In this research the validity of various computational techniques has been determined and applied the appropriate techniques to investigate and propose a good catalytic system for C-H bond activation and functionalization. Methane being least reactive and major component of natural gas, its activation and conversion to functionalized products is of great scientific and economic interest in pure and applied chemistry. Thus C-H activation followed by C-C/C-X functionalization became crux of the synthesis. DFT (density functional theory) methods are well suited to determine the thermodynamic as well as kinetic factors of a reaction. The obtained results are helpful to industrial catalysis and experimental chemistry with additional information: since C-X (X = halogens) bond cleavage is important in many metal catalyzed organic syntheses, the results obtained in this research helps in determining the selectivity (kinetic or thermodynamic) advantage. When C-P bond activation is considered, results from chapter 3 indicated that C-X activation barrier is lower than C-H activation barrier. The results obtained from DFT calculations not only gave a good support to the experimental results and verified the experimentally demonstrated Ni-atom transfer mechanism from Ni=E (E = CH2, NH, PH) activating complex to ethylene to form three-membered ring products but also validated the application of late transition metal complexes in respective process. Results obtained supported the argument that increase in metal coordination and electronic spin state increases catalytic activity of FeIII-imido complexes. These results not only encouraged the fact that DFT and multi-layer ONIOM methods are good to determine geometry and thermodynamics of meta-stable chemical complexes, but also gave a great support to spectroscopic calculations like NMR and Mossbauer calculations.

Les découvertes de systèmes hydrothermaux marins ont permis de dire qu'ils réunissaient les conditions favorables à l'apparition des premières formes de vie car des concentrations appréciables en N2, CO2, H2S, CH4, C2H6 et C3H8 ainsi que des quantités détectables (10-9 mol) de n-alcanes de poids moléculaire élevé (C16-C29) ont été mesurées dans les fluides hydrothermaux de la ride médio-Atlantique. Les premières formes de vie étaient sans doute des êtres microbiens simples et unicellulaires qui ont pu trouver dans les composés organiques l'énergie nécessaire à leur évolution. Les systèmes hydrothermaux marins peuvent avoir constitués un environnement favorable à l'apparition de la vie car ces systèmes sont caractérisés par des fumeurs noirs et des fumeurs blancs avec un écosystème indépendant de l'énergie solaire où vivent les organismes les plus primitifs trouvés dans les environnements actuels, les hyperthermophiles. Ces arguments sont très importants en ce qui concerne les conditions qui régnaient à l'Archéen. Les systèmes hydrothermaux Archéens sont les seuls environnements où la vie primitive a pu être protégée des impacts des météorites et de la vaporisation partielle de l'océan. Ces systèmes sont compatibles avec l'origine et l'évolution de la vie. Les études expérimentales, sur la synthèse et la stabilité des composés prébiotiques dans des conditions hydrothermales sont couplées aux études théoriques en thermodynamique permises par les travaux de mesure expérimentales. L'origine abiogéniques des composés organiques azotés dans les conditions hydrothermales est primordiale dans l'histoire de la Terre / Hydrothermal Systems discovery involve it gather favorable conditions to act for the appearing of the first living shape, because significant concentrations in N2, CO2, H2S, CH4, C2H6 and C3H8 and detectable quantities (10-9 mol) of heavy weights n-alcanes (C19-C29) were measured in hydrothermal fluids of the mid-Atlantic ridge. The first living shape were without no doubt simple or unicellular microbes being which finding in organic compounds the satisfying energize for their evolution. Hydrothermal systems could have constitute a favorable environment for the appearing of life because these systems are characterized by black smokers and white smokers with an ecosystems independent of solar energize where the most primitives organisms live, found in actual environments, the hyperthermophiles. These arguments are very important concerning the conditions ruling in Archean. The hydrothermal systems of Archean were the only environment where the primitive life was protect of meteoritic impact and partial vaporization of the ocean. These systems are compatible with origin and evolution of life. The experimental study, on the synthesis and stability of prebiotic compounds in hydrothermal conditions are gathered with thermodynamic studies permit by the works of experimental measures. Abiogenic origin of nitrogen organic compounds in hydrothermal conditions is primordial in the history of the Earth

abstract: Limited access to clean water due to natural or municipal disasters, drought, or contaminated wells is driving demand for point-of-use and humanitarian drinking water technologies. Atmospheric water capture (AWC) can provide water off the centralized grid by capturing water vapor in ambient air and condensing it to a liquid. The overarching goal of this dissertation was to define geographic and thermodynamic design boundary conditions for AWC and develop nanotechnology-enabled AWC technologies to produce clean drinking water. Widespread application of AWC is currently limited because water production, energy requirement, best technology, and water quality are not parameterized. I developed a geospatial climatic model for classical passive solar desiccant-driven AWC, where water vapor is adsorbed onto a desiccant bed at night, desorbed by solar heat during the day, and condensed. I concluded passive systems can capture 0.25–8 L/m2/day as a function of material properties and climate, and are limited because they only operate one adsorption-desorption-condensation cycle per day. I developed a thermodynamic model for large-scale AWC systems and concluded that the thermodynamic limit for energy to saturate and condense water vapor can vary up to 2-fold as a function of climate and mode of saturation. Thermodynamic and geospatial models indicate opportunity space to develop AWC technologies for arid regions where solar radiation is abundant. I synthesized photothermal desiccants by optimizing surface loading of carbon black nanoparticles on micron-sized silica gel desiccants (CB-SiO2). Surface temperature of CB-SiO2 increased to 60oC under solar radiation and water vapor desorption rate was 4-fold faster than bare silica. CB-SiO2 could operate >10 AWC cycles per day to produce 2.5 L/m2/day at 40% relative humidity, 3-fold more water than a conventional passive system. Models and bench-scale experiments were paired with pilot-scale experiments operating electrical desiccant and compressor dehumidifiers outdoors in a semi-arid climate to benchmark temporal water production, water quality and energy efficiency. Water quality varied temporally, e.g, dissolved organic carbon concentration was 3 – 12 mg/L in the summer and <1 mg/L in the winter. Collected water from desiccant systems met all Environmental Protection Agency standards, while compressor systems may require further purification for metals and turbidity. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2020

abstract: About 20-50% of industrial processes energy is lost as waste heat in their operations. The thermal hydraulic engine relies on the thermodynamic properties of supercritical carbon dioxide (CO2) to efficiently perform work. Carbon dioxide possesses great properties that makes it a safe working fluid for the engine’s applications. This research aims to preliminarily investigate the actual efficiency which can be obtained through experimental data and compare that to the Carnot or theoretical maximum efficiency. The actual efficiency is investigated through three approaches. However, only the efficiency results from the second method are validated since the other approaches are based on a complete actual cycle which was not achieved for the engine. The efficiency of the thermal hydraulic engine is found to be in the range of 0.5% to 2.2% based on the second method which relies on the boundary work by the piston. The heating and cooling phases of the engine’s operation are viewed on both the T-s (temperature-entropy) and p-v (pressure-volume) diagrams. The Carnot efficiency is also found to be 13.7% from a temperature difference of 46.20C based on the measured experimental data. It is recommended that the thermodynamic cycle and efficiency investigation be repeated using an improved heat exchanger design to reduce energy losses and gains during both the heating and cooling phases. The temperature of CO2 can be measured through direct contact with the thermocouple and pressure measurements can be improved using a digital pressure transducer for the thermodynamic cycle investigation. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2020

To shift from a petroleum-based to a biomass-based economy will require the development not only of biofuels, but also of biorenewable replacements for petroleum-derived chemicals. In this regard, environmentally friendly biomass-derived esters may serve as alternatives to fossil-derived chemicals such as toxic halogenated solvents and glycol ethers. Therefore, esterification of various carboxylic acids that find significant applications in the chemical, pharmaceutical, petrochemical, food, and cosmetic industries has been initiated by the chemical industry. At atmospheric condition, esterification is a reversible reaction limited by the low equilibrium conversion and slow reaction rate, and has recently been performed with excess alcohol to shift the equilibrium conversion. Heterogeneous or homogeneous acid catalysts are used to achieve acceptable reaction rates. The conventional acid-catalyzed process has been extensively developed; but it suffers from problems associated with the generation of side reactions, corrosion of equipment, expensive purification procedures, long reaction times and discharge of acidic wastes. Various attempts on esterification of carboxylic acids with ethanol have previously addressed important issues concerning product distribution, catalyst activity, and kinetics of acid-catalyzed esterification at lower reaction temperatures, but kinetics of uncatalyzed esterification at elevated reaction temperatures are still very limited. It is thus of great interest from a practical viewpoint that more information such as kinetic and thermodynamic parameters are required to develop a possible esterification process without using any catalyst. In this work, therefore, a fundamental study on the uncatalyzed esterification of different aliphatic carboxylic acids with stoichiometric amounts of ethanol was undertaken to examine the possibility of converting the biomass-derived carboxylic acids to ethyl esters and to determine the kinetic and thermodynamic parameters for the uncatalyzed esterification. Experiments were conducted with isothermal batch reactors at temperatures ranging from 298 K to 623 K. A 2nd-order reversible kinetics rate expression was used to fit the experimental data. The thermodynamic and kinetic values estimated were found to vary for different esterification systems studied. The dependence of Keq on temperature for esterification of short-chain and long-chain carboxylic acids varied. Despite the nonlinearity of the Van't Hoff plot for esterification of linoleic acid, the Arrhenius and Eyring plots were linear. Two thermodynamic paths were developed for estimating the equilibrium conversions, and the theoretical values compared well with the experimental results reported in this study. Additional experiments performed to assess the corrosive and catalytic influences of metallic materials on esterification reaction indicated Inconel 625 alloy, nickel wire and stainless steel materials have potential corrosion problems on the uncatalyzed esterification reaction at elevated reaction. However, tantalum and grade 5 titanium materials showed acceptable level of compatibility for similar reaction conditions, and this can encourage the design of a flow reactor system.

Ceramics oxides with mixed ionic and electronic conductivity have received a lot of attention due to their wide range of applications in solid oxide fuel cells, interconnects, gas sensors, and ion transport membranes. However, owing to harsh operating conditions, the choice of proper materials and engineering their properties are still challenging. Perovskite and fluorite structures are two promising structures for ceramic membrane applications. The objective of this research is to explore the stability of lanthanum chromite-based perovskite ((La,Sr)(Cr,Fe)O3-δ) as single phases and dual-phase composites with fluorite phases under fabrication and operating conditions of Oxygen Transport Membranes (OTM). The current research has been categorized into two sections: structural and chemical stability of perovskite phases and dual-phase perovskite/fluorite composites. Also, investigation on both categories has been conducted with two separate approaches: experimental examinations and computational Thermodynamic. In the computational part, independent methods have been considered for the single-phase perovskite and dual-phase perovskite/fluorite composites. In the experimental section, the bulk chemical stability of the dual-phase samples has been examined under controlled oxygen partial pressure p(O2) atmospheres at 1400ᵒC for 10 hours with slow and fast cooling rates. Besides, the phase stability of the perovskite structures as a single-phase has been also examined under OTM fabrication conditions. The results present new phenomena in the chemical stabilities of the materials. They include formations of liquid phases, Sr-segregation, and perovskite phase separations. The correlations between compositions/ temperature/ p(O2) and secondary phases have been investigated to improve the chemical stability and extend the lifetime of the materials. The findings in this thesis enhance the knowledge about the chemical stabilities of OTMs and help to develop more reliable materials for ceramic-based OTMs.

No description available.

The topic of this diploma thesis is a condensing steam turbine with one regulated steam extraction. The first part contents design and balance of heat scheme. The heat scheme is the basis for the main part of this work, which is the thermodynamic design of the turbine with reaction blades. At the end, the characteristics of the turbine are created. Drawing of the turbine section is attached to this thesis.

This master thesis is dealing with application of an artificial neural network for calculating specific volume of steam. There is described type and construction of the needed neural network. The main outcome of this work is an executable programme, which calculates specific volume of steam for given pressure and temperature, using neural nets.

The thesis is focused on designing of backpressure steam turbine to drive the crusher in the sugar factory having the power input of the 2 200 kW. Thermodynamic calculation of two conceptual variations is gradually implemented in the thesis with the aim to determine the steam mass flow through the turbine. In the first version the control stage is selected as an A-wheel and in the second version as a Curtis wheel. The stage part of both versions consists of series action stages. Furthermore, it contains basic design of the gland steam system and the nozzle control system. Both radial and thrust bearings are designed based on the acting forces. The thesis also includes strength calculation of the selected components. The final part deals with comparison and evaluation of the optimal solution. Due to the small difference in rotor weight (m =19,72 kg), and especially for the less steam consumption (M = 4,87 kg/s), the first version can be considered as an optimal solution. This thesis is amended by a mechanical drawing of the turbine cross section on a common frame with a gearbox.