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%.

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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).

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.

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

Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-22T17:28:55Z No. of bitstreams: 0 / Made available in DSpace on 2017-11-22T17:28:56Z (GMT). No. of bitstreams: 0 / Neste trabalho os diferentes sistemas eletrocatalíticos PtIn/C, PtRu/C, PtRuIn/C e suas diferentes proporções mássicas foram sintetizados pelo método de redução por Borohidreto de Sódio, a fim de serem utilizados como ânodo na célula a combustível alcalina de metanol direto (DMFC). Os materiais obtidos foram caracterizados pelas técnicas de EDX, DRX e MET. O método de redução aplicado na síntese se mostrou efetivo, uma vez que as partículas apresentaram boa dispersão no suporte de carbono Vulcan XC72, de acordo com as analises de EDX e MET. Os resultados obtidos por DRX evidenciaram em todos os difratogramas apresentados a estrutura CFC da platina e um relativo deslocamento do pico equivalente ao plano (220) para valores maiores e menores que 2θ. O tamanho médio do cristalito e os parâmetros de rede calculados indicaram a inserção de átomos de Índio e Rutênio à estrutura da Platina, supondo a formação de ligas. A oxidação eletroquímica do metanol foi estudada por voltametria cíclica, cronoamperometria e curvas de polarização. Os experimentos eletroquímicos demonstraram que nos eletrocatalisadores binários com maior composição de Índio e Rutênio a eficiência catalítica frente a oxidação do combustível foi melhor e para os ternários, o eletrocatalisador que possuía maior composição de Rutênio se mostrou mais eficiente. Nos experimentos práticos em células a combustível, as curvas de polarização mostraram divergências de resultados com os obtidos por voltametria cíclica e cronoamperometria, justificadas por problemas de prensagem e descolamento de MEA\'s em sistemas que apresentaram maior quantidade de cocatalisador como Índio e Rutênio. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Abstract Exhaust gas emissions, e.g. nitrogen oxides (NOx), hydrocarbons (HCs) and carbon monoxide (CO), are harmful to human health and the environment. Catalysis is an efficient method to decrease these emissions. Unfortunately, the fuels and lubricant oils may contain chemical impurities that are also present in exhaust gases. Thus, catalytic materials with high activity and chemical resistance towards impurities are needed in the abatement of exhaust gas emission. In this thesis, the aim was to gain new knowledge about the effects of chemical impurities on the behaviour and activity of the catalysts. To find out these effects, the impurities existing in the exhaust gas particulate matter after combustion of biofuels and fossil fuels were analysed. The studied zeolite (ZSM-5), cerium-zirconium mixed oxides (CeZr and ZrCe) and silicon-zirconium oxide (SiZr) based catalysts were also treated with impurities to simulate the poisoning of the catalysts by, e.g. potassium, sodium, phosphorus and sulphur, using gas or liquid phase treatments. Several characterization techniques were applied to find out the effects of impurities on catalysts’ properties. The activity of catalysts was tested in laboratory-scale measurements in CO and HC oxidation and NOx reduction using ammonia (NH3) and hydrogen (H2) as reductants. The results revealed that the CeZr based catalysts had a high activity in NOx reduction by NH3 and moderate activity by H2. Sulphur was proven to enhance the activity of CeZr catalysts in NOx reduction. This is due to an increase in chemisorbed oxygen after the sulphur treatment on the catalyst surface. Instead, in HC and CO oxidation reactions, sulphur had a negligible impact on the activity of the SiZr based diesel oxidation catalyst. Thus, both CeZr and SiZr based catalysts can be utilized in exhaust gas purification when sulphur is present. ZSM-5 based catalysts were proven to be resistant to potassium and sodium. Alternatively, the activity of SiZr based catalysts decreased due to phosphorus. Thus, the removal of biomaterial-based impurities from the exhaust gases is needed to retain high catalyst activity in the exhaust gas after-treatment system. / Tiivistelmä Pakokaasupäästöissä olevat typen oksidit (NOx), hiilivedyt (HCs) ja hiilimonoksidi (CO) ovat haitallisia ihmisten terveydelle ja ympäristölle. Katalyysi on tehokas menetelmä vähentää näitä päästökomponentteja. Polttoaineet ja voiteluöljyt sisältävät epäpuhtauksia, jotka siirtyvät myös pakokaasuihin. Tästä johtuen pakokaasupäästöjen hallinnassa tarvitaan katalyyttimateriaaleja, joilla on hyvä vastustuskyky myrkyttymistä vastaan. Tavoitteena oli saada uutta tietoa kemiallisten epäpuhtauksien vaikutuksesta katalyyttien toimintaan. Biopolttoaineiden sisältämät mahdolliset epäpuhtaudet selvitettiin analysoimalla fossiilisen ja biopolttoaineen palamisessa muodostuvia partikkeleita ja vertaamalla niitä polttoaineiden hivenaineanalyysiin. Tutkimuksessa käytetyt zeoliitti (ZSM-5), cerium-zirkonium-sekaoksidi (CeZr) ja pii-zirkonium-oksidipohjaiset (SiZr) katalyytit käsiteltiin epäpuhtauksilla (kalium, natrium, fosfori ja rikki) kaasu- ja nestefaasissa. Tutkimuksessa käytettiin useita karakterisointitekniikoita, joiden avulla selvitettiin epäpuhtauksien vaikutuksia katalyyttien ominaisuuksiin. Katalyyttien toimintaa testattiin laboratoriomittakaavan kokeissa CO:n ja HC-yhdisteiden hapetuksessa sekä NOx:ien pelkistyksessä käyttäen ammoniakkia (NH3) tai vetyä (H2) pelkistimenä. Tulokset osoittavat, että CeZr-pohjaisten katalyyttien aktiivisuus NOx:ien pelkistyksessä oli hyvä käytettäessä pelkistimenä NH3:a ja kohtalainen käytettäessä vetyä. Rikki paransi CeZr-katalyyttien aktiivisuutta NOx:ien pelkistyksessä, mikä johtui kemiallisesti sitoutuneen hapen osuudesta katalyyttien pinnoilla. Vastaavasti hiilivetyjen ja CO:n hapetusreaktioissa rikki ei vaikuttanut SiZr-pohjaisten dieselhapetuskatalyyttien aktiivisuuteen. Sekä CeZr- ja SiZr-pohjaisia katalyytteja voidaan siten käyttää rikkiä sisältävien pakokaasujen puhdistuksessa. SiZr-pohjaisten katalyyttien aktiivisuus laski fosforin vuoksi. ZSM-5-pohjaiset katalyytit olivat vastustuskykyisiä kaliumille ja natriumille. Kestäviä katalyyttejä on siten kehitettävä, mikäli biopolttoaineiden sisältämien epäpuhtauksien poistaminen polttoaineista ei ole mahdollista.