Methods of preparation of an inorganic composite membrane and the performance of the membranes obtained have been investigated in this work. The membranes obtained were microporous silica coated y/alumina and dense palladium coated oc- alumina membranes. The preparations of the membranes have been carried out by the dip coating technique and electroless plating method respectively. Characterization of the membranes obtained with single gas permeation measurements at high temperature and various pressures were accomplished. The performance of both membranes has been examined for methane steam reforming on a commercial nickel/alumina catalyst (ICI 57-4). A simulation study on methane steam reforming for both conventional and membrane reactor has been completed to examine the performance of these membrane reactors. For the dip coating method, a microporous silica/y-alumina membrane was obtained and single gas permeations for hydrogen and nitrogen at high temperature have been measured. At 700 K the H2/N2 selectivity was 4.63. From the correlation between temperature and the permeation of nitrogen in the silica membrane it could be concluded that the permeation occurs in the transition region, which is controlled by both the Knudsen mechanism and some viscous flow. At a range of temperature between 623- 743 K the pore diameter calculated by hydrogen permeation is 0.57 nm. The effects of temperature on the permeation of the membrane and hydrothermal stability have been investigated. A hydrothermal exposure at around 723 K for more than 720 hours during methane steam reforming does not make any membrane transformation that leads to pore changes. A dense palladium coated a-alumina membrane was prepared by the electroless plating method. The single gas permeation for hydrogen and nitrogen at high 1 O temperature has been measured. At 700 K the HI and N2 flux were 7.96 cm /cm .min and 0.05 cm3/cm2.min respectively and the selectivity of H2/N2 was 175.03. The pressure dependence of the tfe flux for the Pd membrane was found to be to the power of 0.5, which is the theoretical value. The Fb diffusion through the metal membrane is activated by temperature and can be described by an Arrhenius equation. The activation energy (Ea) is 17.94 kJ/mol for the temperature range of 673-823 K. Both membranes were studied for methane steam reforming by employing them as membrane reactors. The steam reforming focused on the improvement effects of the membrane on the conversion of methane. The effects of pressure, methane feed flow rate and ratio of steam/methane, as well as sweep gas on reactions have been investigated experimentally under conditions of no diffusion limitation. The influence of the membrane with a hydrogen permeable wall on the conversion of methane has also been simulated for methane steam reforming in a tubular catalytic reactor. The effects of the main variables as applied in the experiments of the methane steam reforming have been investigated in the simulation study either. The results of the simulation have been compared to the results of the experimental works. The general behavior is similar for both silica and palladium membrane reactors, i.e.: by selectively removing one of the products from the reaction mixture, the methane conversion can be improved to values higher than the thermodynamic equilibrium composition. From these results, it was concluded that in line with the permeation studies, the performance of the palladium composite membrane was far superior to that of the silica membrane for the steam reforming of methane.

No description available.

Organic synthesis often requires one functional group of a bifunctionalised compound to be rendered temporarily inert to allow the selective reaction of another moiety. While protecting groups are used to remove the problem of the functional group incompatibility, they also raise other issues such as increasing the length of the synthetic pathway (by at least two steps – protection and deprotection), generally leading to an increase in cost and a decrease in yield. The protecting group is often selected based upon the deprotection conditions, leading to the requirement for orthogonal protecting groups. Crown ethers are commonly associated with the complexation of metal ions, but the 18-crown-6 species also readily bind ammonium ions with complexation occurring via hydrogen bonding. As discussed in Chapter 1, crown ethers have previously been employed for N-protection in this way, to successfully facilitate the reaction of bifunctional compounds, though they have exhibited very little selectivity and reaction control. Isolation of the desired product from the resulting reaction mixture has also proven to be problematic.Over recent years there has been a large increase in the volume of organic protocols conducted in micro and continuous flow reactors. Utilising the high surface to volume ratio obtained under these reaction conditions, greater reaction control of many common and specialised organic syntheses has been reported. Building upon literature precedent, the work herein reports the immobilisation of an 18-crown-6 ether derivativeonto a solid-support and its incorporation into a continuous flow reactor to enable sequestration of the primary amine salt of a bi-functionalised compound. This effectively affords a non-covalent N-protection strategy allowing the selective reaction of the remaining moiety. The desired product is subsequently recovered as the free amine by a simple process of decomplexation using an organic base.

A systematic investigation of the structural stability, evolution and hydrogenstorage properties of Mg-based hydrides was carried out, involving mechanical milling and chemical alloying. The effects of milling on particle size, lattice parameter, microstructure, and phase composition of the powder mixtures were characterised using SEM, X-Ray diffraction and quantitative Rietveld analyses. Mechanical milling was shown to be an effective method of refining the particle size, particularly when MgH2 is involved. The influences of the selected chemical elements, including transition metals, graphite carbon and rare-earth metals, on hydrogen desorption/absorption of various milled mixtures were clearly identified using coupled Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). The as-received MgH2 shows an onset desorption temperature of 420°C. Mechanical milling reduces the onset temperature to 330°C. Chemical alloying, via surface catalysis and/or solid-solutioning, further increases the desorption kinetics and reduces the desorption temperature down to 250°C. The degree of such effect decreases from Ni, Al, Fe, Nb, Ti, to Cu. Further comparison of desorption characteristics of MgH2 mixed and mechanically alloyed with Ni clearly shows that the kinetic improvement and the effective reduction of the desorption temperature is mainly due to a catalytic effect, rather than solid-solutioning of Ni. Although posing little influence on desorption characteristics, graphite improves the absorption behaviour of MgH2. The rare earth metals, Y and Ce, do not seem to influence hydrogen desorption of MgH2 due to the formation of stable hydride phases, but CeO2 in the (MgH2+Ce) mixture provides a beneficial effect on desorption kinetics. Multi-component mixtures of (MgH2+15Fe+5Ce) and (MgH2+Al+Ni+Y+Ce) exhibit relatively fast desorption kinetics and the lowest desorption temperature at about 240°C and 220°C, respectively. Finally, mechanical alloying of the non-stoichiometric compositions of (3MgH2+Fe) and (4MgH2+Fe) effectively generated a new ternary hydride, Mg2FeH6, with a very high yield of about 80wt% from the (3MgH2+Fe) mixture, which is a promising candidate for heat-storage. The research findings laid a clear and valuable foundation for future development of new and cost-effective Mgbased hydrogen storage materials with a high capacity, a low desorption temperature and rapid kinetics.

This thesis is concerned with the development of transannular iodoamination methodology for the synthesis of pyrrolizidine, indolizidine and tropane alkaloids. Chapter 1 introduces the concept of a ‘transannular cyclisation’ and outlines the utility of such cyclisations in the synthesis of a range of [x.y.z]-azabicyclic alkaloids. Chapter 2 describes the development of a three step lithium amide conjugate addition, ring-closing metathesis and transannular iodoamination protocol for the preparation of the pyrrolizidine scaffold ([3.3.0]-azabicycle). Cyclisation of a hexahydroazocine occurs with concomitant N-debenzylation to give a single diastereoisomer of the corresponding C(7)-iodopyrrolizidine product, which is then elaborated to the known pyrrolizidine, (−)-7a-epi-hyacinthacine A1. Chapter 3 delineates an extension of the methodology described in Chapter 2, and an investigation into accessing alternate diastereoisomeric pyrrolizidine scaffolds via the transannular iodoamination process. These studies culminate in the synthesis of two pyrrolizidine alkaloids, (−)-hyacinthacine A1 and (−)-hyacinthacine A2. Chapter 4 details investigations into the further elaboration of the C(7)-iodopyrrolizidine scaffold synthesised in Chapter 2. A nucleophilic displacement reaction with azide leads to the synthesis of novel 7-deoxy-7-aminoalexine analogues, whilst radical-mediated substitution of the iodide by oxygen allows the synthesis and isolation of the pyrrolizidine alkaloid (−)-1-epi-alexine. Chapter 5 outlines the development of the transannular iodoamination reaction to facilitate the synthesis of the tropane architecture ([3.2.1]-azabicycle). A tandem lithium amide conjugate addition and aldol reaction sequence is followed by ring-closing metathesis to give the required aminocycloheptene. Subsequent treatment with iodine results in transannular cyclisation to give a single iodotropane product which, following elaboration culminates in the synthesis of (+)-pseudococaine. Chapter 6 contains full experimental procedures and characterisation data for all compounds synthesised in Chapters 2, 3, 4 and 5.