There has been a growing interest in using lean-burn engines due to their higher fuel economy and associated lower CO2 emissions. However, there are challenges in reducing NOX in an O2-rich (lean-burn) exhaust, and in low temperature soot oxidation. NOX storage/reduction (NSR) and selective catalytic reduction (SCR) are commercial NOX reduction technologies, and both are more efficient with levels of NO2 that are higher than those that are in engine exhaust (engine-out NO2 levels are ~10% of the total NOX). Therefore diesel oxidation catalysts are installed upstream of these technologies to provide NO2 through NO oxidation. The motivation behind this research project was two-fold. The first was to gain a better understanding of the effect of hydrocarbons on NO oxidation over a monolithic diesel oxidation catalyst. The second was to spatially resolve competitive oxidation reactions as a function of temperature and position within the same diesel oxidation catalyst (as that used in the first part). A technique known as spatially resolved capillary-inlet mass spectrometry (SpaciMS) was used to measure the gas concentrations at various positions within the catalyst. Diesel engine exhaust contains a mixture of compounds including NO, CO and various hydrocarbons, which react simultaneously over a catalyst, and each can influence the oxidation rates of the others. While studying the effect of hydrocarbons on NO oxidation in this project, propylene was found to have an apparent inhibition effect on NO oxidation, which increased with increasing propylene concentration. This apparent inhibition is a result of the NO2, as a product of NO oxidation, reacting with the propylene as an oxidant. Experiments with NO2 demonstrate a significant temperature decrease in the onset of NO2 reduction when propylene was present, which decreased further with increasing amounts of propylene, verifying NO2 as an oxidant. Similar results were observed with m-xylene and dodecane addition as well. The results also demonstrate that NO2 was consumed preferentially relative to O2 during hydrocarbon oxidation. With low inlet levels of O2, it was evident that the addition of NO2 had an apparent inhibition effect on propylene oxidation after the onset of NO2 reduction. This subsequent inhibition was due to the NO formed, demonstrating that C3H6 results in reduced NO2 outlet levels while NO inhibits C3H6 oxidation. The development of new models as well as validation of existing models requires the ability to spatially resolve oxidation reactions within a monolith. Spatially-resolved data will also give catalyst manufacturers insight into the location of active fronts, thereby directing the design of more efficient catalysts. In this research project, spatially resolving the oxidation reactions demonstrated that H2 and CO are oxidized prior to C3H6 and C12H26 and clearly show back-to-front ignition of the reductant species. An enhancement in NO oxidation was observed at the same time as dodecane oxidation light off, likely related to dodecane partial oxidation products.

There has been a growing interest in using lean-burn engines due to their higher fuel economy and associated lower CO2 emissions. However, there are challenges in reducing NOX in an O2-rich (lean-burn) exhaust, and in low temperature soot oxidation. NOX storage/reduction (NSR) and selective catalytic reduction (SCR) are commercial NOX reduction technologies, and both are more efficient with levels of NO2 that are higher than those that are in engine exhaust (engine-out NO2 levels are ~10% of the total NOX). Therefore diesel oxidation catalysts are installed upstream of these technologies to provide NO2 through NO oxidation. The motivation behind this research project was two-fold. The first was to gain a better understanding of the effect of hydrocarbons on NO oxidation over a monolithic diesel oxidation catalyst. The second was to spatially resolve competitive oxidation reactions as a function of temperature and position within the same diesel oxidation catalyst (as that used in the first part). A technique known as spatially resolved capillary-inlet mass spectrometry (SpaciMS) was used to measure the gas concentrations at various positions within the catalyst. Diesel engine exhaust contains a mixture of compounds including NO, CO and various hydrocarbons, which react simultaneously over a catalyst, and each can influence the oxidation rates of the others. While studying the effect of hydrocarbons on NO oxidation in this project, propylene was found to have an apparent inhibition effect on NO oxidation, which increased with increasing propylene concentration. This apparent inhibition is a result of the NO2, as a product of NO oxidation, reacting with the propylene as an oxidant. Experiments with NO2 demonstrate a significant temperature decrease in the onset of NO2 reduction when propylene was present, which decreased further with increasing amounts of propylene, verifying NO2 as an oxidant. Similar results were observed with m-xylene and dodecane addition as well. The results also demonstrate that NO2 was consumed preferentially relative to O2 during hydrocarbon oxidation. With low inlet levels of O2, it was evident that the addition of NO2 had an apparent inhibition effect on propylene oxidation after the onset of NO2 reduction. This subsequent inhibition was due to the NO formed, demonstrating that C3H6 results in reduced NO2 outlet levels while NO inhibits C3H6 oxidation. The development of new models as well as validation of existing models requires the ability to spatially resolve oxidation reactions within a monolith. Spatially-resolved data will also give catalyst manufacturers insight into the location of active fronts, thereby directing the design of more efficient catalysts. In this research project, spatially resolving the oxidation reactions demonstrated that H2 and CO are oxidized prior to C3H6 and C12H26 and clearly show back-to-front ignition of the reductant species. An enhancement in NO oxidation was observed at the same time as dodecane oxidation light off, likely related to dodecane partial oxidation products.

Interferentes endócrinos são substâncias que podem causar danos ao meio ambiente e à saúde humana. Estes compostos são usados na produção de vários produtos de uso diário, porém não são completamente eliminados dos efluentes industriais, contribuindo para a contaminação de diversas matrizes ambientais. Nesse contexto, os processos eletroquímicos se destacam com boas eficácias no tratamento de diversos tipos de efluentes. No entanto, uma melhor compreensão do processo é importante para estabelecer tratamentos de efluentes que possam ser mais amplamente aplicados. Esta tese aborda a degradação do metil parabeno (MeP), em diferentes efluentes sintéticos, via eletrólise com ânodos de misturas de óxidos metálicos comercial (MOM-Cl2) e diamante dopado com boro (DDB). Ainda mais importante, o MeP é utilizado como uma molécula modelo para o compreender os efeitos da irradiação de luz UV e de ultrassom (US) durante a eletrólise. É importante lembrar que a composição da matriz deve afetar a eficiência do processo e, assim, também se utiliza o MeP como modelo para entender os possíveis efeitos interferentes de outros compostos orgânicos na sua oxidação. Finalmente, se estuda um efluente simulado da indústria cosmética para melhor compreender os efeitos da eletrólise e da irradiação de US em uma matriz complexa. Foram observadas grandes diferenças entre as eficiências dos tratamentos com MOM-Cl2 e DDB, principalmente com relação ao mecanismo de degradação do MeP. Nos estudos com MOM-Cl2, muitas vezes o efluente final era mais complexo que o inicial, devido à formação de produto sólido, reações de polimerização e alto efeito de interferência quando dois compostos são tratados simultaneamente. Com o DDB, o processo de mineralização é muito mais favorecido, independentemente da complexidade do efluente. O efeito de interferência ganha significância na presença de altas concentrações de um segundo composto orgânico, mas a completa mineralização ainda foi atingida. A irradiação de UV e US representou melhoras no processo de remoção de matéria orgânica, principalmente com relação aos produtos do MeP. Foi observado que surfactantes podem interferir negativamente na degradação de compostos orgânicos devido a formação de micelas. Diante de alto conteúdo micelar a eficiência do processo diminui, porém 90% de mineralização do efluente foi alcançada. A irradiação de US ajuda significativamente no aspecto físico do efluente tratado, sendo possível obter a transformação de emulsões, com alta turbidez e material particulado, em soluções completamente límpidas e mineralizadas. / Endocrine disrupting chemicals (EDCs) are responsible for causing adverse effects on the environment and on human health. Those substances are extensively used in several costumer products, such as pharmaceuticals and cosmetics. However, several EDCs are not completely removed from industrial wastewaters by the most common treatments, contributing on the environmental contamination. In this context, electrochemical processes can be highlighted due to its efficacy presented on the treatment of numerous types of wastewater. Nevertheless, better understanding of the process is important in order to design wastewater treatments that can be widely applied. Hence, this thesis focus on the degradation of methyl paraben (MeP), in different synthetic wastewater, by electrolysis with mixed metal oxides commercial (MMO-Cl2) and boron-doped anode (BDD) anodes. More importantly, MeP is used as a model molecule to understand the effects of the irradiation of UV light and of ultrasound (US) during the electrolysis. It is important to consider that matrix composition must affect the process efficiency. Hence, MeP is also used as model to shed a light on the possible interfering effects of other organics on its oxidation. Finally, a simulated wastewater from cosmetic industry is studied in order to better comprehend the effects of electrolysis and of ultrasound on complex matrix. Great differences were observed on the efficiency of treatments using MMO-Cl2 and BDD, mostly regarding the mechanism of MeP oxidation. With MMO-Cl2, the treated wastewater was often more complex than the initial one, due to the formation of solid product, polymerization reaction and great interfering effect when two compounds are simultaneously treated. Conversely, using BDD, the mineralization process is favored, regardless the complexity of the matrix. Interfering effect on MeP oxidation is relevant under the presence of huge concentrations of a second organic compound, though the complete mineralization is attained. Irradiation of UV and of US resulted in better removals of organic matter, mainly with respect to MeP products. It was observed that surfactants may interfere on the degradation of organic compounds due to the formation of micelles. The efficiency of the process decreases under high micelles content, however 90% of mineralization was achieved. Irradiation of ultrasound notably improves the physical aspect of the treated wastewater, assisting on the transformation of emulsions, with great turbidity and amount of particles, in clear non-organic solutions.