The effect of soot on the catalytic properties of a diesel particulate filter coated with a catalyst for the selective catalytic reduction of NOx with ammonia (SDPF) was studied by means of model-gas experiments. After loading of the SDPF with model soot from 0 to 10 g l-1, the NH3 storage as well as the catalytic DeNOx behavior of the standard SCR reaction was investigated. The model soot present in the filter was shown to have an NH3 storage capacity. The soot deposit inside the SDPF filter wall lead to a decreased NO conversion in SCR experiments of up to 20 %. The NH3 breakthrough was found to be shifted towards earlier time-on-stream during NH3 adsorption on soot loaded SDPF samples. Both effects could be attributed to a diffusive mass transport limitation of the gas species through the soot to reach at the chemically active sites inside SDPF filter wall. The self-diffusion coefficient of NH3 probe molecules within a soot layer could be measured using Pulsed Field Gradient-NMR technique. The unit collector model is capable of describing the backpressure upon soot loading with a depth filtered (inside filter wall) soot amount of 1 g l-1 and 0.36 g l-1, respectively, for both SDPF types under investigation. Based on Scanning Electron Microscopy (SEM) investigation a 1-D microscopic soot filter wall-model was set up. The model implies soot as diffusion barrier for mass transport. It was calibrated based on experimental observations and allows to conclude on the distribution of the soot within the filter wall. Thus, a high soot-coverage of the porous filter wall close to the inlet channel, a slightly covered middle part and a soot free zone close to the outlet explains the observed reduction in NO conversion as well as the NH3 breakthrough at earlier time-on-stream during NH3 adsorption experiments for SDPF samples loaded with soot. A modelled homogeneous soot distribution (0.6 µm soot layer on top of washcoat) within the whole SDPF was shown to result in NO conversion drop up to 45 %.

Les oxydes d’azotes (NOx) sont un des groupes majeurs de polluants primaires émis dans l’atmosphère, principalement par les transports et l’industries, dont leur réduction constitue un enjeu sociétal crucial. Afin de répondre à l’évolution de normes environnementales plus exigeantes, la diminution des NOx est notablement explorée via la réaction clef de Réduction Catalytique Sélective par l’ammoniac (NH3-RCS) en employant des catalyseurs à base de cuivre et de fer. Le développement maîtrisé et perfectionné de cette solution requiert une profonde compréhension du système catalytique et ce à différentes échelles. Cette étude vise ainsi à développer un modèle cinétique multi-sites pour la représentation des performances NH3-RCS, par l’exploration des propriétés physico-chimiques, de surface et catalytiques d’une série de catalyseurs zéolitiques microporeux (Chabazite) supportant le cuivre. Cette série de catalyseurs imprégnés, échangés et « One-pot » permit la profonde caractérisation de différentes configurations de sites actifs dont les impacts sur les comportements catalytiques furent étudiés et identifiés selon différentes conditions opératoires. Ainsi, le modèle permit de prendre en considération, via la distinction selon leur nature, de 5 sites majeurs : la compétition d’adsorption, l’impact de l’eau, la formation et décomposition d’intermédiaires clefs et un schéma réactionnel précis, de représenter les activités des différents catalyseurs. De plus, l’étude In-situ de la surface de ces catalyseurs via spectrométrie infra-rouge à réflexion diffuse (DRIFT) fut complémentaire à la compréhension des dynamiques de surface et l’identification des mécanismes du procédé catalytique / The reduction of atmospheric pollution from stationary and mobile engines is a serious challenge associated with stringent environmental regulations. For nitrogen oxides (NOx) abatement in particular, the selective catalytic reduction using urea or ammonia (urea- or NH3-SCR) over copper- and iron-based catalysts is one of most effective and economic technologies. In this respect, revisiting after-treatment systems by a deep comprehension of the catalyst behavior at different scale may significantly improve their eco- and health-friendliness. This study targets the development of a multi-site kinetic model using a series of copper chabazite-based catalysts, as a selected model SCR catalyst. To qualify these materials as beyond-state-of-the-art catalysts and to better understand the impact on different active site configurations, three catalysts were synthetized by different preparation methods (impregnation, ionic exchange and one-pot), finely characterized by different techniques and their ability to abate NOx via the ubiquitous NH3-SCR reaction was extensively assessed under several operating conditions. Each catalyst behavior was quantified and associated to their respective main active sites (five different configurations described). The diffusion, water impact, adsorption competition between key reactants and storage sites were also ones of the main points spotlighted in this study. In-situ characterization of these catalysts was also performed, using Diffuse Reflectance Infrared Fourier-Transform Spectroscopy (DRIFTS) to understand the surface dynamical properties of the catalyst, and to unveil the mechanistic of the catalytic processes

Stricter requirements on the reduction of Nitrogen Oxides (NOx) in the emissions of heavy-duty diesel vehicles drives development for more efficient aftertreatment systems. An ammonia covered catalyst is one of the most successful technologies in reducing NOx by converting it into the harmless byproducts water and nitrogen. The ammonia injection control is however difficult due to nonlinearities and the impact of external exhaust parameters. The ammonia coverage ratio depends heavily on the surface temperature of the catalyst and a rapid increase in surface temperature would lead to a rapid decrease in ammonia storage capabilities. If the storage capabilities decrease below the current level of stored ammonia, the excess ammonia will flow into the exhaust and convert to NOx, an undesired phenomenon due to the cost of and the pollution caused by the ammonia released, often referred to as ammonia slip. This issue is further amplified by the fact that the problem is asymmetric, that is injected ammonia cannot be actively removed but has to be reduced by the reaction with the NOx present in the exhaust. As such, it is very important to keep the level of ammonia storage ratio low enough to avoid slipping but at the same time sufficiently high to obtain a satisfactory NOx conversion efficiency. These two issues are the main reasons why feedback control has proven to be difficult to implement to solve the dosing problem. As one has to store a lot of ammonia in order to obtain a satisfactory conversion of NOx, one often cannot react to rapid temperature increases in the catalyst. As such, one often experiences a lot of ammonia slip during these scenarios. In this report it is shown that utilizing predicted parameters of the exhaust in a model predictive controller reduces the ammonia consumption by 38% while also improving the tracking of the NOx conversion reference by 5.5%. / Strängare krav på minskning av kväveoxider (NOx) i utsläpp från tunga dieselfordon driver utvecklingen för ett mer effektivt efterbehandlingssystem. En ammoniakbelagd katalysator är en av de mest framgångsrika tekniker för att minska NOx genom att omvandla det till de ofarliga biprodukterna vatten och kväve. Injeceringen av ammoniak är dock svår att reglera på grund av olinjär dynamik och påverkan av externa avgasparametrar. Täckningsgraden av ammoniak beror starkt på yttemperaturen hos katalysatorn, där en ökning av temperaturen skulle leda till en minskad lagringskapacitet av ammoniak. Om lagringskapaciteten minskar under nuvarande täckningsgraden av ammoniak kommer överskottet av ammoniak att frigöras och strömma ut ur katalysatorn tillsammans med avgaserna och omvandlas till NOx, ett oönskat fenomen på grund av kostnaden för och de föroreningar som orsakas av ammoniaken. Detta problem förvärras av det faktum att problemet är asymmetriskt, dvs injicerad ammoniak kan inte aktivt avlägsnas utan måste reduceras genom att reagera med de befintliga NOx som finns i avgaserna. Därav är det väldigt viktigt att täckningsgraden av ammoniak hålls tillräckligt lågt för att undvika att ammoniaken frigörs men samtidigt tillräckligt hög för att erhålla den önskade omvandlingen av NOx. Dessa två problem är de främsta anledningarna till att reglering med återkoppling har visat sig vara svårt att implementera för att lösa doseringsproblemet. Eftersom det krävs en hög täckningsgraden av ammoniak för att få en önskvärd omvandling av NOx hinner en ofta inte korrigera för snabba temperaturökningar i katalysatorn. Det frigörs därför mycket av den lagrade ammoniaken under dessa scenarier. I denna rapport demonstreras att användandet av predikterade avgasparametrar i en modell prediktiv kontroller minskar ammoniakförbrukningen med 38% samtidigt som den önskade NOx omvandlingen förbättrades med 5.5%.

No description available.

Este trabalho propõe um método com base no planejamento estatístico de testes de confiabilidade para proporcionar um tratamento quantitativo aos dois primeiros níveis da abordagem de padrões baseados em metas (Goal-Based Standards). O uso do método é demonstrado em dois exemplos práticos, através da sua aplicação na meta de confiabilidade dos componentes do sistema de pós-tratamento de gases de exaustão, em motores a diesel de veículos automotivos e marítimos. Os fundamentos do trabalho incluem a teoria do planejamento estatístico de testes de confiabilidade, os princípios do GBS, tipos e características de metas de confiabilidade, a ferramenta de avaliação de segurança formal (FSA), e da análise do modo e efeito da falha (FMEA). A originalidade da contribuição do trabalho está na combinação das técnicas de planejamento de testes de confiabilidade com os princípios do GBS para quantificar o nível de atendimento das metas de confiabilidade. Dessa forma, é possível ajustar o programa de testes na verificação das metas de segurança, aumentando o conhecimento sobre o desempenho do sistema. O método é de simples aplicação permitindo a sua aplicação expedita e integrada aos processos de desenvolvimento de sistemas. / This research proposes a probabilistic method based on reliability test planning in order to provide a quantitative approach to the Tier I and II of the Goal-Based Standards (GBS). The use of the method is exhibited through its application in the reliability goal of the components of the exhaust gases post-treatment system in diesel engines for automotive and marine vehicles. The fundamentals of this work includes the theory of statistical design of reliability tests, the GBS principles, a brief description of the types and characteristics of reliability goals, the tool of Formal Safety Assessment (FSA) recommended for marítima projects, and the risk qualitative methodology based on Failure Mode Effect Analysis (FMEA). This theoretical framework was applied to two practical examples, one in the automotive industry and the other in the shipbuilding sector. The originality of this research lies in the combination of the reliability test planning techniques with the principles of GBS, in order to verify, from the whole project tests planning, the reliability goals of the basic components as a fundamental step in the assessment of system safety. The testing program can be adjusted to focus on verifying the safety goals, so that the level of knowledge about the product performance before it is delivered to the client. This work also offers the benefit of providing an easy method of system safety assessment, which allows a large number of companies to use it and to integrate it into their product development process.

Dans cette étude, on s'est intéressé à la modélisation réduite et au contrôle d’organes intervenant dans la réduction des émissions de polluants des véhicules automobiles à basse consommation. Il s’agit des réacteurs catalysés de type « piège à NOx » et SCR, utilisés dans les architectures de post-traitement des gaz d’échappement des véhicules Diesel. Ces systèmes ont en commun la nécessité de contrôler les niveaux des émissions de polluants stockés sur les sites catalytiques et l’optimisation du fonctionnement du GMP en vue d’approcher les futures normes Euro et les nouvelles incitations sur les émissions de gaz à effet de serre.Le piège à NOx est un système catalytique dont la fonction première est de collecter les oxydes d’azote (NOx) des gaz d’échappement afin qu’ils ne soient pas rejetés dans l’environnement. Le réacteur SCR est un système catalytique qui utilise le principe de réduction sélective des NOx par l’ammoniac (NH3), initialment produit et délivré à partir d’un stock d’urée embarqué.La similitude des technologies a permis la mise en œuvre de méthodologies communes de modélisation cinétique et de réduction de modèles, basées sur l’étude thermochimique et cinétique des réseaux réactionnels. Après application aux systèmes respectifs de piège à NOx et SCR, nous avons obtenus des modèles réduits qui ont pu être identifiés, validés et appliqués à l’observation et au contrôle des niveaux de stock des polluants (respectivement NOx et NH3). / The purpose of this study is to develop mathematical reduced order models for components of low consumption motor vehicles : the lean NOx trap and the SCR catalysts, used in the exhaust of Diesel engines and involved in the reduction of pollutants in exhaust emissions. These systems have in common that they aim at controling the boundaries on pollutant emissions in order to achieve the forthcoming Euro standards and they allow the optimization of the aftertreatment systems to reduce greenhouse gases.The lean NOx trap catalyst aims at collecting the NOx in order to avoid the pollution of the environment and the SCR catalyst uses the selective reduction of the NOx by the ammonia (NH3), initially produced by an embedded urea system. The similarity between the two technologies allow the implementation of common methodologies for reduced order modeling of catalytic reactors based on thermochemical and kinetic studies. After application, respectively to the NOx trap and the SCR, we obtain reduced order models which were identified, validated and implemented for the control and diagnosis of the amount of stock of the pollutants (respectively NOx and NH3).

In recent times, as regulations and legislations for exhaust treatment have become more stringent, a major concern in the arena of environmental catalysis is to find new efficient and economical exhaust treatment catalysts. Chapter 1 is a review of the current status of various NOx abatement techniques and understanding the role of “auto-exhaust catalysts” involved therein. Chapter 2 presents the studies on synthesis of ionically substituted precious metal ions like Pd2+, Pt2+ and Rh3+ in CeO2 matrix and their comparative three-way catalytic performances for NO reduction by CO, as well as CO and hydrocarbon oxidation. Ce0.98Pd0.02O2- showed better catalytic activity than ionically dispersed Pt or Rh in CeO2. The study in Chapter 3 aims at synthesizing 1 atom% Pd2+ ion in TiO2 in the form of Ti0.99Pd0.01O2- with oxide ion vacancy. A bi-functional reaction mechanism for CO oxidation by O2 and NO reduction by CO was proposed. For NO reduction in presence of CO, the model based on competitive adsorption of NO and CO on Pd2+, NO chemisorption and dissociation on oxide ion vacancy fits the experimental data. The rate parameters obtained from the model indicates that the reactions are much faster over this catalyst compared to other catalysts reported in the literature. In Chapter 4 we present catalytic reduction of NO by H2 over precious metal substituted TiO2 (Ti0.99M0.01O2-, where M = Ru, Rh, Pd, Pt) catalysts. The rate of NO reduction by H2 depends on the reducibility of the catalysts. Chapter 5 presents the studies on reduction of NO by NH3 in presence of excess oxygen. 10 atom % of first row transition metal ions (Ti0.9M0.1O2-, where M = Cr, Mn, Fe, Co and Cu) were substituted in anatase TiO2 and TPD study showed that the Lewis and Bronsted acid sites are adsorption sites for NH3, whereas NO is found to dissociatively chemisorbed in oxide ion vacancies. The mechanism of the low temperature catalytic activity of the SCR and the selectivity of the products were studied to understand the mechanism by studying the by-reactions like ammonia oxidation by oxygen. A new catalyst Ti0.9Mn0.05Fe0.05O2- has shown low temperature activity with a broad SCR window from 200 to 400 °C and more selectivity than commercial vanadium-oxides catalysts. We attempted NO dissociation by a photochemical route with remarkable success. In Chapter 6 we report room temperature photocatalytic activity of Ti0.99Pd0.01O2- for NO reduction and CO oxidation by creating redox adsorption sites and utilizing oxide ion vacancy in the catalyst. The reduction of NO is carried out both in the presence and in the absence of CO. Despite competitive adsorption of NO and CO on the Pd2+ sites, the rate of reduction of NO is two orders of magnitude higher than unsubstituted TiO2. High rates of photo-oxidation of CO with O2 over Ti0.99Pd0.01O2- were observed at room temperature. In Chapter 7 the results are summarized and critical issues are addressed. Novel idea in this thesis was to see if both noble metal ions and base metal ions substituted in TiO2 and CeO2 reducible supports can act as better active sites than the corresponding metal atoms in their zero valent state.

Este trabalho propõe um método com base no planejamento estatístico de testes de confiabilidade para proporcionar um tratamento quantitativo aos dois primeiros níveis da abordagem de padrões baseados em metas (Goal-Based Standards). O uso do método é demonstrado em dois exemplos práticos, através da sua aplicação na meta de confiabilidade dos componentes do sistema de pós-tratamento de gases de exaustão, em motores a diesel de veículos automotivos e marítimos. Os fundamentos do trabalho incluem a teoria do planejamento estatístico de testes de confiabilidade, os princípios do GBS, tipos e características de metas de confiabilidade, a ferramenta de avaliação de segurança formal (FSA), e da análise do modo e efeito da falha (FMEA). A originalidade da contribuição do trabalho está na combinação das técnicas de planejamento de testes de confiabilidade com os princípios do GBS para quantificar o nível de atendimento das metas de confiabilidade. Dessa forma, é possível ajustar o programa de testes na verificação das metas de segurança, aumentando o conhecimento sobre o desempenho do sistema. O método é de simples aplicação permitindo a sua aplicação expedita e integrada aos processos de desenvolvimento de sistemas. / This research proposes a probabilistic method based on reliability test planning in order to provide a quantitative approach to the Tier I and II of the Goal-Based Standards (GBS). The use of the method is exhibited through its application in the reliability goal of the components of the exhaust gases post-treatment system in diesel engines for automotive and marine vehicles. The fundamentals of this work includes the theory of statistical design of reliability tests, the GBS principles, a brief description of the types and characteristics of reliability goals, the tool of Formal Safety Assessment (FSA) recommended for marítima projects, and the risk qualitative methodology based on Failure Mode Effect Analysis (FMEA). This theoretical framework was applied to two practical examples, one in the automotive industry and the other in the shipbuilding sector. The originality of this research lies in the combination of the reliability test planning techniques with the principles of GBS, in order to verify, from the whole project tests planning, the reliability goals of the basic components as a fundamental step in the assessment of system safety. The testing program can be adjusted to focus on verifying the safety goals, so that the level of knowledge about the product performance before it is delivered to the client. This work also offers the benefit of providing an easy method of system safety assessment, which allows a large number of companies to use it and to integrate it into their product development process.

Fundação de Apoio a Pesquisa e à Inovação Tecnológica do Estado de Sergipe - FAPITEC/SE / The presence of high concentrations of toxic metals in water bodies requires a constant search for new and more effective methods to treat industrial waste. The present work proposes a technique for the removal of chromium present in leather tannery effluent, using a hybrid magnetic adsorbent, CoFe2O4/NOM, synthesized using an environmentally friendly procedure. Salts of the metals (Co and Fe) were used as precursors and natural organic matter (NOM) was used as the gelification agent, replacing the traditional reagents that are toxic and expensive. Comparisons were made of CoFe2O4/NOM produced at ambient temperature (FeAMB) and the materials produced after calcination at 200 (Fe200), 400 (Fe400), and 800 °C (Fe800). The materials were analyzed by X-ray diffractometry and infrared spectroscopy, which revealed the presence of NOM in the structure of the material, together with the formation of cobalt ferrite, hence confirming the suitability of the new synthesis route. Adsorption tests, performed as a function of pH and time, showed the effectiveness of FeAMB at the natural pH of the effluent (pH 4.2), while at pH 6.0 the removal percentages were approximately 94, 100, 98, and 89% for FeAMB, Fe200, Fe400, and Fe800, respectively, with corresponding equilibration times of 60, 120, 120, and 60 minutes, respectively. Kinetics assays showed that high adsorption of 70-87% was achieved after only 20 minutes. The adsorption kinetics could be fitted using a pseudo-second order model, and the likely removal mechanism was electrostatic attraction between carboxylate groups and the cationic chromium species CrOH2+ and Cr(OH)2 +. Amongst the adsorbents studied, the FeAMB/NOM hybrid material was especially attractive because it did not require heat treatment and showed high removal capacities during five reuse cycles, ranging from 96% in the first cycle to 82% in the fifth cycle. The residues remaining after the reuse cycles, comprising the FeAMB hybrid saturated with chromium (FeAMB_Sat) and the desorbed chromium solution (dried and calcined at 500 °C, denoted CrD), showed excellent catalytic activity in the reduction of 4-nitrophenol to 4-aminophenol, the latter being an important compound used in the synthesis of pharmaceuticals and corrosion inhibitors. The conversion rates and times were 99.9% and 55 seconds for vi FeAMB_Sat, and 99.9% and 3 seconds for CrD. A magnetic hybrid material (denoted FeSF) was also synthesized replacing the analytical grade iron salt precursor by a ferric sulfate solution derived from the treatment of iron ore mining waste. This hybrid was highly efficient as an adsorbent, with 98% removal of chromium present in an industrial effluent in only 20 minutes. The technique described here contributes to the development of industrial symbiosis since it uses materials prepared using natural substances and enables the reuse of waste in the production cycle. The procedure is a technologically viable alternative for the remediation of metal-contaminated effluents. / O aumento da concentração de metais tóxicos nos corpos hídricos impulsiona uma busca constante por tratamentos eficientes para remediar resíduos industriais. Portanto, neste trabalho é proposto a remediação do cromo existente em efluente industrial de curtimento de couro utilizando um adsorvente híbrido magnético, CoFe2O4/MON, sintetizado por uma rota modificada, eco-amigável. Utiliza-se como precursores sais dos metais de interesse e a matéria orgânica natural (MON) como substância gelificante, em substituição aos reagentes tradicionais que são tóxicos e de alto custo. Para fins comparativos, a CoFe2O4/MON obtida à temperatura ambiente (FeAMB) foi calcinada a 200 (Fe200), 400 (Fe400) e 800°C (Fe800) e a formação do material foi confirmada por difratometria de raios x, que indicou também, simultaneamente, com o infravermelho, a presença da MON na estrutura do material, a formação da ferrita de cobalto e assim, a eficácia da rota de síntese proposta. Os ensaios de adsorção em função do pH e do tempo, evidenciaram a eficiência da FeAMB, no pH natural do efluente (4,2), enquanto que para os demais, no pH 6,0; com percentuais de remoção de aproximadamente 94, 100, 98 e 89% para FeAMB, Fe200, Fe400, Fe800, respectivamente, e tempos de equilíbrio de 60, 120, 120 e 60 minutos. Entretanto, com apenas 20 minutos de ensaios cinéticos houve uma alta resposta de adsorção, entre 70-87%. A cinética de adsorção ajustou-se melhor ao modelo de pseudo-segunda ordem e o possível mecanismo de remoção ocorre por atração eletrostática entre os grupos carboxilatos e as espécies catiônicas do cromo, CrOH2+, Cr(OH)2 +. O material híbrido FeAMB/MON destaca-se entre os demais adsorventes em estudo por não ter sido submetido a tratamento térmico e porque apresentou uma elevada capacidade de remoção após ser submetido a cinco ciclos de reutilização, variando de 96% no primeiro ciclo para 82% no quinto ciclo. Os resíduos decorrentes dos ciclos de reutilização, o híbrido FeAMB saturado com cromo (FeAMB_Sat) e a solução de cromo dessorvido, seca e calcinada a 500°C (CrD), apresentaram excelentes potenciais catalíticos na redução do 4- nitrofenol a 4-aminofenol, o qual é um importante insumo para a síntese de produtos farmacêuticos e inibidores de corrosão. A taxa e o tempo de conversão da redução, foram de 99,9% e 55 segundos para FeAMB_Sat e 99,9% e 3 segundos para CrD. De modo eminente, também foi sintetizado um material híbrido magnético substituindo o precursor sal de ferro em grau analítico por solução de sulfato férrico oriunda de um resíduo tratado da mineração de ferro, denominado FeSF. Este híbrido revelou uma eficiência notável como adsorvente, pois o percentual de remoção de cromo presente em efluente industrial foi de 98% em apenas 20 minutos. Diante disso, o presente estudo contribuiu para a prática da simbiose industrial ao propor o emprego de substâncias naturais na elaboração de materiais, bem como a reutilização dos resíduos, e sua reinserção no ciclo produtivo desenvolvendo uma alternativa tecnologicamente viável para remediação de metais.

Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-12-21T17:42:04Z No. of bitstreams: 0 / Made available in DSpace on 2016-12-21T17:42:04Z (GMT). No. of bitstreams: 0 / Os catalisadores eletroquímicos binários de PtSn/C, PdSn/C e PtPd/C foram sintetizados em diferentes proporções pelo método da redução via borohidreto, posteriormente estes foram caracterizados por microscopia eletrônica de transmissão, difração de raios X, espectroscopia no infravermelho por transformada de Fourier (PtSn/C e PdSn/C) e energia dispersiva de raios X. As atividades eletroquímicas dos diferentes materiais preparados foram avaliadas por intermédio de voltametria cíclica, cronoamperometria e curvas de polarização em célula a combustível alimentada diretamente por etileno glicol em eletrólito alcalino. As curvas de densidade de potência indicaram que os catalisadores eletroquímicos contendo Sn e Pd são mais ativos para a reação de oxidação do etileno glicol, especialmente a composição 70%:30% - relação molar entre os metais suportados em carbono - dos catalisadores PtSn/C, PdSn/C e PtPd/C todos superando as medidas de potência do Pt/C. Este resultado indica que a adição de Sn e Pd favorece a oxidação do etileno glicol em meio alcalino. O melhor desempenho observado para os catalisadores eletroquímicos PtSn/C, PdSn/C e PtPd/C (70%:30%) poderia estar associado à sua maior seletividade quanto a formação de oxalato, ou seja , a formação deste produto resulta em um maior número de elétrons, por consequência em maiores valores de corrente. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP