The aim of this work is to synthesise glycerol carbonate from carbon dioxide (CO2) and glycerol. Two key challenges that were investigated in this work including: (1) thermodynamic limitation of this work and (2) desirability of using crude glycerol as a feedstock. In this work, carboxylation of glycerol is carried out over La2O3 (commercial) and La2O2CO3 catalysts prepared via co-precipitation, sol-gel and hydrothermal methods. These catalysts are characterised using BET, ATR-FTIR, SEM, XRD, TPD-CO2 and TPD-NH3. The carboxylation reaction is thermodynamically limited, therefore a range of dehydrating agents were introduced to improve the glycerol conversion by shifting the reaction equilibrium to the product side. The impact of dehydrating agents on glycerol conversion and glycerol carbonate formation were therefore studied. Reaction conditions were as follows: 6 wt.% La2O3, relative to glycerol, glycerol to dehydrating agent ratio of 22.5:50 mmol, 160 °C and reaction pressure, 45 bar CO2 and reaction time, 18 hours. High selectivity to glycerol carbonate is observed upon the introduction of adiponitrile (17%), followed by benzonitrile (5%), acetonitrile (4%), and no glycerol carbonate was detected upon the introduction of acetic anhydride. Additionally this work demonstrated for the first time the efficacy of lanthanum-based catalysts to synthesise glycerol carbonate via the direct carboxylation of crude glycerol. Crude glycerol employed herein comprises 74% glycerol, 20% of fatty acid methyl esters, 5 wt.% water, 1% methanol, and 7 g/L of sodium methoxide. It was analysed by GG-MS, ICP-MS and Karl Fisher titration technique. The impact of single and multiple impurities are the aspects investigated in this work. The addition of 10 wt.% water inhibited the formation of glycerol carbonate while blending of glycerol and methanol (80:20 mol%) increased the selectivity to glycerol carbonate to 22%. Only 4% selectivity to glycerol carbonate over La2O3-C was observed in the presence of multiple impurities including methanol, fatty acid methyl ester and sodium methoxide. As a result, modification of La2O3-C catalyst is crucial. Introduction of ZrO2/La2O2CO3/Ga2O3 greatly improved the selectivity to glycerol carbonate (21%); while a selectivity of 5% to glycerol carbonate observed for the direct carboxylation of crude glycerol.

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Changes in pipe flow capacity with time have been reported to be caused by biofilm formation, sediment accumulation and pipe deterioration. Biofilm has been demonstrated to cause increasing hydraulic roughness in natural water flows thus changing the hydraulic properties of the system. However, little work has been done in sewer pipes with heavily polluted wastewater. Sediment accumulation, deposition and erosion processes in sewers have also been reported to be influenced by microbial activity. The thesis reports on the development of a novel method for investigating the influence of wastewater-grown biofilm on pipe flow characteristics and bed sediment stability. This work presents systematic laboratory studies of the biofilm growth under different conditions, pipe flow characterisation at different hydraulic configurations, deposit characteristics for different consolidation periods, with changes of organic matter concentration being monitored for all tests. All laboratory tests were conducted using wastewater. The results obtained indicate that biofilm growth changes flow behaviour in pipes by decreasing flow depth, thus decreasing pipe hydraulic roughness, and increasing average flow velocity. This finding depends on the level and character of biofilm growth conditions in the pipe, as different characteristics of biofilm were obtained at different conditions. For sediment deposits, biofilm growth was observed to increase bed stability with longer consolidation phase, thus reducing bed erosion at higher shear stress. These results vary with the duration and character of the consolidation phase of the sediment bed. The findings obtained provided a better understanding of the role of biofilm in sewer pipes and may contribute to the development of more accurate modelling of pipe flow and sediment accumulation and transport processes in sewers.

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It is a global challenge to develop green, sustainable power source for modern portable devices, and stationary power generation. Energy storage systems (ESS) can improve the stability and quality of the power grid. Moreover, ESS can be used for peak shaving, integration viable renewable sources to the electricity network. Several ESSs technologies are existing, electrical, thermal, mechanical, and electrochemical storage technologies. This thesis proposes the potential of iron-based electrode batteries such as Nickel-Iron (NiFe) batteries to be implemented for large-scale grid power. This proposal applies to other types of iron-based electrode rechargeable batteries. Iron-based electrode batteries such as Ni-Fe batteries are particularly attractive and compelling to utilise the energy generated from renewable resources. NiFe battery clearly stood out in view of their cost-effective, robust, and eco-friendly materials. Numerous problems have hindered their developments. Those limitations are poor discharge capability and charge efficiency. In fact, the performance of these batteries is drastically reduced by the parasitic evolution of hydrogen. The key is to develop electrode/electrolyte electroactive materials as additives to improve the performance of the battery. This approach has been successful in many rechargeable batteries. In this thesis, investigation of several electrode/electrolyte additives for advanced NiFe batteries is conducted. In this, an effort is made to improve the performance of the NiFe battery by including different electrode and electrolyte additives to suppress the hydrogen evolution (HER) despite the fact that the addition of various percentages of Bi2S3, FeS, K2S, CuSO4 or other sulfide elements to the electrode and electrolyte is a very effective method of suppressing the HER. In this study, paste-type and hot-pressed types electrode samples were used to produce the electrode samples. Galvanostatic charge/discharge cycling, and cyclic voltammetry were used to investigate the electrochemical properties of the electrode samples. The prepared and cycled electrode samples were characterised a variety of physical techniques including X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It has been found in this study that, the presence of iron sulfide in the electrode has a real incidence on increasing the reversibility and performance of the electrode samples than using copper alone. Therefore, this improves the overall performance of NiFe batteries; however, due to the fact that we have used commercial grade reactants and materials, this technology definitely has the potential to be further developed in the long run and could provide a cost-effective solution to large-scale energy storage.

There is a growing awareness of the need for fundamental and applied research in energy storage and conversion due to the global climate issue with energy sources, environmental and human health challenges. In this work, development of a new synthesis route for catalysts, physicochemical and electrochemical research is reported for direct formic acid fuel cells. The synthesis method is based on the sodium borohydride reduction of (Pd2+, Cu2+, Au3+) precursor, stabilised by polyvinylpyrrolidone for the preparation of a highly stable catalysts with, well-controlled particle size distribution. The surface and bulk properties of the catalysts were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and electrochemically by cyclic voltammetry and chronoamperometry. The results obtained for Pd-C showed that a uniform XRD estimated the size distribution in a narrow particle size range with an average size of 1.4 ± 0.11 nm. Electrochemical studies for formic acid electrooxidation reveals that Pd-CH3BO3 + NH4F(21wt.%) presents superior catalytic activity (over 44 %) than that of the Pd-CPVP(43.5wt.%) synthesis route. For an equivalent electrode paste, Pd-CPVP(43.5wt.%) exhibited a greater electrochemical surface area (ECSA) than Pd-CPVP(43.5wt.%) but achieved a lower utilisation of palladium. The electrooxidation of the catalyst shows three times higher activity for formic acid oxidation than commercial gold nanoparticles dispersed on the carbon support. The enhanced catalytic performance is attributed to the electronic synergistic effect of copper and the specific gold structure promoting oxidation of adsorbed intermediate species. Overall, these findings have significant implications for practical direct formic acid fuel cells (DFAFCs) technology by the controlled Au-shell Cu-core anode catalysts application. Overall, palladium catalysts demonstrated better electrocatalytic activities for formic oxidation than Au and gold copper catalysts. This work is part of the initial stages of the effort to develop a low-cost gold-catalyst for DFAFCs technology.

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