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1
Xu, Chao. « Transport phenomena of methanol and water in liquid feed direct methanol fuel cells / ». View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?MECH%202008%20XU.
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Dixit, Sanhita. « Molecular models of hydration in methanol-water mixtures ». Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/10880.
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The work presented in this thesis addresses the issue of hydration of a simple amphiphile-like molecule; methanol. High-resolution Raman spectroscopy is used to study methanol-water mixtures over the whole concentration range. A highly non-linear dependence of the carbon-oxygen and carbon-hydrogen stretching frequencies with composition is observed. The data suggest the first global picture of the progressive hydration of methanol: water first breaks up the molecular chains which exist in pure methanol, and then completely hydrates the hydroxyl groups before solvating in hydrophobic methyl groups. In order to corroborate this proposed picture, neutron diffraction experiments using hydrogen/deuterium substitution were performed on a concentrated methanol in water mixture (70 mole% methanol : 30 mole% water) and a dilute methanol in water mixture (5 mole% methanol : 95 mole% water). The diffraction data were modelled using the Empirical Potential Structural Refinement technique. In the concentrated mixture, although there is insufficient water for the classical hydrophobic mechanism to operate, the structural effects observed are consistent with those that might be expected in a hydrophobically driven system. An unexpected reduction is found in the methyl-methyl contact distance compared to pure methanol, which corresponds to an overall compressive effect apparently driven by hydrogen bonding of the added water to the alcohol hydroxyl groups. Surprisingly, the water structure is largely preserved in this mixture. The results obtained provide unambiguous evidence for the preferential interaction of the methanol hydroxyl group with water and suggest that hydrogen bonding interactions between water and polar groups of amphiphilic molecules may be more important than previously thought.
3
Waghe, Aparna. « Computer Simulations of Water and Methanol in Carbon Nanotube ». Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/WagheA2007.pdf.
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Lancaster, N. M. « Excess enthalpies of mixtures containing water and methanol vapours ». Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375388.
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Lee, Christopher. « Computer simulation of ethylene glycol oxidation and methanol-water interactions ». Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/51368/.
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In this project, density functional theory calculations were performed to study the adsorption of ethylene glycol to the MgO (100), MgO (130), Al2O3 (0001), PdO (101) surfaces, as well as Au38 and Au38O16 nanoparticles. Adsorption of ethylene glycol is favourable to all of these surfaces with Al2O3 (0001) and PdO (101) showing the most favourable adsorption at -168 kJ mol-1 and -135 kJ mol-1 respectively. The MgO surfaces showed adsorption energies between -80 kJ mol-1 and -100 kJ mol-1, and the gold nanoparticles showed lower adsorption energies at approximately -35 kJ mol-1. Barriers to O-H activation and C-H activation of ethylene glycol were also studied on these surfaces. The barriers to O-H activation were small over each of the surfaces (between 8 and 46 kJ mol-1) and large for the gold nanoparticles (108 kJ mol-1). The barriers to C-H activation were very large over the MgO surfaces (>300 kJ mol-1), and lower over the PdO (101) surface (63 kJ mol-1) and the gold nanoparticles (68 kJ mol-1). C-H activation was found to not be possible over the Al2O3 (0001) surface. Classical molecular dynamics studies were performed on various water and methanol mixtures as well as in the presence of a hydroxylated Al2O3 (0001) surface. It was found that in methanol there are on average 1.1 oxygen – oxygen close contacts with other methanol molecules in pure methanol, and water has on average between 2.03 and 2.86 oxygen – oxygen close contacts, with more being present at higher temperatures. The presence of a hydroxylated aluminium oxide surface induces local ordering in the methanol molecules resulting in an increase in methanol – methanol and water – methanol oxygen – oxygen contacts, however there is a decrease in water oxygen – water oxygen contacts.
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Hama, Tetsuya. « Photodissociation dynamics of amorphous solid water and amorphous solid methanol ». 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120883.
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Omideyi, T. O. « The economics of heat pump assisted distillation of methanol water mixtures ». Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376879.
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Powell, David Hugh. « The structure of solutions of simple electrolytes in water and methanol ». Thesis, University of Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330038.
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Chatterjee, Amritendu. « Solution properties of sodium carboxymethylcellulose in methanol-water mixed solvent media ». Thesis, University of North Bengal, 2012. http://hdl.handle.net/123456789/1573.
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Genova-Koleva, Radostina Vasileva. « Electrocatalyst development for PEM water electrolysis and DMFC : towards the methanol economy ». Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/462861.
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In this thesis, the hydrogen obtained in a PEM water electrolizer (PEMWE) as a reactant to produce methanol when combined with the CO2 captured from the combustion of fossil fuels is proposed. Methanol is easy to manage as a fuel for DMFCs and this would help to recycle the CO2 responsible for the climate change.
PEMWEs have several advantages in comparison with the alkaline electrolysis such as ecological cleanness, low power consumption, small mass, and high purity of the evolved gases. TiO2 nanoparticles and nanotubes as supports for electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were developed. TiO2 and Nb-doped TiO2 with different Nb contents (3-10 at.% Nb vs. Ti) were synthesized via sol-gel method, whereas TiO2 nanotubes (TNT) and Nb-doped TiO2 nanotubes (Nb-TNT) were prepared by the hydrothermal method. The specific surface areas were in the range of 80-100 m2 g-1 for nanoparticles and in the range 150 – 300 m2 g-1 for nanotubes.
XPS measurements showed a local increase of the electron density on Pt when supported onto Nb-TNT, thus indicating a strong metal-support interaction. According to the electrochemical testing, the highest activity towards HER corresponded to Pt supported on 3 at. % Nb-TNT, obtaining better results than those reported in the literature using other materials.
IrO2 and IrRuOx (atomic ratio Ir:Ru equal to 60:40) as OER catalysts were synthesized via the hydrolysis method. From the electrochemical experiments, the highest OER activity of IrO2/Nb-TNT, due to the better dispersion of IrO2 onto the support, was shown. The catalysts supported onto Nb-doped TNT presented the lowest overpotentials for OER.
MEAs 5 cm2 in section were prepared using a new low temperature decal method. IrO2, IrRuOx and 50 wt. % IrO2/Nb-TNT were applied as the anode electrocatalysts with a catalyst loading optimized to 2.0 mgoxide cm-2. Pt loading on the cathode was optimized to 0.5 mgPt cm-2 (Pt black and 20 wt. % Pt/Vulcan XC72 were used). The best performance at 80 °C corresponded to current densities of 0.100 and 0.500 A cm-2 at 1.430 and 1.494 V, respectively, with 50 wt.% IrO2/Nb-TNT on the anode and 20 wt. % Pt/Vulcan XC72 on the cathode. The increase in cost of the MEA with respect to the use of unsupported IrO2 was not significant.
Different solvents (n-butyl acetate (NBA) and 2-propanol (IPA)) having different polarity were used to prepare the catalyst inks of the DMFC electrodes. The catalysts were commercially available Pt and PtRu blacks. The light scattering experiments indicated that the PtRu-Nafion® aggregates in the inks prepared with NBA were larger. The SEM and porosimetry measurements of the catalyst layers showed that the secondary pore volume between the agglomerates was larger for NBA. The linear sweep voltammetry and electrochemical impedance spectroscopy (EIS) results for the methanol electrooxidation in the three-electrode cell denoted the higher active surface area for NBA. The transport limitation was more apparent for IPA because the corresponding size and porosity of the agglomerates formed by the ionomer and the catalyst nanoparticles were smaller than for NBA.
The polarization curves of MEAs in which the anode catalyst layers were formulated with NBA and IPA were recorded in single DMFCs with 2 mol dm-3 CH3OH aqueous solutions at 60 °C. The cathode feed was dry synthetic air at atmospheric pressure. The power density given by the MEA prepared with NBA was about 74 % greater when compared to that prepared with IPA. The interpretation of the EIS results indicated that the proton resistance for NBA was significantly lower than for IPA, thus confirming the greater number of accessible active sites for methanol oxidation in the former.La economía del metanol contempla el uso de dicho alcohol como combustible, obtenido a partir de hidrógeno y CO2 capturado de la combustión de combustibles fósiles, ayudando a mitigar el cambio climático. Para ello se han preparado nanopartículas y nanotubos de TiO2 y de TiO2 dopados con Nb como soportes de catalizadores para electrolizadores de agua PEM. El Nb permitió aumentar la superficie específica de los soportes hasta 300 m2 g-1 (nanotubos). Mediante XPS se demostró un aumento local de la densidad electrónica sobre el Pt soportado sobre TiO2 dopado con Nb, resultando el de contenido del 3 at. % en Nb el de mejores prestaciones para la reducción del hidrógeno, con valores superiores a los descritos en la literatura. Para el desprendimiento de oxígeno se sintetizaron los catalizadores IrO2 e IrRuOx (Ir: Ru de 60:40 at. %), también aplicados sobre nanotubos de TiO2. Se encontró una mejor actividad para IrO2 soportado sobre nanotubos de TiO2 dopados con Nb debido a una mejor dispersión del catalizador sobre el soporte. Se prepararon MEAs con los mejores electrodos para un electrolizador PEM mediante un nuevo método de calcomanía de baja temperatura. El mejor rendimiento correspondió al IrO2 (50 % en peso) soportado sobre nanotubos de TiO2 dopados con Nb en el ánodo, con escaso impacto económico con respecto al uso del IrO2 sin soportar. En cuanto a la pila de combustible DMFC, se prepararon electrodos de PtRu sin soportar, empleando tintas con Nafion y dos disolventes diferentes, con distinta polaridad, acetato de n-butilo (NBA) y 2-propanol (IPA). El tamaño de los agregados y la porosidad fue superior en NBA debido a su menor polaridad, obteniéndose también en este caso una mayor superficie activa. Las curvas de polarización en CH3OH 2 mol dm-3 y aire a 60 °C de los MEAs formulados con NBA, catalizados mediante negro de PtRu y negro de Pt en ánodo y cátodo, respectivamente, indicaron también mejores prestaciones cuando los MEAs se formularon con NBA en el ánodo en lugar de IPA. La densidad de corriente límite con NBA fue unas tres veces mayor y la densidad de potencia un 75% superior.
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Luk, Chee-wei Jennifer. « Solubility and Pseudo-polymorphic Transitions of L-Serine in Water-Methanol System ». Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6832.
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The research addressed in this thesis is focused on the solubility and pseudo-polymorphic transition of L-serine in mixed water-methanol systems. Cooling re-crystallizations were carried out that varied both temperature and methanol concentration. Solubilities were measured with high-performance liquid chromatography. It is found that the solubility increased with increase in temperature and decreased drastically with methanol concentration. The effect of temperature at which there is a transition of L-serine crystals from the rod-shaped (anhydrous) form to hexagonal (monohydrate) form was confirmed and that transition temperatures decreased with methanol concentrations in a non-linear manner. The solubility data were correlated and plotted using the vant Hoff equation and the enthalpy and entropy of dissolution were determined. These values increased with increase in methanol concentration. The solid crystals were analyzed by optical microscopy and powder X-ray diffraction. The rod-shaped crystals were identified to be anhydrous L-serine, while the hexagonal crystals were L-serine monohydrate. Dehydration of the monohydrated crystals in their solid-state was examined and the onset of such phenomenon was known to start once the crystals were removed from the solutions.
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Dede, Yavuz. « Quantum Chemical Investigation Of Reactions Of Atomic Carbon With Water And Methanol ». Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12609189/index.pdf.
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Reactions of singlet (1S and 1D) and triplet (3P) carbon atoms with water, and 1D and 3P carbon atoms with methanol were studied computationally. In the water and methanol systems, the carbon vapor containing a mixture of C(1S),
C(1D), and C(3P) atoms, is predicted to react by primarily interacting with the oxygen, OH bond and CH bond of the substrate mainly with the 1D state. While C(1S) was proven to be unreactive C(3P) can hardly be supported to be reactive, and can safely be defined as unreactive. The major product, CO forms as a result of oxygen abstraction, which is observed as a fast, energetically quite favorable process. The scheme of this oxygen abstraction is promising to be applicable to substrates with the general formula R1-O-R2 i.e. water, alcohols, and ethers. OH insertion, both for water and methanol, yields trappable carbenesthe carbene being a key species on the distribution of the end products. Water matrix trapping the carbene opens the path to the formation of formaldehyde
and exhibits a prototype reaction for the formation of dialkoxymethanes. Gas phase product spectrum from the reactions are broader, due to the accessibility of the routes originating from the otherwise trapped intermediates
and the excess energy of the reactions being carried by them. In the condensed phase the very early and rapid reactions seem to have chance, the subsequent rearrangements are hard to occur. The conclusions thus far apply to the reactions in the gas phase as well as in condensed phases involving inert matrices
and the experimental isolation of the species is highly dependent on the ability of the medium to trap the intermediates via effective transfer of excess energy. Due to the large excess energies of intermediates involved, subsequent reactions are fast
of the order 1013 s-1 from kinetic rate calculations. In the absence of efficient transfer of non-fixed energies to the surrounding medium, all of the reaction paths will conclude with irreversible dissociation reactions. Plausible mechanisms for all the experimentally observed products are predicted. The results are in agreement with the available experimental data.
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Rothfuss, Christopher John. « The influence of high electric fields on water and methanol surface electrochemistry / ». Thesis, Connect to this title online ; UW restricted, 2002. http://hdl.handle.net/1773/9926.
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Kojima, Hiroyuki. « Statistical-Mechanical Study of Phase Transitions of Thermosensitive Polymer Gels in Water and Mixed Solvents of Water/Methanol ». 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/174960.
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Craig, John Michael. « Theoretical Investigation of the Structure and Vibrational Frequencies of Water and Methanol Complexes ». VCU Scholars Compass, 2007. http://hdl.handle.net/10156/2131.
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Gautam, Devaki Nandan. « Molecular dynamics simulation of horse-heart cytochrome c in water-methanol solvent systems ». Thesis, Wichita State University, 2014. http://hdl.handle.net/10057/10956.
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Molecular Dynamics simulations have been carried out to investigate the dynamics of horse heart Cytochrome C and associated crystallographic water molecules in different water-methanol systems. The 100 ns simulation predicts that hh-CytC undergoes different dynamical transitions with some common conformations in different solvents. With increase of methanol concentration in solvents, hh-CytC has increased flexibility, fluctuating its hydrophobic solvent accessible surface area (SASA), and number of persistent internal hydrogen bonds with long hydrogen-bond-lifetime. The protein became more liquid-like in mixed solvents compared to pure solvents; flexibility increases in the absence of the crystallographic water. Similarly, the number of hydrogen bonds between solvent molecules and hh-CytC decreased with increasing of methanol concentration. Water-protein and methanol-protein hydrogen bond lifetimes were computed 11.5 and 16.6 picoseconds, respectively, in pure solvents. However, in mixtures, solvent-protein hydrogen bond lifetime was higher in twenty percent methanol than in fourty percent in water. The surface crystallographic water molecules diffused easily in bulk solvents within 1 nanosecond and protein surface is stabilized by hydrogen bonds with a solvation layer. The two crystallographic water molecules which are buried internally in hh-CytC have 5 to more than 100 nanoseconds residence time in the conserved sites with 100's of picoseconds of hydrogen bond lifetime depending on the solvent compositions. The residence time might depend on the mechanism of conformational transition of protein in simulation. Solvent water molecules exchange these buried water molecules but exchange is less frequent than that in hydration layer. Even though methanol has succeeded to reside into these conserved sites in pure methanol solvent but its distance with hydrogen bonding partners more than 5 A with labile hydrogen bonding state.Thesis (M.S.)--Wichita State University, Fairmount College of Liberal Arts, Dept. of Chemistry
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Splith, Tobias, Christian Chmelik, Frank Stallmach, Stefan K. Henninger, Gerrit Füldner, Panagiotis D. Kolokathis, Evangelia Pantatosaki et George K. Papadopoulos. « Adsorptive heat transformation with SAPO-34 : diffusion of working fluids water, methanol and ethanol ». Diffusion fundamentals 24 (2015) 51, S. 1, 2015. https://ul.qucosa.de/id/qucosa%3A14570.
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Sutherland, Richard Daniel. « Performance of different proton exchange membrane water electrolyser components / cRichard Daniel Sutherland ». Thesis, North-West University, 2012. http://hdl.handle.net/10394/9214.
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Water electrolysis is one of the first methods used to generate hydrogen and is thus not considered to be a new technology. With advances in proton exchange membrane technology and the global tendency to implement renewable energy, the technology of water electrolysis by implementation of proton exchange membrane as solid electrolyte has developed into a major field of research over the last decade. To gain an understanding of different components of the electrolyser it is best to conduct a performance analysis based on hydrogen production rates and polarisation curves. The study aim was to compare the technologies of membrane electrode assembly with gas diffusion electrode and the proton exchange membranes of Nafion® and polybenzimidazole in a commercial water electrolyser. To determine which of the components are best suited for the process a laboratory scale electrolyser was to be used to replicate the commercially scaled performance. The effect of feed water contaminants on electrolyser performance was also investigated by introducing iron and magnesium salt solutions and aqueous methanol solutions in the feed reservoir. Components to be tested included different PEM types as well as the base component on which the electrocatalyst layer is applied. The proton exchange membranes compared were standard Nafion® N117 and polybenzimidazole meta-sulfone sulfonated polyphenyl sulfone (PBI-sPSU). A laboratory scale electrolyser from Giner Electrochemical Systems was utilised where different components were tested and compared with one another. Experimental results with commercial membrane electrode assemblies and gas diffusion electrodes demonstrated the influence of temperature on electrolyser performance for the proton exchange membranes, where energy efficiency increased with temperature. The effect of pressure was insignificant over the selected pressure range. Comparison of membrane electrode assembly and gas diffusion electrode technologies showed enhanced performance from MEA technology, this was most likely due to superior electrocatalyst contact with the PEM. Results of synthesised Nafion® N117 and PBI-sPSU MEA showed increased performance for PBI-sPSU, but it was found to be more susceptible to damage under severe conditions. The effect of metal cations in the supply reservoir exhibited reduced energy efficiencies and increased specific energy consumption for the test duration. Treatment with sulphuric acid was found to partially restore membrane electrode assembly performance, though it is believed that permanent damage was inflicted on the membrane electrode assembly electrocatalyst. Use of aqueous methanol solutions were found to increase electrolyser performance. It was also found that aqueous methanol electrolysis occurs at lower current densities, whereas a combination of aqueous methanol and water electrolysis occurred at higher current densities depending on the concentration of methanol.Thesis (MIng (Chemical Engineering))--North-West University, Potchefstroom Campus, 2013.
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Bhagan, Salome. « REACTIVITY AND EQUILIBRIUM THERMODYNAMIC STUDIES OF IRIDIUM PORPHYRINS IN WATER AND ALCOHOL ». Diss., Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/213129.
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ChemistryPh.D.
Environmental and energy issues have stimulated renewed interest in utilizing both water and methanol as reagents and reaction mediums. Our current interest is to evaluate the scope of group nine organometallics and establish thermodynamic parameters for their reactivity in aqueous solvent. A comprehensive thermodynamic database for a wide scope of organo-rhodium transformations in a range of reaction media including benzene, water, and methanol has been well established by our group. Aqueous solutions of rhodium porphyrin have been determined to manifest an exceptional range of substrate reactions with carbon monoxide, dihydrogen, olefins, methanol and aldehydes. This study will focus on expansion of the thermodynamic database to all the group nine metals, particularly the iridium porphyrin systems in both water and methanol. Substrate reactivity and development of new mechanistic strategies for the conversion of carbon monoxide, alkanes, and alkenes to organic oxygenates are central objectives. Water/Methanol soluble porphyrin iridium complexes including iridium tetrakis(p-sulfonatophenyl)porphyrin ((TSPP)Ir) and iridium tetrakis(3,5-sulfonatomesityl)porphyrin ((TMPS)Ir) derivatives can be prepared by sulfonation of tetra phenyl porphyrin (H2TPP) and tetra mesityl porphyrin (H2TMP). The reactivity of dihydrogen with aqueous solutions of iridium(III) tetrakis(p-sulfonatophenyl)porphyrin ((TSPP)Ir(III)) complexes produce equilibrium distributions between six iridium species including iridium hydride ([(TSPP)Ir-D(D2O)]-4), iridium(I) ([(TSPP)IrI(D2O)]-5), and iridium (II) dimer ([(TSPP)IrII(D2O)]2-8) complexes. Each of these types of iridium porphyrin species including Ir(I), Ir(II), Ir(III), Ir-H, and Ir-OH function as precursors for a range of organometallic substrate reactions. A primary objective is to define the quantitative relationships pertaining to the distribution of species in aqueous solution as a function of the dihydrogen and hydrogen ion concentrations through direct measurement of five equilibrium constants along with free energy changes of coordinated water and free energy changes of reactions of dihydrogen in water. Reactivity, kinetics and evaluation of equilibrium thermodynamics, including the reactions of iridium hydroxide and methoxide with olefins to produce beta-hydroxyalkyl and beta-methoxyalkyl complexes, reactions of iridium hydride and olefins to produce iridium alkyl complexes, and reactions of iridium hydride with carbon monoxide to produce iridium formyl [Ir-CHO] complexes are also objectives of this research. Another research goal is the design and synthesis of diporphyrin ligands that form dimetal complexes capable of preorganizing transition states for substrate reactions that involve two metal centers. Dirhodium dimetalloradical complexes are observed to manifest large rate increases over mono-metalloradical activation reactions of hydrogen, methane, and other small molecule substrates. In this study, synthesis of diporphyrin (bisporphyrin) ligands and other ligands which will permit dimetallo complexes like anti-aromatic [14]annulene and low steric porphine ligands will be also be examined.
Temple University--Theses
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Chamberlin, Joseph Paul. « Investigating the Water and Methanol Condensation Heat Transfer Performance of Chemically Functionalized Silica Nanospring Coated Aluminum Tubes ». Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami162690676666569.
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Fadaei, Ehsan, et Mohsen Tafazzoli. « Study of the self-diffusion coefficient in the water-methanol binary mixture from the hydrogen bonding viewpoint using DOSY NMR : Study of the self-diffusion coefficient in the water-methanol binary mixturefrom the hydrogen bonding viewpoint using DOSY NMR ». Diffusion fundamentals 24 (2015) 13, S. 1, 2015. https://ul.qucosa.de/id/qucosa%3A14527.
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Weinzierl, Christine Verfasser], et Ulrike [Akademischer Betreuer] [Krewer. « Model Supported Analysis of Water Management in Alkaline Membrane Direct Methanol Fuel Cells / Christine Weinzierl ; Betreuer : Ulrike Krewer ». Braunschweig : Technische Universität Braunschweig, 2017. http://d-nb.info/1175817171/34.
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Gatewood, Marena Dessette. « Solubility and recovery of L-isoleucine from high pH solutions and the cause for L-serine habit differences when crystallized from water and methanol/water solutions ». Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/10916.
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Zhao, Cen. « Advanced Oxidation Processes of Problematic Toxin and Water Contaminants : Cylindrospermopsin, Iopamidol, 4-methylcyclohexane Methanol and Propylene Glycol Phenyl Ether ». FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2235.
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The occurrences of cyanotoxin and organic contaminants threaten drinking water sources and are a serious human health and environmental concern. The control of these problematic contaminants and the remediation of the associated contaminants are critical for ensuring safe drinking water to significant populations. Advanced oxidation processes (AOPs) have received considerable attention as a potential water treatment for various pollutants. In this dissertation, advanced oxidative degradation of four problematic water toxic contaminants (CYN, iopamidol, 4-methylcyclohexane methanol and propylene glycol phenyl ether) were studied to develop the fundamental understanding required to assess AOPs as a potential water treatment process.
UV and visible light activated (VLA) TiO2 photocatalysis using nitrogen and fluorine-TiO2 (NF-TiO2), phosphorus and fluorine-TiO2 (PF-TiO2) and sulfur-TiO2 (S-TiO2) were employed for degradation of 6-hydroxymethyl uracil (6-HOMU), a model compound for the potent cyanotoxin cylindrospermopsin (CYN). NF-TiO2 exhibits the most photoactive, followed by marginally active PF-TiO2 and inactive S-TiO2 under visible light irradiation. Our results indicate that O2-• plays an important role in VLA TiO2 photocatalysis.
Fe (VI), an environmentally friendly oxidant, was employed for the degradation of CYN and 6-HOMU over a range of pH (7 ~ 9.5). The second order rate constants for the reaction of Fe (VI) with CYN decrease from 38.83 ± 0.07 M-1s-1 at pH 7 to 5.02 ± 0.04 M-1s-1 at pH 9.5. Fe (VI) mediated reactions primarily occur via oxidation of the uracil ring in CYN. ELISA results demonstrate that Fe (VI) oxidation process leads to a significant decrease in the bioactivity of CYN as a function of treatment time.
Fe (III)-oxalate/H2O2 process was employed for the remediation of iopamidol, a model for ICM, to determine the formation rates and steady concentrations of •OH and O2-• under UV and visible light irradiation. Reduction by CO2-• and oxidation by •OH contribute to the degradation pathways.
Pulse and gamma radiolysis of 4-methylcyclohexane methanol (MCHM) and propylene glycol phenyl ether (PPh) were studied to determine the bimolecular rate constants and reaction pathways. •OH addition to ortho and para positions in PPh are the predominant reaction pathways; H-abstraction are the primary reaction mechanisms for ∙OH mediated oxidation of MCHM
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Ahmed, Amira Yehya Mohamed [Verfasser]. « Mechanistic investigations of photoelectrochemical water and methanol oxidation on different titanium dioxide single crystal surfaces / Amira Yehya Mohamed Ahmed ». Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2012. http://d-nb.info/1027563767/34.
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Kerasidou, Ariadni. « Investigation of the nonlinear optical response of novel azobenzene-iminopyridine derivatives and the dynamic heterogeneities of water / methanol mixtures ». Thesis, Angers, 2015. http://www.theses.fr/2015ANGE0065.
Texte intégralRésumé :
Cette étude est divisée en deux parties: l'analyse des propriétés optiques non linéaires (NLO) de nouveaux dérivés pi-conjugués d’Azobenzène Iminopyridine et les hétérogénéités dynamiques (DH) des mélanges eau/méthanol. La première partie a été réalisée en utilisant la technique Z-scan ainsi que les techniques de génération de deuxième et troisième harmoniques (SHG/THG). Communément, l'optique non linéaire est le domaine de l'optique qui étudie l'interaction de la lumière avec un système matériel et les changements induits dans les propriétés optiques des matériaux parun champ électromagnétique intense. La non-linéarité réside dans le fait que la réponse du matériau ne dépend pas linéairement de l'intensité du champ électrique. Les matériaux qui possèdent une forte réponse non linéaire sont très utiles pour la photonique et l'optoélectronique. Ils peuvent être utilisés comme limiteurs optiques pour protéger les détecteurs de faisceaux laser de haute intensité, également comme commutateurs optiques, portes optiques logiques, etc., avec un objectif ultime qui est le traitement de signal optique et la fabrication d'ordinateurs optiques. La deuxième partie a été réalisée au moyen de calculs informatiques et plus particulièrement de simulations de dynamiques moléculaires dans l'eau, dans le méthanol et dans des mélanges eau/méthanol à différentes températures. La simulation par ordinateur est un outil très approprié pour explorer les liquides, également dans la plage de régime en surfusion, sans les limitations du processus de nucléation qui a lieu dans l'expérience réelle. Lorsque la température diminue les liquides surfondus subissent a minima une augmentation exponentielle de leur viscosité (Arrhenius). Cette grande modification des propriétés detransport apparaît bien que la structure ne change que légèrement avec la températureThis study is divided into two parts: the investigation of the nonlinear optical (NLO) properties of new (pi)- conjugated Azobenzene Iminopyridine derivatives and the Dynamic Heterogeneities (DH) of water/methanol mixtures. The first part was achieved employing Z-scan, Second and Third Harmonic Generation (SHG/THG) techniques. Generally, nonlinear optics is the domain of optics that studies the interaction of light with a material system and the changes resulted in the optical properties of the materials by an intense electromagnetic field. The nonlinearity lies in the fact that the material response does not depend linearly on the intensity of the electric field. Materials with significant nonlinear response are very useful for photonics and optoelectronics. They can be used as optical limiters to protect sensitive detectors of high-intensity laser beams, as well as optical switches, optical logic gates and etc., with an ultimate objective the processing of optical signal and manufacture of optical computers. The second part was done via computer calculationsand more specifically Molecular Dynamic Simulations in water, methanol and water/methanol mixtures at different temperatures. Computer simulation is a very suitable tool for exploring liquids, also in the range of the supercooled regime, without the limitations of the nucleation process, which takes place in the real experiment. Supercooled liquids undergo an exponential (Arrhenius) or even larger increase of their viscosity, when the temperature decreases. This large modification of the transport properties appear while the structure only slightly changes with temperature
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Fadaei, Ehsan, et Mohsen Tafazzoli. « Study of the self-diffusion coefficient in the water-methanol binary mixture from the hydrogen bonding viewpoint using DOSY NMR ». Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-198103.
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Grima, N. M. M. « Kinetic and mass transfer studies of ozone degradation of organics in liquid/gas-ozone and liquid/solid-ozone systems ». Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/3351.
Texte intégralRésumé :
This work was concerned with the determination of mass transfer and kinetic parameters of ozone reactions with four organic compounds from different families, namely reactive dye RO16, triclocarban, naphthalene and methanol. In order to understand the mechanisms of ozone reactions with the organic pollutants, a radical scavenger (t-butanol) was used and the pH was varied from 2 to 9. Ozone solubility (CAL*) is an important parameter that affects both mass transfer rates and chemical reaction kinetics. In order to determine accurate values of the CAL* in the current work, a set of experiments were devised and a correlation between CAL* and the gas phase ozone concentration of the form CAL*(mol/L) = 0.0456 CO3 (g/m3 NTP) was obtained at 20°C. This work has also revealed that t-butanol did not only inhibit hydroxyl radical reactions but also increased mass transfer due to it increasing the specific surface area (aL). Values of the aL were determined to be 2.7 and 3.5 m2/m3 in the absence and presence of t-butanol respectively. It was noticed that the volumetric mass transfer coefficient (kLa) has increased following the addition of t-butanol. Ozone decomposition was studied at pH values of 2 to 9 in a 500 mL reactor initially saturated with ozone. Ozone decomposition was found to follow a second order reaction at pH values less than 7 whilst it was first order at pH 9. When the t-butanol was added, the decomposition of ozone progressed at a lower reaction order of 1.5 for pH values less than 7 and at the same order without t-butanol at pH 9. Ozone decomposition was found significant at high pHs due to high hydroxide ion concentration, which promotes ozone decomposition at high pHs. The reaction rate constant (k) of RO16 ozonation in the absence of t-butanol was determined. The result suggests that RO16 degradation occurs solely by molecular ozone and indirect reactions by radicals are insignificant. The chemical reaction of triclocarban with ozone was found to follow second order reaction kinetics. The degradation of naphthalene using the liquid/gas-ozone (LGO) system was studied. This result showed that hydroxyl radicals seemed to have limited effect on naphthalene degradation which was also observed when a radical scavenger (t-butanol) was used. Reaction rate constants were calculated and were found around 100 times higher than values reported in the literature due to differences in experimental conditions. From the results of the experimental investigation on the degradation of methanol by ozone it was found that the rate constant (k) of the degradation reaction increased at pH 9. The reaction stoichiometry was found to have a value of 1 mol/mol. The two steps of the liquid/solid-ozone (LSO) system were studied on beds of silica gel and a zeolitic material (D915) and the ozone adsorption process was modeled and found that particle rate controls ozone adsorption step but liquid rate controls the water treatment step. Ozone desorption with pure deionised water was studied. The water flow rate was found to accelerate the desorption rates but pH was found to decrease the desorption rates. In contrast, the effect of pH was insignificant in the presence of t-butanol. Determination of the adsorption isotherms for RO16, naphthalene and methanol revealed that RO16 did not exhibit adsorption on silica gel, but both naphthalene and methanol showed adsorption on D915 described by Langmuir model.
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Hickner, Michael Anthony. « Transport and Structure in Fuel Cell Proton Exchange Membranes ». Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28895.
Texte intégralRésumé :
Transport properties of novel sulfonated wholly aromatic copolymers and the state-of-the-art poly(perfluorosulfonic acid) copolymer membrane for fuel cells, Nafion, were compared. Species transport (protons, methanol, water) in hydrated membranes was found to correspond with the water-self diffusion coefficient as measured by pulsed field gradient nuclear magnetic resonance (PFG NMR), which was used as a measure of the state of absorbed water in the membrane. Generally, transport properties decreased in the order Nafion > sulfonated poly(arylene ether sulfone) > sulfonated poly(imide). The water diffusion coefficients as measured by PFG NMR decreased in a similar fashion indicating that more tightly bound water existed in the sulfonated poly(arylene ether sulfone) (BPSH) and sulfonated poly(imide) (sPI) copolymers than in Nafion.
Electro-osmotic drag coefficient (ED number of water molecules conducted through the membrane per proton) studies confirmed that the water in sulfonated wholly aromatic systems is more tightly bound within the copolymer morphology. Nafion, with a water uptake of 19 wt % (λ = 12, where λ = N H2O/SO3H) had an electro-osmotic drag coefficient of 3.6 at 60°C, while BPSH 35 had an electro-osmotic drag coefficient of 1.2 and a water uptake of 40 wt % (λ = 15) under the same conditions.
Addition of phosphotungstic acid decreased the total amount of water uptake in BPSH/inorganic composite membranes, but increased the fraction of loosely bound water. Zirconium hydrogen phosphate/BPSH hybrids also showed decreased bulk water uptake, but contrary to the results with phosphotungstic acid, the fraction of loosely bound water was decreased. This dissimilar behavior is attributed to the interaction of phosphotungstic acid with the sulfonic acid groups of the copolymer thereby creating loosely bound water. No such interaction exists in the zirconium hydrogen phosphate materials. The transport properties in these materials were found to correspond with the water-self diffusion coefficients.
Proton exchange membrane (PEM) transport properties were also found to be a function of the molecular weight of sulfonated poly(arylene thioether sulfone) (PATS). Low molecular weight (IV ~ 0.69) copolymers absorbed more water on the same ion exchange capacity basis than the high molecular weight copolymers (IV ~ 1.16). Surprisingly, protonic conductivity of the two series was similar. Moreover, the methanol permeability of the low molecular weight copolymers was increased, resulting in lower membrane selectivity and decreased mechanical properties.
The feasibility of converting the novel sulfonated wholly aromatic systems to membrane electrode assemblies (MEAs) for use in fuel cells was studied by comparing free-standing membrane properties to those of MEAs assembled with standard Nafion electrodes. Significantly higher interfacial resistance was measured for BPSH samples. Fluorine was introduced into the copolymer backbone by utilizing bisphenol-AF in the copolymer synthesis (6F copolymers). These 6F copolymers showed a markedly lower interfacial resistance with Nafion electrodes and correspondingly greater direct methanol fuel cell performance. It was proposed that the addition of the hexafluoro groups increased the compatibility of the PEM with the highly fluorinated Nafion electrode.Ph. D.
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Xiao, Caibin. « Thermodynamics of aqueous electrolytes and hydrogen-bonded nonelectrolytes over a wide range of temperature and pressure, the aqueous trivalent lanthanide cations and the methanol-water system ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0007/NQ36216.pdf.
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Wahlund, Bertil. « Rational bioenergy utilisation in energy systems and impacts on CO2emissions ». Doctoral thesis, KTH, Chemical Engineering and Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3490.
Texte intégralRésumé :
The increased concentration of greenhouse gases in theatmosphere, in particular CO2, is changing the Earths climate. Accordingto the Kyoto protocol, where the international community agreedon binding emission targets, developed countries are committedto reduce their greenhouse gas emissions. The increased use ofbiomass in energy systems is an important strategy to reduce CO2emissions. The purpose of this thesis has been toanalyse the opportunities for Sweden to further reduce CO2emissions in the energy system, by rationallyutilising woody biomass energy. The characteristics of currentcommercially operating biofuel-based CHP plants in Sweden aresurveyed and systematically presented. A consistent andtransparent comprehensive reference base for system comparisonsis given. Furthermore, the fuel effectiveness and contributionto CO2reduction is calculated. The governmentalsubsidies of the CHP plantsinvestment, expressed as costof specific CO2reduction, appears to be low.
The competitiveness of biomass-fuelled energy production inrelation to fossil-based production with carbon capture isanalysed, showing that the biomass-fuelled systems provide acompetitive option, in terms of cost of electricity andefficiencies. The remaining Swedish woody biofuel potential ofat least 100 PJ/yr is principally available in regions with abiomass surplus. Transportation is therefore required to enableits utilisation in a further national and international market.Refining the biofuel feedstock to pellets, or even furtherrefining to motor fuels (DME, methanol or ethanol) or power,could facilitate this transport. Different options for fuelrefining are studied and compared. The entire fuel chain, fromfuel feedstock to end users, is considered and CO2emissions are quantified. Substituting fuelpellets for coal appears to be the most costeffectivealternative and shows the largest CO2reduction per energy unit biofuel. Motor fuelsappear more costly and give about half the CO2reduction. Transportation of the upgraded biofuelpellets is highly feasible from CO2emissions point of view and does not constitute ahindrance for further utilisation, i.e. the pellets can betransported over long distances efficiently with only limitedemissions of CO2.
Bioenergy utilisation has additional features forenvironmental improvement, apart from the CO2aspect. Waste heat from biofuel-based CHP can becost-effectively used in conjunction with sewage treatment. Theincoming sewage water to the nitrification process can bepreheated with the waste heat, and thereby substantiallyenhance the nitrification and the reduction of ammoniumnitrogen during the winter season.
Keywords:CO2reduction, energy system, biofuel, CHP, refining,fuel pellets, ethanol, methanol, DME, fuel substitution, sewagewater, nitrification.
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Hopkins, Adam Justin 1980. « In situ analysis of aqueous structure and adsorption at fluorocarbon, hydrocarbon and mineral surfaces ». Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/11267.
Texte intégralRésumé :
xvii, 209 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.Altering and controlling the properties of solid surfaces in aqueous or other liquid phase environments has been a sought after objective for decades. With the discovery of chemisorbed self-assembled monolayers, this dream has become a reality. Oxide and metal surfaces can now be readily coated with an array of commercially available products to produce a desired fnctionality. The presence of these coatings on solid surfaces affects properties of the interfacial region by altering interfacial electrostatic fields, changing the structure of interfacial water molecules and altering the interactions of adsorbed species. This dissertation reports on in situ studies of adsorption at several solid/aqueous interfaces using vibrational sum-frequency spectroscopy, a surface specific technique. These studies are augmented by the use of atomic force microscopy and contact angle goniometry to characterize the prepared surfaces and their interactions with adsorbates. The studies investigate how changes in the surface structure and chemistry, as well as the bulk aqueous phase, affect interfacial structure. The studies within are primarily focused on the interactions of water with bare and functionalized fused silica and the relationship between the aqueous phase composition and the structure of fluorocarbon and hydrocarbon self-assembled monolayers. The variations in aqueous structure are then examined in detail using ionic strength controlled experiments to understand the direct interactions of water hydrophobically coated silica. This analysis is followed by an investigation of the competitive adsorption of methanol and water at fluorocarbon and hydrocarbon monolayers which show spectroscopic signatures of the interaction strength between fluorocarbons and hydrocarbons. Further studies are performed using butylammonium chloride to verify these spectroscopic signatures and reveal different molecular structures of adsorbed species at chemically different hydrophobic surfaces. Lastly, specific ion effects on the CaF 2 /water interface are shown using equilibrium and time-resolved sum-frequency spectroscopy. The results of all these studies have implications for an array of surface chemical applications from mineral flotation to biocompatibility. This dissertation includes previously published co-authored material.
Committee in charge: Thomas Dyke, Chairperson, Chemistry; Geraldine Richmond, Advisor, Chemistry; James Hutchison, Member, Chemistry; Mark Lonergan, Member, Chemistry; Qusheng Jin, Outside Member, Geological Sciences
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Saleh, Jehad. « A Membrane Separation Process for Biodiesel Purification ». Thesis, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19730.
Texte intégralRésumé :
In the production of biodiesel via the transesterification of vegetable oils, purification to international standards is challenging. A key measure of biodiesel quality is the level of free glycerol in the biodiesel. In order to remove glycerol from fatty acid methyl ester (FAME or biodiesel), a membrane separation setup was tested. The main objective of this thesis was to develop a membrane process for the separation of free glycerol dispersed in FAME after completion of the transesterification reaction and to investigate the effect of different factors on glycerol removal. These factors included membrane pore size, pressure, temperature, and methanol, soap and water content.
First, a study of the effect of different materials present in the transesterification reaction, such as water, soap, and methanol, on the final free glycerol separation was performed using a modified polyacrylonitrile (PAN) membrane, with 100 kD (ultrafiltration) molecular weight cut off for all runs at 25°C. Results showed low concentrations of water had a considerable effect in removing glycerol from the FAME. The mechanism of separation of free glycerol from FAME was due to the removal of an ultrafine dispersed glycerol-rich phase present in the untreated (or raw) FAME. The size of the droplets and the free glycerol separation both increased with increasing water content of the FAME.
Next, three types of polymeric membranes in the ultrafiltration range with different molecular weight cut off, were tested at three fixed operating pressures and three operating temperatures (0, 5 and 25oC) to remove the free glycerol from a biodiesel reactor effluent. The ASTM standard for free glycerol concentration was met for the experiments performed at 25°C. The results of this study indicate that glycerol could be separated from raw FAME to meet ASTM and EN standards at methanol feed concentrations of up to 3 mass%. The process was demonstrated to rely on the formation of a dynamic polar layer on the membrane surface.
Ceramic membranes of different pore sizes (0.05 µm (ultrafiltration (UF) range) and 0.2 µm (microfiltration (MF) range)) were used to treat raw FAME directly using the membrane separation set up at temperatures of 0, 5 and 25°C. The results were encouraging for the 0.05 µm pore size membrane at the highest temperature (25°C). The effect of temperature on glycerol removal was evident from its relation with the concentration factor (CF). Higher temperatures promoted the achievement of the appropriate CF value sooner for faster separation. Membrane pore size was also found to affect separation performance.
A subsequent study revealed the effect of different variables on the size of the glycerol droplets using dynamic light scattering (DLS). A key parameter in the use of membrane separation technology is the size of the glycerol droplets and the influence of other components such as water, methanol and soaps on that droplet size. The effect of water, methanol, soap and glycerol on the size of suspended glycerol droplets in FAME was studied using a 3-level Box-Behnken experimental design technique. Standard statistical analysis techniques revealed the significant effect of water and glycerol on increasing droplet size while methanol and soap served to reduce the droplet size.
Finally, a study on the effect of trans-membrane pressure (TMP) at different water concentrations in the FAME phase on glycerol removal using UF (0.03 µm pore size, polyethersulfone (PES)) and MF (0.1 and 0.22 µm pore sizes, PES) membranes at 25, 40 and 60°C was performed. Results showed that running at 25°C for the two membrane types produced the best results for glycerol removal and exceeded the ASTM and EN standards. An enhancement of glycerol removal was found by adding small amounts of water up to the maximum solubility limit in biodiesel. An increase in temperature resulted in an increase in the solubility of water in the FAME and less effective glycerol removal. Application of cake filtration theory and a gel layer model showed that the gel layer on the membrane surface is not compressible and the specific cake resistance and gel layer concentration decrease with increasing temperature. An approximate value for the limiting (steady-state) flux was reported and it was found that the highest fluxes were obtained at the lowest initial water concentrations at fixed temperatures.
In conclusion, dispersed glycerol can be successfully removed from raw FAME (untreated FAME) using a membrane separation system to meet the ASTM biodiesel fuel standards. The addition of water close to the solubility limit to the FAME mixture enables the formation of larger glycerol droplets and makes the separation of these droplets straightforward.
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Westhues, Niklas Franz Verfasser], Jürgen [Akademischer Betreuer] Klankermayer et Walter [Akademischer Betreuer] [Leitner. « Development of molecular transition-metal catalysts for the reverse water-gas shift reaction and the selective transformation of carbon dioxide and hydrogen to formic acid esters and methanol / Niklas Franz Westhues ; Jürgen Klankermayer, Walter Leitner ». Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1227993013/34.
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Westhues, Niklas Franz [Verfasser], Jürgen Akademischer Betreuer] Klankermayer et Walter [Akademischer Betreuer] [Leitner. « Development of molecular transition-metal catalysts for the reverse water-gas shift reaction and the selective transformation of carbon dioxide and hydrogen to formic acid esters and methanol / Niklas Franz Westhues ; Jürgen Klankermayer, Walter Leitner ». Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1227993013/34.
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Douss, Néjib. « Etude experimentale de cycles a cascades a adsorption solide ». Paris 7, 1988. http://www.theses.fr/1988PA077052.
Texte intégralRésumé :
Etude experimentale et simulation dynamique de systemes de pompe a chaleur a adsorption solide. Les systemes methanol-charbon actif et eau-zeolite sont etudies. Les conditions de temperature des composants (adsorbeur, condenseur et evaporateur) doivent etre homogenes pour la simulation. On considere les cycles intermittents (simple effet), a double effet et a triple effet (cycle a cascades). Determination d'un coefficient de performance pour la production du froid
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Vilekar, Saurabh A. « Catalytic and Electrocatalytic Pathways in Fuel Cells ». Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-dissertations/125.
Texte intégralRésumé :
A fundamental understanding of the kinetics and mechanisms of the catalytic reaction steps involved in the process of converting a fuel into hydrogen rich stream suitable for a fuel cell, as well as the electro-catalytic reactions within a fuel cell, is not only conceptually appealing, but could provide a sound basis for the design and development of efficient fuel processor/fuel cell systems. With the quantum chemical calculations on kinetics of elementary catalytic reaction steps becoming rather commonplace, and with increasing information now available in terms of electronic structures, vibration spectra, and kinetic data (activation energy and pre-exponential factors), the stage is set for development of a comprehensive approach. Toward this end, we have developed a framework that can utilize this basic information to develop a comprehensive understanding of catalytic and electrocatalytic reaction networks. The approach is based on the development of Reaction Route (RR) Graphs, which not only represent the reaction pathways pictorially, but are quantitative networks consistent with the Kirchhoff's laws of flow networks, allowing a detailed quantitative analysis by exploiting the analogy with electrical circuits. The result is an unambiguous portrayal of the reaction scheme that lays bare the dominant pathways. Further, the rate-limiting steps are identified rationally with ease, based on comparison of step resistances, as are the dominant pathways via flux analysis. In fact, explicit steady-state overall reaction (OR) rate expression can also be derived in an Ohm's law form, i.e. OR rate = OR motive force/OR resistance of an equivalent electric circuit, which derives directly from the RR graph of its mechanism. This approach is utilized for a detailed analysis of the catalytic and electro-catalytic reaction systems involved in reformer/fuel cell systems. The catalytic reaction systems considered include methanol decomposition, water gas shift, ammonia decomposition, and methane steam reforming, which have been studied mechanistically and kinetically. A detailed analysis of the electro-catalytic reactions in connection to the anode and cathode of fuel cells, i.e. hydrogen electrode reaction and the oxygen reduction reaction, has also been accomplished. These reaction systems have not so far been investigated at this level of detail. The basic underlying principles of the RR graphs and the topological analysis for these reaction systems are discussed.
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Guan, Xiangguo. « The photochemistry of polyhalomethanes in water and the water-catalyzed dehalogenation reactions of selected isopolyhalomethanes, halogenated methanols and halogenated formaldehydes ». Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B38718960.
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Guan, Xiangguo, et 官向國. « The photochemistry of polyhalomethanes in water and the water-catalyzed dehalogenation reactions of selected isopolyhalomethanes,halogenated methanols and halogenated formaldehydes ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38718960.
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Ferhat-Hamida, Zohra. « Caractérisation des catalyseurs cuivre-zinc par thermodésorption d'hydrogène et thermoréaction ». Poitiers, 1987. http://www.theses.fr/1987POIT2011.
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Kotdawala, Rasesh R. « Adsorption studies of hazardous air pollutants in microporous adsorbents using statistical mechanical and molecular simulation techniques ». Worcester, Mass. : Worcester Polytechnic Institute, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-050407-112429/.
Texte intégralRésumé :
Dissertation (Ph.D.) -- Worcester Polytechnic Institute.Keywords: Activated carbons; Hydrogen cyanide; Methyl ethyl ketone; Adsorption; Mercury; Monte-Carlo; Solvents; Molecular simulations; Zeolites; Water; Methanol; Nanopores. Includes bibliographical references (leaves 147-150).
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Felix, Joseph David. « Methanol, formaldehyde, and acetaldehyde in rain ; Development of a method to determine [delta] ¹⁵N-NO₂⁻ and NO₃⁻ in fresh and brackish waters ». View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-3/felixj/josephfelix.pdf.
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Luo, Hongze. « Polymer/nano-organic composite proton exchange membranes for direct methanol fuel cell application ». Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&.
Texte intégralRésumé :
The proton exchange membrane is one key component of direct methanol fuel cells, which has double functions of conducting protons, separating fuels and oxidant. At present, the performance and price of sulfonic acid proton exchange membrane used in direct methanol fuel cells are deeply concerned. In order to reduce membrane 's cost and improve performance of Nafion membrane, three different kinds of membranes have been studied in this thesis. These membranes are SPEEK membranes, SPEEK/ZP composite membranes and Nafion/ZP composite membranes.
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Rossiter, Angelina Jane. « Solubility and crystal growth of sodium nitrate from mixed alcohol – water solvents ». Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/505.
Texte intégralRésumé :
Due to the ductile nature of the sodium nitrate crystal which deforms plastically under high levels of strain, most of the crystal growth studies in aqueous solution have focussed on the influence of tensile strain, supersaturation and dislocation, using x-ray surface topography to characterise the dislocation structure of the crystal. Most of the crystal growth studies have also focussed on growth from the melt since single crystals of sodium nitrate find application in optical pumping experiments, are a potential substitute for calcite in the preparation of polarising prisms and are interesting for the study of plastic properties because two types of plastic deformation, glide and twinning, take place in these crystals at room temperature. Its crystal habit is also difficult to modify and many researchers have used dyes to investigate its effect. Sodium nitrate is also a highly soluble substance with 96g of sodium nitrate dissolving in 100g of water at 30.0°C, making aqueous solutions of this salt and its supersaturation extremely unstable. Literature on its solubility in organic solvents, such as methanol, ethanol and isoproponal, are quite outdated and limited to specific conditions.This study involved the determination of the solubility of sodium nitrate in aqueous methanol, ethanol and isopropanol solutions at different temperatures and weight percents of the organic solvents. Splitting into two liquid phases was observed when using isopropanol, however this phase separation does not occur at low and high mass fractions of alcohol, as at lower concentrations of one solvent the two solvents are miscible. Whereas in the presence of methanol and ethanol the solubility of sodium nitrate in water was significantly reduced, with the solubility decreasing with increasing molecular weight of the alcohol. The experimental data for methanol and ethanol was used for the determination of the ion-specific Non random two liquid (NRTL) parameters by correlating with the modified extended NRTL model. It was observed for both methanol and ethanol that the model was found to satisfactorily correlate the data at low to moderate concentrations of alcohol. However, as the concentration of alcohol rises the model prediction was found to be less satisfactory, probably due to the interaction parameters of NRTL between alcohol and the ions not being able to represent the low solubility of electrolytes.The growth rates of individual faces of sodium nitrate crystals grown in situ in a batch cell and observed with an optical microscope were measured at different temperatures (20.0, 30.0 and 40.0°C) and relative supersaturations (0.02, 0.04, 0.06, 0.08 and 0.1) to determine the kinetics of growth for homogeneous nucleation. A combined growth order, of 1, and activation energy of 23,580 J/mol was obtained indicating that crystal growth in these sets of experiments was diffusion controlled. Crystal growth rates were also obtained for sodium nitrate crystal seeds grown at 20.0°C at a supersaturation of 0.02 and 0.04, in a modified growth cell where the saturated solution was circulated at a flow rate of 4mL/min. The crystal growth rates obtained were much lower in comparison to the growth rates obtained by homogeneous nucleation. In both sets of experiments size independent growth was observed.The surface morphology of the crystals was also observed by optical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) for the crystals grown by homogeneous nucleation to elucidate the mechanism of growth. Liquid inclusions were observed by optical microscopy for crystals that were grown at high temperatures and for a long duration. SEM revealed the presence of pitting on the crystal surface due to the high solubility of sodium nitrate, while AFM images showed the presence of growth hillocks which suggests that crystal growth is surface integration controlled. However, the presence of growth hillocks could have been caused by the formation of some nuclei and surface artefacts when the crystal was taken out from solution. In seeded crystal growth experiments the solute was observed by optical microscopy to deposit onto the crystal surface.The effect of solvent composition on the growth rate and habit modification of sodium nitrate was also investigated with aqueous solutions of methanol and ethanol. Crystal growth rates of sodium nitrate crystals grown in situ in a batch cell by homogeneous nucleation in aqueous ethanol at 30.0°C at 20, 50 and 90 weight percent of ethanol and crystal seeds grown at 20.4°C at a supersaturation of 0.02 and 0.04 at 30, 50 and 90 weight percent of ethanol, in a modified growth cell was measured. It was found that growth rates decrease with increasing amounts of ethanol and the habit of the crystal remains unchanged. The growth rate was also observed to be much lower than the growth rates obtained from pure aqueous solution. For crystals grown by homogeneous nucleation it was observed that with increasing supersaturation, decreasing weight percent of ethanol and with increasing crystal size the number of liquid inclusions observed on the crystal surfaces increased, whereas for seeded crystal growth solute was observed to deposit on to the crystal surface mainly at low alcohol weight percents. Sodium nitrate crystals grown in aqueous methanol was also observed to behave similarly to crystals grown in ethanol, with lower growth rates obtained. For all cases size independent growth was observed.The influence of additives, DOWFAX 3B2 and amaranth was also investigated on the habit modification of sodium nitrate for crystals grown by homogeneous nucleation at 20.0°C at a supersaturation of 0.04. Both additives were observed to be effective in changing the crystal habit of sodium nitrate, with the appearance of triangular truncations or octahedral facets at the corners of the sodium nitrate crystal due to the additive being adsorbed onto the crystal surface. The influence of the additives on the crystal habit modification can be explained due to the presence of the anionic polar group, the sulphonate group. The growth ratio value for DOWFAX 3B2 was also found to decrease with increasing additive concentration.It is believed that the results of this thesis provides up to date data on the solubility of sodium nitrate in aqueous ethanol and for temperatures and weight percents that have not been reported before in literature for the aqueous methanol system. The work reported on crystal growth studies by homogeneous nucleation and using crystal seeds, the effect of solvent and DOWFAX 3B2 on crystal growth rates and habit modification is also new and has not been reported in literature before.
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Liu, Wenpeng. « Methanol, water and heat transport in direct methanol fuel cells for portable power ». 2005. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-869/index.html.
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沙宇軒. « Molecular Dynamics Simulations of Several Physical Property of Liquid Methanol and Mixed Water-Methanol ». Thesis, 2005. http://ndltd.ncl.edu.tw/handle/13608983901868990261.
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Viljoen, Marius. « Design and development of a methanol concentration controller for fuel cells ». Thesis, 2010. http://hdl.handle.net/10352/93.
Texte intégralRésumé :
Thesis (M. Tech.) (Engineering: Electrical, Dept.: Electronic Engineering))--Vaal University of Technology, 2008.The demand for higher efficiency, sustainability and cleaner power sources increases daily. A Direct Methanol Fuel Cell is a power source that can be applied for small to medium household appliances and office equipment. It can ideally be used for operating appliances like notebook computers on remote sites where no electrical power is available. One of the problems in methanol fuel cells is methanol crossover. Methanol crossover occurs when methanol is not completely used in the process of generating electrons, and a certain percentage of the methanol is wasted. Crossover may damage the proton exchange membrane of the fuel cell and reduce the efficiency of a DMFC. Literature reviews were done and suggestions from other writers are discussed on how to reduce methanol crossover. This research focuses primarily on the fact that crossover can be controlled by controlling the methanol / water concentration. A prototype methanol controller was built with an ultrasonic sensor for detecting the density of the methanol/water mixture and a sensor for the temperature of the mixture; this was done because the density of the mixture is dependant on the temperature and the concentration. The controller was calibrated to determine the amount per volume of water and methanol which enables the controller to control the percentage of methanol in the water. The prototype also had the feature built in to adjust the mixture in order to enable the study on the effects of crossover. A data logger function was added to store collected data on a personal computer for the study on methanol and water. It was observed that the sensor was sensitive enough and was able to produce 1% increments of the level of methanol concentration in the water provided the temperature was stable. A methanol controller was successfully built to ensure the correct volume of methanol.
Telkom Centre of Excellence
48
Titmarsh, AM. « Water maser follow-up of the methanol multibeam survey ». Thesis, 2018. https://eprints.utas.edu.au/29627/1/Titmarsh_whole_thesis.pdf.
Texte intégralRésumé :
The Australia Telescope Compact Array has been used to search for 22-GHz water masers towards the 323 6.7-GHz methanol masers detected in the Methanol Multibeam survey between Galactic longitudes 341◦ to 20◦, through the Galactic centre, and we find water masers associated with 156 (∼48 %). Methanol masers with associated water masers have a higher mean integrated luminosity than those without. In sources where both maser species are observed, the luminosities of the methanol and water masers are weakly correlated even after accounting for the partial correlation due to distance. We have inspected the GLIMPSE three colour images of the regions surrounding the masers and cross-matched the maser positions with existing catalogues of Extended Green Objects and Infrared Dark Clouds. We find more Extended Green Objects at sites where both methanol and water masers are present than at sites with only methanol masers, but no significant difference in the fraction embedded within Infrared Dark Clouds. Studying the mid-infrared colours from GLIMPSE, we found no differences between the colours of those sources associated with both methanol and water masers and those associated with just methanol. Analysis of the 1.1-mm thermal dust emission shows dust clumps associated with masers have greater 1.1-mm flux densities and higher column densities than those without. Dust clumps associated with both water and 6.7-GHz methanol masers are generally the most compact clumps followed by those associated with only methanol then the clumps without associated maser emission. Comparing the column density and dust mass calculated from the thermal dust emission at 870 μm, we found no differences between those sources associated with both water and methanol masers and those with methanol only. At 870 μm we found dust clumps at the very highest column densities (above ∼ 1025 cm−2) almost all had an associated methanol maser. We conclude that there is some evidence that protostars with both methanol and water masers are often older than those with only methanol, however, we suggest that the evolutionary phase traced by water masers is not as well defined as for 6.7-GHz methanol masers. Since water masers are collisionally pumped and often show emission further away from their accompanying YSO than the radiatively pumped 6.7-GHz methanol masers, it is likely that water maser properties are not as tightly correlated to the evolution of the parent YSO.
49
Yang, Ching-Jen, et 楊青仁. « DMFC stack development and study of methanol/water crossover ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/24878912357337460316.
Texte intégralRésumé :
碩士元智大學
機械工程學系
96
The characteristics of a 20W direct methanol fuel cell (DMFC) stack were investigated under various operating conditions in order to understand the behavior of the stack. The operating variables included the methanol concentration, the cell temperature, the flow type and flow rate. With the supply of 2M methanol, a maximum power of the stack was found to be 22W (95 mW/cm2) in air. The cell temperature affected performance significantly, and the low flow rate make performance unstable. u-type flow patterns has better performance than z-type flow patterns in the high current. It is because that fluids are moving in the path longer, and cause the flow to remain within a longer time, make the electro-chemical reaction much completely. Operating conditions will affect stack performance, thereby affecting methanol crossover. The experimental results showed that no residual methanol of the recycled water in the cathode, it attributes to the penetration of methanol combust in cathode. The results also showed that the temperature affects methanol crossover significantly and that methanol gas more easily cross over to the cathode at elevated temperature. Water crossover is positively correlated with current, this is attribute to electro-osmotic drag.
50
Wang, Po-wei, et 王柏偉. « Interactions of Oxygen, Water and Methanol with Rutile TiO2(110) ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/dqtyxr.
Texte intégralRésumé :
碩士國立中山大學
化學系研究所
103
In consideration of recent trend in environmental and economical issues of green-process chemistry, the eco-friendly and recyclable titanium oxide has received much attention with the aim of establishing greener, more sustainable photocatalysts. However, the quality of commercial or bench-made TiO2 is somewhat uncontrollable, and thus frequently affects the reproducibility of TiO2-mediated reactions. In order to understand the reaction mechanisms of TiO2-catalyzed interactions of oxygen, water, and methanol, as well as their cross interactions, a single crystal rutile TiO2(110) was selected in this study in order to exclude the complexity caused by powder samples. Ultrahigh vacuum in combination with temperature programmed desorption (TPD), reflection absorption infrared spectroscopy (RAIRS), auger electron spectroscopy (AES), LED UV source and density function theory (DFT) calculations were used to study the TiO2 thermal and photo-chemistry. O2 desorbs molecularly at 270 K and oxygen vacancies (Ov) are responsible for the dissociative adsorption of O2 molecules to form O adatoms (Oa). In the study of water molecules, the multilayer, the second layer and the monolayer molecular desorption peaks were found at 157 K, 180 K and 190 K, respectively. Under 365 nm UV light irradiation, water remained inactive. Methanol was found to turn into formaldehyde which desorbed at 209 K in TPD, once adsorbed on surface and followed by UV irradiation. Coadsorbed O2 and methanol can create methoxy intermediates by OH bond breaking with Oa. Under UV irradiation, formaldehyde and methanol were observed to desorb at 216 K and 260 K. Without UV irradiation, disproportionation of methoxy affords formaldehyde and methanol simultaneously at 500-600 K.