Throughout this thesis work, various catalysts were investigated with combinational approach to develop highly active and selective novel catalysts for direct epoxidation of propylene to PO using molecular oxygen. The promoted and un-promoted silver (Ag), copper (Cu), ruthenium (Ru), manganese (Mn) mono and multimetallic catalytic systems over different silica supports were prepared via sol-gel method and incipient wetness method. In addition to support effect, the effects of different promoters on the catalytic performances of these catalyst candidates were investigated. The study showed that commercial silica (c-SiO2) is the most effective support when compared to silica (SiO2) and silica synthesized with templete (t-SiO2). Among bimetallic catalytic systems containing Ag, Ru, Mn and Cu metals, c-SiO2 supported Cu-Ru catalyst was determined as the most active catalytic system. In addition, the most effective v catalyst and promoter in the epoxidation reaction was determined as NaCI promoted Cu-Ru catalyst supported over c-SiO2 with 35.98% selectivity&amp / 9.55% conversion (3.44% yield) at 3000C and 0.5 feed gas ratio (C3H6/O2).. In the study, the selected catalysts showed low and high PO productivity were also investigated by characterization techniques such as XRD, XPS, BET and FTIR.It was inferred from characterization tests that bimetallic systems reveal a synergistic behavior by exposing more active sites on the silica support material with respect to their monometallic counterparts. Besides, NaCl catalytic promoter has a strong interaction particularly with the Cu sites on the Cu/Ru/SiO2 catalyst surface, altering the electronic structure of Cu sites that favors to PO production.

The plastic mulch films, which are mostly made from LDPE, are used in order to increase the yields and to prevent the weed growth by covering the top of the soil by leaves or straw in nature. After a period, the mulch films turn into unmanageable quantities of soiled plastic films, which cause an environmental problem. Using degradable mulch films for agricultural purposes can be a solution for the environmental problems caused by the plastic mulch films. In this study, to introduce biodegradability to mulch films, a natural biopolymer starch was used. Before blending, starch was transformed into thermoplastic starch in order to make the starch processable. The need, to provide adhesion and interaction between thermoplastic starch and LDPE, citric and stearic acid were considered as compatibilizers. To accelerate the degradation of the LDPE matrix, three pro-oxidants cobalt(II) acetylacetonate, iron(III) stearate and manganase(II) stearate were used. The films prepared were characterized by FTIR spectroscopy / their thermal and mechanical properties were analyzed and buried under soil. The films recovered from soil after 76 days were characterized by FTIR spectroscopy, their weight loss were measured and their thermal and mechanical properties were analyzed. Studies showed that the use of cobalt(II) acetylacetonate gave improved results in terms of the mechanical properties and thermal stabilities of the films. Additionally, it is observed that the use of citric acid as a compatibilizer improved the thermal stabilities of starch in the films. Lastly, it is observed that the mechanical properties of the films were affected by the interactions between compatibilizers and pro-oxidants.

This study aims efficient conversion of cotton stalks to cellulosic ethanol through ionic liquid pretreatment and enhanced enzymatic hydrolysis. Among several ionic liquids, EMIMAc exhibited the most striking impact on cotton stalks with respect to the changes in biomass structure and digestibility. Cotton stalks, which were subjected to EMIMAc pretreatment at 10% (w cotton stalks/w EMIMAc) of biomass loading and 150&deg / C for 30 minutes, were found to be 9 times more digestible than untreated cotton stalks. Besides, glucose and ethanol yields, which were based on the cellulose content of untreated cotton stalks, were found as 67% and 66%, respectively. These yields were insufficient regarding efficient conversion of the cellulosic portion of cotton stalks to glucose and ethanol which is linked to the superior solvation capability of EMIMAc towards biomass. In order to enhance aforementioned yields, EMIMAc pretreatment was conducted at 30% of biomass loading. Though lignin extracted was much lower, higher yields were obtained compared to the former case since 96% of cellulose was recovered upon EMIMAc pretreatment and reduced crystallinity was observed for pretreated biomass. Glucose yield was achieved as 84% even at a substrate loading of 15% (w/v). Additionally, 76% of ethanol yield and 3% (v/v) of ethanol titer were obtained upon fermentation. Accordingly, reduction in biomass crystallinity was satisfactory to improve enzymatic accessibility of the biomass. Besides, EMIMAc maintained its effectiveness as a pretreatment agent upon recycling since no change in terms of hydrolysis of pretreated samples was observed upon EMIMAc recycling for three times.

In this study, conjugated monomers containing fluorene units / 2-(9,9-dihexyl-2-(thiophen-2-yl)-9H-fluoren-7-yl)thiophene (TFT) and 5-(9,9-dihexyl-2-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9H-fluoren-7-yl)-2,3dihydrothieno[3,4b ][1,4] dioxine (EFE) were synthesized on the basis of donor-acceptor-donor approach and their electrochemical polymerization were achieved via potential cycling. Optical and electrochemical properties of their corresponding polymers, poly(2-(9,9-dihexyl-2-(thiophen-2-yl)-9H-fluoren-7-yl)thiophene) PTFT, and poly(5-(9,9-dihexyl-2-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9H-fluoren-7-yl)-2,3dihydrothieno[3,4b ][1,4] dioxine) PEFE, were investigated and it was found that polymer films exhibited quasi-reversible redox behavior (Epox= 1.10 V for PTFT, Epox = 0.70 V and 1.00 V for PEFE) accompanied with a reversible electrochromic behavior, yellow to dark green for PTFT, yellow to parliament blue for PEFE. Their band gap values (Eg) were found to be 2.36 eV and 2.26 eV for PTFT and PEFE, respectively. Furthermore, gold nanoparticles (AuNP) were prepared and their interaction with polymer films, PTFT and PEFE, were investigated using spectroscopic techniques. The fluorescence properties of the polymers and their composites, prepared by the interaction of AuNP with polymers, were also investigated.

ABSTRACT STEREOSELECTIVE SYNTHESIS OF OPTICALLY ACTIVE CYCLITOL PRECURSORS VIA CHEMOENZYMATIC METHOD AND SYNTHESIS OF A NUCLEOSIDE PRECURSOR Oguzkaya, Funda M.S., Department of Chemistry Supervisor: Prof. Dr. Cihangir Tanyeli June 2006, 99 pages &amp / #945 / &#039 / -acetoxylation of &amp / #945 / ,&szlig / -unsaturated cyclic ketones was adjusted via Mn(OAc)3 in regioselective manner. Then, PLE hydrolysis was carried out so as to afford enantiomerically enriched &amp / #945 / &#039 / -acetoxylated and &amp / #945 / &#039 / -hydroxylated cyclic compounds. From our knowledge about the literature and previous works dealing with &amp / #945 / &#039 / -hydroxylated products which are easily racemized, protection was directly adjusted via acetylation so as to prevent this possibility. Resulting enantiomerically enriched products were subjected to Upjohn Dihydroxylation to obtain cyclitol precursors and following Luche Reduction of ketone was adjusted so as to obtain corresponding cyclitols. In addition with such synthetic design, firstly dimethyl cyclopent-3-ene-1,1-dicarboxylate was obtained so as to reach in former manner 3-cyclopentene-1,1-dicarboxylic acid, and in latter manner cyclopent-3-enecarboxylic acid. Resulting compound was converted to 6-iodo-2-oxa-bicyclo[2.2.1]heptan-3-one and followingly to the target nucleoside precursor which is 2-oxa-bicyclo[2.2.1]hept-5-en-3-one.

Co and Pb are soft oxides, making them useful in partial oxidation catalysis. But it is difficult to prepare high surface area, nanometer size particles due to the low melting point of Pb. In the present study, SBA-15 samples are incorporated with Co and/or Pb at different weight loadings to provide a controlled geometry in nanometer scale via using direct synthesis method. The characterization of the synthesized samples was done by XRD, N2 adsorption isotherms, TEM images and XPS analysis. The increase in the metal loading in SBA-15 causes a decrease in the BET surface area due to the filling of pores with metal atoms. No characteristic peaks of metal oxide was observed up to 15 wt %Pb loading into SBA-15 in the large angle XRD pattern indicating that metal particles are dispersed in the SiO2 structure without accumulating and forming crystals. However, 20 wt%Pb loaded SBA-15 showed more appreciable characteristic peaks, indicating appreciable quantities of crystallites of metal oxide on the surface of silica. The introduction of high amount of cobalt and lead oxides to SBA-15 resulted in the loss of long range order of pores according to the low angle XRD patterns. The hexagonal structure of pores of SBA-15 was v confirmed by TEM images for all samples. XPS analysis indicated that binding energies of O 1s and Si 2p are almost similar in Co or Pb loaded samples, while mixed oxide loaded samples showed slightly higher binding energies which means the structure grows into a different type.

Glass has been used to make a variety of artifacts including bottles, drinking cups, vessels, window glasses, beads and bracelets. Although occasional glass bracelets were dated back to 2000 BC, large scale manufacture of glass bracelets was encountered in Central Europe in the last centuries of 1000BC. During the excavations of Mezraa H&ouml / y&uuml / k (Birecik-Sanliurfa) in 2000-20002, a number of glass bracelets were unearthed that belongs to 13th century AD. On going excavations of Mersin Yumuktepe also give quite a lot of 11th-12th centuries Byzantine glass bracelets. In this study a group of those bracelets was started to be examined. After technical drawings, color identification had been carried out by using Munsell color chart. Thin sections of some samples of Mezraa H&ouml / y&uuml / k have been prepared and then observed by an optical microscope in Mineral Research and Exploration (MTA). Observation of thin sections showed the amorphous structure of glass with some impurities and gas bubbles. On some samples deteriorated surface layers were present. XRD traces of those layers showed the typical amorphous background of glass in which no crystalline phase is present. Elemental analysis of the samples has been done using ICP-OES method in METU Central Laboratory. In the analysis major (except SiO2), minor and some trace elements were determined. ICP-OES data showed that glass bracelet samples studied are of soda-lime-silica glass. But percentage of Na2O is less than expected from typical composition of soda-lime-silica glass / being 10.5 wt % as average. This might be due to removal of Na ions from the glass network because of leaching under burial conditions. Concentration of Al2O3 in the samples of Mezraa H&ouml / y&uuml / k is almost same. This may be due to the using one type of quartz sand in bracelet production. Color producing elements seem to be Fe, Mn and Cu.

Polymerization reaction is carried out by the reaction of 2,4,6 trichlorophenol with sodium hydroxide, in the presence of small amount of water by microwave initiation. Synthesis of polymers were successfully performed under microwave enegy. The use of microwave energy was due to advantages of shorter processing time. The main focus of attention was the 90 to 600 watt microwave energy. Polymerizations were performed with different time intervals by keeping the microwave energy and water content constant / or with different energy levels by keeping the time interval and water content constant / or by varying the amount of water by keeping the time and energy level constant.Beside poly(dichlorophenylene oxide), conducting polymer, ion-radical polymer, crosslinked polymer were also be successfully synthesized and characterized. Characterizations of the products were performed by FTIR, 1H-NMR, 13C-NMR, DSC, TGA and elemental analysis. Molecular weight distribution was measured by PL-GPC 220 Polymer Laboratories Instrument. Conductivity measurements were performed by four probe technique.

The present study aims to investigate the composition of historical plasters to get information about their material characteristics and their technology. Plaster samples were obtained from four Ankara Citadel houses built in late Ottoman period. In order to determine the raw material characteristics and mineralogical properties of plasters / chemical analyses, optical observation of cross sections, petrographic analyses of thin sections, elemental analyses by ICP-OES, X-ray powder diffraction analyses for the determination of mineral phases, thermogravimetric analyses and FTIR analyses were carried out. Interpretation of all the analytical examination was used to understand the composition and unique character of plaster samples studied. Observation of thin sections revealed more plaster layers than those observed in cross sections. Up to twelve layers could be observed with different colours, such as blue, red, yellow, green, white and brown. Generally, thicknesses of white plaster layers were found to be thicker than the others. In two samples, two black boundaries between plaster layers were identified which could be an indication of the use of asphalt for isolation purposes, like dampness proofing or heat insulation. Soluble salt contents of the plaster samples were in the range 3.04%-9.22%, with an average being 6.62%. The anions identified were Cl-, SO42-. In few samples, PO43-, NO2- and NO3- were found. Binder was found to be lime and gypsum. The amount of binder in terms of total calcium oxide, CaO, was found to be in the range of 33.5-43.6%, with an average being 37.9%. Amount of aggregate was about 62.1% as average. The main minerals identified in plaster samples were calcite and gypsum. Gypsum might be added to increase the strength of the plaster. Beside calcite and gypsum, quartz and pozzolanic activity related mineral, Opal-A, were found in some of the samples. In red plaster layers hematite mineral was also identified. Other colour effective elements were found to be Fe, Sb, Mn, Cu, Cr and Ni. Presence of organic additives was observed but clear identification was not established.

Ion exchange of heavy metals with zeolites is important in terms of different application areas. Industrial wastewater treatment and antibacterial applications are two essential areas that have taken great attention. While silver, zinc and copper are well known for their toxicity, they are also used as antibacterial agents in zeolites. The objective of this study is to investigate the single and multicomponent ion exchange behavior of zeolite 4A for silver, zinc, copper and sodium ions. For this purpose Ag+-Na+, Zn2+-Na+, Cu2+-Na+ binary systems and Ag+-Zn2+-Na+, Ag+-Cu2+-Na+, Cu2+-Zn2+-Na+ ternary systems were investigated in batch systems at 25&deg / C and 0.1 N. Binary ion exchange isotherms indicate that zeolite 4A has high selectivity for silver, zinc and copper with respect to sodium. All exchange isotherms lie above the diagonal over the whole range. Using the equilibrium data, the thermodynamic analysis of the binary systems were carried out. The thermodynamic equilibrium constants and the standard free energies of exchange were calculated as 340.9 and -14.5 kJ/mol for silver-sodium system, 40.5 and -4.6 kJ/mol for zinc-sodium system, and 161.2 and -6.3 kJ/mol for copper-sodium system, respectively. From these values, selectivity sequence of zeolite 4A was determined as Ag+ &gt / Cu2+ &gt / Zn2+. This selectivity sequence was also verified by the results of ternary ion exchange experiments. The experimental data were compared with the Langmuir and Freundlich isotherms. While Freundlich model gives a better correlation for Ag+-Na+ and Zn2+-Na+ exchange, Langmuir model represents a better fit to the experimental data of Cu2+-Na+ exchange.