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Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Carter, W.B.; Committee Member: Cochran, Joseph; Committee Member: Venugopal, Ganesh. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Hydrotreating reaction of vegetable oil is an alternative method for the production of renewable biodiesel fuel. This reaction involves conversion of triglycerides into normal alkanes, leads to a deoxygenated and stable product, which is fully compatible with petroleum derived diesel fuel. The hydrotreating process uses hydrogen to remove oxygen from triglyceride molecules at elevated temperature in the presence of a solid catalyst. This work focused on the development of microtechnology-based chemical reaction process for liquid biofuel production from oil-based biofuel feedstock. A hydrotreating reaction of oleic acid and triolein as model compounds and jatropha oil as real feedstock was studied in a continuous flow microchannel reactor of inner diameter 500 ��m and of varied length; 1.5 - 5 m. The microchannel reactor was fabricated from SS-316. The walls of the microreactor were coated with a thin Al���O��� film, which was then impregnated with Ni-Mo catalyst containing phosphorus as promoter. The reactions were carried out in the temperature range of 275-325 ��C, residence time in the range of 11-40 s and at constant system pressure of 500 psig. The results showed that the microchannel reactor was suitable for the hydrotreating process. Complete conversion of the fatty acid hydrotreating reaction was achieved at a reaction temperature of 325 ��C. Hydrotreating of fatty acids occurred primarily via hydrodeoxygenation and the main liquid products were octadecane and heptadecane. Fatty alcohol, fatty acid and long chain esters were formed as reaction intermediates. Hydrotreating of triglycerides proceeded via the hydrocracking of triglycerides into diglycerides, monoglycerides and fatty acids. Then fatty acids were subsequently deoxygenated to hydrocarbons. The conversion of fatty acids and triglycerides increased with increasing temperatures. A detailed mathematical model was developed to represent this two-phase chemical reaction process. The mathematical model was entirely based on first principles, i.e. no adjustable or correlation parameters were used. Kinetic parameter estimation was performed and the predicted results were in good agreement with experimental results. / Graduation date: 2013 / Access restricted to the OSU Community, at author's request, from Sept. 17, 2012 - Sept. 17, 2013

Nickel aluminate reduced in hydrogen for 3 h at 500ºC was studied for desulfurization of model fuel comprised of dodecane spiked with benzothiophene (300 ppmw S). The nanopowder adsorbent was synthesized using combustion chemical vapor condensation, which created nickel aluminate with a BET specific surface area of 57.8 m2/g and average particle size of 11.7 nm. The nickel aluminate adsorbent removed 23 µmol of sulfur gram at breakthrough (<15 ppmw S). Regeneration by further heat treatment in hydrogen or air recovered 25% and 40% of original capacity, respectively.

Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-05-03T11:03:05Z No. of bitstreams: 1 lucianohonoratochagas.pdf: 8622580 bytes, checksum: 20a6210f264ae2b6015f16d383e48fb8 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-13T13:13:34Z (GMT) No. of bitstreams: 1 lucianohonoratochagas.pdf: 8622580 bytes, checksum: 20a6210f264ae2b6015f16d383e48fb8 (MD5) / Made available in DSpace on 2017-05-13T13:13:35Z (GMT). No. of bitstreams: 1 lucianohonoratochagas.pdf: 8622580 bytes, checksum: 20a6210f264ae2b6015f16d383e48fb8 (MD5) Previous issue date: 2013-11-22 / O grande interesse na hidrodessulfurização (HDS) de gasolina é realizar remoção profunda de enxofre e, ao mesmo tempo, reduzir a perda do numero de octanos que ocorre no processo de HDS minimizando a hidrogenação (HID) de olefinas, as quais são benéficas para a octanagem. Além do componente ativo e do promotor, o suporte deve ser considerado uma parte integral do catalisador. Nesse sentido, diversos suportes (incluindo aluminas e óxidos mistos) foram preparados a partir da calcinação de diferentes precursores. Uma amostra de Boehmita comercial foi usada como precursora de polimorfos de alumina. Para comparação, três outros precursores foram sintetizados a partir de diferentes métodos. Particularmente, o uso de excesso de ureia promoveu uma forma muito cristalina de carbonato básico de alumínio. Cada precursor foi calcinado em várias temperaturas gerando polimorfos de alumina, os quais foram analisados estruturalmente por DRX e RMN de 27Al. Devido ao interesse em suportes para catalisador, atenção especial foi dada à fase γ-Al2O3, a qual em adição a investigação estrutural foi submetida à análise textural. Essas quatro amostras de γ-Al2O3 foram utilizadas como suportes para catalisadores do tipo CoMo, que foram testados em reações de HDS de tiofeno e HID de cicloexeno. Os testes catalíticos mostraram que as atividades catalíticas crescem com o aumento do diâmetro médio de poros das fases CoMo/γ-Al2O3, e estão diretamente relacionados à dispersão do molibdênio sobre o suporte. Os resultados mostraram que a partir de diferentes rotas de síntese, e usando uma rota comum de calcinação, podem-se obter materiais com a mesma composição, mas com diferentes propriedades estruturais e texturais. Além disso, catalisadores do tipo CoMo suportados, contendo 20 % de MoO3 e 3 % de CoO, foram preparados por impregnação ao ponto úmido com soluções aquosas de molibdênio e cobalto sobre óxidos mistos obtidos a partir de hidrotalcitas. Os precursores contendo variadas quantidades de Mg, Co e Al ou Ni, Co e Al foram sintetizados pelo método de hidrólise de ureia. A calcinação leva a óxidos mistos cujas características estruturais dependem da composição. A caracterização dos suportes foi feita pelas técnicas de BET, DRX, RMN, IV, UV-vis/DRS e TPR. As amostras sulfetadas foram usadas como catalisadores em reações simultâneas de HDS de tiofeno e HID de cicloexeno. Os resultados foram comparados com catalisadores convencionais CoMo/γ-Al2O3, indicando que as atividades catalíticas dependem dos métodos de preparação dos precursores e suportes. Na série Mg-Co-Al o catalisador com maior quantidade de magnésio mostrou as maiores atividades de HDS e HID, sugerindo que a basicidade está associada com a performance catalítica. Adicionalmente, a amostra sem magnésio e contendo alta quantidade de cobalto exibiu as menores atividades e a maior seletividade (HDS/HID = 3,86). Os resultados indicam que o excesso de cobalto diminui a atividade enquanto a presença de magnésio contribui para aumentá-la. Por outro lado, a série Ni-Co-Al exibiu as menores razões HDS/HID. Nesse caso, as altas atividades para hidrogenação são atribuídas às altas quantidades de níquel. Adicionalmente, uma comparação entre catalisadores contendo 10 % de MoO3 e 3 % de CoO, suportados em óxidos mistos derivados de HDL e um catalisador suportado em alumina, revela que o suporte mais ácido tem maior influência sobre a capacidade de hidrogenação do catalisador. Entretanto, apesar da composição e das características estruturais dos suportes, o método de preparação pode influenciar significativamente no desempenho de um catalisador suportado. / The great interest in hydrodesulfurization (HDS) of gasoline is to perform a deep sulfur removal and, at the same time, to reduce the loss of the octane number occurring in the HDS process, by minimizing the hydrogenation of olefins which are beneficial to this property. Besides the active component and the promoter, the support has to be considered an integral part of the catalyst. In this sense, several supports (enclosing aluminas and mixed oxides) were prepared from calcination of different precursors. A commercial sample of Boehmite was used as precursor of alumina polymorphs. For comparison, three other precursors were synthesized from different methods. Particularly, the use of excess of urea promoted a very crystalline form of basic aluminum carbonate. Each precursor of alumina was calcined at various temperatures generating alumina polymorphs, which were structurally analyzed by XRD and 27Al MAS NMR. Due to interest in catalysis supports, special attention was given to the γ-Al2O3 phase, which in addition to structural investigation was subjected to textural analysis. These four γ-Al2O3 samples were used as catalyst supports like CoMo, which were tested in reactions of HDS of thiophene and HID of cyclohexene. The catalytic tests show that catalytic activities increase with pore diameters of CoMo/γ-Al2O3 phases and are directly related to dispersion of molybdenum on the support. The results showed that, from different synthesis procedures and common route of calcination, one can obtain materials with the same composition but with different structural and textural properties. Furthermore, supported CoMo catalysts containing 20 % of MoO3 and 3 % of CoO were prepared by incipient wetness impregnation of molybdenum and cobalt aqueous solutions over mixed oxides obtained from hydrotalcite precursors. The precursors, containing varying amounts of Mg, Co and Al or Ni, Co and Al cátions, were synthesized by urea hydrolysis method. The calcination led to mixed oxides whose structural characteristics depend on the composition. Characterization of the supports by BET, XRD, NMR, FTIR, UV-vis/DRS and TPR techniques was carried out. The sulfided samples were used as catalysts in simultaneous hydrodesulfurization of thiophene and hydrogenation of cyclohexene. The results were compared with conventional CoMo/γ-Al2O3 catalysts, which indicate that the catalytic activities depend on the preparation method of the precursors and supports. In the Mg-Co-Al series, the high magnesium content catalyst show higher HDS and HYD activities, suggesting that the support basicity is associated with catalytic performance. Furthermore, the free magnesium and high cobalt content catalyst show lower activities and higher selectivity (HDS/HYD = 3.86). The results indicate that the excess of cobalt decreases the activities while the presence of magnesium contributes to improve them. Otherwise, the Ni-Co-Al series show the smaller HDS/HYD ratios. In this case, the higher hydrogenation activities are assigned to high nickel content. Additionally, a comparison between catalysts containing 10 % of MoO3 and 3 % of CoO, supported on mixed oxides derived of LDH and a catalyst supported on alumina reveals that the most acidic support (alumina) has great influence over hydrogenation capacity of the catalyst. However, besides the composition and structural characteristics of the supports, the preparation method can to influence significantly the performance of a supported catalyst.

L'hydrotraitement est un procédé catalytique important dans le raffinage du pétrole qui utilise des catalyseurs bimétalliques sulfurés NiWS ou NiMoS (ou CoMoS) supportés sur alumine. Leur mode conventionnel de préparation implique l’imprégnation d'une solution aqueuse de sels de Mo/W et de Ni/Co, puis l’activation par un agent sulfo-réducteur (H2S/H2). Pour répondre aux exigences environnementales et améliorer l'efficacité de l'hydrotraitement, des améliorations permanentes de la performance de ces systèmes catalytiques sont attendues. Ce travail se concentre sur la préparation de catalyseurs d'hydrotraitement hautement actifs par une approche de chimie de surface contrôlée (CSC) qui implique l'imprégnation successive de précurseurs moléculaires de MoV et NiII en solvant organique sur un support silice-alumine traité thermiquement. Dans la première partie de cette thèse, la genèse de la phase active du catalyseur CSC et conventionnel Mo et NiMo est étudiée par quick-XAS combinée à d’autres techniques (chimiométrie, XPS, RPE, STEM-HAADF, modélisation moléculaire). Nous proposons ainsi des structures moléculaires depuis les précurseurs oxydes de Mo et Ni supportés jusqu’aux nombreuses espèces intermédiaires (oxysulfure et sulfures) en fonction de la température. Cette analyse multi-technique permet d'abord de révéler les spécificités de la genèse des catalyseurs CSC et conventionnels qui peuvent expliquer leurs différentes activités catalytiques. Ensuite, elle révèle également de nouvelles connaissances sur les mécanismes d’insertion du Ni dans la phase NiMoS en fonction de la préparation. Dans la seconde partie, la possibilité de remplacer Co et Ni comme promoteurs est explorée. Ceci est entrepris en synthétisant des catalyseurs alternatifs de type XYMoS, où X et Y sont des métaux de transition 3d. Comme suggéré par des études de modélisation quantiques antérieures, certaines formulations XYMoS peuvent présenter un effet de synergie analogue à ceux des phases actives CoMoS et NiMoS. L’étude des formulations les plus prometteuses méritent d'être approfondies afin de mieux comprendre leur fonctionnement. / Hydrotreating is an important catalytic process in petroleum refining which uses sulfided bimetallic catalysts NiWS or NiMoS (or CoMoS) supported on alumina. Their conventional preparation involves an incipient wetness impregnation of an aqueous solution of Mo/W and Ni/Co salts, and then activation by a sulfo-reductive agent (such as H2S/H2). To meet environmental regulations and improve the energy efficiency of hydrotreatment, permanent improvements on the performance of these catalytic systems are expected. This work is thus focused on the preparation of highly active hydrotreating catalysts through a controlled surface chemistry (CSC) approach; which involves the successive impregnation of Mo5+ and Ni2+ molecular precursors in an organic solvent on a thermally treated silica-alumina support. In the first part of this thesis, the active phase genesis of CSC and conventional Mo and NiMo catalysts is studied by in situ quick-XAS combined with various other techniques (chemometrics, XPS, EPR, STEM-HAADF, molecular modeling). We thus propose molecular structures from the oxide of supported Mo and Ni precursors up to the numerous intermediate sulfided species as a function of temperature. This multi-technique analysis enables first to reveal the specific features of the genesis of CSC and conventional catalysts which may explain their different catalytic activities. Then, it also reveals new insights into the mechanisms of Ni promoter incorporation into the NiMoS phase as a function of the preparation. In the second part, the feasibility of replacing Co and Ni as promoters is explored. Using the CSC method, we attempted to synthesize alternative catalysts of the form XYMoS ternary sulfides, where X and Y are 3d transition metals. As suggested by previous quantum simulations, certain XY formulations possibly reveal a synergy effect as observed in CoMoS and NiMoS active phases. The most promising formulations merit further investigations.

Hydrering är en viktig process för att producera produkter med önskade egenskaper samt att uppfylla de lagliga krav som existerar med avseende på miljö och hälsa. Reaktionerna som sker vid hydreringen är katalytiska vilket innebär att förstå sam utnyttja de mest lämpliga katalysatorerna är av yttersta vikt. Avsvavling (HDS) är en av de mest studerade reaktionerna medan avaromatisering (HDA) samt borttagandet av kväve (HDN) är diskuterade samt förstådda i lägre grad. Trots det är aromatiska samt kväverika föreningar naturligt förekommande i matningar till hydreringsreaktorerna där de organiska kväveföreningarna är inhibitorer. I detta arbete är målet att tillverka samt utvärdera några hydreringskatalysatorer med fokus på deras prestanda för HDA och HDN reaktionerna. Den bästa möjliga tekniken idag för tillverkningen av hydreringskatalysatorer utnyttjar kelateringsreagens vid beredningen. Detta har visat sig ha en positiv inverkan på egenskaperna och aktivteten vid hydrering för NiMo-katalysatorer. För att undersöka detta närmare har två typer av katalysatorer tillverkats, en med kelateringsreagens (typ II) och en utan (typ I). Dessa var sedan utvärderade i dess HDA och HDN aktiveter. Katalysatorerna var tillverkade samt karaktäriserade vid KTH och sedan aktiverade via sulfidering samt utvärderade vid Nynas AB. Aktiviteten för de sulfiderade katalysatorerna var utvärderade i ett surrogatsystem bestående av fenantren (PHE) som modell för aromatiska föreningar samt karbazol (CBZ) eller akridin (ACR) som modell för icke-basiskt samt basiskt organisk-kväve. Aktivitetsutvärderingen utfördes i en porlbäddreaktor där aktiviteten undersöktes vid närvarandet samt avsaknandet av de organiska kväveföreningarna. När matningen byttes, en så kallad modeswitch, ändras aktiviteten beroende på de betingelser som undersöktes. Reaktortemperaturen varierade mellan 300 °C och 320 °C vid ett konstant systemtryck på 120 barg. Katalysatornsaktivitet var positivt korrelerad med reaktortemperaturen där en lägre aktivtetuppmättes vid 300 °C jämfört med 320 °C. Det visade sig även att båda typerna av organiskt kväve påverkade aktivteten negativt vid båda undersökta temperaturerna. Utöver det så var de basiska kväveföreningarna mer inhiberande jämfört med de icke-basiska föreningarna för båda katalysatorerna. Inhiberingen orsakad av karbazol visade sig vara helt reversibel medan akridininhiberingen antydde på mer permanenta effekter för typ II katalsatorn. Dessa resultat antyder, trots de preliminära antagandena, att typ I katalysatorn var bättre än typ II katalysatorn. / Hydrotreating processes are of high importance in helping to obtain the desired characteristics of products as well as to comply with the legislation regarding health hazards and environmental pollution. Hydrotreating reactions are catalytic reactions which imply that the understanding and utilization of the most suitable catalysts is crucial. While hydrodesulfurization is a vastly studied branch of hydrotreating, hydrodearomatization (HDA), and hydrodenitrogenation (HDN) processes are less discussed and understood. However, aromatic compounds along with nitrogen-containing inhibitors are naturally present in the hydrotreater feeds. Therefore, the aim of this study was the preparation and evaluation of hydrotreating catalysts with the main focus on HDA and HDN reactions. According to the current state of the art, the utilization of chelating agents during preparation has a positive impact on the characteristics and activity of hydrotreating catalysts therefore NiMo catalysts with (Type II) and without (Type I) a chelating agent were prepared and evaluated towards HDA and HDN reactions. The catalysts were prepared and characterized at KTH and then activated (sulfided) and evaluated at Nynas AB. The activity of the sulfided catalysts was evaluated using surrogate mixture models containing phenanthrene (PHE) as an aromatic compound, and carbazole (CBZ) or acridine (ACR). The latter ones were representing two types of nitrogen-containing inhibitors, non-basic and basic. The activity testing was carried out in a trickle-bed microreactor during three-step experiments in the presence and absence of the organic nitrogen compounds (mode switches). During the mode switches the activity of the catalysts under varying conditions was investigated. The operating temperature of the reactor varied between 300 and 320°C under constant H2 pressure of 120 barg. The catalytic activity was positively correlated with temperature with the catalysts exhibiting lower activities at 300°C than at 320°C. It is noteworthy that the activity of all the catalysts was hindered by the presence of both nitrogen compounds at all temperatures with the basic nitrogen (ACR) being more inhibitory for both catalysts. CBZ inhibition to the HDA reactions showed reversibility, while ACR had a more permanent inhibiting effect in the case of the Type II catalyst. The results indicated that despite the preliminary assumptions, the Type I catalyst outperformed the Type II.