This dissertation describes preparation and characterization of Ni₂P catalysts and their application in hydrodesulfurization (HDS) and hydrodenitrogenation (HDN). The work carried out includes synthesis of Ni₂P on different siliceous supports, SiO2 and MCM-41. It also includes characterization of these catalytic materials using X-ray diffraction (XRD), temperature-programmed reduction (TPR), Fourier transform infrared (FTIR) spectroscopy and X-ray absorbance fine structure (XAFS) spectroscopy. In situ FTIR was employed to study the acidity of Ni₂P/SiO₂ and probe the catalytic sites involved in the HDN of pyridine. Transient and steady-state kinetics of a surface intermediate that is formed upon pyridine adsorption and reaction was studied to elucidate the mechanism of HDN over Ni₂P/SiO₂. Additionally, in situ FTIR and X-ray absorption near edge structure (XANES) spectroscopy was utilized to probe the bonding, mechanism and kinetics of thiophene HDS over a novel MCM-41-supported Ni₂P catalyst. The use of these techniques allowed for better understanding of the surface intermediates, mechanisms and the nature of the active sites involved in HDN and HDS. / Ph. D.

This dissertation describes preparation and characterization of Ni₂P catalysts and their application in deep hydrodesulfurization (HDS) of a model sulfur compound, 4,6-dimethyldibenzothiophene (4,6-DMDBT), one of the most refractory S-compounds. This topic is of great importance in addressing recently enacted environmental regulations limiting the sulfur content in fuels. The work carried out includes synthesis of Ni₂P on different siliceous supports, SiO₂, MCM-41, and ultra-stable Y zeolite (USY). It also includes determining the characteristics of the supported Ni₂P catalysts with a wide range of techniques: X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and X-ray absorption fine structure (XAFS) spectroscopy. The use of these techniques allowed better understanding of the nature of the active sites as well as the effect of supports. Activity tests were conducted in the HDS of 4,6-DMDBT and the HDN of quinoline. The performance of the catalysts will be compared to that of a conventional sulfide hydrotreating catalyst, Ni-Mo-S/Al₂O₃. Investigation of the reaction mechanism in the hydrodenitrogenation (HDN) of 2-methylpiperidine together with in situ FT-IR measurements were conducted to understand how catalyst properties affect activity and selectivity. / Ph. D.

The objective of this project is to investigate hydrodeoxygenation (HDO), a crucial step in the treatment of bio-oil, on transition metal phosphide catalysts. The study focuses on reactions of simple oxygenated compounds present in bio-oil -- ethanol and 2-methyltetrahydrofuran (2-MTHF). The findings from this project provide fundamental knowledge towards the hydrodeoxygenation of more complex bio-oil compounds. Ultimately, the knowledge contributes to the design of optimum catalysts for upgrading bio-oil. A series of transition metal phosphides was prepared and tested; however, the focus was on Ni2P/SiO2. Characterization techniques such as X-ray diffraction (XRD), temperature-programmed reduction and desorption (TPR and TPD), X-ray photoelectron spectroscopy (XPS), and chemisorption were used. In situ Fourier transform infrared (FTIR) spectroscopy was employed to monitor the surface of Ni2P during various experiments such as: CO and pyridine adsorption and transient state of ethanol and 2-MTHF reactions. The use of these techniques allowed for a better understanding of the role of the catalyst during deoxygenation. / Ph. D.

This study considered the potential use of lignin as possible renewable fuel and chemical feedstock source. Among the various polymers present in lignocellulosic biomass, the polyaromatic lignin is the one component that is most chemically similar to petroleum. However, it still contains a much larger amount of oxygen compared to crude oil. As such, two strategies were employed in this study: (1) studying the lignin depolymerization in the presence of high temperature and base catalysts; and, (2) employing hydrodeoxygenation as a means to decrease the O/C ratio in lignin-derived model compounds. The base-catalyzed depolymerization (BCD) of organosolv lignin was done in a 500-mL Monel Parr reactor at temperatures ranging from 165°C to 350°C. Complete solubilization of lignin derivatives was possible in the presence of NaOH and KOH, except at 350°C. NMR experiments revealed formation of oxidized groups (carboxylic and hydroxyl groups) as well as alkyl groups. On the other hand, the use of NH4OH showed N incorporation. Identified and quantified DCM-soluble monomeric compounds were at most 6% of the starting material and are mainly phenolic. This study revealed the apparent susceptibility of syringyl units over guaiacyl units in BCD. This could in turn guide the choice of substrate on which base-catalyzed depolymerization could be applied. Syringaldehyde was used as the starting material to study batch hydrodeoxygenation (HDO) using several non-cobalt/molybdenum based catalysts. A 50-ml Parr reactor was used, pressurized by 1000 psig of H2 and heated to 300°C. Nickel based catalysts (nickel phosphide, nickel oxide and nickel phosphate) as well as supported precious metals (Pt and Pd) were tested as HDO catalysts. Of the three O-containing functional groups of syringaldehyde, the aldehydic group was found to be the most susceptible. In the presence of the Al2O3-supported catalysts, the methyl groups liberated were found to be incorporated back into the aromatic ring, forming alkylated compounds. In the last section of this dissertation, hydrothermally synthesized supported Ni on mesoporous silica (MCF) and acid catalysts (HY and H-Al-MCF) were used for probing the effect of bifunctional metal-acid catalysis on phenol hydrodeoxygenation/hydrogenation. Catalyst configurations were varied from the previously studied wet-impregnated Pt/HY catalyst. Based on a hypothesis that coking catalyzed by the acidic zeolite in the wet impregnated Pt/HY catalyst was the main cause of catalyst deactivation and decreased phenol conversion, separately synthesized metal and acid catalyst systems were tested. Complete phenol conversion was sustained for at least three times longer in a continuous flow reactor operated at 200°C and 0.79 MPa of flowing H2. The separation of the metal and acid sites generated a tunable system capable of producing cyclohexanol, cyclohexane or cyclohexene at very high selectivities, even achieving 99% selectivities for cyclohexane.

In der Entwicklung von Technologien für die nachhaltige Erzeugung, Speicherung und Umwandlung von Energie werden Hochleistungskatalysatoren benötigt. Im Rahmen dieser Arbeit werden verschiedene Übergangsmetall-basierte Katalysatoren, namentlich TiO2/Kohlenstoff-Komposite, anorganisch-organische Hybridsysteme auf Basis von NiFe Phosphonaten sowie Ni Phosphide, synthetisiert, charakterisiert und hinsichtlich ihrer photo- und elektrokatalytischen Eigenschaften untersucht. Es wird gezeigt, dass die Grenzflächeneigenschaften der TiO2/C-Komposite signifikant durch die Gestaltung des Heizvorgangs während der Synthese beeinflusst werden. Insbesondere der Einsatz von Mikrowellenstrahlung vermag die Synthese von Kohlenstoff-basierten Materialien positiv zu beeinflussen. Schnelles Erwärmen führt zu stärkeren Wechselwirkungen zwischen Nanopartikeln und Kohlenstoff, einheitlicheren Beschichtungen und kleineren Partikeln mit schmaleren Partikelgrößenverteilungen, wodurch die photokatalytische Aktivität verbessert wird. Schichtartige, hybride NiFe-Phenylphosphonat-Materialien werden ausgehend in Benzylalkohol dargestellt und ihre Aktivität in der OER im basischen Milieu untersucht. Die Hybridpartikel werden in-situ in NiFe-Hydroxid Nanoschichten umgewandelt. Röntgenspektroskopische Untersuchungen deuten auf eine induzierte, teilweise verzerrte Koordinationsumgebung der Metallzentren im Katalysator hin. Die Kombination der synergistischen Effekte zwischen Ni und Fe mit den strukturellen Eigenschaften des Hybridmaterials ermöglicht einen effizienten Katalysator. Weiterhin werden Nickel-Phosphide durch die thermische Behandlung der Phenyl- oder Methylphosphonate des Nickels, welche Schichtstrukturen aufweisen, in H2(5%)/Ar-Atmosphäre synthetisiert. Ni12P5, Ni12P5-Ni2P und Ni2P Nanopartikel, die mit einer dünnen Schicht aus Kohlenstoffmaterial beschichtet sind, werden erhalten. Ni12P5-Ni2P und Ni2P Nanopartikel katalysieren die Wasserstoffentwicklungsreaktion (HER) im Sauren effektiv. / High-performance catalysts play a key role in the development of technologies for sustainable production, storage, and conversion of energy. In this thesis, transition-metal-based catalysts, including TiO2/carbon composites, hybrid organic-inorganic NiFe phosphonates, and Ni phosphides are synthesized, characterized, and investigated in photocatalytic or electrocatalytic reactions. TiO2 is frequently combined with carbon materials, such as reduced graphene oxide (rGO), to produce composites with improved properties. TiO2 is more efficiently stabilized at the surface of rGO than amorphous carbon. Rapid heating of the reaction mixture results in a stronger coupling between the nanoparticles and carbon, more uniform coatings, and smaller particles with narrower size distributions. The more efficient attachment of the oxide leads to better photocatalytic performance. Layered hybrid NiFe-phenylphosphonate compounds are synthesized in benzyl alcohol, and their oxygen evolution reaction (OER) performance in alkaline medium is investigated. The hybrid particles transformed in situ into NiFe hydroxide nanosheets. X-ray absorption spectroscopy measurements suggest the metal sites in the active catalyst inherited partly the distorted coordination. The combination of the synergistic effect between Ni and Fe with the structural properties of the hybrid results in an efficient catalyst that generates a current density of 10 mA cm-2 at an overpotential of 240 mV. Moreover, nickel phosphides are synthesized through thermal treatment under H2(5%)/Ar of layered nickel phenyl- or methylphosphonates that act as single-source precursors. Ni12P5, Ni12P5-Ni2P and Ni2P nanoparticles coated with a thin shell of carbonaceous material are produced. Ni12P5-Ni2P and Ni2P NPs efficiently catalyze the hydrogen evolution reaction (HER) in acidic medium. Co2P and CoP NPs are also synthesized following this method.