Epoxides have been recently identified as one of the intermediate species in the gas phase oxidation of alkenes. This study investigates the reaction of isoprene oxide and alpha-pinene oxide with sulfuric acid to identify the potential of epoxides as important secondary organic aerosol (SOA) precursors. The reaction was explored using different methods to understand the factors governing the reaction rate and the types of products formed under different conditions. Uptake experiments of epoxides on sulfuric acid using Ion drift-Chemical Ionization Mass Spectrometry (ID-CIMS) showed an irreversible uptake of epoxides at room temperature resulting in the formation of less volatile products like diols, organosulfates and acetals. However, at lower temperatures, dehydration of diols and some rearrangement was the preferred reaction pathway resulting in the formation of higher volatility compounds like hydroxy-alkenes and aldehydes. The uptake coefficients of isoprene oxide and alpha-pinene oxide at room temperature using 96% wt acid were found to be 4x10^-2 and 0.8x10^-2, respectively. Spectroscopic study using Attenuated total reflection-Fourier transform infrared technique (ATR-FTIR) revealed that for both the epoxides, diols were the major identifiable products at low acid concentrations. At higher acid concentrations, acetal formation was observed in case of isoprene oxide, while organosulfate formation was seen for alpha-pinene oxide. No products were identified under neutral conditions due to slow reaction. Bulk studies using Nuclear Magnetic Resonance (NMR) spectroscopy conducted at low acid concentrations showed the presence of 1,2- and 1,4-diols as the major products for isoprene oxide, similar to the results from the ATR-FTIR experiments. Additionally, aldehyde formation was also observed. For alpha-pinene oxide, organosulfate formation was observed in all NMR experiments, unlike ATR-FTIR results, where organosulfate formation was observed only at high acid concentrations. These observations can be attributed to the kinetic isotope effect (KIE) due to use of D2SO4/D2O in NMR experiments rather than H2SO4/H2O. The percent yield of organosulfate products was proportional to the amount of available acidic sulfate. The results from this study suggest that acid hydrolysis of epoxides can result in the formation of a wide range of products under different conditions, that can contribute to SOA growth. It proves that epoxides can be efficient SOA precursors for ambient conditions prevailing in an urban atmosphere.

No description available.

Les procédés industriels de fabrication de composites carbone/carbone consistent en la densification d’un substrat poreux (préforme) par dépôt de précurseurs gazeux. L’objectif de ce travail a été de développer et valider un mécanisme cinétique détaillé modélisant les réactions hétérogènes de dépôt de pyrocarbone par pyrolyse de propane. Les expérimentations ont été réalisées en utilisant un dispositif adapté à l’étude cinétique de réactions hétéro-homogènes. Des analyses par chromatographie ont permis de doser 29 espèces gazeuses, la vitesse de dépôt étant déterminée par pesée. Nous avons étudié l’influence des paramètres opératoires suivants : température (900-1050°C ); temps de passage (0,5-4 s), ratio S/V (20-170 cm-1) et composition de l’alimentation du réacteur (ajout d’hydrogène, acétylène et benzène). Le mécanisme hétérogène est constitué de 275 processus élémentaires impliquant 66 sites de surface. Les paramètres cinétiques des réactions de surface ont été estimés par analogie avec des réactions gazeuses « prototypes ». Les simulations ont été réalisées en utilisant Chemkin Surface. Le modèle permet de prédire de manière quantitative la vitesse de dépôt ainsi que les fractions molaires des principales espèces gazeuses. Les fractions molaires en espèces minoritaires sont reproduites de manière semi-quantitative. L’analyse de flux a montré que le pyrocarbone est principalement formé par dépôt de radicaux méthyles et de petites espèces insaturées (acétylène, éthylène) dans nos conditions opératoires / Industrial Carbon/Carbon composite manufacturing processes consist in the densification of a porous substrate (preform) by deposition of gaseous precursors. The aim of this work was to develop and validate a detailed kinetic mechanism modeling heterogeneous reactions of pyrocarbon deposition by propane pyrolysis. Experiments were carried out using an experimental set-up appropriate for studying the kinetics of hetero-homogeneous reactions. Chromatographic analysis were performed to quantify 29 gas phase species, the deposition rate being measured by weighing. We studied the influence of the following experimental parameters: temperature (900-1050°C), residence time (0.5-4 s), S/V ratio (20-170 cm-1) and composition of the reactor inlet (addition of hydrogen, acetylene and benzene). The heterogeneous mechanism contains 275 surface elementary steps involving 66 surface sites. Kinetic parameters of surface reactions were estimated by analogy with gas phase “prototype” reactions. Simulations were carried out using the Surface Chemkin package. The model is efficient to quantitatively predict the deposition rate as well as the mole fractions of major gas phase species. The mole fractions of minor species are semi-quantitatively predicted. The flow rate analysis demonstrates that the pyrocarbon is mostly formed by deposition of methyl radicals and small unsaturated species (acetylene, ethylene) in our experimental conditions

Many aspects associated with conversion of lignocellulose to biofuels and other valuable products have been investigated to develop the most effective processes for biorefineries. The goal of this research was to improve the efficiency and effectiveness of the lignocellulose conversion process by achieving a more basic understanding of pretreatment and enzymatic hydrolysis at high solids, including kinetic modeling and separation and recovery of glucose. Effects of NaOH pretreatment conditions on saccharide yields from enzymatic hydrolysis were characterized in low- and high-solids systems. Factors associated with pretreatment and hydrolysis were investigated, including duration of pretreatment at different temperatures and NaOH loadings, as well as different solids and enzyme loadings. Under relatively mild pretreatment conditions, corn stover composition was essentially equivalent for all time and temperature combinations; however, components were likely affected by pretreatment, as differences in subsequent cellulose conversions were observed. Flushing the hydrolyzate and reusing the substrate was also studied as a method for inhibitor mitigation while increasing overall glucose yields. Flushing the PCS throughout the hydrolysis reaction eliminated the need to wash the pretreated biomass prior to enzymatic hydrolysis when supplementing with low doses of enzyme, thus reducing the amount of process water required. The robustness of an established kinetic model was examined for heterogeneous hydrolysis reactions in high-solids systems. Michaelis-Menten kinetics is the traditional approach to modeling enzymatic hydrolysis; however, high-solids reactions violate the main underlying assumption of the equation: that the reaction is homogeneous in nature. The ability to accurately predict product yields from enzymatic hydrolysis in high-solids systems will aid in optimizing the conversion process. Molecularly-imprinted materials were studied for use in both bulk adsorption and in column chromatography separations. Glucose-imprinted materials selectively adsorbed glucose compared xylose by nearly 4:1. Non-imprinted materials were neither selective in the type of sugar adsorbed, nor were they capable of adsorbing sugar at as high a capacity as the glucose-imprinted materials. Liquid chromatography with imprinted materials was not a suitable means for separating glucose from solution under the conditions investigated; however, many factors impact the effectiveness of such a separation process and warrant further investigation.

If released in significant amounts, products formed by reactions between ozone (O3) and volatile organic compounds (VOCs) sorbed on activated carbon (AC) filters could degrade indoor air quality (IAQ). Heterogeneous reactions were investigated in laboratory experiments aimed at characterizing reaction products. Effluent air of AC loaded with limonene and exposed to O 3 (5.8 ppm) yielded unreacted limonene (501 ± 197 μg/m 3), low levels of 4-acetyl-1-methylcyclohexene (AMCH) (20 ± 2 μg/m3), and limonene oxides (25 ± 7 μg/m3). Most of the O3-limonene products remained on the AC, and most (58%) of the limonene remained unreacted on the AC after exposure to a stoichiometric excess of O3 for 48 h. Thus, in addition to known homogenous reactions, O3-limonene reactions occur heterogeneously on AC but to a much lesser extent. However, the fate of 95% of the depleted limonene was not determined; much of the missing portion was attributed to desorption from the AC, but the formation of other secondary indoor air pollutants is possible. VOC-loaded AC air filters exposed to O3 seem unlikely, however, to constitute a significant emission source of reaction products. More studies are necessary to investigate other pollutants, effects of environmental conditions, and VOC releases from AC that may be enhanced by O3 exposure.

Emulsion explosives have become the preferred choice as blasting agents for numerous industries including mining, agriculture, and construction. One of the most important components in such an emulsion is an emulsifier, which controls the emulsification properties of the explosive. The present study involves the production of one such emulsifier, which is produced by reacting two immiscible liquids, PIBSA (polyisobutylene succinic anhydride) and MEA (monoethanolamine). The study examines the effect of design variable such as the impeller speed, impeller type and the dispersed phase volume fraction on interfacial area. Experiments were carried out in a 0.15 m diameter fully baffled stirred tank using a 6-bladed Rushton turbine impeller and a marine propeller. Drop size was determined using a microscope with a video camera and image processing system. The transient concentration of PIBSA was determined using FTIR analysis and used to estimate the volume fraction of the dispersed phase (ƒÖ). The effective interfacial area was calculated using the Sauter mean drop diameter, d32 and ƒÖ. Impeller speeds ranging from 150 to 600 rpm and dispersed phase volume fractions, ƒÖ ranging from 0.01 to 0.028 were examined in the experimental study. It was found that that the evolution of Sauter mean drop diameter, d32 has four different trends depending on ƒÖ and impeller speed. At high impeller speeds and high ƒÖ, d32 values decrease initially and reach constant values after a long period of time. This trend is consistent with the findings in previous investigations. Under certain operating conditions, d32 values increase initially with stirring time to reach a maximum value and then decrease to reach a steady state value. The presence of these trends has been attributed to the effect of changing physical properties of the system as a result of chemical reaction. Results indicate that, in general, Sauter mean drop diameter d32 decreases with an increase in agitation intensity. However a decrease in the dispersed phase volume fraction is found to increase d32. These trends are found to be the same for both impeller types studied. Comparing the drop size results produced by the two impellers, it appears that low-power number propeller produces s ignificantly smaller drops than the Rushton turbine. It was found that the concentrations of reactants decrease with time for all impeller speeds thereby leading to a decrease in interfacial area with the progress of the reaction. Interfacial area values obtained at higher impeller speeds are found to be lower in spite of lower d32 values at these speeds. Also, these values decrease with time and become zero in a shorter duration indicating the rapid depletion of MEA. The interfacial area values obtained with the propeller at a given impeller speed are lower as compared to those for Rushton turbine. They also decrease and become zero in a shorter duration as compared to those for Rushton turbine suggesting propeller¡¦s performance is better in enhancing the reaction rate.

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.

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.

L’atmosphère est un milieu complexe, loin d’être parfaitement homogène. Elle contient de nombreuses particules, sous formes solides ou liquides, dénommées aérosols. Ces particules peuvent affecter l’équilibre radiatif de la planète, la qualité de l’air dans les milieux urbains et changer la composition chimique de l’atmosphère malgré leur présence à des très faibles teneurs. Par ailleurs, au niveau du sol, la phase gazeuse atmosphérique peut interagir avec la végétation et le bâtiment, tout particulièrement en zone urbaine. Ce travail se situe donc dans le cadre général de l’étude des réactions photoinduites à l’interface air/solide afin de pouvoir comprendre et décrire leur rôle dans la pollution atmosphérique (principalement urbaine). Cette étude a comme objectif principal l’étude de l’influence du rayonnement solaire sur les cinétiques hétérogènes des réactions impliquant le dioxyde d’azote et des surfaces organiques (pyrene, fluoranthene, phénanthrène) pures et des surfaces organiques/inorganiques (pyrene/KNO3, pyrene/Fe2O3, pyrene/KNO3/Fe2O3) simulant le dépôt urbain. De telles réactions n’ont pas encore été étudiées. Ces travaux ont été menés expérimentalement à l’aide de réacteurs de type « tube à écoulement » couplé à un détecteur spécifique du gaz en trace étudié. Après avoir mis en évidence une capture photoinduite sur ces surfaces, nous avons montré que la capture de NO2 dépend de plusieurs paramètres tels que la concentration de NO2, l’humidité relative, le flux photonique avec l’identification des produits de réactions, en l’occurrence l’acide nitreux HNO2, le monoxyde d’azote, les ions nitrites et le 1‐nitropyrene. L’acide nitreux détecté est un élément favorisant les pics de pollution photochimique à l’ozone. Ainsi ce travail est une avancée importante dans ce champ de recherche. / The atmosphere contains a wide variety of solid and liquid particles, named Aerosol. These particles can affect the radiatif balance, air quality in urban environment and can change the composition of the atmosphere. The atmospheric gas phase can react with the vegetation and the buildings containing the urban grime. This work is focused on the investigations of the heterogeneous chemistry between atmospheric gas phase and the urban grime. The aim of the present work is to study the effect of the irradiation on the heterogeneous kinetic of NO2 on pur organic films (pyrene, fluoranthene, phenanthrene) and on organic/inorganic films (pyrene/KNO3, pyrene/Fe2O3, pyrene/KNO3/Fe2O3) as a first attempt to simulate the complexity of the urban grime. A coated flow tube reactor coupled with a NOx analyzer is used to study this kinetic. This work demonstrates the effect of solar radiation on the heterogeneous reaction between gasphase NO2 and the urban grime. The uptake coefficient calculated is a function of the initial NO2 concentration, the relative humidity and the irradiation intensity. We identified after this reaction the formation of nitrous acid and nitric oxide, nitrite ions and 1‐nitropyrene.The nitrous acid is an important compound which dissociates to form the hydroxyl radical and can promote the ozone formation. The results discussed herein suggest that PAHcontaining urban grime on windows and buildings may be a key player in urban air pollution.

Dans cette thèse, des simulations numériques tridimensionnelles instationnaires d'une installation expérimentale de combustion en boucle chimique sont réalisées. Le pilote expérimental, d'une puissance de 120 kWth, utilise un matériau perovskite, à base de Ca-Mn, comme transporteur d'oxygène. Les simulations numériques sont réalisées par le code NEPTUNE_CFD, selon une approche Euler-Euler pour les deux phases (solide et gazeuse), avec des modèles de fermeture spécifiques pour modéliser les transferts de masse, de mouvement et d'énergie. Les réactions hétérogènes (i.e. réactions gaz-solide) de réduction et d'oxydation sont décrites au moyen d'un modèle à cœur rétrécissant dans le grain, qui prend en compte les mécanismes compétitifs dans le processus global de réaction gaz-solide: réaction chimique à la surface interne des particules,diffusion à travers la couche de produits et transfert externe autour des particules. Les résultats des simulations numériques sont validées avec des mesures expérimentales et analysées afin de mieux comprendre le comportement local/instationnaire de l'écoulement gaz-particules réactif dans ce système de combustion en boucle chimique. L'outil théorique/numérique développé dans ce travail sera utilisé pour le dimensionnement d'une unité pilote à l’échelle des installations industrielles. / In this work, reactive unsteady three-dimensional numerical simulations of a Chemical Looping Combustion (CLC) plant are performed. The plant is a 120 kWth pilot working with Ca-Mn-based material as selected oxygen carrier. Numerical simulations are performed by NEPTUNE_CFD code using an Euler-Euler approach which computes both the gas and the solid phases in an Eulerian fashion accounting for specific closures in order to model interphase mass, momentum and energy transfers. Reduction and oxidation heterogeneous (i.e. gas-solid) reactions are modeled by means of a grain model (shrinking core model in the grain) accounting for both the competing mechanisms of chemical reaction at the particle internal surface and gaseous diffusion through the product layer. Results from numerical simulations are validated against experimental measurements and analyzed in order to gain insight in the local behaviour of the reactive gas-particle flow in the CLC system. The theoretical/numerical tool developed in this work will be used for design upgrade recommendation in the stage of scaling-up from pilot to industrial facilities.