| Summary: | In this thesis the direct synthesis of hydrogen peroxide (H2O2) from hydrogen and oxygen using gold-palladium supported catalysts was investigated. The direct route represents a greener and sustainable alternative to the current industrial manufacturing process. The main objective of this study was to achieve the industrial requirements of H2O2 yields and selectivity, which would make the direct process industrially viable. In order to reach the required target, two innovative approaches for the direct synthesis of H2O2 were examined. The first part of this thesis was dedicated to the development of a biphasic solvent system comprising an organic alcohol and water. The advantages of this system was highlighted and the effect of reaction variables (such as solvent composition, pressure, reagent ratio, temperature and reaction time) were evaluated using two different catalysts. The identification of two optimum conditions resulted in an important enhancement in the H2O2 yield for the two catalysts examined. By finely tuning the reaction conditions and using two different solvent systems ((i) decan-1-o1-water (ii) diisobutyl carbinol-water) H2O2 concentrations between ~ 0.30 and 28 wt. % were achieved. The second part of this thesis was dedicated to studying the direct gas phase synthesis of H2O2 in a continuous gas flow reactor. Two lab scale flow reactors were designed and built in situ: The first was for studying the direct gas phase synthesis of H2O2 at atmospheric pressure and the second for studying the reaction at pressures above atmospheric. The results demonstrate the direct gas phase synthesis of H2O2 was challenging and the absence of solvent seriously compromises the stability of the H2O2. Despite this, the results demonstrate by using gold-palladium nanoparticles and a mixture of hydrogen and oxygen it is possible to not only oxidise organic molecules in the gas phase but the synthesis rates were high enough to detect H2O2 as a product in a fixed bed gas phase reactor and a temporal analysis of products (TAP) reactor. This observation opens up the possibility of synthesising H2O2 directly in a gas phase reaction.
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