Most of the energy produced in the world comes from fossil fuels: coal, oil and gas. Amongst them, coal is the most abundant and widespread fossil fuel in the world. Underground Coal Gasi cation (UCG), an in situ method to extract the calori c value of the coal, has been known for a century but has had very limited implementation throughout the world, mainly due to the availability of cheap oil over that period. It is now gaining relevance in order to unlock vast resources of coal currently not exploitable by conventional mining. However, growing concern on increased levels of carbon dioxide concentration in the atmosphere is pointing out the necessity to reduce the use of fossil fuels. Since alternative sources of energy (e.g. nuclear and renewables) are not in a position to meet the constantly increasing demand in a short term, carbon capture and its geological sequestration (CCS) is considered the best remedial option. An environmental risk assessment framework has been developed for coupling UCG to CCS accounting for bene ts and cost from both global and local perspectives. A UCG site presents signi cant di erences from other typical CCS projected scenarios, most notably the injection of CO2 into a heavily fractured zone. A model which accounts for ow in fractures represented by dual-porosity ow (TOUGH2) is coupled to a geomechanical model (FLAC3D). The impact of this fractured zone in the CO2 injection pressure buildup and stress eld is evaluated. Furthermore the effect of stress-dependent fracture permeability is assessed with the hydro-mechanically i coupled compositional simulator GEM. Simulation results suggest that in such a scenario, CO2 injectivity and dissolution improve though con nement is compromised and commercial injection rates seem unattainable. The e ects of miscibility and relative permeability on pressure buildup implemented in semianalytical solutions are also evaluated. Albeit further research is required, a UCG operation may, therefore, not be able to accommodate the produced CO2 in the gasi ed cavity and its surroundings in a safe and economical fashion. Rigorous studies and management practices are needed to establish the requirements for secure long-term con nement of the carbon dioxide in such scenario.

No description available.

CO₂ photoreduction into fuels has the potential to reduce future dependence on fossil fuels. This work has examined the effects of metal ion doping on the properties and performance of TiO₂ for CO₂ reduction in different photoreactor configurations. Metal (Pd/Rh, Ni, Cu, V, Cr and Co) doped TiO₂ photcatalysts synthesized by the sol-gel method were suspended or immobilized onto monoliths threaded with optical fibers or quartz plates. Doping with Cu, V and Cr facilitated anatase to rutile phase transformation, while Ni and Co doping inhibited transformation to rutile. All the metal atoms were found to be replacing some of the Ti atoms in the cystal lattice of TiO₂ during synthesis, thus causing a shift to longer wavelengths. Metal doping can considerably enhance the photocatalytic activity of TiO₂ for CO₂ reduction to fuels under UV or visible light irradiation when H₂O was used as a reductant. The activities of the best photocatalysts (lwt%Cu-TiO₂ and lwt%Co-TiO₂) were 67 times higher than pure TiO₂. More importantly, the conversion rate, 79.95μmol/g_cath achieved using the quartz plate reactor was near one order of magnitude higher than other reactor configurations due to better accessibility of the catalytic surface to photons and the reactants during photocatalytic reaction.

The aim of this thesis is to develop a robust parametric uncertainty quantification method and a decision making method for a chemical EOR process. The main motivation is that uncertainty is detrimental to the wide scale implementation of chemical EOR. Poor scale-up performance is not in line with the success in laboratory applications. Furthermore, economic uncertainty is also an important factor as low oil prices can deter EOR investment. As an example of chemical EOR we used Surfactant-polymer flooding due to its high potential and complexity. The approach was based on using Value of Flexibility evaluation in order to optimize the surfactant-polymer flooding in the presence of economic and technical uncertainty. This method was inspired by real options theory which provides a framework to value flexibility and captures the effect of uncertainty as the process evolves through time. By doing so, it provides the means to capitalize on the upside opportunities that these uncertainties present or to help mitigate worsening circumstances. In addition, it fulfils a secondary objective to develop a decision making process that combines both technical and economic uncertainty. The Least Squares Monte Carlo (LSM) method was chosen to value flexibility in surfactant-polymer flooding. The algorithm depends on two main components; the stochastic simulation of the input state variables and the dynamic programming approach that produce the optimal policy. The produced optimal policy represents the influence of uncertainty in the time series of the relevant input parameters. Different chemical related parameters were modelled stochastically such as surfactant and polymer adsorption rates and residual oil saturation. Static uncertainty in heterogeneity was incorporated using Gaussian and multiple-point statistics generated grids and dynamic uncertainty in heterogeneity was modelled using upscaling techniques. Economic uncertainties such as the oil price and surfactant and polymer cost were incorporated into the model as well. The results obtained for the initial case studies showed that the method produced higher value compared with static policy scenarios. It showed that by designing flexibility into the implementation of the surfactant-polymer flood, it is possible to create value in the presence of uncertainty. An attempt to enhance the performance of the LSM algorithm was introduced by using the probabilistic collocation method (PCM) to sample the distributions of the technical state input parameters more efficiently, requiring significantly less computational time compared to Monte Carlo sampling. The combined approach was then applied to more complex decisions to demonstrate its scalability. It was found that the LSM algorithm could value flexibility for surfactant-polymer flooding and that it introduces a new approach to highly uncertain problems. However, there are some limitations to the extendibility of the algorithm to more complex higher dimensional problems. The main limitation was observed when using a finer discretization of the decision space because it requires a significant increase in the number of stochastic realization for the results to converge, thus increasing the computational requirement significantly. The contributions of this thesis can be summarized into the following: an attempt to use real options theory to value flexibility in SP flooding processes, the development of an approximate dynamic programming approach to produce optimal policies, the robust quantification of parametric uncertainty for SP flooding using PCM and an attempt to improve the efficiency of the LSM method by coupling it with the PCM code in order to extend its applicability to more complex problems.

Bioalcohols have the potential in the future to become a major renewable fuel and chemical feedstock, replacing fossil fuels. A new homogeneous method for alcohol activation was hypothesised incorporating a low valent, electron rich metal complex, e.g. iridium(l) and rhodium(I), and a hydrogen bonding organocatalyst. Metal complexes with ligands containing thiourea, guanidine or urea groups were therefore synthesised and characterised, with a preference for the hydrogen bonding group to be pendant. The thiourea groups typically coordinated, while the urea groups were generally pendant. Complexation of the guanidine containing ligands showed a variety of complexes with pendant and coordinated guanidine groups. 2D-NOESY spectroscopy was used to establish hydrogen bonding between some of the ligands or complexes, and alcohols.

We propose an alternative method for the sustainable transformation of ethanol to longer-chained alcohols, specifically n-butanol, for use as an advanced biofuel efficient enough to provide an alternative' drop-in' replacement for petrol fuels. Particular attention was made to discovering new catalysts to achieve this transformation, addressing the drawbacks suffered by the first generation catalyst devised within our research group. The first draw back of the first generation catalyst was identified as having intolerance to water build-up during the course of the reaction. This was addressed (chapters 2 and 3) firstly through the screening of water-soluble ruthenium catalysts based on dipyridyl-containing ligands. Optimisation experiments revealed that ruthenium(II) complexes in the presence of N-heterocyclic bidentate ligands and a hydroxide base co-catalyst can successfully couple ethanol to allow unprecedented yields and selectivity to n-butanol to be obtained. These complexes have also shown to remain catalytically active under aqueous conditions, making them ideal candidates for industrial applications. An extensive study into the homogeneity of the catalytic system is reported, indicating that, what may have been anticipated to be homogeneous may in fact possess characteristics of both homogeneous and heterogeneous catalysis. The instability of the first generation catalysts highlighted the second drawback whereby decomposition of the catalysts was often observed due to the harsh reaction conditions. Reported here (chapter 4) is the discovery of a more stable ruthenium-diphosphine catalyst which has shown to be the most active catalyst, to date, toward the coupling of ethanol to higher a1cohols, with unprecedented yields and selectivity to n-butanol achieved. Catalyst loading and catalyst recycling studies were investigated, indicating that catalysts of this type have the greatest potential for the creation of future biofuels. Ruthenium complexes in the presence of higher denticity ligands were studied, highlighting a switch in reaction product from n-butanol to ethyl acetate and 2-butanol.

No description available.

This work in this thesis reports fundamental studies on fuel cell electrocatalysis and membrane stability, and is primarily of relevance to direct ethanol alkaline fuel cells and proton-exchange membranes based on polybenzimidazole (PBI). During the first part of this project, in-situ FTIR spectroscopy was employed to investigate the electrochemical oxidation of ethanol at a polycrystalline Pt electrode in 0.1 M KOH at 25 and 50 oC. Initially, this part of the project was designed to provide a library of IR spectra of intermediates and products to facilitate the study of the electro-oxidation of small organic molecules at novel, non-noble metal anodes. However, the work on Pt has provided some unexpected insights into this area of electrocatalysis, particularly with respect to the role of intermediates bonded through oxygen rather than carbon, as well as of adsorbed CO. Acetate was the only product observed at lower potentials. Above the transition potential, where at least some of the areas of the thin layer in the spectro-electrochemical cell become acidic, acetaldehyde, acetic acid and a small amount of CO2 are produced. The temperature dependence of the production of acetaldehyde and acetic acid strongly suggests that the rate determining step is the removal of the first proton from the initially-adsorbed ethoxide species, and it was tentatively suggested that this is also the rds under alkaline conditions. Ethanol oxidation in alkaline solution at a Pb-modified Pt electrode was also investigated using FTIR. This study provided some very interesting data which support the suggestion that the adsorption mechanism of ethanol is substantially modified in the presence of Pb, with a carbon-bonded intermediate being favoured leading to facile scission of the C-C bond in ethanol. Carbonate formation took place at potentials close to the thermodynamic value and at higher potentials, when Pb was lost to solution, the mechanism of oxidation of ethanol reverts to that found on a normal polycrystalline Pt surface, with the primary product being acetate. During the second part of this project, undoped, cast films of PBI were investigated as a function of humidity using both H2O and D2O, and as a function of temperature up to 100 °C in order to better understand the IR response of this polymer, as well as to provide benchmark data for subsequent studies on acid doped PBI. Marked changes across the mid-IR range were observed during the uptake of water and D2O.

A study of the kinetics of 503 formation has been undertaken in a liquid fuel fired, non-catalytic quartz tube combuster. The effects of excess air, residence time, gas temperature, and steam injection on the level of 503 produced have been investigated. A non-catalytic quartz tube combuster was built with the required safety precautions. Provisions for maintaining near isothermal conditions along the tube and also injecting steam into the combustion chamber were made. An electrically heated temperature controlled chamber evaporated the fuel which was mixed with air and passed through a stainless steel sintered disc and a flat flame was produced just outside the disc. A kinetic study of 503 formation was done with a laminar flame and it was found (a) the excess air, (b) the residence time, (c) the gas temperature all had effects on the formation of 503 in the fluegases. Sulphur trioxide concentration was determi ned by a chemical wet method. The effect of steam injection on the formation of Sulphur trioxide was investigated and shown that steam injection in the flame could provide a method of reducing 503 and hence a reduction of corrosion. The maximum amount of 503 reduction was found to be about 14% when steam was injected at 17.5 mm from the origin of the flame.

The liquid-phase processes occurring during fuel droplet combustion are important in deciding the behaviour of the overall combustion process, especially, for the multicomponent fuel droplets. Hence, understanding these processes is essential for explaining the combustion of the multicomponent fuel droplet. However, the very fast combustion of the too small fuel droplet makes experimental investigation of these processes uneasily affordable. In the present work, a high speed backlighting, and shadowgraph imaging and subsequent image processing leading to quantitative analysis of the multicomponent fuel droplet combustion including liquid-phase dynamics are performed. Two categories of multicomponent fuels – in which diesel is the base fuel – are prepared and utilized. The first category is biodiesel/diesel and bioethanol/diesel blends, while the second category is the water-in-diesel and diesel-in-water emulsions. The portion of the added components is set to 10%, 20%, and 30% of the total mixture volume for all the multicomponent fuel mixtures (blends and emulsions). Specific optical setups are developed in-lab and used for tracking droplet combustion. The first setup is associated with the backlighting imaging with the resulting magnification of the droplet images being 30 times the real size. The second optical setup is used for Schlieren and shadowgraph imaging, with the resulting magnification being 10 times the real size for both techniques. Those magnifications made it possible to visualize the droplet interior at high imaging rates (250, 1000, 10000, and 40000 fps) so that tracking of the droplet liquid-phase processes is easily performed. Using the aforementioned optical setups, spatial and temporal tracking of nucleation, bubble generation, internal circulation, puffing, microexplosion, and secondary atomization during the combustion of the isolated multicomponent fuel droplets are performed. This offered the privilege of full sequential tracking of droplet secondary atomization from initiation to sub-droplet generation. Emulsion fuel droplet fragmentation has also been tracked and visualized using Schlieren imaging. The effect of water content of the emulsion on the intensity of the resulting droplet explosion wave has also been evaluated. Spatial and temporal tracking of the sub-droplets generated by secondary atomization, and their subsequent combustion, in addition to their overall lifetimes have also been performed. Accordingly, a comparison of the burning rate constant between the parent droplet and the resulting sub-droplets is carried out. Specifically written and developed algorithms are used for image processing and feature extraction purposes. These algorithms are executed using Matlab. Using these algorithms, droplet projected area, perimeter, equivalent diameter, flame height and width, and sub-droplet generation rate have been temporally evaluated. The high speed magnified imaging and subsequent image processing revealed that the rate of droplet secondary atomization is higher than those obtained by relatively low imaging rate. Additionally, it is shown that during a large portion of its entire lifetime, the droplet geometry has been affected by combustion significantly. The combustion of two-interacting multicomponent fuel droplets at different spacing distances has also been investigated. The liquid-phase processes inside both droplets have been conceived. The effect of secondary atomization from one droplet on the other neighbouring droplet has also been studied. The burning rate constants evaluated for the interacting fuel droplets are found to have the same trends as the isolated droplet combustion. However, the ratio of the droplet burning rate constant of the interactive droplet combustion to that of the isolated droplet combustion is higher than unity. The nucleation rate within the interacting fuel droplets is also found to be higher than that within the corresponding isolated fuel droplets.