The world energy and product consumption keep increasing steadily over the years as the world population keeps growing and more countries become industrialized. As the world reserves deplete it becomes a necessity to find an alternative way to meet the population’s demand. Biomass conversion seems to be the future of a clean and sustainable world. Lignin is the second most abundant polymer in the biomass. Given the unique structure and chemical properties of lignin, a wide variety of bulk and fine chemicals can be obtained and be used for goods and biofuels production. Catalysis, with its selective bond cleavage and lower energy activation, is considered as a potential key solution in the process of lignin conversion into valuable chemicals. To gain insights into that catalytic system, we performed surface science experiments (X-ray Photoelectron Spectroscopy, Temperature Programmed Desorption and Reflection Absorption Infrared Spectroscopy) under Ultra-High Vacuum conditions (UHV). Due to lignin’s physical properties limitation under UHV conditions, lignin models with the same chemical structure such as phenol, anisole, 2-phenoxyethanol and veratrol were used to gain a better understanding of the reactivity of lignin itself. Dosing anisole and 2-phenoxyethanol on Pt(111) surprisingly gave benzene, carbon monoxide and hydrogen as the main desorbing products of decomposition. With the help of Density Functional Theory (DFT), we successfully explain the unexpected selectivity. In the present work, we show in particular that phenoxy PhO stands as a key intermediate. Although the UHV conditions do not allow the hydrogenation of phenoxy into phenol, i.e. the catalytic product, they reveal the key role of both hydrogen and carbonaceous species. Under UHV conditions, anisole and 2-phenoxyethanol are extensively dehydrogenated: it results in the formation of carbonaceous fragments, which can actually perform the deoxygenation of phenoxy into benzene. The reactivity of veratrol on Pt(111) hindered the formation of benzene and only gave carbon monoxide and hydrogen as the main desorbing products of decomposition. Although carbonaceous fragments were formed on the surface, the deoxygenation of the two oxygenated arm moieties does not occur without the total decomposition of the aromatic ring, hence the formation of coke. This detailed work opens the door to a rational design of metal-based catalysts and a route towards lignin valorization.

Ce travail a eu pour objectif l’étude d’une nouvelle méthodologie de fonctionnalisation aromatique basée sur la déprotonation par les bases magnésiates (alkyl- et/ou amidomagnésiates de lithium) à température ambiante encore très peu étudiée et l’examen de la réactivité nucléophile et dans le couplage croisé catalysé par un métal de transition des complexes (hétéro)arylmagnésiates générés. La première partie a été centrée sur la déprotonation des hétérocycles à 5 chaînons (furane, thiophène, benzoxazole et oxazole) qui a été réalisée avec succès en utilisant essentiellement la base Bu3MgLi. Les complexes hétéroarylmagnésiates dont les formes ouvertes issues de la déprotonation de l’oxazole et du benzoxazole ont révélé d’une part une bonne réactivité nucléophile vis à vis d’agents de deutération, d’halogénation, de sylilation et des aldéhydes aromatiques pour conduire aux hétérocycles substitués avec de bons rendements. D’autre part les complexes magnésiates ont été engagés avec succès dans le couplage croisé avec des partenaires bromo(hétéro)aromatiques catalysé par PdCl2(dppf). La seconde partie a été consacrée à l’étude de l’ortho-fonctionnalisation des dérivés benzéniques. Les conditions d’ortho-magnésiation par les bases tri(tétra)alkylmagnésiates de (di)lithium des oxazolyl-, carboxamido-, pivaloylamino-, et alkoxybenzènes ainsi que du benzène sulfoxyde ont été mises au point. Les complexes arylmagnésiates générés ont révélé d’une part une bonne réactivité nucléophile vis à vis d’agent de deutération, d’halogénation, de sylilation et du méthyloxirane. Seule la réactivité vis-à-vis des aldéhydes s’est révélée moindre mettant à jour deux réactions compétitives, l’addition d’un groupement butyle et la réduction concurrente de la fonction carbonyle. D’autre part, les nouveaux complexes arymagnésiates à l’exception de ceux issus de la déprotonation du benzène sulfoxyde ont été couplés avec succès avec des dérivés (hétéro)aromatiques bromés. De façon plus générale, la méthodologie de fonctionnalisation par déprotonation par les bases magnésiates s’est révélée efficace et apporte de nouveaux avantages par rapport aux méthodes classiques tels que d’une part la déprotonation au voisinage de la température ambiante pour les applications industrielles et d’autre part l’utilisation d’une nouvelle classe de réactifs organométalliques utilisables aussi bien pour le piégeage électrophile que pour le couplage croisé catalysé par un métal de transition. / This present work reports the development of a novel versatile aromatic functionnalization methodology based upon deprotonation with magnesiate bases (lithium alkyl- and /or amidomagnesiates) at room temperature, currently poorly studied and the use of the novel arylmagnesiates complexes formed as nucleophilic agents and organometallic partners in the cross-coupling reaction. The deprotonation of the five-membered heterocycles (furan, thiophene, benzoxazole and oxazole) was first successfully accomplished using mainly Bu3MgLi as base. The arylmagnesiates thus obtained, including the expected ring-opened magnesiate complexes obtained from deprotonation of benzoxazole and oxazole, proved to be effective in several reactions as deuteration, halogenation, silylation and nucleophilic addition on aromatic aldehydes leading to the corresponding substituted heterocycles. Futhermore the heteroarylmagnesiates complexes revealed to be efficient in cross-coupling reaction with bromo(hetero)aromatics catalyzed by PdCl2(dppf). In a second part, works were directed toward the study of the ortho-functionnalization of benzene derivatives. Thus, the deprotonation of oxazolyl-, carboxamido-, pivaloylamino- and methoxybenzenes as well as benzene sulfoxyde was achieved using mainly (di)lithium tri(tetra)magnesiate bases. The arylmagnesiates complexes showed a good nucleophilic reactivity toward deuterative, halogenative and silylative agents and methyloxirane whereas reactions with aromatic aldehydes occurred in more moderate yields due to two side processes, addition of a butyle group and reduction of the aldehyde function. The arylmagnesiates excepted from benzene sulfoxyde could be coupled with bromo(hetero)aromatics under PdCl2(dppf)-catalysis. In summary, the novel aromatic functionnalization based upon the use of magnesiate bases proved to be particularly efficient and represents many advantages compared to classical methods such as metalation at room temperature for direct industrial application as well as the use of a new class of organometallic reagents possessing a good nucleophilic reactivity and directly valuable in the transition metal-catalyzed cross-coupling reaction.

With the increase of global temperature and decrease of fossil fuel sources, biofuels become an excellent alternative in present days. Because of its oxygenated nature, biofuels are found to be more environmentally friendly over fossil fuels. Therefore, in this study, initially two different biofuels: ethanol and 2,5 dimethyl furan (DMF) are considered as an additive to gasoline which shows a significant improvement in its combustion characteristics. Due to this promising result for further studies of these biofuel, details chemical kinetic study of biofuels is considered in this work through generating its mechanism for engine relevant conditions. Detail chemical mechanism PCRL-Mech1 is generated for ethanol which is applicable for wide range of operating conditions. The mechanism is successfully validated with available experimental data of laminar burning speed (LBS) and ignition delay time (IDT). Species concentration at different reactor conditions are also considered for the comparison which shows an excellent agreement. Detail mechanism generation for another newer biofuel anisole is also considered because of its favorable features in combustion properties and potential source of biomass. Anisole is a higher hydrocarbon aromatic component and comparative newer fuel which has limited experimental data. However, with that available experimental data, the developed anisole mechanism shows a good agreement predicting LBS and IDT results. The chemical kinetics of this fuel is also analyzed through reaction path flux and sensitivity analyses. Although, detail mechanisms have higher accuracy, they would be very expensive when using in multiscale computational fluid dynamics (CFD) modeling. Therefore, different mechanism reduction schemes are considered to reduce the mechanism size. Initially direct relation graph (DRG), direct relation graph with error propagation (DRGEP) and sensitivity analysis is implemented to generate a skeleton mechanism for PCRL-Mech1, which successfully reduced its size. In addition, the rate-controlled constraint equilibrium (RCCE) analysis is considered as a reduction scheme. The constraints for RCCE calculation are selected through approximate singular value decomposition of actual degree of disequilibrium (ASVDADD) analysis. A good comparison of temperature profile of RCCE simulation proves the success of ASVDADD method.

Since being discovered, combustion of fuels, especially fossil fuels in the last centuries, has been the dominant source of energy for human life. However, over the years, the adverse effects and shortcomings caused by the vast utilization of these energy sources have been observed; the three most important of which are unreliable resources, unfavorable natural outcomes, and limited performance. Using biofuels is one of the well-established proposed solutions to the scarcity and environmental issues of fossils as they are sustainable sources of energy with acceptable and even superior combustion characteristics. As a second-generation biofuel, anisole has shown promising results with high flame speed and high knock resistance. Therefore, the first chapter of this thesis is focused on experimental investigation of anisole laminar burning speed and stability properties so that it can be used as a benchmark for future kinetic mechanism validations. Stability is another important parameter in combustion systems, especially in diffusion jet flame combustion as used in many applications like thrusters or burners. Different methods are applied to improve the stability of such diffusion flames in propulsion systems, e.g., changing geometrical or flow characteristics of the burner. Most of these efforts have not been practically successful, due to the cost and compatibility issues. Another technique which minimizes such problems is to use electron impact excitation, dissociation and ionization and generate highly concentrated charged/excited species and active radicals. These methods include microwave, dielectric barrier, and repetitive nanosecond pulsed (RNP) discharge and the latter has shown promising results as one of the most effective low-temperature plasma (LTP) methods. In chapters 3 to 5, the benefits and issues associated with using RNP discharge in a single-element concentric methane-air inverse diffusion jet flame are discussed. It has been shown that RNP discharge with adequate discharge properties (voltage and repetition) can increase the stability of the flame and expand the flammability of the jet toward leaner compositions. However, the effectiveness is significant in a certain voltage-frequency ranges which results a non-thermal spark discharge mode. Hence, different modes of discharge were investigated and a parametric study on the transition between these modes were done.

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