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In recent years, there has been an increasing global interest in carbon dioxide capture and storage (CCS) as an important technology for climate change mitigation. However, improved technologies for the CO2 capture process that could possibly lead CCS to be highly competitive against the renewable energy market, are necessary. The evaluation of a CO2 capture system is often driven by energy demands and in adsorption technology this energy is particularly required for the desorption step. As a result, efficient regeneration systems ensuring multiple re-use of adsorbent materials, while minimizing energy use, are required, in an attempt to replace the conventional PSA (Pressure Swing Adsorption) and TSA (Temperature Swing Adsorption) technologies. This study presents and analyses a relatively new approach for CO2 sorbent regeneration, namely Microwave Swing Adsorption (MSA). The aim of this research is to intensify the CO2 desorption process from solid materials, focusing on improving the regeneration efficiency and kinetics as well as the energy spent during this step. The hypothesis that the direct absorption of energy during microwave heating by the solid adsorbent may enable a fast process with a low purge gas flow rate low desorption temperature resulting in low energy demands, is examined. However, MSA depends on numerous parameters, divided in two main categories, namely process parameters (flue gas composition, desorption temperature, moisture presence, gas flow rate) and material parameters (adsorbent shape and size, porosity, surface modifications, dielectric properties). To this regard, an extensive investigation of the above criteria and their connection with the performance of the MSA system is studied. In terms of the adsorption step, it was found that a switch to higher total flow rates results in an increase in the CO2 adsorption capacity of the GAC. Moreover, moisture presence also enhances the CO2 adsorption, as a result of an increase in the total flow rate and in the adsorption temperature. With regards to the desorption step, it was shown that MSA technology leads to enhanced performance efficiency of the sorbent by ~10%, while preserving its porous structure. Moreover, the regeneration time and the energy consumption were also considerably reduced (30% and 40%, respectively), for MSA compared to TSA.

PART I. HETEROCYCLIC IMINES FROM IMIHODIACETONITRILE. Reaction of N-benzyliminodiacetonitrile with alcoholic ammonia under pressure but best as sodamide in formamide under nitrogen gives the imidine, 4-benzyl-2,6-diiminopiperazine. The imino groups of this compound undergo stepwise displacement reaction with water and hydroxylamine. The hydroxylamine product, 4-benzyl-2,6-dihydroxyiminopiperazine, is also obtained by cyclisation of the bisamidoxime and direct from the dinitrile. The dinitrile with aniline and 2-aminopyridine (as anion) affords 4-benzyl-2-imino-6-phenyliminopiperazine and the 6-(2-pyridyl)-imino analogue, although attempts to prepare these compounds from the imidine were abortive. Iminodiacetonitrile itself with sodamide in formamide gives 2,6-diformyliminopiperazine. Iminodiacetonitrile and its N-acetyl and benzoyl derivatives add hydroxylamine at room temperature giving acyclic bisamidoximes which with aqueous alcoholic hydroxylamine hydrochloride at reflux temperature afford the corresponding 2,6-dihydroxyiminopiperazines which are prepared directly from the dinitriles by refluxing with aqueous alcoholic mixture of hydroxylamine and its hydrochloride. However, tri(cyanomethyl)amine under similar reaction condition yields the acyclic trisamidoxime. Nevertheless, the trinitrile with sodamide in formamide gives the imidine, 2,6-diiminopiperazine-4-acetonitrile, which is hydrolysed by water to 6-imino-2-oxopiperazine-4-acetamide. PART II. PYRAZINE N-OXIDES FROM IMINODIACETONITRILE. Iminodiacetonitrile with hydroxylamine under optimum reaction conditions (which was discovered by experiment) affords 2,6-dihydroxyirninopiperazine with hydroxylamine hydrochloride together with 2-amino-6-hydroxyaminopyrazine l-oxide. The former separates as its insoluble complex and after this has been filtered off, the latter crystallises out from the solution as monohydrate. Catalytic reduction of the latter using Adam's catalyst results in uptake of one molecular equivalent of hydrogen and formation of 2,6-diaminopyrazine 1-oxide. Acetylation at room temperature then gives 2,6-diacetamidopyrazine-1-oxide. Treatment of 2,6-dihydroxyiminopiperazine with 10% palladium-on-charcoal catalyst in boiling o-dichlorobenzene affords 2,6-diaminopyrazine in poor yield, which with acetic-anhydride at room temperature gives 2,6-diacetamidopyrazine and is also obtained by deoxygenation of 2,6-diacetamidopyrazine 1-oxide using sodium dithionite.

Carbon dioxide concentration in the atmosphere is continuously and significantly increasing as a consequence of the combustion of fossil fuels. Due to its abundance, lack of toxicity and relatively low price, CO2 has become an attractive raw material for the synthesis of chemicals and fuels. This work reports initial proof-of-concept studies on the heterogeneous catalytic conversion of CO2 under hydrothermal conditions in the absence of the addition of gas phase H2. Evidence for the feasibility of the transformation of CO2 into higher hydrocarbons and oxygenates over iron-containing minerals comes from studies on the origin of life on Earth, where the hydrothermal conditions present in the primitive oceanic vents were mimicked. This research focused on the investigation of the influence of different reaction parameters involved in the hydrothermal conversion of CO2 using Fe powder as the catalyst. The conditions explored were the CO2:H2O mole ratio, the temperature, the solvent and the presence or absence of air in the system. The optimal parameters using Fe powder after 4 h of reaction time were a temperature of 300 ºC, a CO2:H2O mole ratio of 0.26 and 0.56 g of catalyst. Under these optimal conditions, Fe-based materials, zeolites, carbons and alumina were also screened. Among them, Fe3O4 exhibited the highest CO2 conversion with a value of 13.8 %. Hence, a reaction mechanism was suggested using this catalyst. In all cases, the major liquid product identified was methanol. Other liquid species detected included ethanol, acetone, phenol, heptanal, 2-octanone and C5-C8 cyclic ketones among others. Gas phase products encompassed C1 and C2 hydrocarbons and oxygenates. The feasibility of producing valuable species from CO2 under hydrothermal conditions has been successfully demonstrated. Specifically, the performance of Fe-based materials in this reaction may reinforce the hypothesis of the hydrothermal oceanic vents as a potential system for life to emerge.

Hydrogen is considered both a fuel for the future and an ancient fuel for life. Hydrogenases catalyse the interconversion of molecular hydrogen, H2, and protons, H+. A subgroup of hydrogenases, the membrane bound NiFe hydrogenases (MBH), have been the subject of much research interest. This is firstly due to their possible applications in biotechnology, but also because they have been implicated in the virulence of gut pathogens. The MBH are divided into O2 tolerant and O2 sensitive based on their ability to catalyse H2 oxidation in the presence of O2, and the two classes are both structurally and mechanistically distinct. Understanding these distinctions is important both for technology which aims to achieve more minimal models of enzymes, but also for relating the way different MBH are expressed at different stages of infection. The properties of variants of two O2 tolerant MBH, Escherichia coli Hyd 1 and Salmonella enterica Hyd 5 and one O2 sensitive MBH, E. coli Hyd 2, have been examined with regards to how the properties of specific amino acids achieve control over catalysis and O2 tolerance. Red®/ET® recombination methodology has been applied for the first time to hydrogenases. This methodology allows the rapid generation of hydrogenase knockouts and single site variants in E. coli in addition to the incorporation of polyhistidine tags to enable protein purification. Purified native and variant hydrogenases have been studied with protein film electrochemistry. Hyd 1 and Hyd-5 E73A and H229A variants were shown to have diminished O2 tolerance whilst a Hyd 1 E73Q variant had an increased catalytic bias towards H2 production. It was established that Hyd 1 was expressed during growth in glucose limited minimal media, although no change in growth rate or competitive ability was seen in a Hyd 1 knockout strain.

This research was conducted to investigate the effect of hydrogen sulfide on the performance of single solid oxide fuel cells. A test rig was designed and commissioned to test 5x5 cm2 cells (active area: 4x4 cm2). The test rig consists of a gas blender, a humidifier, a high temperature furnace, fuel and air manifolds and a control/data logging system. The characterisation techniques used in this project, include v-i measurement, EIS and SEM/EDX analysis. The first series of experiments were carried out to investigate the effect of time, hydrogen partial pressure and temperature on the performance of the cells operating on clean fuel. The results showed that the current of lowest resistance is independent of the operating temperature, however, depends on partial pressure of H2 and tends to increase as PH2 rises. The lowest resistance of the cell occurs at almost constant fuel utilization which was equal to 17 % in this research. In the second series of tests, the cells were exposed to a range of H2S concentrations i.e. 50, 100, 150 and 200 ppm. The composition of the fuel mixture was 0.1 nl/min (14.5 %) of H2, 0.567 nl/min (82.5 %) of N2 and 0.020 nl/min (3 %) of H2O (steam). All the contamination tests were carried out at 700 ˚C. The cells were exposed to H2S for 12 hours followed by a recovery period for 24 hours. The results revealed that the voltage drop at the end of the exposure period was similar for all degrees of poisoning. However, the performance at the end of the recovery, was different. The degree of recovery tended to decrease as the concentration of H2S increased. The SEM analysis of samples showed that H2S has caused the anode structure to change. This change occurred at the interface of anode functioning and support layers and was more severe at higher concentrations of H2S. In addition, two contamination models were developed based on the H2S degradation mechanism. The models considered the effects of time and H2S concentration. However, they could not predict the performance of the poisoned cells as the voltage drop at the end of exposure time was independent of the H2S concentration for the tested range.

Mixed ionic-electronic conducting (MIEC) membranes are a promising technology for oxygen separation but they are not commercialised yet due to sealing issue and sensitivity to impurities in feedstock. In this study, La0.6Sr0.4Co0.2Fe0.8O3- (LSCF6428) was successfully sealed for long-term operation of 963 h using a gold-glass-ceramic sealant. The membrane was then tested for air separation in presence of hydrogen sulphide for 100 h and results showed that the impurity caused a drop in oxygen flux to zero within few hours. The flux could not be fully restored after hydrogen sulphide removal and only 6 to 35% was recovered. It was proposed that hydrogen sulphide was adsorbed on the membrane in the form of sulphur and it occupied oxygen vacancies. With time, strontium segregates toward sulphur to form irreversible layer of strontium sulphate. To restore the damaged surface, the membrane was treated by 1% (mol) of hydrogen for 20 h and the recovery improved from 6 to 12%. It was discovered that the poisoning mechanism is a function of oxygen partial pressure and change of partial pressure from 0.21 to 0.01 bar resulted in 90% recovery and this can be used as a strategy to reduce the damage. The next step was to test the membrane for hydrogen production using 1% (mol) of methane and results showed that methane conversion was steady at 33% for 350 h. Methane oxidation was also carried in presence of hydrogen sulphide but it resulted in drop of conversion to 8%. However, the conversion was slowly regenerating with time and it reached a constant value of 15%. This recovery was interpreted by the reaction of methane with hydrogen sulphide or methane decomposition and the membrane acted as a catalyst for these reactions. After hydrogen sulphide removal from the feed, the conversion kept on decreasing and this was linked to the change of membrane properties and therefore the membrane could not provide the sites for methane-oxygen reaction. For better stability under hydrogen sulphide, the membrane was modified by adding a powder of LSCF6428 material over the dense membrane. This dual layer membrane was stable for air separation under hydrogen for 33 h and the flux was only reduced by 5%.

Numerous industrial and academic communities have directed their efforts into developing technologies for reducing the emission of CO2 in the atmosphere. Carbon dioxide capture and storage (CCS) is one of the most promising technologies that can eliminate/reduce global warming, helping the world to move towards a low-carbon society. The process comprises of the separation of CO2 from industrial sources, transport to a storage location and then long-term isolation from the atmosphere. CO2- rich pipelines are a key part of any carbon capture and storage projects. Modelling of these types of pipelines are challenging due to the lack of thermo-physical properties of CO2 in presence of impurities. As these properties, particularly density and viscosity, have a significant impact on the sizing of equipment, therefore, it is crucial to investigate the impact of different impurities on the thermo-physical properties of CO2- rich systems. Densities and viscosities of pure CO2, two CO2 – H2 binary systems (with 5 and with 10 mol% H2), and 6 multi-component mixtures (MIX 1 with 5 mol% impurity, MIX 2 with 10 mol % impurity, MIX 3 with 30 mol % impurity, MIX 4 with 50 mol % impurity, MIX 5 with 4 mol % impurity and MIX 6 with 30 mol % impurity) were measured at pressures ranging from 10 to 1,400 bar (1 to 140 MPa) and six different temperatures, 0, 10, 25, 50, 100, 150 °C (273.15, 283.15, 298.15, 323.15, 373.15 and 423.15 K) in the gas, liquid, and supercritical regions using an Anton Paar densitometer and capillary tube technique for density and viscosity measurements, respectively. The experimental density data then were applied to evaluate the models using CO2 correction volume, Peneloux shift parameter and original equation of states (PR and SRK). Also, the obtained viscosity data were employed to tune the correlative Lohrenz-Bray-Clark (LBC) and CO2-LBC models and to evaluate the predictive models. The predictive models in this work are based on corresponding states (CS) theory models. The “One reference fluid” corresponding states model is based on the approach developed by Pedersen et al. and modified for CO2-rich fluids; the “two reference fluids” corresponding states models are based on the model proposed by Aasberg-Petersen (CS2) and CO2-CS2 models. Two models based on the extended corresponding states (ECS) theory, SUPERTRAP and CO2-SUPERTRAP models were also tested. The densities of 95%CO2-5%H2S and 95%CO2-5%SO2 systems were measured continuously using a high temperature and pressure Vibrating Tube Densitometer (VTD), Anton Paar DMA 512 at pressures up to 400 bar (40 MPa) at five different temperatures, 0, 10, 25, 50 and 80 °C (273.15, 283.15, 298.15, 323.15 and 353.15 K) in the gas, liquid and supercritical regions at Mines Paristech, France. The experimental data then were used to evaluate the new CO2 volume correction model by comparing to the original PR and PR-Peneloux equations of state. A good understanding of vapour-solid / vapour-liquid-solid / liquid-solid equilibrium of CO2 and CO2-mixtures at low temperature is an important issue regarding the safety assessment of CO2 pipelines and the possibility of solid or ‘dry ice’ discharge during an accidental release or rapid decompression. The frost points of some of the above systems were measured using the SETARAM BT 2.15 calorimeter at various pressures.

The rheology of crude oil mixtures at equilibrium with carbon dioxide (CO2) was studied at elevated pressures and temperatures, similar to those found for oil reservoir conditions. The focus of the work presented in this thesis concerns the measurement of the rheological properties of CO2 saturated mixtures of crude oil. The rheology measurements were made using a high-pressure rheometer coupled to a fluid flow system designed and built in this project. The flow system comprised a mixing vessel and fluid flow loop that allowed the test fluid to be brought into equilibrium with CO2 by stirring and circulating through the rheometer measurement geometry under the pressure and temperature required. Measurements were made for three different fluids saturated with CO2: a light crude oil from the Gulf of Mexico (GoM), Zuata heavy crude oil, and an emulsion of Zuata crude oil with deionized water. The rheological measurements for the GoM crude oil were performed at temperatures of 23 °C and 50 °C and pressures from ambient to 220 bar. The CO2 addition did not change the Newtonian behaviour of the light crude oil, but reduced its viscosity until the phase equilibrium points of CO2. Beyond the CO2 phase equilibrium points, the CO2 mixture viscosity increased with increasing CO2 pressure, which was expected when the fluid density increased without change in composition. The experiments using the Zuata heavy crude oil and its dilutions with toluene were done at temperatures from 23 °C to 50 °C and pressures from ambient to 220 bar. The Zuata crude oil was changed from a non-Newtonian fluid to Newtonian by CO2 dissolution. All of its toluene dilutions behaved as a Newtonian fluid, as well as their CO2 saturated mixtures, except for one sample. The exception was a diluted crude oil with 30 wt% toluene, which was found to be shear-thinning when CO2 dissolved into it in a certain pressure range. It is believed that the non-Newtonian behaviour in this diluted crude oil was not caused by asphaltene precipitation but instead by the formation of asphaltene micelles or by the multiphase behaviour with liquid CO2. The viscosity of the heavy crude oil and its dilutions was exponentially reduced by CO2 addition until the CO2 phase equilibrium points, above which the viscosity was increased with CO2 pressure. Furthermore, a view cell system was built to study the phase behaviour of the CO2 saturated mixtures with the GoM crude oil, Zuata crude oil and the toluene dilutions of Zuata crude. When brought to equilibrium with CO2, it was found that the CO2 solubility and the oil rich phase volume were inversely correlated to the mixture viscosity. The Zuata crude oil emulsion was prepared by mixing 50 wt% Zuata heavy crude oil and 50 wt% deionized water using a high-shear mixer. The rheology measurement of the emulsion saturated with CO2 was made at 50 °C and pressures up to 120 bar. The emulsion without dissolved CO2 was found to be slightly shear thinning below a critical shear rate, above which the viscosity jumped to a much lower value. After the viscosity jump the shear thinning effect was still observed. The CO2 dissolution not only reduced the emulsion viscosity at low shear while preserving the shear thinning behaviour, but also increased the critical shear rate at which the viscosity jump occurred. The dissolved CO2 eliminated the shear thinning effect after the viscosity jump. The emulsion viscosity jumped to a lower level than that of the original continuous phase (oil), indicating that the viscosity jump occurred due to phase inversion. However, direct evidence of phase inversion was very difficult to provide. In addition, a new correlation to evaluate Newtonian viscosity of hydrocarbons is proposed. In this correlation the hydrocarbon viscosity can be calculated based on its density. This correlation requires less experimental data to work out the parameters compared to the methods given in the literature. The proposed correlation was tested with pure alkanes, alkane mixtures and gas-saturated hydrocarbons, and the prediction gave a reasonable accuracy.

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