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With the emergence of new biorenewable transportation fuels, the role of heteroatoms in combustion has increased tremendously. While petroleum-based fuels are primarily hydrocarbons, many biorenewable fuels contain heteroatoms such as oxygen and nitrogen, introducing new challenges associated with toxic emissions. A fundamental understanding of the chemical kinetics of combustion of these heteroatomic fuels is necessary to elucidate the pathways by which these toxic emissions are formed and may be achieved through the development of combustion models. Reaction sets, the core of these combustion models, may be assembled for individual fuels through a balance of employing vetted rate constants from prior publications, quantum chemistry calculations, and rate constant estimations. For accuracy, reaction sets should be tested against experimental combustion studies such as low-pressure flame experiments using molecular-beam mass spectrometry (MBMS) or chemiluminescence and high-pressure shock-tube experiments. This dissertation presents the development of a new reaction set to describe gas-phase combustion chemistry of fuels containing only hydrogen, carbon, oxygen, and nitrogen. The foundation of this model was a reaction set to describe combustion of ammonia flames. This reaction set contains only H/N/O chemistry for simplicity. The new reaction set was tested against a pyrolysis shock-tube study, as well as 12 MBMS flame experiments under a variety of conditions, including different mixtures of fuels and oxidizers (NH3, N2O, H2, NO, O2), fuel equivalence ratios (lean to rich), pressures, and concentrations of diluent gas. Additionally, the base H/N/O mechanism was expanded to include carbon chemistry and was tested against flames of dimethylamine, ethylamine, and a methane/ammonia mixture. This reaction set was employed to study heterocyclic biofuels including a fuel-rich flame of tetrahydropyran, the monoether analogue to cyclohexane and the basic ring in cellulose. Additionally, the model was used in a study of morpholine, a 6-membered ring with both ether and amine functionalities, testing the model against fuel-rich flame studies using both MBMS and chemiluminescence techniques and high-pressure shock-tube studies for both oxidation and pyrolysis at elevated temperatures and pressures. Lastly, the model was used to study the combustion of hypergolic rocket fuels, specifically monomethyl hydrazine and tetramethylethyldiamine with red fuming nitric acid.

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High molecular weight, soluble polyimides were synthesized by a non-traditional synthetic route utilizing solution imidization techniques and diester-diacid derivatives of various commercially available dianhydrides. "One pot" syntheses were conducted using a solvent system of N-methylpyrrolidinone and σ-dichlorobenzene at temperatures of 170°C to 180°C and times of 24 hours or less. The resulting polyimides were soluble in amide solvents at concentrations of 15 to 20 percent (w/v) at 25°C, were fully cyclodehydrated as determined by non-aqueous potentiometric titrations, possessed molecular weight distributions very close to the theoretical value of 2.0 and displayed glass transition temperatures consistent with accepted values for the same materials synthesized via conventional methods. Model studies indicated that polymerization proceeds via intermediate conversion of the esteracid functional groups to anhydride groups. This method was also successfully employed in the synthesis of controlled molecular weight ethynyl-functionalized thermosetting imides. High T_g's, low end group concentrations and the relatively low cure temperature of the ethynyl end group restricted sample fabrication to thin, solution-cast films; nevertheless, several of these systems were evaluated for high temperature stability and were identified as potential candidates for 700°F (371°C) applications. In addition, a novel polyimide synthesis utilizing diamine dihydrochlorides as substitutes for unstable diamines was also investigated, and a series of novel polyimides based on diaminoresorcinol and commercial dianhydrides was synthesized. Diaminoresorcinol dihydrochloride and dianhydride were heated in an NMP/dichlorobenzene mixture; at sufficiently high temperatures the insoluble dihydrochloride dissociates, liberating hydrogen chloride gas and the soluble free diamine, which rapidly dissolves and reacts with dianhydride before decomposition occurs. The poly(hydroxy-imide)s possess T_g's in excess of 250°C, are soluble in amide solvents and, as might be expected, are extremely hygroscopic. / Ph. D.

The thermochemistry of several species, and the kinetics of various H atom radical reactions relevant to atmospheric and combustion chemistry were investigated using ab initio theoretical techniques and the flash photolysis / resonance fluorescence technique. Using ab initio quantum mechanical calculations up to the G3 level of theory, the C-H bond strengths of several alkanes were calculated. The bond strengths were calculated using two working reactions. From the results, it is apparent that the bond strengths decrease as methyl groups are added to the central carbon. The results are in good agreement with recent experimental halogenation kinetic studies. Hydrogen bond strengths with sulfur and oxygen were studied via CCSD(T) theory, together with extrapolation to the complete basis set limit. The results for the bond dissociation energies (ground state at 0 K, units: kJ mol-1) are: S-H = 349.9, S-D = 354.7, HS-H = 376.2, DS-D = 383.4, and HO-H = 492.6. These data compare well with experimental literature. The rate constants for the isotopic reactions of H + H2S, D + H2S, H + D2S, and D + D2S are studied at the QCISD(T)/6-311+G(3df,2p) level of theory. The contributions of the exchange reaction versus abstraction are examined through transition state theory. The energy of NS was computed via CCSD(T) theory, together with extrapolation to the complete basis set limit. The results were employed with three working reactions to find ΔfH0(NS) = 277.3 ± 2 kJ mol-1 and ΔfH298(NS) = 278.0 ± 2 kJ mol-1. This thermochemistry is consistent with, but much more precise than, earlier literature values. A kinetic study of the reaction of H + CH2CCl2 was conducted over the temperature range of 298 - 680 K. The reaction was found to be pressure dependent and results of the rate constants and their interpretation via unimolecular rate theory are presented.

This thesis is presented in two parts. In part one, the excess molar volumes and the excess molar enthalpies have been determined for several binary systems at 298.15 K using an LKB flow microcalorimeter and/or a 2277 Thermal Activity Monitor and an Anton Paar Digital Densitometer. The excess molar volumes and excess molar enthalpies, V; and H; , have been determined for systems involving an alkanol (I-propanol, 2-propanol) mixed with a hydrocarbon (1hexene, I-heptene, l-octene, I-hexyne, I-heptyne, l-octyne). The results show trends relating to the degree of unsaturation of the hydrocarbon to the position of the hydroxyl group on the alkanol. The excess molar volumes and excess molar enthalpies, V; and H; of di-n-butylamine + diethyl ether or dipropyl ether or di-l-methylethyl ether or dibutyl ether or 1,1 dimethylethyl methyl ether or 1,1 dimethylpropyl methyl ether or tetrahydrofuran or tetrahydropyran or 1,4 dioxane have been measured over the whole composition range at the temperature 298.15 K in order to investigate di-n-butylamine - ether interactions. The V; values for each of the systems studied are negative with the exception of the mixtures of (di-n-butylamine + dibutyl ether or tetrahydrofuran or tetrahydropyran or 1,4 dioxane. The H; results over the whole mole fraction range are formed endothermically. Measurements were also made on mixtures involving (a cycloalkane + a pseudocycloalkane). The congruency theory was tested for the (cycloalkane + pseudo-cycloalkane) mixture. The cycloalkane mixtures studied here did not satisfy the null test of the congruency principle. In the second part of this thesis the main aim of the investigation was to apply ambient temperature hydrogen peroxide bleaching techniques to a novel non-woven fabric and to optimize the treatment conditions for this technique. Five cold-pad batch bleaching formulas were applied to the non-woven and the sample fabrics were analyzed for the following properties a) fluidity (measure of degree of degradation of the cotton fibre as a result of the bleaching process) b) wettability (absorbency) c) whiteness (using instrumental techniques) d) inherent fibre surface properties (SEM) A method was elucidated for the cold batch bleaching of the non-woven which produced a fabric with minimum fibre damage, an acceptable degree of whiteness and excellent absorbency properties. The treatment parameters of time (Xl), temperature(x2) and hydrogen peroxide concentration (x3) for this method were optimised using a multiple regression analysis for three variables and response surface plots. / Thesis (M.Sc.)-University of Natal, Durban, 1993.

O objetivo deste trabalho é estudar as reações de isomerização e cisão dos isômeros C2F2Cl2, e determinar entalpias de formação e potenciais de ionização para derivados halogenados do eteno, através de cálculos ab initio, e ainda, para algumas reações determinar a constante de velocidade microcanônica k(E*), segundo o formalismo da teoria RRKM. Foram obtidas a barreira energética e a estrutura do estado de transição para a reação de isomerização do (Z)-CFCl=CFCl ao isômero (E)-CFCl=CFCl, que ocorre através de um estado de transição com uma barreira de energia calculada de 54,223 kcal/mol com o método CASSCF. Foi analisada a possibilidade de a isomerização ocorrer via intermediários etilidenos halosubstituídos, porém as barreiras de energia para estas reações e resultados obtidos para a constante de velocidade k(E*) indicam que a reação direta predomina sobre as vias de formação de etilideno halosubstituído em baixas energias, até cerca de 154 kcal/mol pelo menos. A não observação, experimentalmente, de formação do isômero CF2=CCl2 a partir desses intermediários também corrobora com os resultados obtidos através dos cálculos. Para as reações de cisão de ligação C=C dos compostos CF2=CCl2, (Z) e (E)-CFCl=CFCl e CF2=CCl, as curvas de energia em função do comprimento desta ligação mostram que a cisão do CF2=CCl ocorre a uma energia menor do que para as demais substâncias. Porém, a cisão da ligação C-Cl na substância CF2=CCl2 é a que possui a menor barreira energética. Utilizando a teoria variacional do estado de transição, determinamos a estrutura do estado de transição para esta reação e a constante de velocidade microcanônica, k(E*), sendo esta maior que as determinadas para a formação dos etilidenos halosubstituídos. Potenciais de ionização adiabáticos (PIA) e verticais (PIV) de haloetenos foram obtidos utilizando as teorias G2 e G3. Os resultados obtidos com a teoria G3 são mais próximos dos valores experimentais, ou tão exatos quanto, comparados aos valores calculados encontrados na literatura. As mudanças na energia de correlação eletrônica e energia de relaxação dos orbitais são importantes para a obtenção de resultados de PIV quantitativamente melhores em comparação com os resultados obtidos a partir da energia do HOMO. Também foram feitos cálculos de entalpias de formação para etilenos halogenados utilizando as teorias G2 e G3 utilizando reações isodésmicas. A comparação entre os valores calculados por nós e outros valores calculados encontrados na literatura mostram que apesar das reações isodésmicas serem um método capaz de gerar bons resultados, devido ao cancelamento dos erros nos valores calculados, o resultado final é dependente dos valores experimentais escolhidos. / We report ab initio calculations on the isomerization and fission reactions of C2F2Cl2 isomers and also the enthalpies of formation and the ionization potentials of halogenated ethylenes. We have also evaluated the microcanonical rate constant k(E*) using the RRKM formalism to gain more insight into mechanistics details of some reactions. The energy barrier and the structure of the transition state for the isomerization reaction of (Z)-CFCl=CFCl to (E)-CFCl=CFCl, occurs by a transition state with a calculated barrier of 54,223 kcal/mol using the CASSCF method. The isomerization reactions through ethilidene halosubstituted intermediates was also tested, however the energy barriers to these reactions showed be greater and the results obtained for the rate constant k(E*) stated that the direct reaction predominates over the formation of the halosubstituted ethilidene at low energies, until 154 kcal/mol at least. The experimentaly unobserved formation of CF2=CCl2 from intermiaries confirms the calculated results. For the fission reaction of the C=C bond on CF2=CCl2, (Z) and (E)-CFCl=CFCl and CF2=CCl , the plots of energy as a function of the bond length show that the fission of CF2=CCl occurs with the lowest energy of all these reactions. However, the fission of C-Cl on the CF2=CCl2 shows to have the lowest energy barrier. By the variational transition state theory, we have determined the structure of the transition state for that reaction and the rate constant k(E*), beeing this higher than that determined to the halosubstituted ethylenes. Adiabatic ionization potentials (AIPs) and vertical ionization potentials (VIPs) for haloethylenes were obtained applying G2 and G3 theories. The results obtained with G3 theory are the nearest within the experimental values or, at least, with the same exactness, compared with other earlier calculated methods. The changes in eletronic correlation energy and orbital relax energy are important to achieve quantitatively better results comparativily with results obtained from HOMO energy. Moreover, we have done calculations of enthalpies of formation of haloethylenes using G2 and G3 theories using isodesmic reactions. The comparison among the values calculated by us and other values found in the literature shows that, however the use of isodesmic reactions may be a method able to achieve good results, because the calculated errors in the energy values are being cancelled , the final result is very dependent on the choosen experimental values.

A bondingness term is further developed to aid in heat of formation (ΔfHº) calculations for C, N, O and S containing molecules. Bondingness originated from qualitative investigations into the antibonding effect in the occupied MOs of ethane. Previous work used a single parameter for bondingness to calculate ΔfHº in an alkane homologous series using an additivity scheme. This work modifies the bondingness algorithm and uses the term to parameterise a test group of 345 molecules consisting of 17 subgroups that include alkanes, alkenes, alkynes, alcohols, ethers, aldehydes, ketones, carboxylic acids, esters, amines, amides, diazenes, nitriles, nitroalkanes, nitrates, thiols and benzenoids. Comparing experimental with calculated ΔfHº values, a standard deviation for the residuals of 6.3 kJ mol 1 can be achieved using bondingness with a simple steric repulsion term (SSR) in a bond additivity scheme, and a standard deviation of 5.2 kJ mol 1 can be achieved using a Lennard-Jones potential. The method is compared with the group method of Pedley, which for a slightly smaller set of 338 molecules, a subset of the test set of 345 molecules, gives a standard deviation of 7.0 kJ mol 1. Bondingness, along with SSR or a Lennard-Jones potential, is parameterised in the lowest level of ab initio (HF-SCF) or semiempirical quantum chemical calculations. It therefore may be useful in determining the ΔfHº values for the largest molecules that are amenable to quantum chemical calculation. As part of our analysis we calculated the difference between the lowest energy conformer and the average energy of a mixture populated with higher energy conformers. This is the difference between the experimental ΔfHº value and the ΔfHº calculated for a single conformer. Example calculations which we have followed are given by Dale and Eliel et al.. Dale calculates the energy difference for molecules as large as hexane using relative energies based on the number of 1,4 gauche interactions. We have updated these values with constant increments ascertained by Klauda et al. as well as ab initio MP2 cc-pVDZ relative energies and have included calculations for heptane and octane.

Polymer solutions in which there are strong specific interactions between the polymer and the solvent are of interest in a number of biological applications. Of particular interest are polymer solutions in which supercritical carbon dioxide (CO2) is the solvent, because polymer processing with CO2 is an important application of green chemistry. Unfortunately, experimental data on the phase behavior of polymer - CO2 systems are relatively scarce, as are models that describe the phase behavior of such systems. The focus of this research is therefore on developing a thermodynamic model based on lattice theory for calculating phase behavior of high pressure polymer solutions with specific intermolecular interactions. A new model, termed the LELAC (Lattice-based Extended Liquid Activity Coefficient) model is proposed based on the gART-L model of Sukhadia and Variankaval. The new model incorporates the compressibility effect at high pressures. The parameters of the model are (1) the equilibrium constant for association between a polymer segment and a solvent, (2) the specific interaction energy between a polymer segment and a solvent, and (3) the dispersion interaction energy. The dispersion interaction energy is calculated using Regular Solution Theory and therefore depends on the pure component properties. One or both of the remaining parameters is obtained from independent measurements such as FT- IR spectra. Alternatively, the two parameters can be obtained by fitting data. Cloud point curves of polymer - CO2 systems have been successfully correlated (1.3 % error) with the new model. Also, using fitted parameters from cloud point data, the sorption behavior of CO2 in polymers has been predicted. The polymer investigated include PBMA, PVAc and Polyacrylates. Comparison of cloud points with those obtained using the SAFT model revealed that the new model performs better than the SAFT model (3.6% error) with two adjustable parameters. The use of FT-IR to investigate interactions between CO2 and a number of polymers has been studied. The results confirm that complexes are formed between CO2 and PMMA, PEMA, PBMA, PVMK, and PVAc. A complex of PVC and CO2 is reported and a new mechanism involving a carbon oxygen triple bond is postulated for this system.

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