Poly(vinyl acetate) (PVAc) has a major application as an indoor wood adhesive. Low water stability is however, one of the greatest drawbacks of PVAc. By grafting PVAc from a chitosan (CS) backbone (CS-graft- PVAc) water stability of adhesive is increased while good mechanical and adhesive properties are retained. Simultaneously the percentage of bio-based content is increased. This work investigates the proposed re- action mechanisms between chitosan and cerium(IV) ammonium nitrate (CAN) which is used as an initiator for the grafting reaction. Litera- ture studies showed one dominating reaction mechanism and some not as common. The reaction mechanisms and their shortcomings are pre- sented and discussed in the report. / Poly(vinyl acetat)(PVAc) har ett stort användningsområde som ett trälim för möbler som ska användas inomhus. Den dåliga vatten stabiliteten är ett av de största problemen för användning av PVAc. Genom att ympa PVAc med chitosan(CS) (CS-graft-PVAc) kan vatten stabiliteten ökas samtidigt som en god limfunktion finns kvar och delen fossilbaserad monomer blir mindre och byts ut mot en biobaserad polymer. I detta arbete undersöks de föreslagna reaktionsmekanismerna mellan CS och cerium(IV) ammonium nitrat(CAN) som används som en katalysator för att grafta PVAc med CS. Litteraturstudier visade en dominerade reaktionsmekanism och några mindre förekommande. Reaktionsmekanis- merna och eventuella tillkortakommanden som finns gällande hur de fortlöper presenteras och diskuteras i detta arbete.

<p>Single junction silicon photovoltaic cells (SJSPVCs) are unable to transform all the energy in the solar spectrum into electricity, due to the broad nature of the solar spectrum and the limits imposed by a single bandgap. Furthermore, high surface recombination velocity reduces the SJSPVC external quantum efficiency response, particularly to ultraviolet photons. It is the goal of spectral engineering to optimize the light that is incident on the cell, by down-shifting high energy photons to lower energies, for example, to improve the performance of photovoltaic cells.</p> <p>This thesis represents a study into the luminescence of ion implanted films, involving silicon nanocrystals (Si-NCs) and rare-earth ions in fused silica or silicon nitride. Quantum efficiency measurements taken with an integrating sphere were used to characterize some of the samples. Other photoluminescence (PL) characterization work was carried out with a single-wavelength laser and a collection lens normal to the sample. Variable angle spectroscopic ellipsometry (VASE) was used to estimate the optical constants of the implanted films. In secondary work, Rutherford backscattering spectrometry, time-dependent PL, infrared-PL measurements, and electrical conductivity measurements were used to characterize select samples.</p> <p>It was found that the conversion efficiency of Si-NCs in fused silica was about 1% – too low to be useful according to modeled results. However, considerable variation in the peak wavelength of the Si-NC PL was obtained, depending on the peak concentration of implanted silicon. Si-NC-type PL was also produced by low-energy implantation of oxygen into a Czochralski silicon wafer.</p> <p>Oxygen was also implanted into films of cerium-doped high-purity silicon nitride, and it was shown that the photoluminescence from these films is largely dependent on the level of oxygen doping. The internal conversion efficiency of a cerium-doped fused silica sample was found to approach 20%, which indicates that this is a promising avenue for future research.</p> <p>Finally, energy transfer was demonstrated between Si-NCs and erbium ions. The lifetime of the erbium PL appears to increase with increasing implanted silicon fluence.</p> / Master of Applied Science (MASc)

Cerium oxide nanoparticles have the unique ability to accept and donate electrons, making them powerful antioxidants. Their redox nature is due to oxygen defects in the lattice structure, which are more abundant at the nanoscale. Reactive oxygen species (ROS) are pro-oxidants whose presence is increased during periods of inflammation in the body. ROS damage tissues and cellular function by stripping electrons from proteins, lipids, and DNA. We investigated the ability of nanoceria to quench ROS in vitro and in vivo, and examined the biodistribution and biocompatibility of nanoceria in murine models. Nanoceria was internalized in vitro by macrophages, is non-toxic at the concentrations we investigated, and proteins, mRNA, and oxidative markers of ROS were abated with nanoceria pretreatment in immune stimulated cells as measured by western blot, real time RT PCR, and Greiss assay respectively. In vivo, nanoceria was deposited in the spleen and liver, with trace amounts in the lungs and kidneys as determined by ICP-MS. Using IVIS in vivo imaging, it appeared that nanoceria deposition occurred in lymph tissue. Histology grades show no overt pathology associated with nanoceria deposition, although white blood cell (WBC) counts were generally elevated with nanoceria treatment. Nanoceria suspect particles were seen in lysosomes from kidney samples of IV injected mice in HRTEM images. Lastly, IV nanoceria treatment appears to reduce markers of oxidative stress in mice treated with carbon tetrachloride (CCl4) to induce ROS production. Taken together, our data suggest that nanoceria treatment has the potential to reduce oxidative stress. / Master of Science

This dissertation focuses on the assessment and development of heterogeneous catalysts for the deperoxidation of cyclohexyl hydroperoxide and oxidation of cyclohexane, which will be based in metal oxides and gold nanoparticles. For this endeavour a multidisciplinary approach will be used combining theoretical chemistry, kinetic studies and synthesis and characterisation of materials. The starting choice for the catalyst to carry out the process is supported gold nanoparticles. The approach of this dissertation is to first model the mecha- nism of cyclohexyl hydroperoxide decomposition and oxidation of cyclohexane on gold nanoparticles by theoretical calculations, and use these findings to synthesise efficient heterogeneous catalysts which will be subsequently tested and optimised experimentally. But as it will be seen, some metal oxides are active rather than acting as mere supports, which will also be studied both theoretical and experimentally. Each chapter has a specific focus and constitutes a strand of the overall goal: Chapter 1 provides an introductory background on the topics that this dissertation lies upon: oxidation of cyclohexane, heterogeneous catalysis and catalysis by gold and metal oxides. Chapter 2 outlines the objectives of the thesis, formulating the relevant hypotheses of this research and the subsequent validation tests. Chapter 3 exposes the methodology with a brief conceptual background that has been used to carry out this work. Chapter 4 is the first chapter dealing with results. It consists in a theoretical study using density functional theory of the reaction mechanism over different models of gold nanoparticles, in order to study the influence of several parameters on their catalytic activity: the particle size, atom coordination, and presence of additional species like oxygen atoms and water. Chapter 5 uses the findings found in chapter 4 to drive the synthesis of supported gold nanoparticles. It consists in a experimental study of gold-based catalysts, which is combined with a theoretical study which takes into account an additional variable: the support. Chapter 6 exploits one of the findings of chapter 5. One of the supports used for anchoring the gold nanoparticles is active by itself, namely cerium oxide. This chapter comprises an experimental work about its activity, studying parameters like particle size, morphology and the effect of doping. Chapter 7 continues with the catalytic activity of cerium oxide-based materials, but now from a theoretical point of view. It first presents a systematic study of the parameters relevant for the proper quantum mechanical description of cerium oxide, which is followed by a mechanistic study on different models. Chapter 8 outlines the conclusions obtained in this dissertation, present- ing them in a summarised way. Even though each chapter presents its corresponding conclusions at its end, this chapter groups them all in a structured way for the reader's convenience, so a global view of the project can be swiftly grasped. The results herein further the knowledge of heterogeneous catalysis for the oxidation of cyclohexane, one of the most important industrial reactions, and which continues to be a challenge. Although the ultimate goal is to develop an industrial catalyst, the dissertation also aims to show how computational chemistry can drive the design of novel materials, and how it can help to understand catalytic reactions at the atomic level. / El presente trabajo se centra en el estudio y desarrollo de catalizadores heterogéneos para la desperoxidación de ciclohexil hidroperóxido y la oxidación de ciclohexano, basados en óxidos metálicos y nanopartículas de Au. Para lograr tal objetivo se ha usado un enfoque multidisciplinar, que combina química teórica y estudios cinéticos, a la vez que síntesis y caracterización de materiales. El candidato inicial para llevar a cabo el proceso consiste en partículas de Au soportadas. El camino a seguir pasa primero por modelizar el mecanismo de descomposición de ciclohexil hidroperóxido y oxidación de ciclohexano mediante cálculos teóricos, y utilizar el conocimiento generado por este estudio para dictar la síntesis de catalizadores heterogéneos, comprobando y optimizando posteriormente su actividad de forma experimental. Sin embargo, como será visto a lo largo de este trabajo, algunos óxidos metálicos dejan de lado su papel como mero soporte físico para las partículas de Au y son activos por sí mismos. Tal hecho será estudiado tanto teórica como experimentalmente. Cada capítulo tiene un objetivo específico, y es a su vez una parte del objetivo global de esta investigación: El capítulo 1 provee al lector de una breve introducción a los temas sobre los que yace este trabajo: oxidación de ciclohexano, catálisis heterogénea y catálisis mediante Au y óxidos metálicos. El capítulo 2 expone de una forma breve y concisa los objetivos de esta investigación, formulando la hipótesis de partida y los correspondientes experimentos para su validación. El capítulo 3 describe la metodología utilizada junto a una explicación de los fundamentos en los que se basa cada técnica. El capítulo 4 es el primer capítulo que discute los resultados obtenidos en esta investigación. Se trata de un estudio usando la teoria del funcional de densidad para investigar el mecanismo de reacción del proceso sobre diferentes modelos teóricos de Au, con el objetivo de comprender la influencia de diversos factores en la actividad catalítica, tales como el tamaño de partícula, la coordinación de los á'tomos de Au y la presencia de especies adicionales como átomos de O y agua. El capítulo 5 hace uso de los resultados obtenidos en el estudio anterior, y los utiliza para dirigir la síntesis de nanopartículas soportadas de Au. Se trata de un estudio experimental en el que se investigan diversos factores que pueden afectar a su actividad catalítica. Este estudio se combina a su vez con uno de tipo teórico en el que se tiene en cuenta la influencia del soporte en la actividad catalítica de las particulas de Au. El capítulo 6 se basa en uno de los resultados obtenidos en el capítulo 5. Uno de los soportes utilizados para anclar las partículas de Au resulta de por sí activo: el CeO2. Su notable actividad para catalizar este proceso exige un estudio en mayor profundidad, el cual se lleva a cabo en este capítulo. Parámetros como el tamaño de particula, la morfología de superficie y el dopaje entre otros se investigan en este punto. El capítulo 7 sigue la estela del trabajo anterior sobre CeO2, pero ahora desde el punto de vista de la química teórica. Presenta primero un estudio sistemático de parámetros relacionados con la mecánica cuá'ntica que afectan al CeO2, con el objetivo de alcanzar una descripción satisfactoria de los modelos teóricos para este óxido. Tras esto, se lleva a cabo un estudio del mecanismo de reacción en dichos modelos de CeO2, a fin de comprender el origen de su actividad catalítica. El capítulo 8 presenta de forma estructurada y concisa todas las conclusiones que se han sacado a raíz de los resultados obtenidos. Aún a pesar de que cada capítulo presenta sus correspondientes conclusiones al final, aquí se presentan de una forma agrupada a comodidad del lector, para que pueda obtener de forma ágil una visión global de los resultados de esta investigación. / Aquest treball es centra en l'estudi i desenvolupament de catalitzadors hetero- genis per a la desperoxidació de ciclohexil hidroperòxid i la oxidació de ciclohexà, basats en òxids metàl·lics i nanopartícules de Au. Per aconseguir aquest objectiu s'ha utilitzat un enfocament multidisciplinari, en el qual es combinen química teòrica i estudis cinètics amb síntesi i caracterització de materials. El candidat inicial per dur a terme el procés consisteix en partícules de Au suportades. El camí a seguir passa primer per modelitzar el mecanisme de descomposició del ciclohexil hidroperòxid i la oxidació de ciclohexà mitjançant càlculs teòrics, i utilitzar el coneixement generat per aquest estudi per dirigir la síntesi de catalitzadors heterogenis, comprovant i optimitzant posteriorment la seua activitat de forma experimental. No obstant això, com es veurà al llarg d'aquest treball, alguns òxids metàl·lics deixen de costat el seu paper com a suport físic de les partícules de Au y són actius per si mateixos. Aquest fet s'ha estudiat tant teòrica com experimentalment. Cada capítol té un objectiu específic i és al mateix temps una part de l'objectiu global d'aquesta recerca: El capítol 1 proporciona al lector una breu introducció als temes tractats en aquest treball: oxidació de ciclohexà, catàlisi heterogènia i catàlisi mitjançant Au i òxids metàl·lics. El capítol 2 exposa d'una forma breu i concisa els objectius d'aquesta investigació, formulant la hipòtesi inicial i els corresponents experiments per a la seua validació. El capítol 3 descriu la metodologia utilitzada conjuntament amb una explicació dels fonaments en els quals es basa cada tècnica. El capítol 4 és el primer capítol que discuteix els resultats obtinguts en aquesta investigació. Es tracta d'un estudi usant la teoria del funcional de densitat per investigar el mecanisme de reacció del procés en diferents models teòrics de Au, amb l'objectiu de comprendre la influència en l'activitat catalítica de diversos factors, com ara la grandària de partícula, la coordinació dels àtoms de Au i la presencia d'espècies addicionals, com àtoms de O i aigua. El capítol 5 fa ús dels resultats obtinguts en l'estudi anterior, i els utilitza per dirigir la síntesi de nanopartícules suportades de Au. Es tracta d'un estudi experimental en el qual s'investiguen diversos factors que poden afectar a la seua activitat catalítica. Aquest estudi es combina amb un altre de caràcter teòric en el qual es té en compte la influència del suport en la activitat catalítica de les partícules de Au. El capítol 6 es basa en un dels resultats obtinguts en el capítol 5. Un dels suports utilitzats per fixar les partícules de Au resulta de per si actiu: el CeO2. La seua notable activitat per catalitzar aquest procés demana un estudi de major profunditat, el qual es duu a terme en aquest capítol. Paràmetres com la grandària de partícula, la morfologia de superfície i el dopatge, entre altres, s'investiguen en aquest punt. El capítol 7 continua l'estudi anterior sobre el CeO2, però ara des del punt de vista de la química teòrica. Presenta en primer lloc un es- tudi sistemàtic de paràmetres relacionats amb la mecànica quàntica que afecten al CeO2, amb l'objectiu d'aconseguir una descripció satisfactòria pels models teòrics d'aquest òxid. Després, es duu a terme un estudi del mecanisme de reacció en aquests models de CeO2, a fi de com- prendre l'origen de la seua activitat catalítica. El capítol 8 presenta de forma estructurada i concisa totes les conclusions que s'han extret arran dels resultats obtinguts. Encara que cada capí- tol presenta les seues corresponents conclusions al final, ací es presenten d'una forma agrupada per a la comoditat del lector, per què puga obtindre de forma àgil una visió global dels result d'una forma agrupada per a la comoditat del lector, per què puga obtindre de forma à / López Auséns, JT. (2016). From Quantum Mechanics to Catalysis: Studies on the oxidation of alkanes by gold and metal oxides [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/76806

Yes / In this work, the effect of the nanosized CZA2 (cerium-zirconium-aluminium) on the performance and emissions in a two- cylinder indirect injection (IDI) diesel engine, was studied. CZA2 was dispersed in diesel (D100) and waste cooking oil and tallow origin biodiesel-diesel blends (B10, B20, B30) and tested at different engine loads and constant speed. The nanocatalyst (CZA2) increased the brake specific fuel consumption (BSFC) and decreased the brake thermal efficiency (BTE, %) of all tested fuels, at all loads, except B20 at the lowest load. CZA2 reduced nitrogen oxides (NOx) from D100 at low and high engine loads, as well as carbon monoxide (CO) and unburned hydrocarbons (HC) at medium and high tested loads. The dispersion of CZA2 promoted the combustion of the biodiesel blends by almost eliminating HC while reducing NOx and CO emissions at various loads. Thermogravimetric analysis (TGA) coupled with Attenuated Total Reflectance- Fourier Transform Infrared (ATR-FTIR) spectroscopy revealed that the addition of CZA2 in diesel and biodiesel under pyrolysis and oxidation conditions resulted in the presence of saturated species like ketones and final oxidation products such as CO2, supporting their improved combustion and emissions’ reduction in the engine tests.

The fate of nanoparticulate cerium oxide from the diesel fuel catalyst Envirox was studied from its presence in the additive to its transformations during combustion through its exposure to plants and soils using a broad range of analytical techniques. Envirox is a fuel-borne catalyst comprised of nanoparticles of cerium oxide suspended in kerosene. The particles suspended in Envirox were confirmed by synchrotron X-ray diffraction, dynamic light scattering, and electron microscopy to be 5-7 nm crystals of CeO2 present as 15 nm aggregates. Significant changes to the particles were induced by the combustion process, resulting in 50-300 nm euhedral crystals of CeO2 in the exhaust as discovered using high resolution transmission electron microscopy. Single particle electron diffraction of the emitted cerium oxide particles showed evidence of ordered oxygen vacancies, indicative of a superstructure. Variations in the engine operating load resulted in no significant differences in the emitted cerium oxide particles. The mobility through soils and impacts on the plant Brassica napus (dwarf essex rape) of the emitted cerium oxide were compared to small and large CeO2 nanoparticles as well as diesel particulate matter emissions with very low cerium. The small CeO2 nanoparticles exhibited high mobility through soils and significant uptake and translocation in the plants. The large CeO2 nanoparticles showed extremely low mobility in soils and no significant increase in cerium anywhere in the plants. Cerium emissions from a diesel engine utilizing Envirox was found to have moderate mobility through the soils as well as an increased association with the roots of the plants, though translocation of the cerium into the aboveground biomass was not statistically significant. Despite uptake and translocation of some materials by B. napus, exposure to these cerium sources at 100 ppm Ce in the topsoil showed no significant impacts on the growth or overall health of the plants when compared to unexposed control samples. This dissertation shows that CeO2 nanoparticles employed as catalysts suspended in diesel fuel are altered during their use resulting in changes to their mobility and interaction upon entering the environment. This dissertation lays the groundwork for a new approach to nanotoxicology. / Ph. D. / Understanding the environmental impacts – and subsequently the impacts on mankind – of the use of nanomaterials is an enormously complex problem. The bottomup approach, whereby one can predict impacts from fundamental principals, is not practical because nanotechnology implementation into products is occurring far too rapidly and it is impossible for environmental toxicologists to keep pace. The properties of a nanomaterial are controlled by small changes to its physical/chemical properties that can be tuned to suit many different practical applications. During their use and subsequent release into the natural environment, nanomaterials are exposed to incredibly complex spaces that are capable of modifying the original nanomaterial still further. Thus, the originally produced nanomaterial will continue to evolve, and therefore change in its interaction with biotic and abiotic systems. In this dissertation, we examine the use of nanoparticulate cerium oxide in fuelborne catalysts as a case study. As a fuel-borne catalyst, nanoparticulate cerium oxide is employed to reduce carbon dioxide (a greenhouse gas and contributor to global climate change) and particulate matter (a known carcinogen) emissions from combustion in a diesel engine. Fuel-borne catalysts achieve this through the suspension of cerium oxide nanoparticles in the fuel, which go through the combustion process and exit the tailpipe with the rest of the diesel exhaust. Concerns over the emission of this emerging contaminant have resulted in its limited market penetration. Here we show that the nanoparticulate cerium oxide in fuel-borne catalysts is substantially altered by the combustion process and is emitted as significantly larger particles in the exhaust. We suspected that the emitted cerium oxide would have different behavior in the environment from previously studied, laboratory synthesized cerium oxide nanoparticles. The behavior of emitted cerium oxide was compared with that of laboratory synthesized cerium oxide nanoparticles by exposure to the plant Brassica napus. The exposure experiments showed that cerium oxide emitted from the combustion of a fuel-borne catalyst did indeed behave differently in the environment, though none of the exposures proved toxic to the plants at the realistic concentrations utilized in the study.

Three-way catalysis (TWC) involves simultaneous removal of the three pollutants (i.e., CO, NOx, and HCs) which led to the branch of auto-exhaust catalysis. CeO2 has become the main component of TWC catalyst because of its oxygen storage storage (OSC) property to supply oxygen under excess fuel condition and store oxygen under lean condition. Substitution of smaller isovalent cations like Ti4+, Zr4+ and Hf4+ ions in CeO2 forming Ce1-xMxO2 (M = Ti, Zr &Hf) solid solution enhance the OSC property. XRD along with EXAFS study showed that cations arrange in FCC lattice but oxygen coordination around metal ions is split into 4 + 4 coordination in Ce1-xMxO2 instead of ideal 8 coordination in CeO2. The longer Ce/Ti/Zr – O bonds are weakly bound and can be easily removed by H2 giving high OSC value than pure CeO2. Among the three OSC systems studied here, Ce0.5Zr0.5O2 showed exceptionally high OSC which lead to formation of a new a pyrochlore, Ce2Zr2O6.3. This compound is nearly metallic. Ce0.85-xTi0.15PtxO2- (x = 0.01 & 0.02) crystallizes in fluorite structure and Pt is ionically substituted with 2+ and 4+ oxidation states. H/Pt atomic ratio at 30 oC over Ce0.84Ti0.15Pt0.01O2- is 5 and over Ce0.99Pt0.01O2-δ is 4 against just 0.078 for 8 nm Pt metal particles. Carbon monoxide and hydrocarbon oxidation activity are much higher over Ce1-x-yTixPtyO2 (x= 0.15, y= 0.01, 0.02) compared to Ce1-xPtxO2 (x= 0.01, 0.02). Synergistic involvement of Pt2+/Pt0 and Ti4+/Ti3+ redox couples in addition to Ce4+/Ce3+ due to the overlap of Pt(5d), Ti(3d), and Ce(4f) bands near EF is shown to be responsible for enhanced redox property and higher catalytic activity. On substitution of Pd ion in Ce1-xTixO2, more lattice oxygen is found to be more labile than Pd in CeO2. The easy removal of oxygen from the more reducible Ti4+ containing support plays a major role in showing higher catalytic activity of this material for CO oxidation, N2O and NO reduction by CO. The catalyst shows 100% N2 selectivity  240 oC in NO+CO reaction. It has been shown that oxide ion vacancy creation created by removal of lattice oxygen by CO is responsible for dissociation of NO or N2O at a lower temperature. Ionicity of Pd2+ ion in different support could be varied by varying the ionicity of the oxide support itself. Rates of CO oxidation increases or activation energy decreases over Ce1-xPdxO2-δ, Ti1-xPdxO2-δ and Ce1-x-yMxPdyO2-δ (M = Ti, Zr, Hf ; x = 0.25, 0.4 ; y = 0.02) is increased with ionicity of Pd2+ ion. The substitution of Sn in CeO2 forming Ce1-xSnxO2 (x = 0.1-0.5) solid solution was prepared using tin oxalate precursor by solution combustion method. These oxides can be promising support for noble metals because of the Sn4+  Sn2+ redox couple in addition to Ce3+/Ce4+. The two electron process involved in the redox reaction of Sn as well as easy reducibility of Sn4+ to Sn2+ offers a far better redox catalytic system hitherto not reported. Ce1-xSnxO2 solid solutions as well as Pd ion substituted Ce1-xSnxO2 was prepared for the first time.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2014-11-10T11:38:41Z No. of bitstreams: 0 / Made available in DSpace on 2014-11-10T11:38:41Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2014-11-10T11:38:41Z No. of bitstreams: 0 / Made available in DSpace on 2014-11-10T11:38:41Z (GMT). No. of bitstreams: 0 / A análise por ativação com nêutrons é um método utilizado na determinação de diversos elementos em diferentes tipos de matrizes. Entretanto, quando a amostra contém altos teores de U ocorre o problema de interferência devido aos produtos de fissão do isótopo 235U. Um dos métodos de tratar este problema é fazer a correção usando fatores de interferência devido à fissão do U para os radionuclídeos utilizados nas análises dos elementos. No presente estudo foram determinados os valores dos fatores de interferência devido à fissão do U para os radioisótopos 141Ce, 143Ce,140La, 99Mo, 147Nd, 153Sm e 95Zr no reator nuclear de pesquisas IEA-R1 do IPEN-CNEN/SP. Esses fatores de interferência foram determinados experimentalmente, por meio da irradiação dos padrões sintéticos em uma determinada posição do reator, e teoricamente, determinando a razão dos fluxos de nêutrons epitérmicos e térmicos na mesma posição onde os padrões sintéticos foram irradiados e utilizando parâmetros nucleares da literatura. Os fatores de interferência obtidos foram comparados com os valores reportados em outros estudos. Para avaliar esses fatores de interferência, eles foram aplicados em análises dos elementos alvo deste estudo, nos materiais de referência certificados NIST 8704 Buffalo River Sediment, IRMM BCR-667 Estuarine Sediment e IAEA-SL-1 Lake Sediment. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas 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.