Laboratory and modeling studies were performed with a mixed-anaerobic-culture obtained from the Evanite site in Corvallis, Oregon. The culture completely transforms trichloroethene (TCE) to cis-dichloroethene (c-DCE), vinyl chloride (VC), and finally to ethene. Acetylene inhibition studies were used to examine the culture's microbial activities. Kinetic studies determined the half-saturated constant (K[subscript s]), the maximum utilization rate (k[subscript max]X), and inhibition constants (K[subscript I]). The kinetic constants were used to model the results of inhibition studies using competitive and uncompetitive inhibition models. Acetylene was found to function as a reversible inhibitor and was used to probe the activities of reductive dechlorination. Various acetylene concentrations were used to differentiate microbial processes, including methanogenesis, acetogenesis, and halorespiration. Acetylene concentrations of 48, 192, and 12 ��M, respectively, were required to achieve 90% inhibition in the rates of methanogenesis, TCE and VC transformation. H���-dependent acetate production was not inhibited by acetylene. K[subscript s] values for TCE and VC were 12 ��M and 63 ��M, respectively. Model fitting of acetylene inhibition constants (K[subscript IC]) for TCE and VC transformations yielded the same value (0.4 ��M) for a competitive inhibition model. However, for uncompetitive inhibition the estimated K[subscript IU] for TCE to c-DCE, TCE to 1,1-DCE and VC to ethene were 13.3, 14.1 and 2.2 ��M, respectively. Competitive and uncompetitive inhibition models simulated experimental data equally well for results obtained at high TCE and VC concentrations. The models were further verified to fit transient data of acetylene inhibition at lower TCE and VC concentrations, and competitive inhibition resulted in a better fit to the experimental data. 1-chloro-1-fluoroethene (1,1-CFE) was found to track the rate of VC transformation well, since VC and 1,1-CFE had similar maximum transformation rates and K[subscript s] values. A competitive inhibition model with the measured K[subscript s] values, 63 and 87 ��M. was used to predict the rates of VC and 1,1-CFE transformation, respectively. The similar rates and results of acetylene and compound inhibition studies indicated VC and 1,1-CFE were transformed by the same enzyme. 1,1-CFE transformation by three different cultures, clearly demonstrate that 1,1-CFE was an excellent surrogate to track rates of VC transformation. / Graduation date: 2004

Carbon is a fascinating element which can be observed in a large variety of morphologies and atomic structures due to its chemical ability to form different hybridizations. The present PhD thesis proposes the synthesis of several carbon-based materials using a unique and quite simple technique: the oxy-acetylene combustion flame method. From crystalline sp3- diamond to planar sp2- graphite, from the unidirectional nanotubes, needles and rods to bidimensional petals, a large variety of carbon materials are synthesized under the atmospheric pressure. These various carbon forms have been produced using a set of different experimental parameters. Both the input gas ratio and the substrate temperature are found to play a key role in the synthesis of these new carbon materials. The high quality of the graphitic phases can be correlated to the large acetylene content in the gas and to the high temperature of the substrate. Some specific morphologies such as petal-like single graphite crystals have been synthesized. Their sizes reach up to 20 mm. These bidimensional carbon materials are of particular importance to investigate fundamental physics in ideal low-dimensional systems. Polyhedral graphite crystals, which exhibit a unidirectional morphology, have also been produced. Their crystal structure is found to be highly graphitic although they display a cylindrical/polyhedral shape. Preliminary measurements of their field emission properties reveal a huge emission current, which is higher than the emission current obtained for multi-wall carbon nanotubes. The latter have also been synthesized in large amount and high quality using our oxy-acetylene combustion flame technique. At last, using again the same experimental set-up, a crystalline carbon nitride phase has been synthesized for the first time using a specific molecule called “melamine” as an organic precursor. Several experimental techniques, such as Energy Dispersive X-ray (EDX), X-ray Photoelectron Spectroscopy (XPS), Electron Energy Loss Spectroscopy (EELS), X-ray diffraction and Raman and infra-red spectroscopies have been used to analyze both the chemical composition and the crystalline structure of this new material, revealing a graphitic-C3N4 phase.

Utilization of natural gas in remote locations necessitates on-site conversion of methane into liquid fuels or high value products. The first step in forming high value products is the production of ethylene and acetylene. Non-thermal plasmas, due to their unique nonequilibrium characteristics, offer advantages over traditional methods of methane reforming. Different kinds of non-thermal plasmas are being investigated for methane reforming. Parameters of these processes like flow rate, discharge size, temperature and other variables determine efficiency of conversion. An efficient process is identified by a high yield and low specific energy of production for the desired product. A study of previous work reveals that higher energy density systems are more efficient for methane conversion to higher hydrocarbons as compared to low energy density systems. Some of the best results were found to be in the regime of warm discharges. Thermal equilibrium studies indicate that higher yields of ethylene are possible with an optimal control of reaction kinetics and fast quenching. With this idea, two different glow discharge reactor systems are designed and constructed for investigation of methane reforming. A counter flow micro plasma discharge system was used to investigate the trends of methane reforming products and the control parameters were optimized to get best possible ethylene yields while minimizing its specific energy. Later a magnetic glow discharge system is used and better results are obtained. Energy costs lower than thermal equilibrium calculations were achieved with magnetic glow discharge systems for both ethylene and acetylene. Yields are obtained from measurements of product concentrations using gas chromatography and power measurements are done using oscilloscope. Energy balance and mass balances are performed for product measurement accuracy and carbon deposition calculations. Carbon deposition is minimized through control of the temperature and residence time conditions in magnetic glow discharges. Ethylene production is observed to have lower specific energies at higher powers and lower flow rates in both reactors. An ethylene selectivity of 40 percent is achieved at an energy cost of 458MJ/Kg and an input energy cost of 5 MJ/Kg of methane.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 80-85).

Thesis (M.B.A.)--University of Hong Kong, 1985.

published_or_final_version / Chemistry / Master / Master of Philosophy

19 Dec 2004. / Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 1948" Jamie Marie Rintelman. 12/19/2004. Report is also available in paper and microfiche from NTIS.

La cémentation gazeuse à basse pression est un procédé de traitement de surface qui consiste à renforcer des pièces en acier par diffusion d’atomes de carbone provenant de la pyrolyse d’hydrocarbures gazeux. Une partie de l’hydrocarbure craqué est adsorbée sur le métal mais une autre partie réagit en phase gazeuse et conduit, entre autres, à la formation de HAP. Or, de nombreux HAP sont toxiques, voire cancérigènes, et les salariés en charge du nettoyage ou de la maintenance des fours de cémentation peuvent y être exposés. Des expériences de pyrolyse d’acétylène ont été réalisées à 900°C et 8 kPa, conditions proches de celles des procédés de cémentation gazeuse à basse pression. Un réacteur auto-agité par jets gazeux et des réacteurs tubulaires ont été utilisés. A la sortie de la zone réactionnelle, les produits de la pyrolyse ont été analysés. Entre autres, 16 HAP considérés comme des polluants prioritaires par l’Agence de Protection de l’Environnement aux Etats-Unis (US EPA) ont été observés. L’influence du taux de dilution du réactif en entrée et du temps de passage dans le réacteur a été étudiée. Les résultats expérimentaux ont été comparés à ceux obtenus avec un modèle cinétique détaillé. Ce modèle a été développé dans le but de décrire la formation des HAP lors de la pyrolyse d’hydrocarbures légers. Une attention particulière a été portée aux voies de formation des premiers cycles aromatiques et des 16 HAP de la liste de l’EPA. En plus des données expérimentales obtenues dans le cadre de cette étude, le modèle a été validé à partir de données expérimentales de la littérature. Le but de l’étude est de comprendre les phénomènes de formation et de croissance des HAP afin de trouver des conditions opératoires permettant de rendre plus surs les procédés de cémentation gazeuse à basse pression / Low-pressure gas carburizing is a heat treatment process used to harden surface of steel by enriching the metal with carbon atoms coming from pyrolysis of hydrocarbons. At the same time, a wide variety of molecules and radicals are also formed in the gas phase. They react together, leading to the formation of PAHs. PAHs are toxic and even carcinogenic, and activities such as furnace maintenance may thus represent a risk to workers. Experiments of acetylene pyrolysis were carried out in conditions close to low-pressure gas carburizing processes, at 900°C and 8 kPa. Two kinds of reactors were used: a jet stirred reactor and tubular reactors. At the outlet of the reaction zone, products of pyrolysis were analyzed. Among other products, 16 PAHs classified as priority pollutants by the United States Environmental Protection Agency (US EPA) were observed. Influence of residence time and of reactant dilution was studied. Experimental results were compared to those obtained with a detailed kinetic model. This model was developed in order to describe PAH formation during light hydrocarbon pyrolysis. The focus was placed on formation pathways of the first aromatic rings and of the 16 EPA-PAHs. In addition to the experimental data obtained in this study, the model was validated using experimental data from the literature. The aim of the study is to understand the phenomena of PAH formation and growth in order to find operating conditions to make safer the low-pressure gas carburizing processes

O objetivo deste trabalho foi iniciar o estudo de uma nova metodologia sintética para a obtenção do sistema 11-oxabiciclo[6.2.1]undecano, o esqueleto estrutural básico de uma classe de produtos naturais conhecidos como furanoeliangolidos. A abordagem sintética proposta envolveria a formação de um composto bicíclico através da reação de Diels-Alder com derivados de furano, seguida pela formação de um hexanel e, finalmente, ruptura de uma ligação central para formação do sistema macrocíclico. Além disso, a reação de Diels-Alder entre derivados de furano e acetileno dará origem a compostos que apresentam como esqueleto estrutural o sistema 7-oxabiciclo[2.2.1]heptano, que podem ser utilizados como material de partida para a síntese de diversos produtos naturais. Iniciamos este estudo com a reação de Diels-Alder entre o 3,4-dimetoxi-2-metil furano e o bromopropiolato de metila, onde foi obtido o produto 85, que após algumas modificações deu origem ao composto 92. Entretanto, após inúmeras tentativas não conseguimos transformar o composto 92 no triciclo desejado. Para evitar essas transformações que se mostraram problemáticas, resolvemos estudar a reação de Diels-Alder entre derivados de furano e benzoquinonas 2,5-dissubstituídas, que dará origem aos adutos devidamente funcionalizados para serem transformados no derivado do sistema 11-oxabiciclo [6.2.1]undecano. No entanto, após o estudo dessas reações de cicloadição, observamos que elas têm o equilíbrio fortemente deslocado no sentido dos materiais de partida. Por esse motivo, a continuidade desta metodologia sintética mostrou ser inviável. Iniciamos então, um estudo da reação de Diels-Alder entre os diverso derivados de furanos e acetilenos. Após o estudo dessas reações de Diels-Alder foi possível verificar que a maioria dos adutos derivados dos furanos é instável no meio reacional. Os melhores resultados obtidos nessas reações de Diels-Alder foram usando o acetilenodicarboxilato de dimetila como dienófilo. Os adutos obtidos são intermediários importantes e bem funcionalizados, que podem ser utilizados na continuidade do estudo de desenvolvimento de nova metodologia sintética para a obtenção do sistema 11-oxabiciclo[6.2.1]undecano / The aim of this work was to start the study of a new methodology to synthesize the 11-oxabicycle[6.2.1]undecane system, the main carbon skeleton of the furanoheliangolides. The proposed synthetic approach involves the preparation of a bicyclic compound through a Diels-Alder reaction with furan derivatives, followed by formation of a six membered ring and, finally, cleavage of the central bond to obtain of the macrocyclic system. The Diels-Alder reaction between furan and acetylene derivatives gives a compound with the 7-oxabicyclico[2.2.1]heptane system, that is a potential starting material for the synthesis of several natural products. We started this study with the Diels-Alder reaction between the 3,4-dimethoxy-2-methylfuran and methyl bromopropiolate, and obtained the product 85 that after some modifications furnished the compound 92. However, after various attempts we were unable to convert the compound 92 into the desired tricycle. We have then decided to study the Diels-Alder reaction between furan and 2,5-disubstituted benzoquinone derivatives, that could furnish the adducts properly functionalized to be transformed in the 11-oxabicyclico[6.2.1]undecane system. However, we observed that the equilibrium is strongly shifted towards the starting materials in these cycloaddition reactions. This methodology has thus showed to be impracticable. As a third alternative, we affected the study the Diels-Alder reaction between the furans derivatives and the acetylenes. The adducts obtained present 7-oxabicyclico[2.2.1]heptane system that could be used to synthesizes of structural skeleton of furanoheliangolide.

The goal of this thesis work is to investigate the possibility to grow graphene by Chemical Vapor Deposition (CVD) on copper foil with acetylene as a precursor and varigon (5\% H$_2$ in Ar) as a carrier gas. The possibility of nitrogen doping by ammonia treatment during the growth process is also investigated. The possibility of graphene transfer, with the use of Poly(Methyl Metacrylate) (PMMA), from the copper onto another target substrate, Flourine doped Tin Oxide (FTO), is also explored. The main technique of characterization of the grown and transfered graphene is Raman spectroscopy, a great tool for investigating the number of graphene layers and amount of defects. Other characterization methods used are Scanning Electron Microscopy (SEM) X-ray Photoelectron Spectroscopy (XPS) to investigate morphology and elemental composition, respectively. The result of this thesis study is that graphene growth is entirely possible with acetylene as a precursor, as shown by the Raman spectroscopy, XPS and SEM. The grown graphene has a high quality with few layers and a low number of defects. The ammonia treatment, however, doesn't seem to have an immediate effect on the graphene growth. The XPS data indicates that there are no nitrogen doping in the graphene, though there might be a correlation between the ammonia and the number of layers, but further investigations has to be made. Transfer is also proven possible with the method developed. However, improvements to the transfer method can be done since there are both larger tares, caused by the transfer onto the FTO, as well as microscopic tares, possibly caused by thermal expansion of the PMMA.