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1
Keiffer, M. "High-temperature reactions of alkyl and peroxy species." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382582.
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Morozov, Aleksandr [Verfasser], Wolfgang H. [Akademischer Betreuer] Müller, Alexander [Akademischer Betreuer] Freidin, Wolfgang H. [Gutachter] Müller, Alexander [Gutachter] Freidin, Victor [Gutachter] Eremeev, and Holm [Gutachter] Altenbach. "Numerical and analytical studies of kinetics, equilibrium, and stability of the chemical reaction fronts in deformable solids / Aleksandr Morozov ; Gutachter: Wolfgang H. Müller, Alexander Freidin, Victor Eremeev, Holm Altenbach ; Wolfgang H. Müller, Alexander Freidin." Berlin : Technische Universität Berlin, 2021. http://d-nb.info/1228978379/34.
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Kanbe, Yuichi. "Control of Alloy Composition and Evaluation of Macro Inclusions during Alloy Making." Doctoral thesis, KTH, Tillämpad processmetallurgi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-27773.
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In order to obtain a good performance and predict the properties of alloys, it is necessary to control the contents of alloying elements and to evaluate a largest inclusion in the product. Thus, improved techniques for both control of alloy elements and evaluation of the large inclusion in products will enable us to provide better qualities of the final products. In the case of one Ni alloy, (NW2201, >99 mass%Ni), the precise control technique of Mg content is important to obtain a good hot-workability. Hereby, the slag/metal reaction experiments in a laboratory have been carried out at 1873 K, so that the equilibrium Mg content and kinetic behavior can be understood. More addition of Al in the melt as well as higher CaO/Al2O3 value of slag resulted in higher amount of Mg content in Ni. For the same conditions of Al content and slag composition, the mass transfer coefficient of Mg in molten Ni was determined as 0.0175 cm/s. By applying several countermeasures regarding the equilibrium and kinetic process to the plant trials, the value of the standard deviation for the Mg content in an alloy was decreased till 0.003 from 0.007 mass%. The size measurements of largest inclusions in the various alloys (an Fe-10mass%Ni alloy, 17CrMo4 of low-C steel and 304 stainless steel) were carried out by using statistics of extreme values (SEV). In order to improve the prediction accuracy of this method, three dimensional (3D) observations were applied after electrolytic extraction. In addition, the relationship of extreme value distribution (EVD) in the different stages of the production processes was studied. This was done to predict the largest inclusion in the products at an early stage of the process. A comparison of EVDs for single Al2O3 inclusion particles obtained by 2D and 3D observations has clarified that 3D observations result in more accurate EVD because of the absence of pores. Also, it was found that EVD of clusters were larger than that of single particles. In addition, when applying SEV to sulfide inclusions with various morphologies, especially for elongated sulfides, the real maximum sizes of them were able to be measured by 3D observations. Geometrical considerations of these particles clarified the possibility of an appearance of the real maximum inclusion sizes on a cross section to be low. The EVDs of deoxidation products in 304 stainless steel showed good agreement between the molten steel and slab samples of the same heat. Furthermore, the EVD of fractured inclusion lengths in the rolled steel were estimated from the initial sizes of undeformed inclusions which were equivalent with fragmented inclusions. On the other hand, from the viewpoint of inclusion width, EVD obtained from perpendicular cross section of strips was found to be useful to predict the largest inclusion in the final product with less time consumption compared to a slab sample. In summary, it can be concluded that the improvement of the techniques by this study has enabled to precisely control of alloy compositions as well as to evaluate the largest inclusion size in them more accurately and at an earlier stage of the production process.QC 20101222
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Syal, Sham. "The non-equilibrium kinetics of reversible bimolecular reactions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0017/NQ45195.pdf.
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BERTOLINI, THARCILA C. R. "Estudo comparativo sobre a adsorção de diferentes classes de corantes em zeólitas de cinzas de carvão: modelagem cinética e de equilíbrio." reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10557.
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IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Painter, D. M. "Kinetic and equilibrium studies at solid/liquid interfaces." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384026.
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Gicquel, Alix. "Etude des processus catalytiques heterogenes dans les milieux plasmas basse pression hors-equilibre." Paris 6, 1987. http://www.theses.fr/1987PA066396.
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Etude des reacteurs tubulaires a plasma basse pression dans le cas de reactions consecutives cinetiquement controlees par une etape endothermique. Le role catalytique d'une feuille de tungstene se traduit par une augmentation de l'excitation vibrationnelle des molecules dans la couche limite; a contrario, le transfert d'energie vers le solide est d'autant moins important que le solide est meilleur catalyseur. L'excitation vibrationnelle se communique aux molecules reactives au cours de transfert vibration-vibration. Les especes reactives sont alors susceptibles de franchir les verrous reactionnels soit en phase gazeuse (etape endothermique) soit en phase heterogene (etape de chimisorption)
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Napier, Duncan George. "Far-from-equilibrium gas kinetic theory : reactive systems and sound propagation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25127.pdf.
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Rabbitt, Lynsey C. "Some kinetic and equilibrium studies of the reactions of nitrobenzofurazan derivatives with nucleophiles." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4623/.
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The reactions of 4,6-dinitrobenzofuroxan, (DNBF) with aniline and six of its N- and ring- substituted derivatives have been studied. It is known that aniline usually reacts as a nitrogen nucleophile, forming nitrogen-bonded σ-adducts with trinitrobenzene, (TNB) in the presence of a strong base. However, in acidic solutions, a-adducts are formed with bonding between a ring carbon atom of the anilines and the 7-position of DNBF. A value of 2.0 for k(_H)/k(_D), the kinetic isotope effect, indicates that bond formation is largely rate determining in the substitution pathway. Estimates were made for the pK(_a) values relating to carbon protonation of the anilines. In solutions of aniline buffered with aniline hydrogen chloride it was possible to distinguish an initial, rapid reaction via the nitrogen centre to give anionic a-adducts. The thermodynamically more stable carbon-bonded σ-adducts were observed to form over time. In the presence of excess amine, these zwitterionic σ-adducts were in rapid equilibrium with the deprotonated forms. Equilibrium constants for this acid-base process were measured, and indicate that the negatively charged DNBF moiety is electron withdrawing relative to hydrogen. Kinetic and equilibrium studies are reported for the reactions of several aliphatic amines with a selection of nitrobenzofurazan derivatives in DMSO. Rapid reaction at the 5- position to yield σ-adducts was followed by slower formation of the thermodynamically more stable adducts at the 7-position. Proton transfer from the zwitterionic intermediates to a second molecule of amine was generally rapid, and the attack of the amine rate determining. This is in direct contrast with reactions involving TNB, where the proton transfer step is usually rate limiting. The reactions of four nitrobenzofurazan derivatives with sulfite have been studied in aqueous solutions. The stability of the initially formed 5-adducts was remarkably high in comparison with the corresponding σ-adducts formed from attack of sulfite on TNB. A slow isomerisation was observed to yield the thermodynamically more stable 7-adducts, except in the reaction with 4-nitro-7-chlorobenzofurazan, where attack at the 7-position would lead to nucleophilic substitution of the chloro-group to yield the substitution product. The mechanism of the isomerisation was found to occur via an intermolecular rearrangement, and not according to an intramolecular Boulton-Katritzky rearrangement. Sulfite attack on DNBF was also studied. A value for the equilibrium constant for the formation of a 1:1 adduct, K(_7) 1.1 x 10(^13) dm(^3) mol(^-1) was determined. This high value is a reflection of the high carbon basicity of the sulfite ion, and the highly electrophilic character of DNBF. Evidence was also obtained for the formation of 1:2 di-adducts in the presence of excess sulfite, which are present in the isomeric cis and trans forms.
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Blount, Jay Adam. "Synthetic, equilibrium, kinetic and mechanistic studies of the reactions between azo dye ligands and Ni²+." Thesis, University of Warwick, 2008. http://wrap.warwick.ac.uk/59448/.
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12 azo dye ligands LI-LI2 that are used in the inkjet printer industry have been synthesised and characterised. The dyes L5B and L3765 were supplied as gifts by the chemical company Avecia. All dyes were fully examined by IH NMR, 13e NMR, IR spectroscopy, electrospray mass spectroscopy, atomic absorption spectroscopy, UV-Visible spectroscopy and microanalyses. Melting points were also determined. pKa values have been determined by visible spectroscopy for the dyes PAN(Aldrich), L7, L3765, Ll, L5 and L5B. Stability constant measurements have been attempted for the Ni(II) complexes of PAN, LI and L5 using UV-Visible spectroscopy. Single wavelength stopped-flow kinetic studies of the reactions of Ni(II) with PAN(Aldrich), PADA(Aldrich), SUDAN I(Aldrich), L3765 and L7 were carried out. Multi wavelength stopped-flow kinetic studies of the reactions of Ni(II) with L 1, L 7, L5 and L5B were examined and rate constants for complex formation (kf ) were determined. Rates of dissociation of [Ni(PAN)2] using ligand exchange with either EDTA or 2,2' :6' ,2" -Terpyridine (Terpy) were investigated using UV -Visible spectroscopy. Relative stabilities of [Ni(II)(PAN)t, [Ni(II)(L 7)] and [Ni(II)(L3765)r have been determined. Dissociation of Ni(II) complexes of Ll, L5, L5B, L6, PAN, L7 and L3765 using excess Terpy have been studied using UV -Visible spectroscopy and relative stabilities have been compared.
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Leroux, Alain. "Modélisation d'écoulements supersoniques hors-équilibre chimique et thermique." Rouen, 1997. http://www.theses.fr/1997ROUES064.
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Cette thèse concerne l'étude des écoulements supersoniques hors-équilibre chimique et vibrationnel. Le gaz étudié est l'air constitué de cinq espèces ( N2, O2, NO, N et O) et les trois types de molécules sont en déséquilibre vibrationnel. On s'intéresse plus particulièrement à la modélisation du déséquilibre. Dans cette optique, différents modèles de cinétique chimique sont testés. Dans le cas du déséquilibre thermique, notre intérêt s'est porté sur l'étude des temps de relaxation des collisions translation-vibration dans les équations de conservation des énergies de vibration. Après la présentation des équations de Navier-Stokes qui régissent ce genre d'écoulements, on présente les différents modèles de déséquilibre chimique et thermique. La deuxième partie de la thèse présente la méthode numérique utilisée pour résoudre les équations de conservation. Basée sur le principe des volumes finis, un schéma TVD non-MUSCL d'ordre deux en espace et en temps est utilisé pour le traitement des flux eulériens, les flux visqueux étant traités de manière centrée. Différents cas tests sont ensuite étudiés pour valider cette méthode. Les résultats constituent la troisième partie de ce mémoire. On présente d'abord la configuration expérimentale qui a inspiré ce travail de thèse. Après cela, on s'intéresse à l'effet des modèles de déséquilibre sur l'écoulement dans une tuyère supersonique galbée et dans le jet issu de cette tuyère.
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Smith, Ian J. "Some kinetic and equilibrium studies of the reactions of carbonyl compounds with amines and/or sulfite." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/3733/.
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Studies have been made of the reaction of several carbonyl compounds with sulfite in aqueous solution. (^1)H NMR results indicate the formation of hydroxyalkanesulfonates, HXS, of general structure, RR'C(0H)(S0(_3)Na). Equilibrium and kinetic studies of the decomposition reactions have been made making use of the rapid reaction of iodine with liberated sulfite. The decomposition shows an acidity dependence; above pH 3 reaction mainly involves the dianion, RR'C(0’)(S0(_3)"), while below pH 3 the monoanion, RR'(OH)(S0(_3)’) is involved. In the case of adducts from propanal values obtained for the rate constants for decomposition were 370 s(^-1) and 3.9x10(^-6) s(^-1) for the dianion and monoanion respectively. pK(_a) values for acid dissociation of several HXS compounds were measured and found to be in the range 9-12. The reactions of hydroxypropanesulfonate, HPS, with aniline and aniline derivatives have been studied. (^1)H NMR spectra accord with formation of anilinopropanesulfonates, APS, kinetic and equilibrium measurements were made spectrophotometrically in the presence of added sulfite ions. The overall equilibrium constant for the reaction with aniline was found to be 84 dm(^3) moI(^1) The mechanism of the reaction is thought to involve decomposition of HPS to yield propanal which reacts with the amine to yield a carbinolamine intermediate. This subsequently dehydrates giving an imine which reacts rapidly with free sulfite to give the product, APS. The results suggest a change in rate limiting step from the^reaction of aniline with propanal at low pH to carbinolamine dehydration at high pH, the change occurring at pH 6 -7, the effects of ring substituents in the aniline on reactivity have been examined. Reaction of propanal with aniline in acetonitrile yields the imine. Kinetic studies of its decomposition back to reactants in the presence of aqueous sulfite solutions confirm the conclusion reached from measurements on the forward reaction. Reactions of hydroxymethanesulfonate, HMS, with benzylamine and some derivatives were observed by (^1) H NMR spectroscopy. Equilibrium constants for the formation of 1:1 and 1:2 adducts were measured and the variations of values with pH were examined. Trimerisations of the imines formed from formaldehyde and benzylamine and its derivatives were successfully achieved.
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Gallagher, Richard Thomas. "Kinetics and equilibria of ion-molecule association reactions : studied using temperature variable high pressure ion sources." Thesis, University of Warwick, 1987. http://wrap.warwick.ac.uk/4160/.
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Interest in termolecular association reactions of the type shown below, stems from their importance in the chemistry of planetary atmospheres, gas-cooled nuclear reactors and gas-phase cluster ions. This study is concerned with evaluating the rate constants of such X+ + X + M ------> X2+ + M k3 (1) reactions as both a function of temperature and of the third body M. The values of the third order rate constant k3 are expressed conventionally in terms of k3 = CT-m where T is the temperature and C and m are constants characteristic of the reaction which depend also on the nature of M. Literature now shows a general measure of agreement on values of C and m in several studies for which X=M, however, inconsistent values have been reported on the M=He system. This thesis describes an investigation of the two systems X=N2, CO and M= the reactant or a rare gas. Experiments were conducted in a conventional high pressure ion source and a pulsed drift ion source fitted to an updated Kratos MS9 mass spectrometer. Results obtained for the one component studies show good agreement with other literature values for the temperature dependence, m. In general, for both N2 and CO systems, He was found to have the same efficiency as the parent molecule as a third body at 300K, but the temperature dependence of k3 is markedly lower. Ar was found to behave very similarly to the parent molecule in both systems. For the CO system, although good agreement is found for the temperature dependence result with literature, there is still an uncertainty of about a factor of 2 in the room temperature values of k3.
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Sötz, Veronika Anna [Verfasser], and André [Akademischer Betreuer] Thess. "Chemical equilibria and intrinsic kinetics of reactions in molten nitrate salt / Veronika Anna Sötz ; Betreuer: André Thess." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2021. http://d-nb.info/1231794402/34.
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Zhang, Fan. "A NEW PARADIGM OF MODELING WATERSHED WATER QUALITY." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2387.
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Accurate models to reliably predict sediment and chemical transport in watershed water systems enhance the ability of environmental scientists, engineers and decision makers to analyze the impact of contamination problems and to evaluate the efficacy of alternative remediation techniques and management strategies prior to incurring expense in the field. This dissertation presents the conceptual and mathematical development of a general numerical model simulating (1) sediment and reactive chemical transport in river/stream networks of watershed systems; (2) sediment and reactive chemical transport in overland shallow water of watershed systems; and (3) reactive chemical transport in three-dimensional subsurface systems. Through the decomposition of the system of species transport equations via Gauss-Jordan column reduction of the reaction network, fast reactions and slow reactions are decoupled, which enables robust numerical integrations. Species reactive transport equations are transformed into two sets: nonlinear algebraic equations representing equilibrium reactions and transport equations of kinetic-variables in terms of kinetically controlled reaction rates. As a result, the model uses kinetic-variables instead of biogeochemical species as primary dependent variables, which reduces the number of transport equations and simplifies reaction terms in these equations. For each time step, we first solve the advective-dispersive transport of kinetic-variables. We then solve the reactive chemical system node by node to yield concentrations of all species. In order to obtain accurate, efficient and robust computations, five numerical options are provided to solve the advective-dispersive transport equations; and three coupling strategies are given to deal with the reactive chemistry. Verification examples are compared with analytical solutions to demonstrate the numerical accuracy of the code and to emphasize the need of implementing various numerical options and coupling strategies to deal with different types of problems for different application circumstances. Validation examples are presented to evaluate the ability of the model to replicate behavior observed in real systems. Hypothetical examples with complex reaction networks are employed to demonstrate the design capability of the model to handle field-scale problems involving both kinetic and equilibrium reactions. The deficiency of current practices in the water quality modeling is discussed and potential improvements over current practices using this model are addressed.Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering
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Yu, Jing. "A THREE-DIMENSIONAL BAY/ESTUARY MODEL TO SIMULATE WATER QUALITY TRANSPORT." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2434.
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This thesis presents the development of a numerical water quality model using a general paradigm of reaction-based approaches. In a reaction-based approach, all conceptualized biogeochemical processes are transformed into a reaction network. Through the decomposition of species governing equations via Gauss-Jordan column reduction of the reaction network, (1) redundant fast reactions and irrelevant kinetic reactions are removed from the system, which alleviates the problem of unnecessary and erroneous formulation and parameterization of these reactions, and (2) fast reactions and slow reactions are decoupled, which enables robust numerical integrations. The system of species transport equations is transformed to reaction-extent transport equations, which is then approximated with two subsets: algebraic equations and kinetic-variables transport equations. As a result, the model alleviates the needs of using simple partitions for fast reactions. With the diagonalization strategy, it makes the inclusion of arbitrary number of fast and kinetic reactions relatively easy, and, more importantly, it enables the formulation and parameterization of kinetic reactions one by one. To demonstrate the general paradigm, QAUL2E was recasted in the mode of a reaction network. The model then was applied to the Loxahatchee estuary to study its response to a hypothetical biogeochemical loading from its surrounding drainage. Preliminary results indicated that the model can simulate four interacting biogeochemical processes: algae kinetics, nitrogen cycle, phosphorus cycle, and dissolved oxygen balance.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering
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Manyusa, Susan. "The cytochrome bâ‚… fold : equilibrium and kinetic studies of folding and unfolding reactions in wild type, apo and variant proteins." Thesis, Queen Mary, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324916.
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Cortinovis, Giorgia Francine. "Desenvolvimento da obtenção do etanoato de 2-butoxietila a partir de etanoato de 2-etoxietila e 2-butoxietanol." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-12062013-173247/.
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Neste trabalho foi estudada a reação de transesterificação em fase líquida entre etanoato de 2-etoxietila (CAS 111-15-9) e 2-butoxietanol (CAS 111-76-2), catalisada com óxido de nióbio, para obtenção do etanoato de 2-butoxietila (CAS 112-07-2). Aplicando-se a técnica de planejamento de experimentos (Design of Experiments, DOE), foram avaliados os efeitos de temperatura, catálise, agitação e composição inicial no resultado de conversão do reagente limitante. Foi identificada a forte influência da razão molar inicial de reagentes na velocidade de reação, além das influências também significativas da temperatura e % de catalisador. O melhor resultado de conversão foi de 76,1 % do reagente limitante, obtido para a temperatura de 130°C, 20 % de catalisador e razão molar de 6 mols de etanoato de 2-etoxietila para 1 mol de 2-butoxietanol, ao final de 5 horas de reação. O modelo cinético pseudo-homogêneo de segunda ordem foi utilizado para descrever a velocidade da reação no intervalo de reação de 110 a 130°C. As constantes cinéticas e de equilíbrio foram calculadas a partir das concentrações molares e atividades dos componentes da mistura reacional. As velocidades de reação no intervalo de temperatura estudado são mais baixas em relação às outras reações de transesterificação. As constantes de equilíbrio de reação obtidas para o intervalo de temperatura estudado são próximas do valor unitário, estando de acordo com o que a literatura relata para reações reversíveis de 2° ordem. O modelo pseudohomogêneo ajustou-se bem aos resultados de conversão. O catalisador (óxido de nióbio) apresentou alta seletividade. Para o cálculo das atividades utilizadas na obtenção da constante cinética de reação, foram realizados ensaios de equilíbrio líquido-vapor para estimativa dos parâmetros do modelo de atividade NRTL (Nonrandom, two-liquid). Os resultados dos ensaios de equilíbrio líquido-vapor mostraram pequenos desvios de idealidade para as seis misturas binárias estudadas. O modelo de atividade e seus parâmetros estimados mostraram bom ajuste dos resultados experimentais.In this work, the transesterification reaction in liquid phase between 2-etoxyethyl acetate (CAS 111-15-9) and 2-butoxyethanol (CAS 111-76-2) to obtain the 2- butoxyethyl acetate (CAS 112-07-2) catalyzed by niobium oxide was studied. The effects of temperature, catalysis, agitation and initial composition on the result of conversion for limiting reagent were evaluated applying the technique of Design of Experiments (DOE). The strong influence of the initial molar ratio of reactants and also significant influences of temperature and % catalyst in reaction rate were indentified. The best result of conversion of limiting reagent was 76.1%, obtained for the 130°C, 20% catalyst and the molar ratio of 6 moles of 2-etoxyethyl acetate to 1 mol of 2-butoxyethanol, at the end 5 hours of reaction. The second order pseudohomogeneous kinetic model was used to describe the reaction rate in the range 110- 130°C. The kinetic and equilibrium constants were calculated from the molar concentrations and activities of the mixtures components. The reaction rates in the temperature range studied are lower when compared to other transesterification reactions. The reaction equilibrium constants obtained for the temperature range studied are close to the unit value, which is consistent with literature reports for the reversible reactions of 2nd order. The pseudo-homogeneous model fitted well the results of conversion. The catalyst (niobium oxide) showed high selectivity. Vaporliquid equilibrium assays were performed to estimate parameters of the NRTL (nonrandom, two-liquid) activity model for the calculation of components activities used to obtain the kinetic constant of reaction. The kinetic models proposed showed a good fit of the experimental data. The results of vapor-liquid equilibrium assays showed small deviations from ideality for the six binary mixtures evaluated. The activity model and its estimated parameters showed good fit of the experimental results.
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Tsai, Suh-Jen Jane. "Equilibrium and kinetic studies of metal ion promoted hydration and enolization reactions of oxaloacetate in various buffers : the cooperativity with base catalysts /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487258254024045.
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Castilho, Paula C. M. F. "Some spectroscopic, kinetic and equilibria studies of cyano- and nitro- substituted anisoles and phenols and their reactions with nucleophiles." Thesis, Durham University, 1990. http://etheses.dur.ac.uk/6577/.
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The reactions of ring-activated alkyl aryl ethers with nucleophiles have been examined. The main pathways involve attack by the nucleophiles at the alkyl carbon to give substituted phenoxide ions, or at ring carbon atoms to give σ-adducts. The dealkylation reactions have been observed by both (^1)H nuclear magnetic resonance spectroscopy and spectrophotometrically using dimethyl sulphoxide as solvent. The reactivity order for nucleophiles in this solvent is SCN- < I- < Br- < C1- < CN(_3)- and is markedly different from that found for Sn2 reactions in protic solvents. These differences probably reflect changes in the relative salvation of the nucleophiles on charge of solvent. Dealkylation is also observed in dimethyl sulphoxide alone and is thought to yield S-alkylated DMSO. In methanol reaction of 4-cyano-2,6-dinitroanisole and 2-cyano4,6-dimtro- anisole with methoxide ions results in competition between attack at ring carbon and at the cyano-group. Kinetic and equilibrium data are reported for reaction of 4-cyano-2,6-dinitroanisole where rapid formation of the 1,1-dimethoxy adduct is followed by slower equilibration with the imido-ester solvate. There is evidence for strong association with cations of the 1,1-dimethoxy adduct, and values of the association constants decrease in the order of cations, Ba(^2+) > Ca(^2+) > K(^+) > Na(^+) > Li(^+). This explains a longstanding discrepancy in the literature between the values of equilibrium constants for attack of lithium methoxide and of sodium methoxide. In concentrated solutions of sodium or potassium methoxide in methanol nitro-activated anisoles form adducts with 2:1 and 3:1 stoichiometry. Here methoxide addition occurs at two or three ring positions respectively. Such equilibria have been examined spectrophotometrically for 2,4,6-trinitroanisole, the isomeric cyanodinitroanisoles and the spiro-adduct formed by cyclisation of picryl glycol ether. For these equilibria the "basicity" of sodium methoxide solutions jn methanol is appreciably greater than that of corresponding potassium methoxide solutions. This is in contrast with other measures of basicity and is attributed to the association of the multi-charged adducts with cations which is stronger with sodium ions than with potassium ions. The infrared spectra of the parent and nitro-cyanoanisoles and their Meisenheimer complexes have been examined in the N0(_2) group, benzene ring and CN group regions. In order to attempt to understand their chemical and spectral behaviour the corresponding phenols and their Na(^+) and K(^+) salts have also been studied both in solution in dimethyl sulphoxide and in the solid state. Band shifts, widths and intensities have been interpreted in terms of the nature and extent of intra-molecular electronic rearrangements caused by the intermolecular interactions (hydrogen-bonding and cation coordination). Interesting, although not fully understood, differences in behaviour between the 2 and 4-CN substituted dinitrophenols and anisoles have been noted.
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Khare, Neeraj Prasad. "Predictive Modeling of Metal-Catalyzed Polyolefin Processes." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11065.
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This dissertation describes the essential modeling components and techniques for building comprehensive polymer process models for metal-catalyzed polyolefin processes. The significance of this work is that it presents a comprehensive approach to polymer process modeling applied to large-scale commercial processes. Most researchers focus only on polymerization mechanisms and reaction kinetics, and neglect physical properties and phase equilibrium. Both physical properties and phase equilibrium play key roles in the accuracy and robustness of a model.
This work presents the fundamental principles and practical guidelines used to develop and validate both steady-state and dynamic simulation models for two large-scale commercial processes involving the Ziegler-Natta polymerization to produce high-density polyethylene (HDPE) and polypropylene (PP). It also provides a model for the solution polymerization of ethylene using a metallocene catalyst. Existing modeling efforts do not include physical properties or phase equilibrium in their calculations. These omissions undermine the accuracy and predictive power of the models.
The forward chapters of the dissertation discuss the fundamental concepts we consider in polymer process modeling. These include physical and thermodynamic properties, phase equilibrium, and polymerization kinetics. The later chapters provide the modeling applications described above.Ph. D.
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Marti, Mustafa Esen. "Reactive Extraction Of Pyruvic Acid From Aqueous Single And Mixed Acid Solutions." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612261/index.pdf.
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Interest in recovery of carboxylic acids from their aqueous solutions and production media has been growing with the improvements in the production techniques. Reactive extraction is proposed as a promising method to achieve high distribution coefficients with good selectivity. In the present study, equilibrium and kinetic studies, needed for the design of a recovery unit were carried out. Reactive extraction of pyruvic, acetic and lactic acids from their single and mixed acid solutions were carried out with tertiary amines, Alamine 336 and trioctylamine, dissolved in diluents, 1-octanol and oleyl alcohol. The kinetic parameters such as reaction order and rate constant were calculated by using the aqueous solution of pyruvic acid with 1-octanol solution of trioctylamine.
The distribution coefficient of pyruvic acid was obtained as 0.30 and 0.07 with 1-octanol and oleyl alcohol respectively. The trend did not change after the addition of the extractants to the diluents. As expected, the more polar diluent extracted more acid than the less polar one. The extractant was observed to be the limiting reagent of the reversible complexation reaction in the organic phase. It was seen that loading ratio was not affected by the concentration of the extractant in the organic phase but increased with the equilibrium concentration of the acid in the aqueous phase. The results showed that mainly (1-1) acid-amine reaction occurred in the organic phase. Because tertiary amines can react with only undissociated acids, the increase in the initial pH of the aqueous phase caused a decrease in the distribution coefficients of the carboxylic acids studied. The effect of the concentration of the organic phase disappeared when the initial pH of the aqueous phase was 4.0 and a distribution coefficient value of 0.1 was achieved for all concentration levels of organic phase. Similar results were obtained for acetic and lactic acids and this behavior was used to propose a selective recovery of the acids from their mixed acid solutions.
The presence of acetic acid prevented the extraction of pyruvic acid. The increase in the concentration of the extractant in the organic phase caused an increase in the distribution coefficient of pyruvic acid. During the extraction process, lactic acid could not be recovered from ternary acid solutions because of its high hydrophilicity. The results of reactive extraction of lactic and pyruvic acids from their binary acid solutions showed that at higher concentration of lactic acid, the distribution of pyruvic acid was negatively affected. On the other hand, the presence of lactic acid at a low concentration level did not affect the distribution of pyruvic acid.
It was found that the reaction between pyruvic acid and trioctylamine in 1-octanol was first order with respect to the reactants with a second order rate constant of 0.94 L mol-1 s-1. The enhancement factor of the system was obtained as 25.
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Killian, Marie Coy. "Kinetics of Atmospheric Reactions of Biogenic Volatile Organic Compounds: Measurement of the Rate Constant ofThujone + Cl· at 296 K and Calculation ofthe Equilibrium Constant for the HO2CH2CH2O2· H2O Complex." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3642.
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Biogenic volatile organic compounds (VOCs) react with Cl and OH radicals and the resulting radicals combine with oxygen to form peroxy radicals RO2. Organic peroxy radicals can then react with NO to form NO2, a precursor of tropospheric ozone. The work presented here explored the initial reaction between Cl and thujone, a VOC emitted by Great Basin sagebrush. The rate constant for the reaction of thujone + Cl at 296 K was measured with the method of relative rates with FTIR for detection of reactants. LEDs were used to photolyze Cl2 to generate Cl in the reaction cell. Thujone was also photolyzed by the LEDs and therefore the relative rates model was revised to account for this photolysis. With toluene as the reference compound, the rate constant for thujone + Cl at 296 K is 2.62 ± 1.90 × 10-12 molecules-1 s-1, giving an atmospheric lifetime of 0.5--2.6 minutes for thujone. Cline et al. showed that the rate of the self-reaction of HO2CH2CH2O2 (β-HEP) increases in the presence of water vapor. This enhancement has a strong temperature dependence with a greater enhancement observed at colder temperatures. The observed rate enhancement has been attributed to the formation of a β-HEP--H2O complex. In this work, the equilibrium constant for the formation of the β-HEP--H2O complex was calculated by ab initio calculations. Given the energy available at room temperature, the complex will populate three local minimum geometries and β-HEP will populate two local minimum geometries. The partition function for each of these geometries was calculated and used to calculate the equilibrium constant for complex formation as a function of temperature. Based on these computational results, the observed temperature dependence for the rate enhancement can be attributed to the strong temperature dependence for the rate constant of the reaction of β-HEP--H2O + β-HEP rather than the temperature dependence of complex formation.
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Rodrigues, Rodolfo. "Modelagem cinética e de equilíbrio combinadas para simulação de processos de gaseificação." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/140478.
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A gaseificação é um processo de conversão termoquímica que compreende a oxidação parcial de um combustível para convertê-lo em uma mistura gasosa (“syngas”). Geralmente a modelagem desses processos utiliza uma descrição cinética detalhada ou os aproximam ao equilíbrio químico. Ambas as abordagens têm vantagens e desvantagens, bem como limitações. O objetivo deste trabalho foi o desenvolvimento de uma nova modelagem fenomenológica de processos de gaseificação através de um modelo “híbrido” aqui chamado de modelo híbrido adaptativo por zonas (HAZ). Este modelo assumiu que o gaseificador é representado por zonas de dois tipos: uma dominada pela cinética química, representada por um modelo cinético, e outra onde a cinética química é rápida e as espécies químicas estão em equilíbrio químico, representada por um modelo de equilíbrio. Um critério de transição entre as zonas foi proposto através de um número de Damköhler (Da) que relaciona tempos de residência e de reação química. Desta forma, o modelo adapta-se conforme os processos dominantes em cada zona. Em um primeiro momento, um modelo de equilíbrio multifásico (EM) foi desenvolvido e aplicado para um estudo da cogaseificação de carvão mineral e biomassas disponíveis no Brasil. A seguir, o modelo HAZ foi construído através da técnica de rede equivalente de reatores químicos (ERN) a partir do modelo EM e de um modelo cinético, também desenvolvido neste trabalho. Uma metodologia de aplicação do modelo HAZ foi proposta, aplicada e validada para duas configurações de gaseificadores: dois casos de gaseificadores de biomassa em leito fluidizado borbulhante e um caso de gaseificador de carvão mineral em leito de arraste. Para os dois primeiros casos foi estimada que a transição ocorra para Da ≥ 10+5 e para o último caso; chegou-se a Da ≥ 10+3. A aplicação do modelo HAZ se mostrou satisfatória sendo que foi possível a redução do tempo computacional em pelo menos 40% com relação a uma abordagem puramente cinética. Cabe ressaltar ainda que o modelo HAZ possibilitou um maior entendimento físico e químico ao identificar os processos dominantes locais.Gasification is a thermochemical conversion process consisting of partial oxidation of a fuel to convert it to a gas mixture (“syngas”). Generally, the gasification process modeling uses a kinetic detailed description, or approach it to a chemical equilibrium state. Both approaches have advantages and disadvantages, as well as limitations. The objective of this work was to develop a new phenomenological modeling of gasification processes through a “hybrid” model here called hybrid adaptive zone model (HAZ). This proposed modeling assumed the gasifier is represented by two types of zones: one dominated by chemical kinetics, represented by a kinetic model, and another where chemical kinetics is fast so chemical species are assumed in chemical equilibrium states, represented by an equilibrium model. A transition criterion between zones was defined by a Damköhler number (Da) which relates residence time and chemical reaction time. Therefore, the HAZ model can adapted according to the dominant processes in each zone. Firstly, a multi-phase equilibrium model (ME) was developed and applied to study the coal-biomass co-gasification of Brazilian sources. Hereafter, the HAZ model was built using the technique of equivalent reactor network (ERN) with the ME model and a kinetic model developed in this work. A methodology of use of the HAZ model was proposed, applied and validated for two configurations of gasifiers: two cases of biomass bubbling fluidized-bed gasifiers and one case of coal entrained-flow gasifier. In the first two cases the transition was estimated to occur on Da ≥ 10+5 and in the last case; we estimated on Da ≥ 10+3. The application of the HAZ model proved to be satisfactory since it could reduce the computation time by at least 40% compared to a pure kinetic approach. It should already be emphasized that the HAZ model allowed a better physical and chemical understanding of gasification by identifying the dominant local processes.
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Reis, Marcelo Martins dos. "Estudo da cinética, do equilíbrio e dinâmica de biossorção do íon manganês (II) pela biomassa Sargassum filipendula." Universidade do Estado do Rio de Janeiro, 2008. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=951.
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O crescente aumento no uso de metais e outros produtos químicos nos processos industriais tem resultado na geração de grandes quantidades de efluentes aquosos que contém altos níveis de metais tóxicos, o que gera sérios problemas ambientais associados ao descarte destes efluentes. O objetivo deste trabalho foi realizar uma investigação da biossorção do íon manganês II de uma solução aquosa utilizando a biomassa seca Sargassum filipendula. O processo foi conduzido em batelada com um posterior estudo dinâmico do processo em regime contínuo em um reator de leito fixo. No processo em batelada, a influência de diferentes parâmetros experimentais foram avaliados: pH inicial, tempo de biossorção, temperatura e concentração inicial do íon manganês II no equilíbrio de biossorção do sistema. No processo em regime contínuo, foi utilizada uma coluna de leito fixo, sendo avaliados os seguintes parâmetros: vazão de alimentação e concentração inicial de manganês II em solução. Os resultados obtidos indicam que a capacidade de biossorção não foi afetada pelo pH na faixa de 3,0 a 7,0, mas diminuiu de modo significativo para pH inferior a 3,0. A isoterma de Langmuir foi a que melhor descreveu o equilíbrio de biossorção, que foi pouco afetado pela temperatura. O processo de biossorção obedeceu a uma cinética de pseudo segunda-ordem, cuja taxa também não sofreu efeito significativo da temperatura. Os resultados obtidos nos estudos em batelada indicam que a Sargassum filipendula possui potencial para a remoção de íons manganês, apresentando capacidade de adsorção igual a 0,80 mmol/g, valor comparável àqueles observados para outros íons tóxicos. Os valores para capacidade de biossorção calculados no sistema contínuo foram superiores aos encontrados para o estudo em batelada, o que foi associado às diferentes condições de equilíbrio existentes nos dois sistemas. O processo de biossorção do manganês em leito fixo, mostrou-se eficiente para concentrações iniciais do efluente menores que 500 mg/L. Para uma concentração inicial de 60 mg/L, com 9 horas de processo o ponto de ruptura foi alcançado, 26 L de solução foram tratados de acordo com a concentração exigida pelo CONAMA para o despejo em um corpo receptor.The increasing use of metals and other chemicals in industrial processes has resulted in the generation of large quantities of aqueous effluents containing high levels of toxic metals, which cause serious environmental problems associated with the disposal of effluents. This work was doing a research on removing manganese II ions of an aqueous solution using the dry biomass Sargassum filipendula. A basic investigation on the removal of manganese II ions from aqueous solutions by dead Sargassum filipendula was conducted in batch and in a fixed- bed column. The influence of different experimental parameters was evaluated in batch conditions: initial pH, sorption time, temperature, and initial concentrations of manganese II ions on metal uptake. Continuous-flow sorption experiments were conducted in a fixed-bed column. The parameters evaluated were: effluent flow rate and initial concentration of manganese II solution. The results indicate that the metal uptake capacity was not affected by pH in the range of 3.0 to 7.0, but decreased significantly to less than pH 3.0. The equilibrium biosorption was better described by Langmuir isotherm, which was little affected by temperature. The process of biosorption followed the kinetics of a pseudo-second order, whose rate also has not suffered significant effect of temperature. The results obtained in a batch studies indicate that the Sargassum filipendula has potential for the removal of manganese ions, its maximum uptake capacity equal 0.80 mmol/g, a result comparable to those observed for other toxic ions. The results for capacity of biosorption calculated in continuous system were higher than those found in batch for the study, which was associated with the different conditions of balance in the two existing systems. The process of biosorption of manganese in fixed-bed reactor, has proved effective for initial concentrations lower than 500 mg/L. For an initial concentration of 60 mg/L, with nine hours to process the breaking point was reached, 26 L of solution were treated in accordance with the concentration required by CONAMA for emptying into a body receiver.
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Marinoni, Marianna. "Implémentation des isotopes dans un modèle hydrogéochimique couplé." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAH001/document.
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Ce travail décrit le développement d’un outil de simulation du transport réactif, nommé SpeCTr (Spéciation Cinétique Transport), intégrant le fractionnement isotopique. Ce modèle est obtenu à travers le couplage d’un module décrivant le transport et d’un module décrivant les principales réactions chimiques (approche de séparation d’opérateur). Une grande partie du travail est dédiée à l’amélioration des algorithmes du module décrivant les réactions chimiques pour la résolution des équations de l’équilibre thermodynamique (méthode de Newton Raphson modifiée à travers les techniques du scaling et des Fractions Continues Positives) et du mélange de réactions cinétiques et à l’équilibre (étude sur la formulation et résolution des systèmes d’équations différentielles et différentielles-algébriques). L’outil est validé à travers la résolution de plusieurs tests (batch et transport réactif) et appliqué pour la simulation d’expériences de laboratoire en 1D, 2D et 3D portant sur la dissolution des cristaux de calcite dans une colonne de milieu poreuxThe work describes the development of a reactive transport code named SpeCTr (Spéciation Cinétique Transport in French). The code, able to describe isotopic fractionation, is obtained through the coupling of a transport module and a reaction module that describes the main chemical reactions (operator splitting approach). A consistent portion of the work is dedicated to the improvement of the numerical methods employed in the reaction module for solving thermodynamic equilibrium (Newton Raphson method modified with scaling and Positive Continuous Fractions) and mixed equilibrium and kinetic reactions (formulation and solution of systems of differential and differential-algebraic equations). The code was verified through the solution of different benchmarks (batch and reactive transport simulations) and applied to perform 1D, 2D and 3D simulations of laboratory experiments dedicated to calcite crystals dissolution in a column of porous medium
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Oliveira, Silvia Priscila Dias de. "Remoção do corante Azul Reativo 5G utilizando o adsorvente comercial Dowex Optipore SD-2." Universidade Estadual do Oeste do Parana, 2013. http://tede.unioeste.br:8080/tede/handle/tede/1850.
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In this work, removal of Reactive Blue 5G dye using a commercial Dowex Optipore SD-2 adsorbent was investigated regarding variations on pH (1-12), temperature (20-50oC) and shaking (90-200 rpm) values in order to establish best adsorption conditions. The point of zero charge (pcz) was determined varying solution pH from 2 to 12 and defining the pH range where the adsorbent surface is electrically neutral. Batch kinetic experiments at pH 2 consisting on a mixture of 5 mg adsorbent and 50 mL dye solution (150 mgL-1) were performed considering four temperatures (20, 30, 40 and 50°C), under 120 rpm shaking. Regarding temperature of 30°C and shaking of 120 rpm as suitable to improve the removal of Dowex Optipore SD-2 adsorbent, batch equilibrium adsorption experiments were carried out at pH values ranging from 1 to 12 and considering dye solutions with concentration varying from 5 to 300 mg L-1. From pcz results, pH values between 4 and 10 have evidenced electrically neutral behavior on adsorbent surface. Adsorption kinetic data were interpreted according to film diffusion, superficial adsorption and pores diffusion kinetic models. Six isotherm models such as Langmuir, Freundlich and Temkin were used to describe the equilibrium data, being the Langmuir isotherm fitted better to the data with a maximum adsorption capacity (qmax) of 315 mg L-1. Performing a comparison with other adsorbents, such as orange peel, macrophyte Egeria Densa, eggshell and activated charcoal reported in literature for reactive dye removal, the Dowex Optipore SD-2 adsorbent exhibits greater adsorption capacity than the other ones, being more effective for reactive dye removal, but with a slow kinetic response.
O objetivo principal deste trabalho foi estudar a remoção do corante Azul Reativo 5G utilizando o adsorvente comercial Dowex Optipore SD-2. Foram realizados testes preliminares em sistema fechado e batelada variando o pH de 1 a 12, a temperatura de 20 a 50°C e a velocidade de agitação de 90 a 200 rpm. O ponto de carga zero (pHpcz) do adsorvente foi obtido a partir do método da titulação potenciométrica. O teste cinético foi conduzido em sistema fechado e batelada, misturando 5 mg de adsorvente com 50 mL de solução de corante (150 mg L-1), com pH 2, em quatro temperaturas (20, 30, 40 e 50°C)sob agitação constante de 120 rpm. O teste de equilíbrio foi realizado para pHs entre 1 e 12 e a concentração da solução de corante variando de 5 a 300 mg L-1, neste teste a temperatura e a velocidade de agitação foram fixadas em 30°C e 120 rpm, respectivamente. A partir da análise do pHpcz observou-se que para valores de pH entre 4 e 10 a carga superficial líquida do adsorvente é nula. A cinética de adsorção foi descrita por três modelos matemáticos: difusão no filme, adsorção na superfície e difusão nos poros. Seis modelos de isoterma, dentre eles Langmuir, Freundlich e Temkin foram utilizados para descrever dos dados de equilíbrio, sendo que Langmuir foi o que melhor se ajustou aos dados experimentais de equilíbrio. O adsorvente apresentou uma capacidade máxima de adsorção (qmax) de 315 mg L-1. Comparando com outros adsorventes, tais como bagaço de laranja, Macrófita Egeria Densa, casca de ovo e carvão ativado, encontrados na literatura para a remoção de corantes reativos, o adsorvente Dowex Optipore SD-2 apresenta capacidade máxima de adsorção muito superior aos demais adsorventes, sendo mais efetivo na remoção de corante reativo, no entanto apresenta uma cinética lenta.
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Bowen, Sean Michael. "The Application of Dynamic Nuclear Polarization Enhanced NMR to Non-Equilibrium Systems." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10271.
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Nuclear magnetic resonance (NMR) yields remarkably detailed structural information about virtually any molecule. However, its application to non-equilibrium systems is hampered by a lack of sensitivity. To increase the amount of signal that can be obtained from a NMR experiment, various hyperpolarization schemes have been previously introduced. One such technique is dynamic nuclear polarization (DNP), which can enhance NMR sensitivity by several orders of magnitude. The work detailed here focuses on the development of methods utilizing DNP to study non-equilibrium systems such as chemical and biochemical reactions in real-time.
To work with hyperpolarized samples, we have designed and constructed a rapid injection and mixing system. This system allows samples to be transported between superconducting magnets used for polarization and for NMR spectroscopy in less than two seconds. Rapid transport is essential for successful use of samples with short spin-lattice relaxation times. For the study of reactions under non-equilibrium conditions, the system provides the additional capability for samples to be mixed with a second, unpolarized reagent.
A chromogenic trypsin catalyzed ester hydrolysis reaction was used to validate the DNP-NMR technique as a tool for kinetic analysis. It is shown that the DNP-NMR method agrees with the conventional UV method within the uncertainty of the measurement. Hyperpolarization in this modality presents both challenges and opportunities, each of which motivate the development of new NMR techniques. In addition to the determination of kinetics, DNP-NMR is amenable to mechanistic analysis of a reaction. We have developed a technique based on selective inversion of spin-polarization, which allows for mapping of atoms between reactant and product of a reaction. This scheme was applied to a Grignard reaction, demonstrating applicability to organic reactions.
Signal averaging, as it is applied for conventional multi-dimensional correlation spectroscopy cannot always be applied easily when using hyperpolarized sample. For the rapid measurement of heteronuclear correlation spectra, we have developed a technique utilizing the differential scaling of scalar coupling under off-resonance irradiation.
Although DNP-NMR yields spectra of outstanding quality even with small quantities of sample, peak intensities are not quantitative. It is nevertheless possible to compare peak multiplets obtained from fractionally isotope labeled samples. Using biosynthetically labeled lipids from E. Coli cells, we showed that the resulting labeling patterns reflect their biosynthetic pathways.
As a final case-study employing several of these newly developed methods, the uronate isomerase catalyzed isomerization of glucuronate into fructuronate was studied. The ability to follow the reaction in real-time while directly observing all anomeric forms of the reactant and product permits the independent determination of kinetics for each anomeric form of substrate and product. This study revealed the anomeric specificity of the enzyme.
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Chang, Tsai Ming, and 蔡明蒼. "Kinetic Study of the Equilibrium between C2H5S and O2 and the Reaction of C2H5SO2 with NO2." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/49581744726288911036.
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碩士國立交通大學
應用化學系
89
A Laser Photolysis─Laser Induced Fluorescence (LP─LIF) system has been used to study the reaction kinetics of the equilibrium between C2H5S and O2 and the reaction of C2H5SO2 with NO2 at 223－258 K, and 50－200 torr of total pressure.C2H5S radicals were produced by photolyzing C2H5SSC2H5 molecules with an excimer laser output at 248 nm.The concentration of C2H5S radicals was monitored at 410.3 nm with an excimer-pumped dye laser. We observed bi-exponential decay of C2H5S in the presence of O2 which implied an equilibrium between them.The equilibrium constants were determined at temperatures 228－258 K, Keq(T)＝(1.44±0.35) ×10－27 exp[(5325±512)/T] cm3 molecule－1.The rate constant of C2H5SO2 with NO2 was also derived as k2(T)＝(4.88±1.35) ×10－12 exp [(886±219)/T] cm3 molecule-1 s-1 at 234－254 K.
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"Modeling Aqueous Organic Chemistry in Experimental and Natural Systems." Doctoral diss., 2017. http://hdl.handle.net/2286/R.I.46328.
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abstract: In many natural systems aqueous geochemical conditions dictate the reaction pathways of organic compounds. Geologic settings that span wide ranges in temperature, pressure, and composition vastly alter relative reaction rates and resulting organic abundances. The dependence of organic reactions on these variables contributes to planetary-scale nutrient cycling, and suggests that relative abundances of organic compounds can reveal information about inaccessible geologic environments, whether from the terrestrial subsurface, remote planetary settings, or even the distant past (if organic abundances are well preserved). Despite their relevance to planetary modeling and exploration, organic reactions remain poorly characterized under geochemically relevant conditions, especially in terms of their reaction kinetics, mechanisms, and equilibria.
In order to better understand organic transformations in natural systems, the reactivities of oxygen- and nitrogen-bearing organic functional groups were investigated under experimental hydrothermal conditions, at 250°C and 40 bar. The model compounds benzylamine and α-methylbenzylamine were used as analogs to environmentally relevant amines, ultimately elucidating two dominant deamination mechanisms for benzylamine, SN1 and SN2, and a single SN1 mechanism for deamination of α-methylbenzylamine. The presence of unimolecular and bimolecular mechanisms has implications for temperature dependent kinetics, indicating that Arrhenius rate extrapolation is currently unreliable for deamination.
Hydrothermal experiments with benzyl alcohol, benzylamine, dibenzylamine, or tribenzylamine as the starting material indicate that substitution reactions between these compounds (and others) are reversible and approach metastable equilibrium after 72 hours. These findings suggest that relative ratios of organic compounds capable of substitution reactions could be targeted as tracers of inaccessible geochemical conditions.
Metastable equilibria for organic reactions were investigated in a natural low-temperature serpentinizing continental system. Serpentinization is a water-rock reaction which generates hyperalkaline, reducing conditions. Thermodynamic calculations were performed for reactions between dissolved inorganic carbon and hydrogen to produce methane, formate, and acetate. Quantifying conditions that satisfy equilibrium for these reactions allows subsurface conditions to be predicted. These calculations also lead to hypotheses regarding active microbial processes during serpentinization.Dissertation/Thesis
Doctoral Dissertation Biochemistry 2017