Izmir Institute of Technology

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Adsorption of olive leaf antioxidants on silk fibroin
(Izmir Institute of Technology, 2006) Bayçın Hızal, Deniz; Bayraktar, Oğuz
This study focused on producing protein based functional food with antioxidative and antimicrobial properties by adsorption of olive leaf antioxidants on silk fibroin. In accordance with this aim, extraction and adsorption of two most abundant polyphenols in olive leaves, oleuropein and rutin were studied. Furthermore, desorption studies were performed to increase the purity of polyphenols.In this study, effect of various parameters on extraction and adsorption were investigated by HPLC and antioxidant analyses. The adsorption isotherms of oleuropein and rutin were plotted at different temperatures, pH values and solid-liquid ratios. After adsorption, the adsorbed polyphenols on silk fibroin was subjected to SEM, FTIR, color, antioxidant and antimicrobial analyses to observe the changes in the silk fibroin.The experimental data of adsorption isotherms were well-fitted to Langmuir model. The maximum adsorption capacity was determined as 108 mg oleuropein/g silk fibroin and 21 mg rutin/g silk fibroin. In desorption process, 81% of rutin and 85 % of oleuropein were removed from the adsorbent surface in 70 % aqueous ethanol solution.After adsorption of oleuropein and rutin, the antioxidant capacity of silk fibroin increased from 1.93 mmol TEAC/g to 3.61 mmol TEAC/g. Silk fibroin also gained antimicrobial activity against Staphylococcus aureus and Klebsiella pneumoniae after adsorption of olive leaf antioxidants. Desorbed polyphenols exhibited higher antioxidant capacity than the same amount of olive leaf extract due to the increase in the purity of oleuropein and rutin after desorption.Consequently, silk fibroin is a promising protein for the production of functional food or dietary supplements and for the purification of oleuropein and rutin.
Adsorption of reformer off-gas on NaX zeolite and metal organic framework (mil53(AI)): Equilibria and kinetics
(Izmir Institute of Technology, 2013) Güneş Yerkesikli, Alev; Çakicioğlu Özkan, Seher Fehime
Synthetic gas produced from steam methane reforming (SMR off -gas) is a mixture of H2, CO, CO2, and CH4 can be used in fuel cell after purification. In this study adsorption as a purification tool was used to obtain high H2 content of gas mixture from SMR off gas. Zeolites and metal organic framework were used as an adsorbent. CO2 equilibrium studies on K rich NaX zeolites, prepared with ultrasonic and traditional methods, and metal organic framework MIL53 (Al) shows high adsorption on zeolites than MIL53(Al) up to 1 atm. K rich zeolites give lower adsorption than NaX zeolite. Adsorption isotherms obtained for MIL53 (Al) is linear ( favorable for zeolites). This makes MIL53(Al) is an promising adsorbent for high pressure application. Adsorption equilibrium at 5 atm shows that NaX zeolite is good adsorbent for the SMR off gas with the following orders: CO2>CH4>CO> H2. Kinetics of SMR off gas in MIL 53 (Al) were studied by using Zero Length Column (ZLC) method. The results show that the calculated diffusivities are strongly dependent on temperature but weakly dependent on purge flow rate. The study reveals that transport is controlled by intracrystalline diffusion. The activation energy on diffusion are nearly same (about 41 kJ/mol) and not change with respect to kinetic diameter of SMR off gases. Heat of SMR off gas adsorption on MIL53(Al) obtained from Henry’s constant shows that adsorption is exothermic. The study shows that the ZLC method is an effective tool to investigate the diffusion kinetics of SMR off-gas gases in MIL53(Al).
Adsorptive characteristics of aflatoxin B1 in the presence of purified clinoptilolite rich mineral and lactobacillus plantarum S2
(Izmir Institute of Technology, 2012) Bulut Albayrak, Çisem; Ülkü, Semra
The human diet contains a wide variety of natural carcinogens. Aflatoxin B1 (afB1) is the most toxic and most prevalent compound. Both probiotic lactic acid bacteria and clinoptilolite rich zeolite mineral have potential to eliminate this toxin. This study was planned in order to investigate adsorptive characteristics of afB1 by local purified clinoptilolite rich mineral (PNZ) and probiotic strains which were isolated from different natural sources (fermented cabbage, boza ) in the present work. PNZ and isolated strains were characterized by using several physical, chemical and biological techniques. Adsorption characteristics of both probiotic lactobacilli and PNZ were investigated in simulated gastrointestinal solutions. The chosen probiotic strain was identified as L. plantarum .The studies indicated that, both L. plantarum S2 and PNZ can eliminate afB1 in the phosphate buffer solution. They are more effective when they were used together (45% for L. plantarum S2, 32% for PNZ, 86%for L. plantarum S2 and PNZ together). AfB1 adsorption equilibrium data were best represented by Sips isotherm model for PNZ, whereas by Langmuir isotherm model for L. plantarum S2. Thermodynamic studies implied that afB1 adsorption by mineral and L. plantarum S2 was physical adsorption. Experiments with different temperatures showed that afB1 adsorption by PNZ was exothermic but afB1 adsorption by lactobacilli was endothermic. Adsorption kinetics were analysed by diffusional models and reaction models for afB1 adsorption by PNZ mineral. Both film diffusion and /or intra particle diffusion were effective on adsorption kinetics depending on the experimental conditions (Temperature, pH, agitation speed, etc).
Anaerobic digester modelling for production of biogas from waste hazelnut husk
(Izmir Institute of Technology, 2022-07) Demir, Ozan; Şeker, Erol
Anaerobic digestion is a degradation process of complex organic matters into methane and carbon dioxide in an oxygen-free environment maintained by microorganisms. An advantage, besides energy production, is it is a waste management technique. Hazelnut husk is a valuable raw material for the anaerobic digestion process with more than 55 % cellulose and hemicellulose content. Anaerobic Digestion Model No. 1 (ADM1) developed by IWA Group was used in this study. This master thesis modeled biogas production by co-digestion of cattle manure and hazelnut husk process in MATLAB. The goal was to evaluate the methane amount of a household bioreactor. Tanks-in-series model with 3 CSTRs was chosen after residence time distribution (RTD) analysis. Ten different cases were investigated to show the effects of carbon source/manure ratio, temperature, carbon source type, total solid (TS) amount, reactor type, and RTD analysis. The carbon source/manure ratio improves the methane yield as it increases. When the ratio is 1, methane yield is 0.229 L/kgVS whilst yield is 0.224 L/kgVS if the ratio is 0.1. The temperature effect on the process is significant. In the thermophilic case, the methane production is 0.432 L/d which is the highest amount compared to mesophilic and psychrophilic cases. When food waste is used as a carbon source with a ratio of food waste/manure of 0.1, the methane production is 0.410 L/d while it is 0.403 L/d in hazelnut husk digester. When the TS amount is doubled, the methane yield goes down from 0.224 to 0.149 L/kgVS because the residence time is not long enough to digest it as well as in case with lower total organic carbon level. In unmixed, mixed, and Chinese Dome Digester types of reactors, methane productions are 0.403, 0.646, and 0.552 L/d, respectively. In the ideal case, the methane production is 1.525 L/d which indicates the necessity of RTD analysis.
Analysis and re-design of an outdoor fitness equipment's mechanism
(Izmir Institute of Technology, 2011) Kaya, Nazife Aslı; Erkarslan, Önder
This research study emphasizes the importance of biomechanics and mechanics knowledge in industrial design as an interdisciplinary approach for designing safety products through an example, FE02 Stepper. First of all, the concurrency of FE02 Stepper with human movements was analysed. After the errors were determined, a new mechanism was designed and analysed by using algebraic position analysis method and implemented in Microsoft Excel 2007® and modeled by using Rhinoceros Evolution v4.0®.
Application of silk fibroin in controlled-release of theophylline
(Izmir Institute of Technology, 2004) Özgarip, Yarkın; Bayraktar, Oğuz
Polimerik malzemeler kullanılarak ilaç salınım proseslerini modellemek amacı ile çalımalar yapılmaktadır. Organik bazlı polimerik çözeltiler ile ilaçların kaplanması hala çok yaygın olmasına ramen ,organik bazlı polimerik çözeltilerin toksik ve çevreye zaralı olması nedeni ile ilaç endüstrisi farklı kaplama malzemeleri üzerine çalımaya balamıtır. Su bazlı kaplama teknikleri, organik polimerik çözeltilerin neden olduğu toksik özellikleri ortadan kaldırmak amacı ile kullanılmaktadır. Bu çalımada kontrollü ilaç salınım mekanizmasını elde etmek için kaplama malzemesi olarak su bazlı fibroin çözeltisi ve model ilaç olarak da teophylline kullanılmıtır. laç tabletleri ısıl isÌ§lem görmü silk fibroin, polietilenglikol (PEG) ve fibroin çözeltisi karıımı ile kaplanmıtır. Ek olarak EDC ile kroslink edilmi fibroin çözeltisiden elde edilen kaplamanın ilaç salınımına etkisi aratırılmıtır. Bütün örneklerin ilaç salınım profilleri UVspectrofotometre kullanılarak dissolusyon testi ile yapılmıtır. Ayrıca PEG konsantrasyonunun ve film kaplama kalınlıının etkileri aratırılmıtır. Taramalı elektron mikroskobu kullanılarak filmlerin morfolojisi ve film kaplama kalınlıkları bulunmutur. PEG in plastikletirici etkisinin ve fibroinin EDC ile kroslink edilmesinin, ilacın kontrollü bir ekilde salınmasını saladıı gözlemlenmitir. Hedef profile göre %17 PEG içeren fibroin çözeltisi ile kaplanan tabletlerin %70 salınım profilinde çözünme süresi 345 dakika olarak bulunmutur. laç salınım hızı ve tablet kaplama kalınlıı arasında bir baıntı elde edilmitir. EDC ile kroslink edilen fibroin çözeltisiyle kaplanan tabletlerde , kaplama kalınlıı arttıkça ilaç salınımı azalmıtır. Film kaplama kalınlıını 7.68 mm.ye getirilerek istenen ilaç salınımı elde edilmitir.
Application of tubular ceramic nanofiltration membranes for textile waste water desalination
(Izmir Institute of Technology, 2017-07) Yaldız, Safiye; Çiftçioğlu, Muhsin
Textile industry generates coloured wastewater containing a significant level of dye/inorganic salts. Environmental concerns and efficient energy use make the recovery of reusable water and salts from textile wastewater vital globally. Ceramic nanofiltration (NF) membranes are becoming increasingly important for the recovery and purification of dyes and salts (e.g., NaCl) in high salinity waste streams. They have superior chemical/mechanical/thermal properties compared to their polymeric counterparts. Desalination performances of the ceramic NF membranes depend on the concentration and chemical structure of the target ions, pH of feed and the wastewater stream along with the chemical/surface/nanostructural properties of the selective NF layer. Metal oxides are generally used as NF layer materials due to their amphoteric behaviour. Repulsive/attractive forces between the ionic species in the solution and the NF layer may make the separation of ionic species possible. In this work, zirconia doped titania based NF layers were designed. Desalination experiments were conducted with 10-3 M Na2SO4 and MgSO4 salts at different pH values. Salt retention capacities of 5 different membranes were determined. Percent retention was calculated using ion concentrations in permeate and retentate streams. The Mg2+ and SO4 -2 ion concentrations were determined by titration with 0.01 M EDTA and by spectrophotometer at 420 nm, respectively. A clear pH dependency of the salt retention was found in filtration tests. The highest SO4 -2 and Mg+2 ion retentions were obtained with using MF+disperel (boehmite)+P2 (600 0C)+TTIP hydrosol+Ti/Zr polymeric (double layer) membrane as 95% and 91%, respectively.
An approch to the security problems in the TCP/IP protocol suite for a network security monitor design
(Izmir Institute of Technology, 1999) Mutaf, Pars; Koltuksuz, Ahmet Hasan
There are a number of security problems in the TCP/IP protocol suite. In this thesis these problems will be analyzed in detail. The problems in several existing prevention methods will be analyzed as well in order to show that security policies based merely on preventive measures are not completely secure and convenient. Therefore, "network security moniJoring" will be proposed as an alternative and supplementary approach against Internet attacks.
As a case study of the impact of food-based festivals in rural development Urla Artichoke Festival
(Izmir Institute of Technology, 2022-07) Aslan, Onur Bora; Akpınar, Figen
As a result of globalization's impact throughout the past century, rural areas have experienced a change in their social, cultural, and economic landscape. With the change of agricultural production practices, population decline, depletion of natural resources, and threat of new housing constructions, rural communities have undergone deep transformation and under the therat of change of the rural identity. The idea of rural tourism, which was created to stop rural regions from the transformation, has taken center stage in rural development and, by extension, regional and national development. Improved living conditions, a better quality of life and built environment, and increased economic activity are all examples of rural development concepts. In areas with unique gastronomic, environmental and cultural values, rural tourism has emerged as a viable alternative to the tourists. Food festivals are among the most effective motor for growth in areas with distinctive culinary values. Events that promote unique gastronomic values on a national or international level and contain product sales are called as a food festivals. In the context of this study, the Urla Artichoke Festival, which has been hosted since 2015 and celebrates a geographical indicator for gum artichoke, has been successful to promote the rural areas and their branding. The stakeholders of the Urla Artichoke Festival were identified as a first step in the research. To learn more about these stakeholders' contributions to the festival and their opinions on the economic, cultural, and social impacts of the event on rural areas, semi-structured interviews were undertaken. In the research systematic tables were used to present the information which were collected during the interviews. The conclusion section includes a critical discussion of the collected data. The concept of gastronomic tourism has been reviewed in the context of the Urla Artichoke Festival in this study. Issues have been found and solutions have been established to deal with rural development practices in a more planned, sustainable and efficient manner.
Bilayer chitosan/zein based nanofibers for antimicrobial wound dressing application
(01. Izmir Institute of Technology, 2021-12) İskeçman, Nilsu; Tıhmınlıoğlu, Funda; 01. Izmir Institute of Technology
Nowadays, modern functional wound dressings have become prominence due to their biocompatible, biodegradable, and non-toxic nature and ability to mimic ECM of skin. To enhance their mechanical and prolonged cumulative release of drugs in media, environmentally friendly inorganic nanofillers are preferred. Recently, halloysite nanotubes (HNTs) which is a new class of inorganic filler are using to improve mechanical properties and thanks to their tubular structure various agents encapsulated into these tubes to make drug release more controlled. In this thesis, it was aimed to fabricate and characterize bilayer wound dressing by using Zein-Vancomycin loaded HNTs nanofibers as upper layer to mimic ECM of skin and provide antibacterial protection and chitosan sponge as bottom layer to absorb the excess exudates of wound, provide gas transmission and facilitate the migration of inflammatory and fibroblast cells into the healing wounds. The morphology of nanofibers and encapsulation efficiency of HNTs are optimized to achieve similar homogeneous fiber structure with skin tissue and controlled release of Vancomycin drug. Chemical interaction between Vancomycin-HNT and Zein-HNT were characterized by FT-IR. The surface charge differences of HNTs by encapsulating drug into tubes was determined by zeta potential analysis. The weight loss percentage of nanofiber with the addition of HNTs into zein media was characterized by using thermogravimetric analysis (TGA). Bilayer sponges were characterized by SEM, FT-IR, porosity, mechanical properties, contact angle, water vapor transmission rate, swelling, degradation, cumulative drug release and their kinetics and antimicrobial activity analyzes. The diameter of drug loaded HNT-Zein nanofibers were found 202,7±0,05–225,2±0,06 nm which is in the range of native skin collagen fibril (50-500 nm) than can mimic ECM. The water vapor permeability of the wound dressings is between 2833 and 2490 g/m2day which is found in the appropriate range for wound healing. Bilayer dressings reached 78% cumulative release at the end of 14 days and the release medium showed antimicrobial activity against E. coli and for S. epidermidis. In conclusion, the developed drug-loaded bilayer mat has been found as a potential candidate for wound dressings applications to treat the chronic infections.
Biofuels and biochemicals production from microalgae over solid catalysts
(Izmir Institute of Technology, 2020-07) Deliismail, Özgün; Şeker, Erol
The target of this study was the investigation of biofuel and/or biochemical production from microalgae in growth medium or its lipids over heterogenous catalyst. The primary aim was to study the conversion of 6 wt. % N. Oculata into biofuels without harvesting and dewatering over Ni-Al2O3-SiO2 catalyst at 80oC and 1 atm for 24 h. Solgel method was used to synthesize the catalyst by using the acids of H2SO4, HCl, and HNO3 to investigate the effect of acid type on catalytic activity. The catalyst prepared with H2SO4 yielded the highest conversion. The treatment of the catalyst prepared by H2SO4, with NaCl increased the conversion from 74 % to 91.5 % under same reaction conditions. The products included poly- or monosaccharides, esters and fatty acids. To achieve this conversion, Ni presence was significant beside total acidity of 25 µmol per gram of catalyst, and acidic strength ranging between 130-380oC. A new industrial application was proposed for direct conversion of 6 wt. % N. Oculata into biofuels at 80oC and 1 atm. The capacity of the plant was 1669 liters biofuel per year from 1064 liters microalgae solution per hour. The catalyst prepared with H2SO4 was used to coat either inner surface of tubes or 1-meter pluggable monoliths in tubular reactor having 20 m length and 1000 tubes each of which had 4 cm diameter. The microalgae solution was heated with Therminol®66 heated via parabolic troughs. For operation continuity, ~46000 kg of oil was stored in the tank at 120 o C for 12 h. The production of ethyl ester biodiesel from Spirulina sp. and N. Oculata lipids over 60 % CaO/Al2O3 was studied at 50oC and 1 atm. Ethanol: lipid molar ratio, catalyst amount and reaction time were investigated parameters to identify their effects on catalytic activity. The study showed that ~59 % biodiesel yield was obtained in the presence of the catalyst which was 6 wt. % of lipids, in 30 min. at ethanol: lipid molar ratio of 12 while 90 %-99 % yield was acquired at ethanol: lipid molar ratios of 24 and 48. To achieve these yields, weak basic strength in the form of bicarbonate was necessary while high basicity was not essential. Pure alumina and CaO did not yield any lipid conversion. Glycerolysis of triacylglycerol took place in series with reverse transesterification of triacylglycerol at catalyst amount which was 6 wt. % of lipids, ethanol: lipid molar ratio of 24 and 48, and 60 min. reaction time.
Biofuels production using starch over heterogeneous catalysts
(Izmir Institute of Technology, 2017-07) Uçaroğlu, Merve; Şeker, Erol
In this study, the effect of acidity and acidic strength on the product distribution in the hydrolysis of starch was investigated on mixed oxide supported Ni catalysts prepared using different types of metal oxides with varying compositions and, the calcination temperatures. SiO2/Al2O3 (mass ratios of 30/70, 50/50, 70/30) and ZnO/TiO2 (mass ratios of 10/90, 30/70, 50/50) catalysts were synthesized using a sol-gel method. For all the ratios and metal oxide types, Ni weight loading was 1%, 5.5% and 10%. The calcination temperatures used for all the SiO2/Al2O3 catalysts were 500 oC, 700 oC and 900 oC. The calcination temperatures used for all the ZnO/TiO2 catalysts were 300 oC, 400 oC and 500 oC. The starch hydrolysis reaction was carried out at 90 oC for the reaction time of 24 h. The concentration of the products was determined using HPLC and acidity/acidic strength of the catalyst were measured using NH3-TPD. This study showed that the product distribution was affected by catalyst compositions and calcination temperatures that resulted varying total acidity and acidic strength. Unidentifiable saccharides, maltotriose, xylose, and glucose were produced during the hydrolysis of starch on all the SiO2/Al2O3 supported Ni catalysts while there were only unidentifiable saccharides on all the ZnO/TiO2 supported Ni catalysts. The products distribution was found to strongly dependent on the nature of the acid type; for instance, Al2(SO4)3 crystalline phase was more active than the acid type on ZnO and TiO2 anatase crystalline phases. In addition, the glucose yield increased on the large Al2(SO4)3 crystallite sizes, e.g. the catalyst having 42 nm of Al2(SO4)3 crystallite size gave ~15% glucose yield whereas that having 10.5 nm of Al2(SO4)3 crystallite size gave 0%. Besides, acidic strength was more important than total acidity for the same acid type. In fact, the lower the acidic strength, such as located at 150 oC, higher the glucose yield was obtained.
Biolubricant production over sulfated TI-SBA-15 and TIO2-SIO2 based mesoporous catalysts
(01. Izmir Institute of Technology, 2022-05) Özperçin, Tuğçe; Yılmaz, Selahattin; 01. Izmir Institute of Technology
Production of ecofriendly biodegradable lubricants from vegetable oils is an attractive alternative to petroleum derived lubricants for environmental protection. This study presents an investigation for the production of biolubricants via ring opening reaction of epoxidized soybean oil using the mesoporous solid acid catalysts. SO4/SBA- 15, SO4/Ti-SBA-15, SO4/TiO2-SiO2 and SO4/La-TiO2-SiO2 catalysts were prepared and characterized. In addition, effect of increasing titanium content on SO4/Ti-SBA-15 (Si/Ti: 10, Si/Ti: 6) and effect of sulfation source (ammonium sulfate and chlorosulfonic acid) on Ti-SBA-15 and La-TiO2-SiO2 properties, activities and stabilities were studied. Activity and stability of all the catalysts were tested in the ring opening reactions of epoxidized soybean oil with 2-propanol at 80 oC with 10/1 alcohol-epoxide mol ratio. After determination of the two most stable and active catalysts, reactions were also performed with 2-ethylhexanol at 100 oC with 6/1 alcohol-epoxide mol ratio. Products were analyzed by titration, FTIR and H-NMR. Also, thermal stability and low temperature behavior of products were determined by thermogravimetric analysis and differential scanning calorimetry. Prepared catalsysts had mesoporous structure and stronger acid sites by attachment of sulfate groups The catalysts showed a serious leaching when they were sulfated with ammonium sulfate. On the other hand, chlorosulfonic acid treatment enhanced significantly stability of catalyst. Furthermore, increasing of titanium content and sulfation with chlorosulfonic acid increased the acidity of catalysts compared to ammonium sulfate. The SO4/Ti-SBA-15-6(CS) catalyst (Si/Ti:6 mole ratios and chlorosulfonic acid sulfated) was found as the most stable and active catalyst. It provided 62 % (12 h) and 90 % (18 h) conversion in the reactions with 2-propanol and 2-ethylhexanol, respectively. All products were found as thermally stable up to 300 oC showing that ring opening reaction did not affect thermal stability. Nevertheless, it affected positively low temperature properties and better low temperature properties were obtained from the products of reactions with 2-ethylhexanol. However, its influence on the products obtained from 2-propanol was not prominent.
Biosorption of aqueus Pb2+, Cd2+, and Ni2+ ions by Dunaliella salina, Oocystis sp., Porphyridium cruentum, and Scenedesmus protuberans prior to atomic spectrometric determination
(Izmir Institute of Technology, 2008) Karaca, Meral; Eroğlu, Ahmet Emin
In this study, the possibility of using four different algae for the sorption of heavy metals, namely, Pb, Cd, and Ni, from waters was investigated. Dunaliella salina, Oocystis sp., Porphyridium cruentum, and Scenedesmus protuberans were shown to be good candidates for the sorption/removal of the metals from waters prior to atomic spectrometric determination. Characterization of the algae was carried out by scanning electron microscopy, FTIR, elemental analysis, and thermogravimetric analysis.All biomasses behaved similarly in the optimization of sorption parameters.Solution pH of 6.0, sorbent amount of 10.0 mg for 10.0 mL sample volume, shaking time of 60 min, and reaction temperature of 25C were used in the sorption experiments. It was demonstrated that the primary sorption mechanism is the electrostatic attraction between the negatively charged functional groups on the surface of the biomass and the positively (+2) charged metal ions in the solution. Among the biomasses investigated, Dunaliella salina has shown the highest sorption capacity for all the metal ions. It was followed by Oocystis sp., Scenedesmus protuberans and Porphyridium cruentum. Additionally, the biomasses examined have demonstrated the highest affinity towards Pb2+ which was followed by Cd2+ and Ni2+.The competitive biosorption experiments have shown that the uptake of Pb2+ ions was not influenced by the presence of other ions for all the algae studied.However, the general trend for the other biomasses was a decrease in their sorption efficiency towards Cd2+ and Ni2+ ions with the increase in the concentration of the competitive ions.It can be proposed that the algal biomasses investigated in this study can be utilized successfully in the sorption and selective removal of the studied heavy metal ions from waters.
Catalytic conversion of glucose to alkyl glucosides
(Izmir Institute of Technology, 2020-06) Mutlu, Vahide Nuran; Yılmaz, Selahattin
In this study, it was pursued to develop acidic mesoporous catalysts for the synthesis of octyl glucosides. Butyl glucoside synthesis was used for catalyst screening. Tungstophosphoric acid (TPA) incorporated mesoporous silica (TPA-SBA-15), sulfated La incorporated titania-silica (SO4/La-TiO2-SiO2), organosulfonic acid functionalized mesoporous silica (Propyl-SO3-SBA-15), and sulfated mesoporous carbon (SO4/CMK-3) catalysts were prepared for this purpose. The effects of the active species (sulfates, tungstophosphoric acid and organosulfonic acid) and promoter (La) on the catalyst properties and activity were investigated. All the catalysts had mesoporous structure and high surface area. The acidity and acid site character varied depending on the catalyst type and amount of the active sites. La promoter was found effective to enhance the sulfation performance and to improve the stability of sulfates. The TPA-SBA-15 catalysts provided high glucose conversions (over 99%) and butyl glucoside yields (over 95%) due to their acidity, Keggin ion structure and pore size. The SO4/La-TiO2-SiO2 catalysts and SO4/CMK-3 catalysts were also active with glucose conversions of 74.4 % and 70 % respectively. The reaction parameters such as the reaction temperature (117 and 100 oC) and catalyst amount (20 and 30 wt% wrt. glucose) were studied in butyl glucoside synthesis over TPA-SBA-15 and SO4/La-TiO2-SiO2 which were the most active catalysts. These catalysts were found to be reusable in glycosidation with 1-butanol. Octyl glucoside synthesis was carried out via direct glycosidation. The octyl glucoside yields obtained over TPA-SBA-15 and SO4/La-TiO2-SiO2 catalysts were above 55 % and 43 % respectively. The catalysts were found promising for further investigations.
Catalytic methanol combustion
(Izmir Institute of Technology, 2015-07) Demirkaya, Emre; Şeker, Erol
Throughout this study, the major goal is to analyze the product distribution of methanol combustion at different reaction conditions, such as, varying space velocities, different initial temperatures, on 2% Pt/Al2O3 catalyst. The catalyst support material, alumina, was prepared by using a single-step sol-gel method and platinum was added by using the impregnation method. The reaction was conducted in a tubular reactor. In this work, the maximum steady state temperature at room temperature experiment was achieved almost same within the error for 2.4 s-1 and 2.8 s-1 space velocity for fresh catalyst, and also, the conversion to CO2 during the methanol combustion reaction for all the space velocities (2.4 s-1, 2.8 s-1 and 3.1 s-1) were found to be ~100%. Another parameter that was studied was the temperatures below the room temperature. The reaction was performed at -13oC, 0oC, 7oC and 15oC temperatures. With decreasing initial temperature, the steady state temperature was also found to be decrease. This was correlated with the product distribution and with decreasing initial temperature, CO2 conversion decrement was observed.. Methyl formate was detected to be the main byproduct that was produced under all the space velocities at temperatures lower than room temperatures. The catalyst was active even at -13oC. Therefore, it showed that it could be used as a catalyst for an external heater to provide necessary heat to reach the direct methanol fuel cells operating temperature at and below room temperature. Other than the other catalysts that was investigated in literature, our catalyst does not need to heat up the reactor. Once the fuel is supplied, the system reaches the necessary operating temperature by itself. This is desirable especially in portable DMFCs. The catalytic methanol combustion system investigated in this study seems to be promising to easily replace the lithium-ion batteries for portable electronic systems, especially ones used in the military.
Catalytic oxidation of volatile compounds generated during frying process using sunflower oil
(Izmir Institute of Technology, 2014) Aytaç, Arda; Şeker, Erol
The main goal of this study is to investigate the effect of metal type, metal oxide type and metal/oxide loading on the conversion as a function of temperature for the combustion of sunflower oil over modified single step sol-gel made Al2O3 supported metal and mixed metal oxides. All catalysts were tested at 170 oC and catalysts giving good activity among them were tested also at 195 oC. As a monometallic catalysts, Ni/Al2O3 (10, 25, 50 % Ni loaded), Ni/Al2O3 (50 % Ni loaded) derived from different Ni precursors, Mn/Al2O3 (50, 70 % Mn loaded) and as a bimetallic catalysts, Ni- Mn2O3/Al2O3 with Ni/Mn mass ratios of 20:56 and 23:66 catalysts were synthesized by a modified single step sol-gel method. In addition, in synthesizing step of bimetallic catalysts, the order of adding precursor was studied. The catalytic activities of all the catalysts were compared to 3% Pt/alumina. The combustion performances of pure Al2O3 and catalyst coated aluminum plates were also considered and volatile compound analysis was monitored by GC-MS and the amounts of CO and CO2 generated during the combustion were calculated quantitatively from GC analyses. The characterization of the samples was performed by XRD and BET techniques and it was observed that among the monometallic oxide catalysts, 50% MnxOy/Al2O3 showed slightly better activity at 170 oC due to the its highly reducible oxide property. Among mixed metal/metal oxide catalysts, 20% Ni/56% Mn2O3/Al2O3 (First Ni precursor added) was the catalyst demonstrated the highest catalytic activity at both temperatures. It seems to be due to the interaction between nickel and manganese oxide. In addition, the combustion was also carried out by using catalyst coated aluminum plates to observe if the best catalyst formulation found from the studies on the powder catalysts would be applicable for the self-cleaning metal plates used in the household ovens. In fact, the catalyst coated plates showed higher conversion at 170 oC in 1 h than that observed on the powder catalyst due to the elimination of internal mass transfer limitation.
Cation exchange (Ag+, Zn2+, Cu2+) behavior of natural zeolites
(Izmir Institute of Technology, 2001) Top, Ayben; Ülkü, Semra
In this study, clinoptilolite, most abundant zeolite present in nature, was proposed as a low cost antibacterial material. As a preliminary work, antibacterial activities of the original, Ag, and Zn forms of the clinoptilolite were investigated against several strains and compared to the commercial antibiotics. No antibacterial action was observed for the original clinoptilolite. Ag loaded clinoptilolite was found to be superior to the Zn-form against Proteus spp. and Pseudomonas aeruginosa.The original, Na, Ag, Zn, and Cu forms of the clinoptilolite samples were characterized by FTIR spectroscopy, thermal analyses (TGA, DTA, and DSC), and N2 physisorption studies. Specific attention was given in to the chemical analysis of the clinoptilolite by ICP-AES. Using the standard addition method, the respective idealized formulas of the original and Na-clinoptilolite based on 72 oxygen atoms in the unit cell were calculated as:(Na0.816 K2.070) (Ca1.060 Mg0.264) (Al5.653 Fe0.390) (Si30.084) O72. 20.023 H2O, and (Na4.763 K1.057) (Ca0.076 Mg0.094) (Al5.843 Fe0.221) (Si29.911) O72.17.049 H2O.In the FTIR spectra of the original and exchanged forms of the clinoptilolite, considerable shifts (from 3460 to 3494.8 cm-1) were observed in the band, which is formed due to the interactions of water molecules with the framework via hydrogen bonds. The positions of the other bands were not affected by cation exchange significantly. From the TGA curves, the water contents ranged between 14.31 and 11.00 % for the original and the cation-exchanged forms of the clinoptilolite. Mainly, two endotherms and one exotherm were obtained in the DTA curves. The first endotherm occurred up to about 150 oC, the second endotherm lied between 200 and 700 oC, and the exotherm was obtained at about 850 oC. Significant differences observed between the shapes of the DSC curves indicated that the cations control the dehydration behavior of the samples. N2 physisorption isotherms of five samples were all, Type IV with BET surface areas ranging between 34.97 and 46.76 m2/g.Ag, Zn and Cu ion exchange equilibria were investigated at 25 oC for both the original clinoptilolite and Na-clinoptilolite. In the former case, from the plateau of the isotherms cation exchange capacities were determined as 1.184, 0.439, 0.539 meq/g clinoptilolite for Ag+, Zn2+, and Cu2+ respectively. The major portion of the exchanges was contributed by Na+ and Ca2+. Distribution coefficient values indicated that at Ag, Zn and Cu ion exchange equilibria were investigated at 25 oC for both the original clinoptilolite and Na-clinoptilolite. In the former case, from the plateau of the isotherms cation exchange capacities were determined as 1.184, 0.439, 0.539 meq/g clinoptilolite for Ag+, Zn2+, and Cu2+ respectively. The major portion of the exchanges was contributed by Na+ and Ca2+. Distribution coefficient values indicated that at relatively low initial concentrations, the preference of the clinoptilolite for Zn2+ and Cu2+ was significant. At higher concentrations, higher distribution coefficients were obtained for Ag+ compared to Zn2+ and Cu2+. Langmuir and Freundlich models were applied for each equilibrium data. For Zn2+ and Cu2+ exchanges, Langmuir model gave better correlation and Freundlich model fitted experimental data slightly better in the case of Ag+ exchange.Equilibrium isotherms for Ag+-Na+, Zn2+-Na+, and Cu2+-Na+ pairs were investigated. Silver exchange isotherm lied above the diagonal over the whole composition range. For zinc and copper exchanges, the isotherms were above the diagonal up to equivalent fractions of exchanging ion in solution phase (As) at about 0.2. While full exchange was attained for silver, partial exchanges were obtained in the case of zinc and copper. The standard free energy of exchange values were found as .6.0, 2.03 and 3.09 kj/equiv for Ag+-Na+, Zn2+-Na+, and Cu2+-Na+ pairs respectively. From these values selectivity sequence was obtained as Ag+ > Na+ > Zn2+ > Cu2+.Consequently, by considering the preliminary antibacterial activity results, specific cation exchange capacities, and selectivity sequence of the clinoptilolite, Ag-clinoptilolite seemed to be promising antibacterial material. The results of the current study compared to the literature data pointed out that cation exchange behavior of the clinoptilolite is dependent on its original cationic composition. Therefore, it is necessary to carry out specific studies on representative samples from the deposit before any practical application.
Characterization of pigments used in the execution of wall paintings in Kadıkalesi
(Izmir Institute of Technology, 2010) Demir, Serap; Böke, Hasan
Since prehistoric times wall paintings have been remarkable symbols of existences, identities, cultures and life-styles of human beings and societies and considerable integral parts of art and architecture. In this context, determination of painting techniques and materials employed and deterioration problems of the wall paintings, as of being part of built cultural heritage, have been crucial in terms of conservation. In this study, wall paintings existing in the Byzantine church-monastery edifice which have been uncovered in Kadıkalesi (Anaia) archaeological site were investigated for the purpose of identification of the original materials and painting technique. Mineralogical, chemical and micro-structural characteristic of the pigments and binding mediums employed in the fabrication of paintings; and basic physical properties, raw material compositions, mineralogical, chemical and micro-structural features of surface renderings underlying the painting layers were established. In the analyses, X-Ray diffraction (XRD), scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), optical microscope, Fourier transform infra-red (FT-IR) spectroscopy and thermo-gravimetric analyzer (TGA) were used. On the basis of analyses results, it was determined that lime-secco technique was used in the fabrication of the investigated wall painting fragments; pigments were applied after mixed with lime (generally dolomitic lime) as binder on the surface of dry fine plaster. The density and porosity values of the fine plasters which paintings were executed are 1.20 g/cm3 and 40 % by volume respectively. The fine plasters were constructed with pure lime with small amount of soil material. Iron oxide-based pigments in red, yellow and purple paintings and aluminosilicate-based pigments; such as celadonite, glauconite in green paintings, lazurite and glaucophane in blue and dark blue paintings were employed.
A chromatographicstudy of carbon monoxide adsorption in clinoptilolite
(Izmir Institute of Technology, 2001) Narin, Güler; Ülkü, Semra
Adsorption equilibrium and kinetic parameters for CO/clinoptilolite adsorbate/adsorbent pair were determined by perturbation gas chromatography. Chromatographic experiments were performed at temperatures in the 60-120°C range and at carrier gas flow rates in the range of 10.31-24.36 em/sec. The chromatographic response peaks were obtained by concentration pulse method. A packed column of 10 em length and 0.46 em inlet diameter which was packed with clinoptilolite particles with narrow size distribution (500-850 §) around mean diameter of301.9 § was used. The clinopti10lite particles were excavated from Gordes, Western Anatolia. The moments of the response peaks were calculated by integration of experimental chromatographic data and matched to the .model parameters in order to determine the equilibrium constants and diffusion coefficients. The dynamic model (Haynes and Sarma, 1973) was applied to describe the adsorption and diffusion processes in the packed column. This model includes axial dispersion, external mass transfer resistance, micropore and mesopore diffusion resistances. The equilibrium constants (Henry's law constants, K) were calculated in the range of 40 - 952 and were found to be in good agreement with the results in the literature. These constants were found to decrease with increasing temperature. The heats of adsorption were obtained in the range of 54.15 - 57.14 kl/mol from the slope of van't Hoff plots and compared with those in the literature. The heats of adsorption were found to be lower than those reported in the literature obtained for the same adsorbate/adsorbent pair. The higher heats of adsorption were explained by the smaller pore size, higher cation content of the clinoptilolite and more accessibility of the cations in the clinoptilolite framework by CO molecules. Heats of adsorption remained almost constant over the carrier gas velocity range studied. The contributions of axial dispersion and other mass transfer resistances Indiffusion of CO in clinoptilolite were also determined. The total dispersion exhibited slight change (average 0.035 see) with temperature implying that the micropore diffusional resistance was not dominant for diffusion of CO in clinoptilolite under the experimental conditions studied. The axial dispersion coefficient was determined in the range of 1.149.88 cm2/sec and the total mass transfer resistances were found between 0,02-0.06 sec. The results showed that the mesopore diffusion resistance was the controlling mechanism in CO diffusion in clinoptilolite. Mesopore diffusion coefficient was estimated as 2.98xlO-3 cm2/sec. This value was in good agreement with the theoretically determined value.

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