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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Redox Study of Cobalt(II)-Cobalt(III) Polypyridyl

Long, Larry 01 August 1978 (has links)
The rate of reduction of [Co(dipy)3]3+ by [Co(tripy)2]2+ has been examined in six nonaqueous solvents and water. The kinetic results in these solvents were compared with those obtained in nine other solvents where the same reaction was investigated. Activation parameters were obtained over a temperature range of 5° to 50°C with the ionic strength at 0.0027 or 0.0046 M. The slowest rate of electron transfer was found in acetonitrile while the fastest occurred in acetophenone, the solvent of lowest dielectric constant. A linear correlation between ln k and the reciprocal dielectric constant of the solvent was obtained for most solvents when corrections for differences in ionic strength and free energy drive were made. Only nitromethane and acetonitrile exhibited marked deviations from linearity. Solvent properties such as viscosity, refractive index, surface tension, and density had little if any effect on the redox rate. The redox rate constants in the aprotic aromatic solvents, nitrobenzene, benzonitrile, and acetophenone paralleled the free energy drive of their respective reactions. No such trend was found with the other solvent groups. In fact, the polar solvents exhibited nearly the reverse trend. The kinetic results of this study have been interpreted in terms of the theoretical predictions of Marcus. The effects of ionic strength and ion pairing in the different solvents have also been discussed.
82

A Spectrophotometric Equilibrium Study of Nickel(II)-3, 4', 4", 4'"-Tetrasulfophthalocyanine

Lowery, Stephen 01 August 1975 (has links)
There have been several studies made on the effects of various central metal ions on the aggregation of tetrasulfonated Phthalocyanine dye complexes in aqueous solution, but there have been no studies made on the aggregation of the nickel(II)-4, 4', 4", 4'"-tetrasulfoohthalocyanine (NiII-TSPC) complex. Therefore, a study of the effects of nickel(II) on the aggregation of its aqueous tetrasulfonated Phthalocyanine dye complex was Proposed so that a comparison might be made with nrevious studies of central metal ion effects. It was found, however, that NiII-TSPC gives a much higher degree of aggregation in water than the metal complexes Previously studied and that common equilibria were absent in the concentration range of 1.0 x 10-3 to 1.0 x 10-7 M. The spectra indicated the presence of a single species in this concentration range. Therefore, a comparison of the effects of nickel (IT) on the aggregation of tetrasulfonhthalocyanines in aqueous solutions could not be made with analogous dye systems examined previously using other transition metals. A study of the literature revealed that there have been no studies made on the effects of a pure organic solvent on the aggregation of transition metal complexes of tetrasulfonhthalocyanine dyes. Therefore, this study was made to determine such solvent effects on the NiII-TSPC complex.
83

Investigation of the Role of Phenols in Oxidative Degradation of Coal-Derived Naphthas

Macke, Jeffrey 01 May 1982 (has links)
The oxidative instability of coal liquids is a possible problem for the utilization of these alternate fuels. Past experience with both petroleum and coal-derived distillates indicates that heteroatomic species are intimately involved in such degradation. However, the exact nature of the chemistry is, in many cases, unclear. The goal of this work is to study the role of phenols in the chemistry of oxidative degradation of naphthas from a variety of current conversion processes. The effects of exposure to oxygen, metal surfaces, and metal salts have been investigated in order to identify the major routes leading to gum formation. Coal-derived naphthas were aged under 02 and N2 as received and in contact with copper or cuprous chloride at various temperatures. The rate of 02 consumption was measured manometrically, and compositional changes were monitored via infrared, nuclear magnetic resonance, and mass spectrometry. The observed rates of 02 consumption, catalytic effects, and compositional changes were analyzed to identify the major chemical reactions responsible for precipitate formation.
84

The Partial Oxidation of Methane to Methanol & Formaldehyde

Matthews, Terry 01 December 1987 (has links)
The conversion of methane into methanol is viewed as one approach to utilizing the vast reserves of natural gas. One such prospect for the utilization of natural gas is the partial oxidation of methane to methanol. Methanol ranks high on the commodity market. As a liquid it is easily transportable and therefore skirts the issue of vast amounts of a gas having to be transported either by pipeline or by liquifying. The catalytic partial oxidation of methane to methanol is investigated. Two different reactor systems are employed. The first system is a fixed bed system. The second is a fluid bed system. Areas to be addressed are different catalyst systems, different loading rates, elemental promotion, different supports, surface area, catalyst particle mesh size, and effects of preparation.
85

Electron Transfer Reactions of an Osmium (II) Polypyridyl Complex with Oxidizing Agents

McClanahan, Stephen 01 December 1978 (has links)
Redox rates between polypyridyl osmium (II) complex, OsCl(py)3(bipy)+, with tris(1,10-phenanthroline) cobalt (III), Co(phen)33+, and Ce(IV) were examined in aqueous solution. Both reaction systems exhibited second order kinetics. The osmium (II) - cobalt (III) redox reaction was found to have a rate constant of 2.3 x 105 M-1 sec-1 at 22°C and µ = 0.003M from which the isotopic electronic exchange rate constant for the OsCl(py)3(bipy)+/2+ system was estimated to be 1.5 x 109 M-1sec-1. Ionic strength effects on the Ce(IV) - Os(II) redox reaction were studied as well as the effects of Ce(IV) and NaN03 concentrations on the solution pH. The redox rate constant was 52 M-1sec-1 at 22°C and µ = 0.01M. The reaction rate decreased with increasing ionic strength and a Bronsted plot was consistent with Ce(IV) present as Ce(NO3)5(OH)23-. Activation parameters were determined and a mechanism of electronic transfer was proposed for each system. The Os(II) - Co(III) redox reaction is believed to occur via an outer-sphere mechanism while an inner-sphere mechanism was proposed for the Os(II) - Ce(IV) system. Since relatively high acid concentrations were used in the Ce(IV) - Os(II) study, the acid hydrolysis rate of the Os(II) complex was measured and found to be sufficiently slow so as not to interfere with the redox rate. This reaction exhibited third-order kinetics.
86

An Alternate Solution to the Two-Dimensional Ising Model

Meyers, B. Craig 01 August 1974 (has links)
An alternate solution for the two-dimensional Ising model in a zero external magnetic field is presented. Following Kaufman, the partition function is written as the trace of a certain matrix product. The trace can be evaluated by computing the determinant of a related matrix. The determinant is evaluated by finding the product of its eigenvalues; in the thermodynamic limit the result is equivalent to that found by Onsager.
87

Characterization of Potassium Promoted & Unpromoted Fischer-Tropsch Catalysts

Miller, Steven 01 December 1985 (has links)
The technique of x-ray photoelectron spectroscopy (XPS) has been applied to characterize iron-manganese catalysts used in Fischer-Tropsch synthesis. The catalysts, which vary in composition from 10 FE/90 Mn, to 50 Fe/50 Mn are analyzed after being placed in a slurry reactor and having synthesis gas reacted over them. Changes, in catalyst composition are investigated further using in situ techniques. Additionally, 20 Fe/80 Mn catalysts containing potassium in the range of 0.1 wt.% to 1.3 wt.% are analyzed in the same manner. These studies have permitted the identification of some of the factors influencing activation and deactivation, product selectivity, and surface speciation.
88

Cyclic Voltametry Studies of Various Ylide Metallocenes

Mojesky, Mark 01 May 1981 (has links)
The redox potentials of [Fe(CpSMe2)2]2+ (CpSMe2= dimethysulfoniumcyclopentadienflide), [Ni(CpSMe2)2]2+, [Co(CpSMe2)2]2+, [Mn(CpSMe2)2]2+, (CpPPh3)HgBr2 (CpPPh3= triphenylphosphoniumcyclopentadienylide), (CpPPh3)HgCl2, and MoPC (PC = phthalocyanine) were examined using cyclic voltammetry (CV). The experimentation was carried out in a temperature controlled environment. With the exception of the mercury and molybdenum complexes, the solvent system consisted of 15 milliliter mixture of acetonitrile and water. Due to the solubility problems of the mercury bromide complex, dimethylformamide (DMF) was used as the solvent. Pure acetonitirile was used for the mercury chloride and molybdenum complexes. The emphasis of this research was directed towards the iron complex. Its complimentary pure metallocene FeCp2(Cp = cyclopentadiene) is well characterized, thereby permitting a comparison of the two complexes. The iron sulfonium ylide complex was found to have lower redox potentials. This supports the anticipated effect of the added dimethylsulfonium (SMe2) group.
89

The Anodic Stripping Voltammetry Determination of Trace Elements in Coal Ash

Montoya, Jesus 01 December 1981 (has links)
The application of anodic stripping voltammetry (ASV) to the determination of several trace metals in coal ash was studied. An ashing and ash digestion method was developed which limited the total salt and acid concentration of the analyte solutions, a necessary step for routine analysis. The simultaneous determination of cadmium, copper, lead, and zinc in eight Pennsylvania State University Coal Bank Samples and in the National Bureau of Standards SRM 1632a coal sample were made. Chromium was separated from the prepared coal ash solutions and determined independently in the form of chromate(VI). All values determined by ASV methods were in good agreement with those determined by auomic absorption spectrophotometry. There was also good agreement between the anodic stripping voltammetry values and those reported for the NBS 1632a coal sample, and most of the values reported for the Pennsylvania State University coal samples.
90

Part I: Oxidation of Heavy Metal Sulfides in Relation to the Environment; Part II: Fundamental Theory & Experiments Concerning Gas Chromatography & Mass Spectrometry

Morgan, Judith 01 November 1990 (has links)
Oxidation of heavy metal sulfides is a thermodynamically spontaneous process. Because of this, metal sulfides in the presence of oxygen are not stable. Currently there are over 100 streams and rivers, within the U.S., contaminated with heavy metal mine drainage; therefore an approved method of restoration is necessary. Precipitation of heavy metals as sulfides using H2S as a reductant has been favorably reviewed as a restorative technique to clean up mining areas. However, using this technique on the laboratory scale does not prove to be a viable answer and shows strong pH dependence. In the past three years the ILI (Instrumentation and Laboratory Improvement) has awarded funding to over 50 institutions, in the U.S., for the purchase of GC/MS. Therefore, there is a great need for laboratory experiments to properly train students in this field in American universities. A strong theoretical treatment for sophomore-level students is presented within this thesis and from this, three experiments have been developed in order to educate young professionals seeking a career in the field of chemistry.

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