No description available.

The effects of noble metal (NM) promotion and deposition order (co-deposition of NM with the final Co deposition [co-dep] or sequential deposition of NM after Co deposition [seq-dep]) on surface area, pore size, metal retention, crystallite size, noble metal distribution and bonding in Co Fischer Tropsch (FT) catalysts were studied as were the resulting Co reducibility and Fischer Tropsch activity/selectivity properties. Catalysts containing nominally 25wt% Co with either 0.3 wt% Ru, 0.58 wt% Pt, 0.55wt% Re, or no NM on a La-stabilized-Al2O3 support were prepared by wet deposition. The Co, Pt, and Re were uniformly dispersed, but Ru distribution and retention were problematic and deposition-order dependent—85% was lost with co-dep, but it was uniformly distributed while 54% was lost with seq-dep and it was concentrated at the pellet edge. The co-dep catalysts all have smaller reduced Co crystallite size than their corresponding seq-dep catalysts. The average crystallite diameters for all 3 co-dep catalysts are between 4.1 and 4.3nm and ~90% of the crystallites are < 6nm. XAFS measurements showed that after reduction at 360°C, Pt is bonded with Co even with mild calcination between the final Co and the Pt deposition. On the other hand, neither Ru nor Re formed direct bonds with Co. Ru remained in a separate metal phase after reduction even at low loadings. Re remained as Re2O7 and still promoted Co reduction well (e.g. 42% reduced to Co metal compared to none for the unpromoted catalyst). By all measures of reducibility (TPR, EOR, H2 uptake), all NM promoted catalysts were more reducible than the unpromoted catalyst. The co-dep catalysts have lower TPR peak temperatures, but lower extents of reduction than their corresponding seq-dep catalysts. The NM type effect on overall extent of reduction trend was Co/Pt-seq>Co/Re-seq>Co/Ru-seq=Co/Pt-co>Co/Re-co>Co/Ru-co>Co. The Co/Pt-co catalyst was the most active of all the catalysts both on rate per mass and per site basis. The co-dep catalysts were all more active than the corresponding sequentially deposited catalysts. The co-dep Pt and Re catalyst activity is greater due to higher activity per site, while co-dep Ru activity is greater due to a higher abundance of active sites.

No description available.

<p> A rapid and simple radiochemical neutron activation technique involving tellurium coprecipitation of Au, lr, Pd and Pt was evaluated using the U.S.G.S. standards PCC-1 (peridotite) and DTS-1 (dunite) as well as a house standard, JHC-6 (spinifex zone of a komati itic peridotite). It was then applied to the analysis of samples of Archean greenstone from the Red Lake area.</p> <p> The technique gives detection limits of 0.01-0.02, 0.02, 0.1-0.4 and 1-2 ppb for Au, Ir, Pd and Pt respectively and precisions of <25-35%. The method can be successfully applied to the analysis of PGE levels in sulphur-poor rocks, and large numbers of samples can be processed in a short period of time.</p> <p> A comparison of PGE content between several types of mafic rocks was made as well as an investigation of possible secular trends (Archean vs. Phanerozoic) in PGE concentration.</p> / Thesis / Master of Science (MSc)

<p> The Au, Pt, Pd and Ir content of Fred's flow (a layered komatiite flow), Theo's flow (a layered tholeiite flow) and two peridotitic komatiite flows at Pyke Hill, all from Munro Township, were determined using radiochemical neutron activation analysis. In addition, the potential of Pyke Hill peridotitic komatiites as a gold source was evaluated. X-ray fluorescence spectroscopy, atomic absorption spectroscopy and a Leco automatic carbon determinator were used to determine major and trace element content in a total of 43 samples. </p> See Chart in text. <p> The peridotitic komatiite magma at Pyke Hill has the most mantle like proportions of Pt and Pd. None of the flows studied have been saturated with respect to sulphur. No leaching of siderophile and chalcophile elements has taken place prior to extrusion and cooling.</p> <p> The low gold content of the unaltered Pyke Hill peridotitic komatiites (average 2.8 ppb) do not make them obvious source rocks for gold deposits. </p> / Thesis / Master of Science (MSc)

<p> Ophiolites are generally regarded as fragments of ancient oceanic crust and upper mantle emplaced on the continents. Thetford Mines ophiolites probably formed in a marginal or back-arc basin by three separate but related igneous events. The first event involved the partial melting of a rising mantle diapir. The melt produced later underwent extensive fractional crystallization involving olivine, spinel, pyroxene and plagioclase to form a layered sequence of dunitic, pyroxenitic and gabbroic cumulate rocks. The residual magma fraction after this extensive fractional crystallization was later erupted as part of hypabyssal rocks and MgO, Cr and Ni poor lavas. During the second and third stages, the residual mantle material from the first episode of melting was remelted to produce melts from which low TiO2 lavas were formed. The low TiO2 lavas are also depleted in other incompatible elements such as Zr and Y which presumably were lost into the magma produced by the first stage melting of the mantle. The mantle residue after the multi-stage melting of the mantle is believed to be represented by the harzburgite occurring at the base of the ophiolite suite.</p> <p> The cumulates display wide variability in their major and trace as well as noble metal contents principally in response to fractional crystallization while the harzburgite displays uniform chemistry, compatible with its origin as a residue of extensive partial melting of the mantle. However, on the average, Thetford Mines plutonic rocks have similar noble metal contents to Mt. Albert pluton, Gaspe, but have higher PGE than the Troodos ophiolites. Thetford Mines rocks are also depleted in the noble metals in comparison to the stratiform layered complexes such as Bushveld and Stillwater. The volcanic rocks can be classified into three groups on the basis of their noble metal contents viz., i) low Ir, low Pd lavas, ii) low Ir, high Pd and iii) high Ir, high Pd lavas. These groups correspond to the lavas produced during the first, second and third igneous events respectively. The noble metal contents of the first group are similar to most ocean floor basalts while the third group lavas are comparable only to oceanic island and intraplate basalts.</p> <p> During fractional crystallization of the parental magma of the cumulates, Ir was strongly partitioned into early formed rocks such as the olivine-chromite cumulates while Pt and Pd were progressively enriched in the residual magma fraction. Au, however, was less sensitive to fractional crystallization than the PGE.</p> <p> After the formation of the ophiolites, the lavas and hypabyssal rocks were metamorphosed to greenschist facies by hydrothermal sea water, and the ultramafic rocks were serpentinized, first in the oceanic environment by sea water and later on the continent by meteoric water, Most of the major and trace elements were mobilized during the hydrothermal alteration of the lavas but the PGE were immobile. It is suggested that the redox potential of the hydrothermal solution was not high enough to oxidize the noble metals and so permit mobilization. Au, however, shows some degree of mobilization, and it is believed that some Au occurred along grain boundaries and was carried as particulate material (mechanically) by hydrothermal solution. The noble metals were only slightly mobilized during the continental serpentinization episode. Their inertness during the oceanic serpentinization episode is attributed to the reducing condition of the oceanic environment which prevented formation of soluble noble metal complex ions.</p> <p> Unlike many ophiolite occurrences, Thetford Mines rocks appear to have very little economic potential with respect to base and noble metals, principally because of lack of abundant sulfides to act as concentrators of the metals.</p> / Thesis / Doctor of Philosophy (PhD)

Deux configurations différentes, à savoir en microcanal et en cuve de spectroscopie utilisant un laser UV, sont conçues pour effectuer la photodéposition de plots métalliques uniques sur du TiO2. Des nanoparticules cristallines d’anatase de formes et de tailles variées sont synthétisées à dessein et utilisées comme semi-conducteurs pour cette réaction photochimique. Quatre précurseurs de métaux avec différents états de valence (Ag (I), Au (III), Pd (II) et Pt (IV)), sont réduits de manière photochimique à la surface de TiO2. Plusieurs techniques, notamment XPS, TEM / HRTEM, spectroscopie UV-vis, sont utilisées pour caractériser l'état chimique, la distribution en taille et en nombre des points métalliques et le comportement d'absorption des nanoparticules Metal-TiO2. On obtient des nano-hétérodimères avec un plot Ag, Au, Pd et Pt par TiO2, ce qui montre que le dépôt au laser semble être beaucoup plus efficace dans ce cas que celui de la photodéposition par lampe UV habituelle, suggérant que le flux de photons compte beaucoup plus que l'énergie déposée. Les hétérodimères Ag-TiO2 sont synthétisés avec succès par les deux méthodes de dépôt au laser. Le nombre et la distribution de taille des plots d’Ag dépendent des capteurs de trous, du pH et du précurseur métallique. Un modèle de croissance prédit bien la variation de la taille de l'argent dans le processus de photodéposition. L'extension de la synthèse à d'autres précurseurs métalliques (KAuCl4, Na2PdCl4 et H2PtCl6) à l'aide des deux configurations a conduit à la formation d'hétérodimères de TiO2 à base d'or, de palladium et de platine. La loi de croissance de l'or peut aussi être raisonnablement prédite, bien qu'elle ne soit pas aussi bonne que dans le cas de l'Ag, alors que notre modèle ne fonctionne pas dans le cas de Pd et de Pt. Enfin, des nanoobjets bimétalliques à structure coeur-écorce (Au@M)-TiO2 (M = Ag, Pd, Au et Pt) ont été synthétisés avec succès par une méthode de dépôt simple par laser UV en deux étapes en configuration cuve de spectroscopie. / Two different setups, namely microchannel and cuvette setups using UV laser, are built to perform the photodeposition of a single metal dotson TiO2. Crystal anatase TiO2 nanoparticles with various shapes and sizes, are synthesized on purpose and used as semiconductors for this photochemical reaction. Four metal precursors with different valence states, i.e. Ag(I), Au (III), Pd(II) and Pt(IV) ions, are photochemically reduced on the surface of TiO2. Several techniques, including XPS, TEM/HRTEM, UV-vis spectroscopy, are performed to characterize the chemical state, size and number distribution of metal dots, and the absorption behaviours of the Metal-TiO2 nanoparticles. Nano-heterodimers with one Ag, Au, Pd and Pt per TiO2 are obtained showing that laser deposition seems to be much more efficient in this case than of the usual UV lamp photodeposition, suggesting that the flux of photons matters much more than the deposited energy. Ag-TiO2 heterodimer nanoparticles are successfully synthesized by the two laser deposition methods. The number and size distribution of Ag dots are dependent on hole scavengers, pH and metal precursor. A growth model well predicted the silver size variation in the photodeposition process. Extending the synthesis to other metal precursors (KAuCl4, Na2PdCl4 and H2PtCl6) using both setups led to the formation of gold, palladium and platinum-based heterodimers with TiO2. The growth law of gold can reasonably be predicted as well, although it is not as good as in the case of Ag, while our model did not work in the case of Pd and Pt. Finally, bimetallic core-shell structured (Au@M)-TiO2 (M=Ag, Pd, Au and Pt) nanoobjects were successfully synthesized by a simple two-step UV laser deposition method in the cuvette setup.

Les vignerons du Val de Loire souhaitent faire évoluer les différents types de vins liquoreux produits actuellement dans leurs appellations en lien avec l’élaboration d’une qualité de raisin correspondant à ces types. Pour cela, il est nécessaire de caractériser objectivement les baies de raisin et leur qualité.Notre étude porte sur le développement d’une méthode multicritères combinant des mesures physiques et biochimiques des raisins, permettant d’identifier et de caractériser différents niveaux de développement de la pourriture noble sur raisins de Chenin blanc dans un objectif de production de vins liquoreux.Pour cela, des raisins correspondant à trois niveaux de pourriture noble ont été sélectionnés, lors de deux millésimes, 2012 et 2013. Des analyses classiques de qualité du raisin ont été réalisées et complétées par des analyses de couleur, de texture et de composés phénoliques.Outre la caractérisation phénolique du Chenin (sain et botrytisé), cette étude met en évidence la présence de myricétine, que l’on retrouve traditionnellement dans les variétés de raisin rouge, et qui semblerait être aussi synthétisée dans les baies de raisins blancs fortement atteintes par la pourriture noble.Nous avons également montré qu’une analyse multicritères permet une très bonne différenciation des baies plus ou moins botrytisées. Une combinaison des teneurs en myricétine, astilbine et glycérol permet notamment une très bonne discrimination des baies en fonction de leur niveau de botrytisation. Enfin, nous avons détectés de nouveaux composés dans les baies suite à l’attaque fongique, qui pourraient provenir de réactions d’oxydation. Ces résultats restent toutefois à confirmer. / Winemakers from the Loire valley are willing to improve the various types of sweet wines currently produced in their designation of origin altogether with the elaboration of grape quality that corresponds to these wines. For that purpose, it is necessary to objectively characterize the grapes and their quality. Our study implies the development of a multcriteria method that combines physical and biochemical measures on the grape, allowing the identification and characterization of the different levels of noble rot development on Chenin blanc grapes for the production of sweet wines. To do so, grapes corresponding to three noble rot levels were selected during two vintages, 2012 and 2013. Classical analysis of grape quality were carried out and complemented with color, texture and phenolic composition analysis. Besides the phenolic characterization of Chenin (healthy and botrytised), this study revealed the presence of myricetin, that is traditionally detected on red grape varieties, and that seems to be also synthetized on white grapes strongly affected by noble rot. We have also showed that a multicriteria analysis brings a very good differentiation of grapes more or less botrytised. A combination of myricetin, astilbin and glycerol concentrations showed a significantly good discrimination of grapes according to botrytisation level. Finally, we have detected new compounds on the grapes after the fungal attack that could be the result of oxidative reactions. These results are to be confirmed

Les campagnes du Maine conservent encore aujourd’hui de nombreux logis nobles maçonnés, qui se démarquent assez facilement de l’habitat paysan et dont les constructions ont été réalisées essentiellement entre le XIVe et le XVIe siècle. Partant de ce constat, une étude se basant sur un inventaire le plus exhaustif possible de ces demeures semble être l’un des meilleurs moyens pour mieux connaître le mode de vie des seigneurs de cette période par l’intermédiaire de leur habitat. Ainsi a été constitué un corpus rassemblant deux-cent-quinze sites encore visibles aujourd’hui dans l’actuel arrondissement de Mamers (cantons de Beaumont-sur-Sarthe, Bonnétable, Bouloire, Conlie, La Ferté-Bernard, Fresnay-sur-Sarthe, La Fresnaye-sur-Chedouet, Mamers, Marolles-le-Braults, Montfort-le-Gesnois, Montmirail, Saint-Calais, Saint-Paterne, Sillé-le-Guillaume, Tuffé et Vibraye). L’étude architecturale montre les caractéristiques et particularismes de ces sites. Il s’avère qu’ils sont en général bâtis sur un plan rectangulaire et leur mode de construction semble être assez similaire d’un édifice à l’autre. Ainsi, il existe des caractéristiques qui font que ces maisons sont facilement reconnaissables. L’organisation intérieure témoigne de l’évolution des logis entre le XIVe et le XVIe siècle. Quelques sites présentent des aménagements fonctionnels reflétant une recherche de confort. Certains d’entre eux s’avèrent aussi être symboliques comme les escaliers et les cheminées qui arborent les prétentions du détenteur avec parfois la présence d’écus. La présence d’éléments décoratifs révèle les goûts des détenteurs ainsi que leurs moyens financiers. Si certains des logis étudiés présentent un répertoire décoratif totalement issu du goût gothique ou renaissance, certains d’entre eux présentent des ornements « hybrides » entre les deux styles. Ce fait, témoigne que les logis bâtis ou restaurés après la guerre de Cent Ans, sont élaborés selon un modèle architectural de transition entre Moyen Âge et Renaissance. / Nowadays, Maine’s countryside still keeps a lot of noble houses which were built by stonework. These houses differentiate themselves easily from peasantry habitat and were essentially built between the 14thand the 16thcenturies. Based from that information, a study based on an inventory (the much complete as possible) of these houses seemed to be the best working way to know about the Lord’s lifestyles, through their habitats, during this period. A corpus was realized and has bring more than 215 sites together, which are still visible today, in the actual arrondissement de Mamers (cantons de Beaumont-sur-Sarthe, Bonnétable, Bouloire, Conlie, La Ferté-Bernard, Fresnay-sur-Sarthe, La Fresnaye-sur-Chedouet, Mamers, Marolles-le-Braults, Montfort-le-Gesnois, Montmirail, Saint-Calais, Saint-Paterne, Sillé-le-Guillaume, Tuffé and Vibraye). Architectural study shows characteristics and particularities of these sites. They are generally built in accordance with a rectangular plan and these methods of construction seemed to be similar from an edifice to another: the characteristics of these houses easily helped to recognize them. The internal organization gives evidence of the house’s evolution between the 14thand 16thcenturies. Some sites contain functional facilities which show a comfort research. Some of them are more symbolic as the staircases and fireplaces which show the holder’s ambitions with sometimes the presence of shields. Decorative elements show the owner’s taste and their financial resources. If some of the home’s studies present a decorative repertory from Gothic taste or Renaissance taste, some of them present hybrid ornaments between the two styles. This fact testify that houses built or restored after the Hundred Years War were elaborate in accordance with an architectural model of transition between Middle Age and Renaissance.

Climate change is one of the biggest global threats of the 21st century. Fossil fuels constitute by far the most important energy source for transportation and the different governments are starting to take action to promote the use of cleaner fuels. Biomass-derived fuels are a promising alternative for diversifying fuel sources, reducing fossil fuel dependency and abating greenhouse gas emissions. The research interest has quickly shifted from first-generation biofuels, obtained from food commodities, to second-generation biofuels, produced from non-food resources. The subject of this PhD thesis is the production of second-generation biofuels via thermochemical conversion: biomass is first gasified to synthesis gas, a mixture of mainly H2 and CO; synthesis gas can then be catalytically converted to different fuels. This work summarizes six publications, which are focused on the synthesis gas conversion step. Two processes are principally examined in this summary. The first part of the PhD thesis is devoted to the synthesis of ethanol and higher alcohols, which can be used as fuel or fuel additives. The microemulsion technique is applied in the synthesis of molybdenum-based catalysts, achieving a yield enhancement. Methanol cofeeding is also studied as a way of boosting the production of longer alcohols, but a negative effect is obtained: the main outcome of methanol addition is an increase in methane production. The second part of the PhD thesis addresses wax hydroconversion, an essential upgrading step in the production of middle-distillate fuels via Fischer-Tropsch. Bifunctional catalysts consisting of noble metals supported on silica-alumina are considered. The deactivation of a platinum-based catalyst is investigated, sintering and coking being the main causes of decay. A comparison of platinum and palladium as catalyst metal function is also carried out, obtaining a fairly different catalytic performance of the materials in terms of conversion and selectivity, very likely due to dissimilar hydrogenation power of the metals. Finally, a kinetic model based on the Langmuir-Hinshelwood-Hougen-Watson formalism is proposed to describe the hydroconversion reactions, attaining a good fitting of the experimental data. / Klimatförändringarna är ett av de största globala hoten under det tjugoförsta århundradet. Fossila bränslen utgör den helt dominerande energikällan för transporter och många länder börjar stödja användning av renare bränslen. Bränslen baserade på biomassa är ett lovande alternativ för att diversifiera råvarorna, reducera beroendet av fossila råvaror och undvika växthusgaser. Forskningsintresset har snabbt skiftat från första generationens biobränslen som erhölls från mat-råvaror till andra generationens biobränslen producerade från icke ätbara-råvaror. Ämnet för denna doktorsavhandling är produktion av andra generationens biobränslen via termokemisk omvandling. Biomassa förgasas först till syntesgas, en blandning av i huvudsak vätgas och kolmoxid; syntesgasen kan sedan katalytiskt omvandlas till olika bränslen. Detta arbete sammanfattar sex publikationer som fokuserar på steget för syntesgasomvandling. Två processer är i huvudsak undersökta i denna sammanfattning. Den första delen av doktorsavhandlingen ägnas åt syntes av etanol och högre alkoholer som kan användas som bränsle eller bränsletillsatser. Mikroemulsionstekniken har använts vid framställningen av molybden-baserade katalysatorer, vilket gav en höjning av utbytet. Tillsatsen av metanol har också studerats som ett sätt att försöka få en högre koncentration av högre alkoholer, men en negativ effekt erhölls: huvudeffekten av metanoltillsatsen är en ökad metanproduktion. Den andra delen av doktorsavhandlingen handlar om vätebehandling av vaxer som ett viktigt upparbetningssteg vid framställning av mellandestillat från Fischer-Tropsch processen. Bifunktionella katalysatorer som består av ädelmetaller deponerade på silica-alumina valdes. Deaktiveringen av en platinabaserad katalysator undersöktes. Sintring och koksning var huvudorsakerna till deaktiveringen. En jämförelse mellan platina och palladium som funktionella metaller genomfördes också med resultatet att det var en ganska stor skillnad mellan materialens katalytiska egenskaper vilket gav olika omsättning och selektivitet, mycket sannolikt beroende på olika reaktionsmönster hos metallerna vid vätebehandling. Slutligen föreslås en kinetisk modell baserad på en Langmuir-Hinshelwood-Hougen-Watson modell för att beskriva reaktionerna vid vätebehandling. Denna modell ger en god anpassning till experimentella data. / El cambio climático es una de las mayores amenazas del siglo XXI. Los combustibles fósiles constituyen actualmente la fuente de energía más importante para el transporte, por lo que los diferentes gobiernos están empezando a tomar medidas para promover el uso de combustibles más limpios. Los combustibles derivados de biomasa son una alternativa prometedora para diversificar las fuentes de energía, reducir la dependencia de los combustibles fósiles y disminuir las emisiones de efecto invernadero. Los esfuerzos de los investigadores se han dirigido en los últimos años a los biocombustibles de segunda generación, producidos a partir de recursos no alimenticios. El tema de esta tesis de doctorado es la producción de biocombustibles de segunda generación mediante conversión termoquímica: en primer lugar, la biomasa se gasifica y convierte en gas de síntesis, una mezcla formada mayoritariamente por hidrógeno y monóxido de carbono; a continuación, el gas de síntesis puede transformarse en diversos biocombustibles. Este trabajo resume seis publicaciones, centradas en la etapa de conversión del gas de síntesis. Dos procesos se estudian con mayor detalle. En la primera parte de la tesis se investiga la producción de etanol y alcoholes largos, que pueden ser usados como combustible o como aditivos para combustible. La técnica de microemulsión se aplica en la síntesis de catalizadores basados en molibdeno, consiguiendo un incremento del rendimiento. Además, se introduce metanol en el sistema de reacción para intentar aumentar la producción de alcoholes más largos, pero los efectos obtenidos son negativos: la principal consecuencia es el incremento de la producción de metano. La segunda parte de la tesis estudia la hidroconversión de cera, una etapa esencial en la producción de destilados medios mediante Fischer-Tropsch. Los catalizadores estudiados son bifuncionales y consisten en metales nobles soportados en sílice-alúmina. La desactivación de un catalizador de platino se investiga, siendo la sinterización y la coquización las principales causas del problema. El uso de platino y paladio como componente metálico se compara, obteniendo resultados catalíticos bastante diferentes, tanto en conversión como en selectividad, probablemente debido a su diferente capacidad de hidrogenación. Finalmente, se propone un modelo cinético, basado en el formalismo de Langmuir-Hinshelwood-Hougen-Watson, que consigue un ajuste satisfactorio de los datos experimentales. / <p>QC 20160308</p>