, Nahide Nuran; Yılmaz, SelahattinGlycosidation of glucose with n-butanol was studied over sulphated Zr incorporated SBA-15 and tungstophosphoric acid (TPA) incorporated SBA-15 catalysts. The catalysts were prepared with different Zr, TPA and SO4 amounts via hydrothermal synthesis. SBA-15 structure was preserved and Zr and TPA were successfully incorporated. Sulphation improved the acidity of Zr-SBA-15 and the ratio of Brønsted to Lewis acid sites (B/L) increased. Thus, much higher butyl glucoside yields (about 70 %) were obtained over SO4/Zr-SBA-15 catalysts. However, 15 % activity loss was observed after 2 re-use due to sulphate leaching. TPA-SBA-15 catalysts had the highest B/L and provided very high catalytic activity with butyl glucoside yields above 95 %. The initial rate of butyl glucoside formation over TPA-SBA-15 catalysts were close to that of H2SO4. These catalysts were found stable and reusable. Reaction temperature and catalysts amount was studied as the reaction parameters over the most active and selective catalyst. © 2020 Elsevier B.V.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: 165Citation - Scopus: 174Heterogeneous Fenton-Like Degradation of Rhodamine 6g in Water Using Cufezsm-5 Zeolite Catalyst Prepared by Hydrothermal Synthesis(Elsevier Ltd., 2010) Dükkancı, Meral; Gündüz, G.; Yılmaz, Selahattin; Prihod’ko, R. V.In this study, heterogeneous Fenton-like degradation of reactive azo dye Rhodamine 6G in water was investigated over a CuFeZSM-5 zeolite catalyst prepared by hydrothermal synthesis. At initial pH of 3.4, a color removal of 100% was achieved after a reaction time of 45min. TOC elimination was measured to be 51.8% after 2h of oxidation. Initial decolorization rate was described by an equation of -rA0=4.56×102 e-24.83/RTCR6G,0CH2O2,00.35 where R is in kJ/mol. The leaching of iron and copper cations from zeolite structure into the solution during oxidation was dependent on pH strongly. The regulation of pH from 6.5 (dye solution pH) to 3.4, increased leaching for iron from 0.7 to 0.8mg/dm3 and for copper from 1.4 to 2.1mg/dm3. The copper was totally leached from the catalyst during the process at pH 3.4. © 2010 Elsevier B.V.Master Thesis Selective Hydrogenation of Citral Over Mesoporous Ru/Tio2 Catalysts(Izmir Institute of Technology, 2013) Hassan, Hassanain Abbas; Yılmaz, SelahattinThe liquid phase citral hydrogenation was investigated over Ru/SiO2, Ru/TiO2 and Ru/TiO2/SiO2 catalysts. TiO2/SiO2 supports were prepared by sol-gel deposition, impregnation and absorption methods. The effect of the supports and catalyst reduction temperature, 300 ï‚°C (LTR) and 450 ï‚°C (HTR) on citral conversion and selectivity to unsaturated alcohols were examined. A well-defined crystalline anatase phase was only observed on the support prepared by absorption method, TiO2/SiO2-ABS. A high dispersion and interaction of Ru were observed over TiO2 for Ru/TiO2. Ru/TiO2/SiO2-ABS also displayed similar properties but to a lower extent. Ru/TiO2/SiO2-ABS catalyst showed the highest citral conversion (57.7 %) at LTR among the different Ru/TiO2/SiO2 catalysts. Its selectivity to UA was also high (70.2 %). This was attributed to a better metal support interaction and dispersion obtained by this method. However, a selectivity of 62.6 % was obtained over Ru/TiO2. Activity of the catalysts was mostly observed to decrease as reduction temperature increased from 300 ï‚°C to 450 ï‚°C. Citral conversion decreased from 57.7 % to 42.3 % over Ru/TiO2/SiO2-ABS. However, selectivities to unsaturated alcohol (nerol and geraniol) over Ru/TiO2 and Ru/TiO2/SiO2 catalysts were increased at HTR, reaching about 80 %. This was suggested to be due to more interaction of TiO2 with the Ru (strong metal support interaction). There was no significant change in the selectivity to UA obtained at HTR for Ru/SiO2. This was related to the inert nature of SiO2.