Master of Science / Department of Food Science / Delores Chambers / Research has shown that trans fat consumption increases the levels of low-density lipoprotein (LDL) and has a direct correlation to the incidence of heart disease. It is now widely believed that trans fat intake adversely affects the health of consumers. A Food and Drug Administration (FDA) ruling, effective January 1, 2006, required declaration of trans fat content on all Nutrition Facts labels of food products. Around the same time local governments, such as the city of New York, and some restaurants followed suit by eliminating trans fats from their menus. The food industry’s initial concern with trans fat elimination/reduction was the loss of some functionality such as shelf life, stability, and creaming ability with trans-free fats and oils. Researchers are working to develop new trans-free fats and oils that do not have negative sensory properties and maintain the functionality of traditionally hydrogenated oils when used in baked and fried goods. This is an overview of the chemistry, health risks, and research that has been performed to either reduce or eliminate trans fats in food products.

Doctor of Philosophy / Department of Chemical Engineering / Peter H. Pfromm / Mary E. Rezac / Multiphase reactions are often constrained by mass transfer limitations which in many cases lead to low reaction rates and undesirable product distribution. Here we fabricate integral-asymmetric polymeric membranes decorated with metal catalysts, to supply hydrogen directly at or near the surface of the catalyst, thus minimizing mass-transfer limitations. The metal decorated polymeric membranes were used for partial hydrogenation of soybean oil with the goal to minimize trans fatty acid (TFA) formation. It was discovered that polymeric membranes with “defective” metal coatings are well suited to achieve low-TFA hydrogenation of soybean oil at quite moderate process conditions. The metal decorated polymeric membranes studied produced significantly lower trans fatty acid as compared to traditional reactors (3.5 wt% at an Iodine Value of 95 as compared to 8 wt% in slurry reactor), at pressures and temperatures which are compatible with the existing systems. The process concept is simpler than some of the alternatives being studied and no catalyst recovery from the oil is needed since the catalyst is immobilized on the membrane. Metal decorated polymeric membranes having a variety of hydrogen fluxes, skin defects, and catalyst loadings were evaluated. All the metal decorated polymeric membranes evaluated produced low TFA. Membranes with high hydrogen fluxes resulted in higher hydrogenation rates but had little influence on TFA formation. Membranes with higher catalyst loadings resulted in lower TFA but increased saturate formation. Metal decorated polymeric membranes behaved differently to changes in temperature and pressures when compared to traditional slurry reactors. They showed a minor increase in TFA with temperature (50-90 °C) as compared to traditional slurry reactors. The hydrogenation rate and cis-trans isomerization also showed a modest dependence on pressure. Due to the defective nature of the metal layer on the polymeric membrane skin and the low temperatures (50-90 °C) at which the reactor is operating, the hydrogen permeability of metals has a minor influence on hydrogenation reaction. A range of metal catalysts can be used for the given system. Repeat runs using the same membrane showed a decrease in hydrogenation activity, without any change in isomerization or hydrogenation selectivity. Initial results indicate the decreased activity may not be from leaching of catalyst from membrane surface nor from sulfur poisoning.

Achiral wide bite angle ligands have been shown to be highly active and to induce excellent chemo- and regioselectivities in many homogeneously catalyzed reactions. However, only a few examples of chiral wide bite angle ligands are known so far. A diphenyl ether backbone was selected to allow maximum synthetic versatility and potential for a modular approach to design and synthesize such chiral diphosphorus ligands. Three synthetic strategies have been explored in this thesis: i) introduction of chiral substituents in the ligand backbone, ii) the use of P-stereogenic donor atoms and iii) the synthesis of chiral mixed-donor ligands bearing chiral auxiliary groups on the phosphorus atoms. Functionalization of the 3,3'-positions of 2,2'-bis(diphenylphosphino)diphenyl ether by carboxylic acid or ether auxiliaries was achieved via straightforward four-step routes to generate a library of ligands that were tested in various catalytic reactions. In the Pd-catalyzed asymmetric allylic alkylation of l,3-diphenyl-2-propenyl acetate and cyclohexyl-2-enyl acetate with dimethyl malonate the enantioselectivity was found to depend on the size of the chiral auxiliary introduced within the diphenyl ether backbone and its proximity to the phosphorus donor groups and hence to the active metal centre. Two types of mixed donor bidentate diphosphorus ligands based on the diphenylether backbone have been established, i.e. phosphine-phosphite and phosphine-phosphonite derivatives. A small ligand library bearing different chiral auxiliaries was accomplished via straightforward syntheses that enable derivatization of the respective phosphite and phosphonite moieties in the final step. In the Rh-catalysed hydrogenation of several benchmark substrates high conversion and moderate to high enantioselectivities (up to 97% for dimethyl itaconate) were obtained. The enantioselectivity was influenced by the size of the ortho-substituent on the chiral auxiliary group of the phosphite or phosphonite fragment. Two modular synthetic approaches for the preparation of novel wide bite angle diphosphine ligands containing stereogenic P-atoms have been developed. Both protocols involved diphenylether as backbone and the chiral ephedrine based precursor (2R[subscript(P)],4S[subscript(C)],5R[subscript(C)])-oxazaphospholidine borane as initial auxiliary to induce chirality at phosphorus. Various novel diphosphines were isolated as highly enantioenriched compounds with dr-ratios up to 95:5.

The bidentate ligand 1,2-bis(ditertbutylphosphinomethyl)benzene has been shown to be a very efficient catalyst for operating the alkoxycarbonylation of alkenes and unsaturated esters and carboxylic acids giving a very high selectivity to the linear product with very few exceptions to this general rule. Due to the increasing prices of petroleum feedstock and petroleum-derived chemicals, the preparation of chemicals starting from renewable resources and waste products from the industry becomes an interesting alternative. Fatty acids and fatty esters, due to the existence of one or more unsaturation in their alkyl chain are subjected to the alkoxycarbonylation reactions in presence of 1,2-bis(ditertbutylphosphinomethyl)benzene, palladium, methane sulfonic acid, carbon monoxide and methanol, yielding diesters with a long carbon chain (up to 19 carbon atoms). The diesters are shown to be readily prepared from unpurified olive, rapeseed or sunflower oils as well as from tall oil. In the last case triesters are also formed. The diesters are subjected to hydrogenation in the presence of 1,1,1-tris(diphenylphosphinomethyl)ethane, ruthenium and hydrogen, in a mixture of dioxane and water at high temperature, yielding the corresponding diols. The resulting products of the reactions are monomers for preparing polyesters having the potential to replace some existing petroleum-based polymers (for instance polyethylene). The aminocarboxylation reaction in the presence of the same palladium/1,2-bis(ditertbutylphosphinomethyl) benzene catalyst, in the presence of aniline, 2{naphthol and potassium iodide in diethylether, is employed for preparing esteramides, which are subjected to hydrogenation. Aromatic polyamides are prepared by melting together an aromatic diamine and diacids obtained from methoxycarbonylation. Finally, N-Heterocyclic Carbene (NHC) ligands are employed for preparing new palladium complexes which are used in the Suzuki-Miyaura cross-coupling reaction in a water/isopropanol mixture. Other complexes based on copper are employed for developing an inexpensive transmetallation reaction for transferring a NHC ligand from copper to palladium and gold.

No description available.

A test system for the performance analysis of a novel thermally regenerative fuel cell (TRFC) using propiophenone and hydrogen as the oxidant and fuel respectively was designed and built. The test system is capable of either hydrogen-air or hydrogen-propiophenone operation. Membrane electrode assemblies (MEAs) were made using commercial phosphoric acid-doped polybenzimidazole (PBI) membranes and commercial electrodes. Using Pt/carbon paper electrodes with a catalyst loading of 1mg/cm2 and a membrane with an acid doping level of 10.2 mol acid/mol of polymer repeat unit, a maximum performance of 212 mW/cm2 at a current density of 575 mA/cm2 was achieved for baseline hydrogen-air testing at 110°C. Problems were encountered, however, in achieving consistent, reproducible performance for in-house fabricated MEAs. Furthermore, ex-situ electrochemical impedance spectrometry (EIS) showed that the phosphoric acid-doped PBI was unstable in the propiophenone and that acid-leaching was occurring. In order to have MEAs with consistent characteristics for verifying the test system performance, commercial phosphoric acid-doped PBI membrane electrode assemblies were used. At a temperature of 160°C and atmospheric pressure with hydrogen and air flowrates of 150 mL/min and 900 mL/min respectively a maximum power density of 387 mW/cm2 at a current density of 1.1 A/cm2 was achieved. This performance was consistent with the manufacturer’s specifications and these MEAs were subsequently used to verify the performance of TRFC test system despite the EIS results that indicated that acid-leaching would probably occur. The Pt catalyzed commercial MEAs achieved very limited performance for the hydrogenation of the ketone. However, the performance was less than but comparable to similar results previously reported in the literature by Chaurasia et al. [1]. For pure Pt catalyst loading of 1 mg/cm2, using a commercial PBI MEA operating at 160°C and atmospheric pressure, the maximum power density was 40 µW/cm2 at a current density of 1.3 mA/cm2. A 16 hour test was conducted for these conditions with a constant 1 ohm load, successfully demonstrating the operation of the test system. The test system will be used in the development of better catalysts for ketone hydrogenation. / Thesis (Master, Chemical Engineering) -- Queen's University, 2012-10-12 10:00:58.854

Catalysis plays a key role in chemical conversions by making them faster and more selective. Despite its widespread use and decades of academic and industrial research, limited catalyst selectivity and stability still call for major improvements in catalyst performance to meet the demands of a sustainable society. Phosphine ligands are ubiquitous in transition metal chemistry and lead to extremely reactive and versatile homogeneous catalysts. Fast development of tailor-made catalysts and catalyst recovery are key issues in (asymmetric) homogeneous catalysis. Therefore libraries of ligands have to be synthesised and screened in an efficient way, which could be facilitated by Solid Phase Synthesis (SPS). Currently, most polymer bound ligands are anchored to the support after the synthesis in solution. However, the main advantages of synthesising the ligands directly on the polymeric support are not only easy catalyst recycling and product separation, but also the ease of purification during the synthesis steps, namely by simple washing and filtration. The use of SPS is very efficient for high throughput synthesis and screening of ligand libraries, however applications of SPS towards libraries of phosphorus ligands are rare, because the synthetic methodologies are still lacking. Here we present the development of methodologies towards novel immobilised bis(phosphine) ligands synthesised on polystyrene and JandaJel™ resin. By performing the synthesis steps on a solid support, the advantages of SPS are fully utilised. Successful routes have been developed towards immobilised secondary phosphine-boranes, which were versatile synthons to prepare a variety of new polymer-supported (C-chiral) bis(phosphine) ligands. These ligands were then tested for their catalytic activity in rhodium catalysed hydrogenation reactions.

The work described in this thesis is focused on exploring the efficacy of iridium-catalysed asymmetric hydrogenation of precursors to chiral alcohols and chiral cyclohexanes. A range of allylic alcohols including γ,γ-dialkyl allylic alcohols and (Z)-allylic alcohols were prepared and evaluated in the asymmetric hydrogenation using iridium catalysts resulting in chiral alcohols in high yields and excellent enantioselectivity. This methodology was applied in the formal synthesis of Aliskiren, an efficient renin inhibitor drug, using the asymmetric hydrogenation of an allylic alcohol as a key-step. Another project concerned the dynamic kinetic resolution of racemic secondary allylic alcohols using Ir-N,P catalysts under hydrogenation conditions. A range of secondary allylic alcohols and protected alcohols were evaluated in the asymmetric hydrogenation via dynamic kinetic resolution using Ir-N,P catalysts. The corresponding chiral saturated alcohols were formed in good yield with excellent diastereoselectivites (up to 95/5) and enantioselectivities (&gt;99% ee). The last part of this thesis is directed towards the development of highly regio- and enantioselective asymmetric hydrogenation of 1,4-cyclohexadienes and its application in the preparation of useful chiral cyclohexenone intermediates. Non-functionalised, functionalised and heterocycle-containing cyclohexadienes were evaluated. Good yield of regioselectively mono-hydrogenated silyl protected enol ethers were obtained in most cases with excellent enantioselectivity. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 5: Manuscript.</p>

La synthèse d'amines chirales par catalyse asymétrique à l'aide de complexes de métaux de transition suscite un grand intérêt, puisque cela conduit à la production de molécules à haute valeur ajoutée. La voie catalytique offre une alternative avantageuse par rapport aux voies de synthèses conventionnelles, dont les inconvénients sont d'une part des produits de départ coûteux et d'autre part un grand nombre de produits secondaires, sans parler des étapes de synthèse souvent nombreuses. Dans le cadre d'un projet industriel visant à développer des outils catalytiques performants pour la synthèse d'amines chirales, nous nous sommes orientés vers le développement d'un système qui permettrait de réaliser l'hydroaminométhylation d'alcènes de façon énantiosélective. L'hydroaminométhylation est une réaction tandem combinant deux réactions catalytiques, l'hydroformylation et l'hydrogénation. A partir de molécules modèles, nous avons développé une approche permettant de rationnaliser la création de centres asymétriques en fonction du type de substrat utilisé, soit au cours de l'hydroformylation, soit au cours de l'hydrogénation de l'énamine intermédiaire. La réaction a été étudiée en version intermoléculaire et intramoléculaire. Le cycle catalytique de l'hydroformylation et celui de l'hydrogénation possèdent chacun des exigences différentes au niveau de la sphère de coordination du métal. De plus, les conditions de la réaction tandem ont une influence sur les espèces catalytiques formées et les sélectivités de la réaction. Grâce à des études de RMN sous pression, confirmées par des calculs théoriques, nous nous sommes attachés à étudier le comportement des complexes du rhodium mis en jeu, sous pression et dans les conditions d'hydroaminométhylation. Ces études nous ont permis d'approfondir la connaissance des espèces catalytiques impliquées dans cette réaction tandem. L'ensemble du travail de recherche a été mené en combinant les approches fondamentale et appliquée, nous permettant ainsi de proposer un outil catalytique adapté au substrat de départ considéré, dans la perspective d'une application industrielle de la réaction. / Amines are of great importance as building blocks or reactants in the chemical industry. The development of catalytic processes for their synthesis is thus of particular interest from an industrial point of viewsince they can afford an alternative to conventional synthetic pathways. In the context of an industrial project aiming to synthesize chiral amines, we focused on the development of a catalytic system adapted to the asymmetric hydroaminomethylation of alkenes. This tandem reaction includes two transition metal catalyzed reactions under CO and H2 pressure: the hydroformylation and the hydrogenation reactions. Starting from model molecules, we proposed an approach to carefully study the creation of asymmetric centers during the reaction sequence, either in the hydroformylation step or in the enamine intermediary hydrogenation step. The reaction was studied in its inter- and intramolecular version.Rhodium is often used for the hydroaminomethylation reaction, since it is able to complete both catalytic cycles of hydroformylation and hydrogenation. However, requirements in the coordination sphere of the metal center and species involved in each catalytic cycle are presumed to be different. Thanks to high pressure NMR experiments, combined with DFT calculations, the behaviour of rhodium complexes involved in the catalysis was investigated under conditions close to those of hydroaminomethylation. The knowledge of the rhodium species involved in the reaction was also improved thanks to these spectroscopic and catalytic experiments. The fundamental and applied approaches result in a deeper understanding of the tandem reaction sequence and allow us to design a catalytic system adapted to the starting substrate, in the purpose of an industrial application of the reaction.

L’objectif de cette étude est de préparer des catalyseurs bimétalliques Ni-X/SiO2, de les caractériser, et de comparer leur activité en hydrogénation du styrène en éthylbenzène,ainsi que leur sélectivité en hydrogénation de la double liaison oléfinique du styrène, par rapport à l’hydrogénation du noyau benzénique. L’élément X est greffé de manière contrôlée sur le nickel, et est choisi selon son électronégativité, soit inférieure (Zr), soit égale (Sn), soit supérieure (Au) à celle du nickel, dans le but d’étudier les effets géométriques et/ou électroniques qu'il pourrait induire. Parmi les échantillons préparés, le catalyseur Ni-Au/SiO2s’est révélé presque aussi actif que le catalyseur non dopé et nettement plus sélectif dans l’hydrogénation du styrène en éthylbenzène. / The aim of the present study is to prepare silica-supported Ni-X bimetallic catalysts, tocharacterize them, and to compare their catalytic activity in the hydrogenation of styrene, as well as their selectivity in the hydrogenation of the styrene’s olefinic double bond instead of the hydrogenation of the aromatic ring. The element X is grafted in a controlled way on the supported nickel particles, and is chosen according to its electronegativity, which is eitherlower (Zr), or equivalent (Sn), or higher (Au) than the electronegativity of Ni, in order to study the geometrical and/or electronic effects due to the doping of Nickel. Among the prepared samples, the Ni-Au/SiO2 catalyst has exhibited high activity and high selectivity in the hydrogenation of styrene into ethylbenzene, which makes the doping of Ni by Au apromising alternative for PyGas selective hydrogenation catalysts.