Direct synthesis of hydrogen peroxide in water at ambient temperature

The direct synthesis of hydrogen peroxide (H2O2) from hydrogen and oxygen has been studied using an Au–Pd/TiO2 catalyst. The aim of this study is to understand the balance of synthesis and sequential degradation reactions using an aqueous, stabilizer-free solvent at ambient temperature. The effects of the reaction conditions on the productivity of H2O2 formation and the undesirable hydrogenation and decomposition reactions are investigated. Reaction temperature, solvent composition and reaction time have been studied and indicate that when using water as the solvent the H2O2 decomposition reaction is the predominant degradation pathway, which provides new challenges for catalyst design, which has previously focused on minimizing the subsequent hydrogenation reaction. This is of importance for the application of this catalytic approach for water purification

Acetylene hydrochlorination using Au / Carbon: a journey towards single site catalysis

The replacement of mercuric chloride in the production of vinyl chloride monomer, a precursor to PVC, would greatly reduce the environmental impact of this large scale industrial process. The validation of single Au cations supported on carbon as the best catalyst for this reaction at an industrial scale has resulted from nearly 35 years of research. In this feature article we review the development of this catalyst system and address the limitations of a range of characterisation techniques used previously which may induce damage to the fresh catalyst. Following our latest findings using X-ray absorption spectroscopy, we show that under operating conditions the catalyst is atomically dispersed and can be classed as a single site catalyst, we give a perspective on future directions in single atom catalysis

Identification of single-site gold catalysis in acetylene hydrochlorination

There remains considerable debate over the active form of gold under operating conditions of a recently validated gold catalyst for acetylene hydrochlorination. We have performed an in situ x-ray absorption fine structure study of gold/carbon (Au/C) catalysts under acetylene hydrochlorination reaction conditions and show that highly active catalysts comprise single-site cationic Au entities whose activity correlates with the ratio of Au(I):Au(III) present. We demonstrate that these Au/C catalysts are supported analogs of single-site homogeneous Au catalysts and propose a mechanism, supported by computational modeling, based on a redox couple of Au(I)-Au(III) species. View Full Tex

Mapping professional lives: the study of the professionalisation of actors and dancers

This thesis explores the under-theorised and under-mapped area of labour supply within the field of artistic production. It agrees with cultural economists that the neoclassical economic theoretical models used to analyse the behaviour of artistic labour supply are inadequate - hampered by a lack of differentiated understanding of the employment modes, transactional roles and internal market relationships of artistic production. This thesis argues that generating a more powerful dynamic model for artistic labour behaviour depends on factoring in variables associated with work mode and functional role. There is evidence to suggest that artists and in particular, actors and dancers who are the subject of this study, mix a variety of functional roles in a mixed portfolio of entrepreneurial and employed work and the "mix" may change at different points in the career. Moreover, artists make apparently "irrational" work choices which cannot be explained by neo-classical economic theory. The thesis uses an empirical study of the working lives of eight performing artists to investigate the ways in which they act and inter-act within the artistic labour market. It finds that rational work choices are made which balance opportunities for accumulating reputation, investing in expertise, creative engagement and the minimising of financial risk

Gas phase stabiliser-free production of hydrogen peroxide using supported gold-palladium catalysts

Hydrogen peroxide synthesis from hydrogen and oxygen in the gas phase is postulated to be a key reaction step in the gas phase epoxidation of propene using gold–titanium silicate catalysts. During this process H2O2 is consumed in a secondary step to oxidise an organic molecule so is typically not observed as a reaction product. We demonstrate that using AuPd nanoparticles, which are known to have high H2O2 synthesis rates in the liquid phase, it is possible to not only oxidise organic molecules in the gas phase but to detect H2O2 for the first time as a reaction product in both a fixed bed reactor and a pulsed Temporal Analysis of Products (TAP) reactor without stabilisers present in the gas feed. This observation opens up possibility of synthesising H2O2 directly using a gas phase reaction

Transition State Theory: Thermodynamics and Kinetics of Ammonia Production via DFT Functional

The thermodynamics and kinetics of a proposed mechanism for ammonia production from nitrogen and hydrogen gas were analyzed by utilizing transition state theory (TST) and density functional theory (DFT). The enthalpy and entropy for the overall reaction were computed via DFT functionals, PBE0 and B3LYP, and were compared to literature values for the thermodynamics of ammonia production. PBE0 produced an enthalpy and entropy for the overall reaction of -81.32 kJ/mol and -197.75 kJ/mol K with percent errors of -11.5 % and -0.18 %, respectively. In comparison, B3LYP produced an enthalpy and entropy for the overall reaction of -1923.02 kJ/mol and -244.25 kJ/mol K with percent errors of 1990 % and 24 %, respectively. Therefore, the PBE0 functional provided a better approximation to the thermodynamics of ammonia production due to the limitations of B3LYP’s empirical approximations. The approximations of B3LYP considers experimental values for specific systems and geometries; however, if the experimental values do not reflect the proposed geometries in the mechanism, it will not be as accurate. Thus, the forward and reverse rate constants of ammonia production were predicted for each step utilizing the DFT functional PBE0

Addressing stability challenges of using bimetallic electrocatalysts: the case of gold?palladium nanoalloys

Bimetallic catalysts are known to often provide enhanced activity compared to pure metals, due to their electronic, geometric and ensemble effects. However, applied catalytic reaction conditions may induce restructuring, metal diffusion and dealloying. This gives rise to a drastic change in surface composition, thus limiting the application of bimetallic catalysts in real systems. Here, we report a study on dealloying using an AuPd bimetallic nanocatalyst (1 : 1 molar ratio) as a model system. The changes in surface composition over time are monitored in situ by cyclic voltammetry, and dissolution is studied in parallel using online inductively coupled plasma mass spectrometry (ICP-MS). It is demonstrated how experimental conditions such as different acidic media (0.1 M HClO4 and H2SO4), different gases (Ar and O-2), upper potential limit and scan rate significantly affect the partial dissolution rates and consequently the surface composition. The understanding of these alterations is crucial for the determination of fundamental catalyst activity, and plays an essential role for real applications, where long-term stability is a key parameter. In particular, the findings can be utilized for the development of catalysts with enhanced activity and/or selectivity

Population and hierarchy of active species in gold iron oxide catalysts for carbon monoxide oxidation

The identity of active species in supported gold catalysts for low temperature carbon monoxide oxidation remains an unsettled debate. With large amounts of experimental evidence supporting theories of either gold nanoparticles or sub-nm gold species being active, it was recently proposed that a size-dependent activity hierarchy should exist. Here we study the diverging catalytic behaviours after heat treatment of Au/FeOx materials prepared via co-precipitation and deposition precipitation methods. After ruling out any support effects, the gold particle size distributions in different catalysts are quantitatively studied using aberration corrected scanning transmission electron microscopy (STEM). A counting protocol is developed to reveal the true particle size distribution from HAADF-STEM images, which reliably includes all the gold species present. Correlation of the populations of the various gold species present with catalysis results demonstrate that a size-dependent activity hierarchy must exist in the Au/FeOx catalyst

Towards a dance technique for the secondary school

In recent years the approach to dance in education has undergone considerable change, generating a need to reappraise the role of technique within the educational context. In this thesis it is argued: (1) that when dance is taught as an art form, with a contribution to make to aesthetic education, greater attention must be paid to the technical aspect of performance; (2) that such technical aspects are best taught through the vehicle of an Educational Dance Technique rather than a professional training technique. It is further argued that an educational dance technique would act: (1) as a practical basis for the teaching of performance skills; (2) as a conceptual basis for the comparison of the style characteristics of theatre dance techniques. A core of basic performance skills is identified and proposals are made for teaching strategies appropriate to the eleven to fourteen age range and the fourteen to eighteen age range. Selected techniques, relevant to the major Western Theatre Dance Genres, are examined in order to elicit their style characteristics in terms of action vocabulary and spatial and dynamic qualities. These characteristics are then summarised and appropriate teaching strategies are proposed

Study to determine the rate of kill of anti-leishmanial drugs using a novel bioluminescence-based assay

Leishmaniasis is a neglected tropical disease associated with poverty, deprived socio-economic settings and population displacement, primarily due to conflict. The causative agent are species of Leishmania parasites that are transmitted by sand flies. It is a disease that affects millions every year and manifests into three primary forms; cutaneous, mucocutaneous and visceral leishmaniasis. Each of these forms are extremely debilitating to the everyday life of those living with leishmaniasis. The current drugs used are re-purposed treatments that are far from ideal. Emerging reports of resistance, poor patient cooperation as a result of long treatment regimens and highly toxic side effects are indicative of essential improvements needed.This thesis focuses on using a transgenic Leishmania cell line in a novel bioluminescence-based assay to determine the rate of kill of four current anti-leishmanial drugs: amphotericin B, miltefosine, pentamidine and potassium antimonyl tartrate. This axenic in vitro assay is studied to address the pharmacodynamic gap in the early drug discovery process and to evaluate the use of a novel technique and its potential in the development of more dynamic and predictive assays. At 3-fold the EC50 concentration, amphotericin B had completely eliminated all viable parasites within 4 hours, demonstrating that it is a fast-acting drug. Miltefosine on the other hand, failed to reduce total parasite viability after 72-hour exposure and we therefore characterised miltefosine as slow-acting. Pentamidine and potassium antimonyl tartrate exhibited an intermediate rate of kill, reaching maximal effect on parasite growth within 72 hours at 9 x the EC50. The bioluminescence-based assay provides a dynamic reporter for parasite viability and exciting potential for fast, sensitive results in early drug screening as shown by the ability to quickly discriminate between fast- and slow- acting compounds. Addressing and identifying this research gap can aid with treatment regimens and dosage improvements of current and novel drug treatments for leishmaniasis