The impact of H2 partial pressure (H2 pp) during the hydrotreating of heavy gas oil, derived from Athabasca bitumen, over commercial NiMo/¥ã-Al2O3 catalyst was studied in a micro-trickle bed reactor. The experimental conditions were varied as follows: temperature: 360 to 400¨¬C, pressure: 7 to 11 MPa, gas/oil ratio: 400 to 1270 mL/mL, H2 purity range of 0 to 100 vol. % (with the rest either CH4 or He), and LHSV range of 0.65 to 2 h-1. The two main objectives of the project were to study the nature of the dependence of H2 pp on temperature, pressure, gas/oil ratio, LHSV (Liquid Hourly Space Velocity), and H2 purity. The project was divided into three phases: in phase one the effect of H2 purity on hydrotreating of heavy gas oil (HGO) was studied, in phase two the nature of H2 pp dependency and the effect of H2 pp on hydrotreating of HGO was investigated, and in phase three kinetic studies were carried out using different kinetic models.<p> The objective of phase one was to study the effect of hydrogen purity on hydrotreating of HGO was studied in a trickle bed reactor over a commercial Ni−Mo/¥ã-alumina catalyst. Methane was used as a diluent for the hydrogen stream, and its effect on the catalyst performance was compared to that of helium, which is inert toward the catalyst. Furthermore, a deactivation study was conducted over a period of 66 days, during which the catalyst was subjected to H2 purities ranging from 75 to 95% (with the rest methane); no significant deterioration in the hydroprocessing activities of the catalyst was observed. Therefore, it was concluded that methane was inert toward a commercial Ni−Mo/¥ã-alumina catalyst. However, its presence resulted in hydrogen partial pressure reduction, which in turn led to a decrease in hydrodesulphurization (HDS), hydrodenitrogenation (HDN), hydrodearomatization (HDA) conversions. This reduction can be offset by increasing the total pressure of the system. HDS, HDN, HDA, and mild hydrocracking (MHC) conversions were studied. Also determined were cetane index, density, aniline point, diesel index, and fractional distribution of the products.<p> The main objective of phase two was to study the effects of H2 pp on hydrotreating conversions, feed vaporization, H2 dissolution, and H2 consumption were studied. The results show that HDN and HDA are significantly more affected by H2 partial pressure than HDS; with the HDN being the most affected. For instance as the inlet H2 partial pressure was increased from 4.6 to 8.9 MPa HDS, HDN, and HDA conversions increased for 94.9%, 55.1%, and 46.0% to 96.7%, 83.9%, and 58.0% , respectively. Moreover, it was observed that H2 dissolution and H2 consumption increased with increasing H2 pp. No clear trend was observed for the effect of H2 pp on feed vaporization.<p> In phase three the kinetics of HDS, HDN, and HDA were studied. The power law, multi-parameter, and Langmuir - Hinshelwood type models were used to fit the data. The prediction capacities of the resulting models were tested. It was determined that, while multi-parameter model yielded better prediction, L-H had an advantage in that it took a lesser number of experimental data to determine its parameters. Kinetic fitting of the data to a pseudo-first-order power law model suggested that conclusions on the effect of H2 pp on hydrotreating activities could be equally drawn from either inlet or outlet hydrogen partial pressure. However, from the catalyst deactivation standpoint, it is recommended that such conclusions are drawn from the outlet H2 partial pressure, since it is the reactor point with the lowest hydrogen partial pressure.

The impact of H2 partial pressure (H2 pp) during the hydrotreating of heavy gas oil, derived from Athabasca bitumen, over commercial NiMo/¥ã-Al2O3 catalyst was studied in a micro-trickle bed reactor. The experimental conditions were varied as follows: temperature: 360 to 400¨¬C, pressure: 7 to 11 MPa, gas/oil ratio: 400 to 1270 mL/mL, H2 purity range of 0 to 100 vol. % (with the rest either CH4 or He), and LHSV range of 0.65 to 2 h-1. The two main objectives of the project were to study the nature of the dependence of H2 pp on temperature, pressure, gas/oil ratio, LHSV (Liquid Hourly Space Velocity), and H2 purity. The project was divided into three phases: in phase one the effect of H2 purity on hydrotreating of heavy gas oil (HGO) was studied, in phase two the nature of H2 pp dependency and the effect of H2 pp on hydrotreating of HGO was investigated, and in phase three kinetic studies were carried out using different kinetic models.<p> The objective of phase one was to study the effect of hydrogen purity on hydrotreating of HGO was studied in a trickle bed reactor over a commercial Ni−Mo/¥ã-alumina catalyst. Methane was used as a diluent for the hydrogen stream, and its effect on the catalyst performance was compared to that of helium, which is inert toward the catalyst. Furthermore, a deactivation study was conducted over a period of 66 days, during which the catalyst was subjected to H2 purities ranging from 75 to 95% (with the rest methane); no significant deterioration in the hydroprocessing activities of the catalyst was observed. Therefore, it was concluded that methane was inert toward a commercial Ni−Mo/¥ã-alumina catalyst. However, its presence resulted in hydrogen partial pressure reduction, which in turn led to a decrease in hydrodesulphurization (HDS), hydrodenitrogenation (HDN), hydrodearomatization (HDA) conversions. This reduction can be offset by increasing the total pressure of the system. HDS, HDN, HDA, and mild hydrocracking (MHC) conversions were studied. Also determined were cetane index, density, aniline point, diesel index, and fractional distribution of the products.<p> The main objective of phase two was to study the effects of H2 pp on hydrotreating conversions, feed vaporization, H2 dissolution, and H2 consumption were studied. The results show that HDN and HDA are significantly more affected by H2 partial pressure than HDS; with the HDN being the most affected. For instance as the inlet H2 partial pressure was increased from 4.6 to 8.9 MPa HDS, HDN, and HDA conversions increased for 94.9%, 55.1%, and 46.0% to 96.7%, 83.9%, and 58.0% , respectively. Moreover, it was observed that H2 dissolution and H2 consumption increased with increasing H2 pp. No clear trend was observed for the effect of H2 pp on feed vaporization.<p> In phase three the kinetics of HDS, HDN, and HDA were studied. The power law, multi-parameter, and Langmuir - Hinshelwood type models were used to fit the data. The prediction capacities of the resulting models were tested. It was determined that, while multi-parameter model yielded better prediction, L-H had an advantage in that it took a lesser number of experimental data to determine its parameters. Kinetic fitting of the data to a pseudo-first-order power law model suggested that conclusions on the effect of H2 pp on hydrotreating activities could be equally drawn from either inlet or outlet hydrogen partial pressure. However, from the catalyst deactivation standpoint, it is recommended that such conclusions are drawn from the outlet H2 partial pressure, since it is the reactor point with the lowest hydrogen partial pressure.

Hydrogen storage for stationary and mobile applications is an expanding research topic. Using liquid organic hydrides for hydrogen storage is one of the most promising alternatives as it provides simple and safe handling. Liquid organic hydrides are largely compatible with current transport infrastructure, whereas alternatives such as liquid and gaseous hydrogen and metal hydrides would require a completely new infrastructure. An attractive storage system is the so-called MTH system (Methylcyclohexane, Toluene and Hydrogen). The dehydrogenation of methylcyclohexane is a highly endothermic reaction. To improve the reaction kinetics, this research was to develop a structured catalyst with a conductive metal support (Fecralloy) which could hold an adherent catalytic washcoat (γ - Al2O3). The active phase was impregnated onto this support and the developed catalyst was tested for the dehydrogenation of methylcyclohexane. The catalyst preparation involved three key steps which were support oxidation, loading of an adherent washcoat and finally impregnation of the active phase. The oxidation and washcoat stages required significant optimisation. The optimum oxidation conditions were found to be 950 °C for 10 h. The washcoating procedure was optimised by modifying a one-step hybrid washcoating method suggested in patent literature. Characterization techniques including SEM, XRD and EDX were used to study each step of catalyst preparation. In addition the technique of STEM was used to study platinum dispersion on the catalytic washcoat. Finally the catalytic activity of the developed catalyst was compared with an in-house pelleted catalyst based on the material used to prepare the structured catalyst and commercially available platinum on γ - Al2O3. Three key factors: activity, selectivity and stability were evaluated. The activity and selectivity were studied at varied operating conditions of T = 340 °C - 400 °C, W/F = 7345 - 14690 g s/mol, H2/MCH molar ratio = 0 - 9 and P = 1.013 bar. The dehydrogenation reaction of methylcyclohexane was found to be very selective to toluene (above 99%). Compounds, which are considered coke precursors, were identified, to attempt to explain the mechanism of catalyst deactivation. By-product distribution was monitored and possible reaction pathways were postulated. To gauge the stability of the catalyst, long term life tests were also performed on the structured catalyst at 400 °C and W/F = 14690 g s/mol for approximately 400 h. The stability study investigated the different types of deactivation mechanisms. The catalyst evaluation study helped identify the effect of the alloy support, the alumina washcoat and platinum dispersion on the selectivity of the catalyst.

Yes / In order to meet the environmental legislations related to sulfur content, it is important to find an alternative techniques for deep removal of sulfur components from fuels. So, in this study, a novel nano-catalyst based on iron oxide (Fe2O3) as active component prepared over composite support (γ-Alumina + HY-zeolite) is developed here for efficient removal of sulfur compounds from fuel via oxidation process. The precipitation method is employed first to prepare the composite support and then the impregnation method is utilized to generate a novel synthetic homemade (Fe2O3/ composite support) nanocatalysts that has not been developed in the literature (iron oxide over composite support). The characterizations of the prepared catalysts display that the surface area of the catalyst increases with increasing the amount of Y-zeolite in composite support. The effectiveness of the catalysts is tested by utilizing oxidative desulfurization (ODS) operation under several operating conditions. The results of the experimental work show that the activity of oxidative desulfurization enhances with increasing Y-zeolite, temperature, and batch time under moderate operating conditions. The oxidative desulfurization efficiency followed the order: CAT-1 < CAT-2 < CAT-3. The CAT-3 performed the high removal of sulfur compounds (90.73%) at 100 min and 423 K. The best values of the kinetic parameters of the ODS process are then determined based on experimental data and model based techniques within gPROMS package. Finally, the reactor model is used to determine the optimal operating conditions while maximizing the removal of sulfur compounds leading to cleaner fuel. Where, 99.3% of the sulfur removal has achieved at batch time of 190.6 min, temperature of 543.56 K and initial sulfur content at 0.8668 wt% in the presence of CAT-3 based on the optimal kinetic parameters (order of reaction (n) of 1.9865719, activation energy (EA) at 29.942 KJ/mol and pre-exponential factor (ko) with 622.926 wt-0.9865719. min-1).

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L'objectif de ce travail de thèse est la compréhension de l'impact des propriétés acido-basiques des supports oxydes sur l'interaction métal-support ainsi que les effets du milieu réactionnel sur les propriétés structurales, électroniques, thermodynamique et réactives des catalyseurs métalliques hyper-dispersés. Le catalyseur modèle choisi est un agrégat monométallique de platine déposé sur alumine qui est la référence des études fondamentales pour permettre des progrès dans la compréhension de ce système complexe. La mise en œuvre de calculs dans le formalisme de la théorie de la fonctionnelle de la densité, réalisés à partir de modèles moléculaires périodiques, a permis de déterminer l'état de surface du catalyseur pour des conditions de température et de pression représentatifs de l'expérience. L'influence de la taille des particules conjointement à la présence de chlore sur la stabilité thermodynamique des agrégats de Pt supportés sur alumine-γ a démontré une stabilisation significative des agrégats Pt3 lors de la migration d'espèces de surface (H, OH et Cl) sur la particule. La reconstruction d'une morphologie biplanaire (la plus stable en absence d'hydrogène) vers une morphologie cuboctaédrique pour les forts taux de recouvrement en hydrogène sur les particules de Pt supportées a été démontrée et permet d'expliquer plusieurs observations expérimentales encore mal comprises. L'impact du milieu réactionnel sur la rupture C-C et C-H à partir de l'éthane sur l'agrégat Pt13 supporté sur alumine- γ a été démontré. Les résultats obtenus permettent de mieux comprendre l'importance des conditions de température et de pression du milieu réactionnel (notamment du rapport P(H2)/P(C2H6)) sur la stabilité des intermédiaires réactionnels. Ces résultats sont en accord avec les observations expérimentales et permettent de mettre en évidence que l'optimum de pression en hydrogène est relativement élevé dans le cas des réactions de reforming catalysées par du Pt seul. / The aim of this work is the understanding of the impact of acido-basic properties of oxide supports on the metal-support interaction as well as on the effects of reactive conditions on the structural, electronic, thermodynamic and reactive properties of hyper-dispersed metallic catalysts. The chosen model catalyst is a monometallic platinum cluster supported on alumina which is the reference of fundamental studies to improve the understanding of this complex system. DFT calculations were performed from periodic models to determine the surface state of the catalyst under representative experimental temperature and pressure. The influence of nano-clusters' size combined with the presence of chlorine on the thermodynamic stability of supported Pt clusters on γ-alumina demonstrated a significant stabilization of Pt3 clusters with the migration of surface species (H, OH and Cl) on the particle. The morphology reconstruction from biplanar (the most stable in absence of hydrogen) to a cuboctahedral morphology for the high hydrogen coverages on the supported Pt13 cluster is demonstrated and explains several experimental observations still controversial. The impact of the reactive conditions on the C-C and C-H bond scission from ethane on the Pt13 cluster supported on γ-alumina was demonstrated. Results helps to better understand the importance of temperature and pressure conditions in the reactive medium (notably the P(H2)/P(C2H6) ratio) on the stability of reactive intermediates. These results are in agreement with experimental observations and highlight that the optimum of hydrogen pressure is relatively high in the case of catalytic reforming reactions catalyzed by Pt only.

Glyphosate (N-(phosphonomethyl)glycine, PMG, H3L) is a widely used organophosphorous herbicide. It interacts with metal ions and mineral surfaces, which may affect its mobility, degradation and bioavailability in the environment. However, these interactions are far from fully understood. This thesis is a summary of five papers discussing the complexation of PMG with metal ions in aqueous solution and the adsorption of PMG and/or Cd(II) on different mineral surfaces. The complexation of PMG with the metals Cd(II) or Al(III) in aqueous solution was investigated with macroscopic and molecular scale techniques. Potentiometric titration data were combined with EXAFS, ATR-FTIR and NMR spectroscopic data to generate solution equilibrium models. In the PMG-Cd(II) system, only mononuclear complexes were formed, while both mono and binuclear complexes were observed in the PMG-Al(III) system. EXAFS, ATR-FTIR, and XPS measurements showed that PMG adsorbs to the surfaces of goethite (α-FeOOH), aged γ-alumina (γ-Al2O3) and manganite (γ-MnOOH) through one oxygen of its phosphonate group to singly-coordinated surface sites. Surface complexation models consistent with these spectroscopic results were fit to adsorption data using the 1pK reaction formalism. Electrostatic effects were accounted using either the Extended Constant Capacitance Model (ECCM) or the Basic Stern Model (BSM), and the charge of the surface complexes was distributed over the different planes. The formation of the surface complexes was described according to the following reactions: ≡MeOH(0.5-) + H3L &lt;=&gt; ≡MeHL(1.5-) + H2O + H+ ≡MeOH(0.5-) + H3L &lt;=&gt; ≡MeL(2.5-) + H2O + 2H+ The coadsorption of PMG and Cd(II) on the surfaces of goethite and manganite results in the formation of ternary mineral-PMG-Cd(II) surface complexes, as suggested from EXAFS results. Previous EXAFS measurements have also established the coordination geometries for the binary goethite-Cd(II) and manganite-Cd(II) surface complexes. In addition to the surface reactions in the binary mineral-Cd(II) and mineral-PMG systems, a single ternary complex with the stoichiometry ≡MeLCd(OH)(1.5-) was sufficient to explain coadsorption data: ≡MeOH(0.5-) + H3L + Cd2+ &lt;=&gt; ≡MeLCd(OH)(1.5-) + 3H+ It was concluded that the affinity of PMG for the three mineral systems decreases within the series: goethite &gt; aged γ-Al2O3 &gt; manganite. The formation of the ternary surface complex is more significant on goethite surfaces than on manganite surfaces.

Με αφορμή τις πολλές εφαρμογές που έχουν οι διεπιφάνειες μετάλλου με κεραμικό υπόστρωμα όπως τη μικροηλεκτρονική και την ετερογενή κατάλυση, τα συστήματα αυτά έχουν μελετηθεί με πρότυπα πειράματα σε συνθήκες υπερυψηλού κενού (UHV). Στην εργασία αυτή μελετήθηκε η αλληλεπίδραση κατά τη θέρμανση σε UHV υπέρλεπτων υμενίων NIκαι NiO με επιφάνειες οξειδίων. Συγκεκριμένα, η μελέτη έγινε σε μοκνοκρυσταλλικές επιφάνειες ζιρκονίας σταθεροποιημένης με ύττρια (YSZ), α-αλούμινας και σε πολυκρυσταλλική επιφάνεια γ-αλούμινας ανεπτυγμένης σε φύλλο αλουμινίου. Έμφαση δόθηκε στην επίδραση που έχει η κατεργασία της επιφάνειας του οξεοιδίου στη συμπεριφορά του Ni και του NiO κατά τη θέρμανση. Τα πειράματα έγιναν σε σύστημα UHV με επιφανειακά ευαίσθητες τεχνικές φασματοσκοπίας φωτοηλεκτρονίων και ηλεκτρονίων Auger από ακτίνες-Χ(XPS/XAES). Βρέθηκε ότι το Ni σε YSZ οξειδώνεται κατά τη θέρμανση από ευκίνητα ιόντα οξυγόνου της YSZ και ο ρυθμός οξείδωσης εξαρτάται σημαντικά από την κατάσταση της επιφάνειας. Η κατάσταση της επιφάνειας επηρεάζει την θερμική σταθερότητα του NiO αφού η ελάττωση του οξυγόνου στο εσωτερικό της YSZ οδηγεί σε σημαντική μείωση της θερμοκρασίας διάσπασης του NiO. Σε επιφάνεια α-Al2O3 η κατεργασία έχει σαν αποτέλεσμα το Ni είτε να συσσωματώνεται είτε να οξειδώνεται ενώ η θερμική σταθερότητα του NiO επίσης εξαρτάται από την παρουσία επιφανειακών ατελειών που δημιουργούνται με την κατεργασία. Επίσης, βρέθηκε ότι το πάχος του υμενίου γ-Al2O3 είναι καθοριστικό για την οξείδωση του αποτιθέμενου Ni από τα επιφανειακά υδροξύλια της γ-Al2O3 και το σχηματισμό επιφανειακής ένωσης NiAlx μέσω διάχυσης του Ni προς το φύλλο Al από μικροοπές του υμενίου. / Metal-ceramic systems have many technological applications in composite materials, microelectronics and heterogeneous catalysis. The interaction of Ni and NiO ultrathin films with different oxide surfaces yttria stabilized zirconia (9% mol Y2O3, YSZ)and α-alumina monocrystalline and polycrystalline γ-alumina films developed on Al foil upon heating in ultrahigh vacuum (UHV) was examined. Upon heating the Ni/YSZ system at 480-850K, nickel was oxidized via the substrate oxygen ions excess and the rate of oxidation depended strongly on the state of the surface. Reduction of oxygen excess leads to a decrease of the NiO decomposition temperature, which is higher than 900 K in UHV. The oxidation capability of the YSZ is restored after heating in oxygen atmosphere. The Ni/α-Al2O3 interaction depended on the chemical state of the surface, on the presence of C, -OH and non-lattice oxygen (surface defects).Interaction between deposited nickel and surface defects leads to Ni coalescence, partial oxidation and NiAlxOy chemical compound formation. The surface defects affects the thermal stability of NiO, which decomposes to Ni at lower temperature than 900K. On clean α-Al2O3 surfaces the NiO is stable up to 900K. Upon heating to 600K Ni deposits on γ-Al2O3/Al surfaces, the reduction of the alumina film thickness leads on the one hand to a decrease of the tendency of surface -OH groups to oxidize nickel and on the other hand to an increased formation of a NiAlx due to Ni diffusion on the Al substrate through the microholes in the alumina film. Upon heating up to 790K, the initially formed NiO decomposes to metallic Ni, whereas the Ni of the NiAlx compound diffuses inside the metallic Al.