Fuel processing is one of the essential parts for development of intermediate solid oxide fuel cells (IT-SOFC). Natural gas (methane) is considered as the most abundant and cost effective fuel for the production of hydrogen for IT-SOFC. The primary aim of this thesis is to use a novel precursor material—layered double hydroxide (LDH) – for developing a new type of cost effective, highly active and long lasting catalyst which can reform natural gas in IT-SOFC anode environment. Small amount of noble metals Pd, Rh and Pt are used as promoters to enhance the catalyst’s performance as while maintaining the cost relatively low. The research objectives are achieved by a series of studies including catalysts synthesis, characterisation and the catalytic activities. The thesis initially gives a comprehensive review on fuel cell and SOFC technology, steam methane reforming and reforming catalyst to provide better understanding of the research. Experimental studies include the effects of the synthetic conditions of the LDH precursors and thermal treatments on the physical, chemical behaviours and catalytic activities of the catalysts and promotional effects by noble metals. The LDH derived catalysts compositions, promoter quantities and operating conditions are optimised for the best performance in the IT-SOFC anode environment. A new method for the development of precursor sol for easy coating of the anode is developed and studied. The sol preparation is achieved by acid attack. The sol developed is found to produce better coating and has very high catalytic properties after activation. The catalysts developed were tested for their stability and self-activation ability to ensure its use in the commercial cells. The findings of the present study indicate that the catalysts developed show excellent catalytic performance and these catalysts have very high potential for further commercialisation in IT-SOFC.

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In this work, a micro-model of the catalyst layer of polymer electrolyte membrane fuel cell (PEMFC) was developed. The micro-model includes the transport phenomena and the reaction kinetics within a three dimensional micro-structure representing a sample of PEMFC catalyst layer. Proper physical boundary conditions have been described on the surfaces of the sample as well as on the interfaces between the regions through which all constituents are solved in a coupled manner. A four-phase micro-structure of CL was reconstructed, the platinum particles were resolved in the computational grid generation and the governing equations were solved within platinum region. A body-fitted computational mesh was generated for the reconstructed micro-structure of CL. The number of computational cells were optimized based on how close to an analytical sphere the magnitude of the surface area of a sphere can be captured after generating the computational cells. The interfaces with important physical phenomena were more refined than the rest of the interfaces, specially the electrochemically active reaction surface. The computational mesh was checked for a grid independent numerical solution. The Knudsen effects was included by calculating the characteristic length in the pore region. Four different cases of including Knudsen effects were studied. Also, a comparison was made between solution with and without Knudsen effects. A physical model of oxygen dissolution was developed, the oxygen dissolution at the interface between pore and ionomer was treated as an superficial phenomenon. The performance curves were produced and provided for the reconstructed micro-structure along with the distribution of field variables. A length study of the reconstructed micro-structure was conducted such that the results from the micro-modeling can capture the trend in variable distributions observed in the macro-modeling of CL or experiments. A platinum loading study was preformed and the anomalous phenomena of dramatic increase in oxygen transport resistance observed in some experimental works was explained by isolating the ionomer region of the CL micro-structure and numerically calculating the shape factor for diffusive transport. It was found that the increase in oxygen transport resistance is due to the increase in diffusion pathway and decrease in the transport surface area. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-03-06 15:55:21.564

Mozambique has vast forestry resources and also considerable biomass waste material such as bagasse, rice husks, sawdust, coconut husks and shells, cashew nut shell and lump charcoal waste. The potential of the total residues from the agricultural sector and the forest industry is estimated to be approximately 13 PJ. This amount of energy covers totally the production of charcoal which amounted to approximately 12.7 PJ in 2006. Although biomass is an attractive renewable source of energy, it is generally difficult to handle, transport, storage and use due to its lower homogeneity, its lower energy density and the presence of non-combustible inorganic constituents, which leads to different problems in energy conversion units such as deposition, sintering, agglomeration, fouling and corrosion. Therefore, a pretreatment of the biomass to solve these problems could lead to a change of current biomass utilization situation. The aim of this study is to convert Mozambican woody biomass residue into a solid biochar that resembles low-grade coal. In this work the current energy situation in Mozambique has been reviewed, and the available and potential renewable sources including residues from agricultural crops and forest industry as energy have been assessed. It was found that the country is endowed with great potential for biofuel, solar, hydro and wind energy production. However, the production today is still far from fulfilling the energy needs of the country, and the majority of people are still not benefiting from these resources. Charcoal and firewood are still the main sources of energy and will continue to play a very important role in the near future. Additionally, enormous amounts of energy resources are wasted, especially in the agricultural sector. These residues are not visible on national energy statistics. The chemical composition and the fuelwood value index (FVI) showed that by failing to efficiently utilise residues from Afzelia quanzensis, Millettia stuhlmannii and Pterocarpus angolensis, an opportunity to reduce some of the energy related problems is missed. An evaluation of effect of a mild wet torrefaction pretreatment showed that the chemical composition of the biochar is substantially different than the feedstock. The use of diluted acid as catalysts improves the biochar quality, namely in terms of the energy density and ash characteristics; however, the increment of the S content in the final product should be considered for market acceptance (because the fuels have a maximum allowance for S concentration). The thermal behaviour of the untreated and treated biomass was also investigated. The pyrolytic products of umbila and spruce were affected by the treatment and catalyst in terms of yield and composition of the vapours. / <p>QC 20150202</p>

A study was done to examine the effect of surface orientation as well as heterogeneous epitaxy at an interface between two materials with a large lattice mismatch. Silver nanoparticles of different diameters were grown in an effort to study methods of preferentially orienting the geometry of metal nanoparticles. Arrays of calcium fluoride nanorods were grown on silicon substrates using oblique angle thermal vapor deposition. The chamber operated at an ultra high vacuum pressure of 10^-10 Torr during the deposition of the rods and an oblique angle of 75° was kept between the silicon substrate normal and the direction of incident flux. A method was then developed to grow silver nanoparticles exclusively on the (111) facet of the calcium fluoride tips. This was accomplished by once again using oblique angle deposition with an angle of 75° along with the larger size of the (111) calcium fluoride tip facet. Cross sectional scanning electron microscopy and transmission electron microscopy imaging was used to verify that the nanoparticles adhered exclusively to the desired facet of the tip. Using selected area diffraction, (SAED) and dark field in the TEM, it was shown that the nanoparticles did grow at a (111) orientation at the interface between them and the calcium fluoride rods. Different thicknesses and diameters of nanoparticles were then grown to determine what an ideal size was to achieve the most (111) orientation of the nanoparticles. Thicknesses of the particles varied between 5 nanometers and 15 nanometers. Through characterization it was shown that all three of the different thicknesses grown exhibited (111) orientation of the silver nanoparticles, both at the interface and in the overall nanoparticle as well with the 10 nanometer sample being the most ideal in terms of the desired result. Lattice straining of the silver nanoparticles was also observed by characterization through diffraction and SAED.

A dissertation submitted to the Faculty of Science, University of the Wtlwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science / This dissertation focusses on the deactivation of SAP0-34 and modified SAPOs during methanol conversion under various conditions, in comparison to H-ZSM-5. SAPO-34 was found to deactivate rapidly during methanol conversdon. This was shown by the decrease in activity, surface area and pore volume of the catalyst. The deposited "coke" was analysed by in situ diffuse reflectance infra-red Fourier Transform spectroscopy,solid-state magic angle spinning nuclear magnetic resonance, gas chromatography mass spectroscopy (GCMS) of the HF- and dichloromethane-extracted to "coke"; and GCMS of the organic specfes released during regeneration of the catalyst and trapped in resin capillary inlet tubes.The "coke" consisted of alkylated aromatics and naphthalenes which probably formed on the surface or in the large cavities of SAPO-34. The amount of "coke" deposited during methanol conversion increased with reaction temperature, decreased with dilution of the methanol with water or nitrogen. and decreased with increased pressure, Incorporation of Ni into the SAPO framework did not decrease the rate of deactivation, but the "coke" that Has deposited was less bulky than that deposited in SAPO-34. Modification of the SAPO-34 with trlmethyl silylchloride decreased the rate at deactivation of the catalyst. / AC 2018

A reatividade dos complexos do tipo [RuCl2(PPh3)2(amina)], onde a amina = 3,5-dimetilpiperidina (complexo 1) ou piperidina (complexo 2), foi investigada na polimerização via metátese por abertura de anel (ROMP) de norborneno (NBE) e norbornadieno (NBD), na presença de etildiazoacetato (EDA), como fonte de carbeno, em CHCl3. O objetivo foi observar a combinação dos efeitos eletrônicos e estéricos da PPh3 com uma amina como ligantes ancilares na reatividade em ROMP. Os resultados com o complexo 1 foram comparados aos resultados obtidos com o complexo 2. Na ROMP de NBE, o complexo 1 proporcionou um rendimento de 70% de poliNBE (Mn = 8,3 &times; 104 g/mol; IPD = 2,03), enquanto o complexo 2 promoveu reação quantitativa (Mn = 1,2 x 105 g/mol; IPD = 1,90) com razões molares [NBE]/[Ru] = 5000 e [EDA]/[Ru] = 48 e 1,1 &micro;mol de Ru por 5 min a 25 &deg;C. Os poliNBEs apresentaram um &sigma;c = 0,38, determinado por RMN de 13C{1H} e uma Tg = 37 &deg;C, determinada através das análises de DSC e DMTA. Na ROMP de NBD com o complexo 1 obteve-se rendimento quantitativo, com IPD = 2,62 com razão molar [NBD]/[Ru] = 5000 por 20 min a 25 &deg;C, enquanto que a reação com o complexo 2 resultou em um rendimento de 55%, com IPD = 2,16 nas mesmas condições. Concluiu-se que a presença dos dois grupos metila no anel piperidina no complexo 1 proporcionou um aumento no período de indução para produzir a espécie metal carbeno, o que justifica os menores rendimentos na ROMP de NBE quando comparado com o complexo 2. No entanto, o maior sinergismo eletrônico amina&rarr;Ru&rarr;monômero contribuiu para uma melhor ativação de olefinas mais difíceis de serem polimerizadas como o NBD, como ocorre no caso com o complexo 1.<br />Poli[NBE]-co-[NBD] foram obtidos via ROMP com os complexos 1 e 2 como iniciadores. As reações de copolimerização foram realizadas utilizando uma quantidade fixa de NBE ([NBE]/[Ru] = 5000) com diferentes concentrações de NBD ([NBD]/[Ru] = 500, 1000, 1500 e 2000) em CHCl3, iniciadas com EDA à temperatura ambiente. A presença de NBD nas cadeias de poliNBE foi caracterizada por RMN de 1H e de 13C{1H} para todos os casos onde a quantidade de NBD foi variada, suportando a formação de poli[NBD]-co-[NBD]. Considerando que a microestrutura do poli[NBD]-co-[NBD] não foi influenciada pela quantidade de NBD nem pelo tipo de iniciador, os valores de Mn e de IPD foram otimizados quando se aumentou a concentração de NBD no meio reacional. O aumento da quantidade de NBD propiciou um aumento na densidade de entrecruzamento resultando em um aumento na Tg e no módulo de armazenamento (E\'). A análise morfológica da superfície dos polímeros por MEV mostrou uma estrutura altamente porosa para os poliNBEs sintetizados e indicou uma diminuição no tamanho desses poros para os poli[NBD]-co-[NBD] isolados, alcançando uma superfície totalmente lisa com a composição [NBE]5000[NBD]2000, para ambos os catalisadores. / The reactivity of the new complex [RuCl2(PPh3)2(3,5-Me2piperidine)], complex 1, was investigated for ring opening metathesis polymerization (ROMP) of norbornene (NBE) and norbornadiene (NBD) in the presence of ethyl diazoacetate (EDA) in CHCl3. The aim is to observe the combination of PPh3 and an amine as ancillary ligands in the reactivity for ROMP. Thus, the results with the complex 1 were compared to the results obtained when the amine is piperidine (complex 2). Reaction with the complex 1 provides 70% yield of isolated polyNBE (Mn = 8.3 &times; 104 g/mol; PDI = 2.03), whereas the complex 2 provides quantitative reaction (Mn = 1.2 &times; 105 g/mol; PDI = 1.90) with [NBE]/[Ru] = 5000, [EDA]/[Ru] = 48 and 1.1 &micro;mol of Ru for 5 min at 25 &deg;C. The resulting polymers showed a &sigma;c = 0,38, determined by 13C NMR, and Tg =37 &deg;C, determined by DSC and DMTA. For ROMP of NBD, the complex 1 showed quantitative yield with PDI = 2.62 when [NBD]/[Ru] = 5000 for 20 min at 25 &deg;C, whereas the reaction with the complex 2 reached 55% with PDI = 2.16 in the same conditions. It is concluded that the presence of the two methyl groups in the piperidine ring provides an increase in the induction period to produce the Ru-carbene species justifying better polyNBE results with the complex 2, and a greater amine&rarr;Ru&rarr;monomer synergism which contributed to the best activation of olefin with greater difficulty of being polymerized as NBD, as in the case with the complex 1.<br />Copolymers of NBE with NBD were obtained via ROMP with the complexes 1 and 2 as initiators. The copolymerizations reactions were performed using a fixed quantity of NBE ([NBE]/[Ru] = 5000) with different concentrations of NBD ([NBD]/[Ru] = 500, 1000, 1500 and 2000) in CHCl3, initiated with EDA at room temperature. The presence of NBD in the polyNBE chains was characterized by 1H and 13C NMR. Whereas the copolymer microstructure was influenced neither by the NBD quantity nor by the initiator type, the Mn and PDI values were improved when increasing the NBD quantity in the medium. When raising the NBD amount, DMA results indicated increased cross-linking with increasing Tg and E\' storage modulus, as well as the fact that SEM micrographs indicated decreased pore sizes in the porous isolated copolymers.

Thesis advisor: Amir H. Hoveyda / Chapter 1. Exploring Ligand Effects in Ruthenium Dithiolate Carbene Complexes. Ruthenium dithiolate metathesis catalysts discovered in the Hoveyda group have been a valuable addition to the field of olefin metathesis. While the catalyst shows unique selectivity and reactivity, quantifying and mapping key interactions in the catalyst framework to elucidate and explain causes is difficult. We, therefore, decided to use the neutral chelating or monodentate ligand, controlling initiation, as a structural probe. By altering its properties and observing changes in the catalyst, we sought to deepen our understanding of these complexes. We established a trans influence series with over 20 catalysts and correlated the impact on catalyst initiation. Further, we show that in the case of strongly σ-donating and π-accepting ligands such as phosphites and isonitriles, the complex exhibits fluxional behavior. The catalysts ground state is elevated to such a degree that thiolate Ruthenium bonds become labile and rapidly exchange. While Ruthenium dithiolate catalysts were readily applied to metathesis polymerization, their use in the synthesis of small molecules was initially less forthcoming. Specifically, reactions involving terminal olefins lead to rapid catalyst deactivation and only low conversion. We were able to determine that the potential energy stored in the trans-influence between the thiolate ligand and the NHC can be released in a sulfur shift to reactive Ruthenium methylidene species. Since methylidenes are formed by reaction with terminal olefins, use of an excess of internal olefins can prevent their formation. Chapter 2. Harnessing Catalyst Fluxionality in Olefin Metathesis. Depending on its use, material requirements can vary significantly. Materials that can easily be adapted to a given application, for example by varying tensile strength, melting point or solubility, are desirable. Controlling the polymers tacticity (the adjacent stereocenters in a polymer chain) is a straight forward way to achieve just that. Ru dithiolate catalysts should give highly syndiotactic polymers due to their single stereocenter undergoing inversion during every metathesis step. The fluxional nature of the catalyst allows for control of polymer tacticity from 50% (atactic) to ≥95% syndiotacticity by changing monomer concentration. We determined the factors which are responsible for fluxionality and synthesized complexes that give either high or low levels of tacticity over a broader range of monomer concentration. Chapter 3. Harnessing Catalyst Fluxionality in Olefin Metathesis. The importance of fluorine-containing molecules is hard to understate, keeping in mind the surge of new methodologies for their synthesis and the medical breakthroughs they enable. However, efficient and practical syntheses of stereodefined alkenyl fluorides are rare. In this context, we have developed enantioselective boryl allylic substitution of allylic fluorides, which yield enantioenriched γ-alkenyl fluoride substituted allyl boronate esters. The reaction is catalyzed by Cu-based catalysts that are prepared in-situ and delivered as products with high yield and enantioselectivity. Mechanistic inquiry shows the reaction is not a concerted allylic substitution. An intermediate Cu alkyl complex is formed after the Cu boron addition is made to the double bond, which only slowly undergoes β-fluorine elimination in the presence of a Lewis acid. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Transition metals have been used to mediate bioorthogonal reactions within a biological environment. In particular, applications of biocompatible palladium catalysis currently range from biomolecules modification to the in cellulo synthesis or activation of drugs. Here, the scope of palladium-mediated chemistry in living systems has been further extended with the development of a new homogenous palladium catalyst. This water-soluble, biocompatible, and traceable catalysts is based on a palladium-carbene complex coupled to a fluorescent labelled homing peptide for targeted delivery inside cells. This “SMART” catalyst is designed to activate both caged fluorophores and drugs through the cleavage of protecting groups or cross-coupling reactions. A second strategy for targeted delivery of a biocompatible palladium catalysis involves metal nanoparticles loaded onto a heterogeneous solid support. This “modular” catalyst can be implanted in vivo at the desired site of action, e.g. a tumour, and locally activate biomolecules. These two catalytic systems will allow us to selectively activate pro-drugs in vivo, with spatial control, thus minimising the side effects of the treatment on the whole body.