In this thesis the direct synthesis of hydrogen peroxide from hydrogen and oxygen using gold-palladium supported catalysts is described. The direct route presents a greener and sustainable alternative to the current industrial manufacture process. This work aims to meet industrial requirements set by Solvay® which would make the direct process industrially viable. The drawback preventing the requirements being met is the reaction of hydrogen and oxygen over a catalyst can yield water as well as hydrogen peroxide. Once H2O2 is formed, it can be consumed by either reduction or decomposition. Thus, the rates of the subsequent reactions must be minimized to increase the selectivity and therefore H2O2 concentration to a desirable level. Aspects of the catalyst design and reaction variables have been studied over three results chapters. Firstly, the thermal treatment conditions have been altered, ultimately producing a catalyst with no activity to the H2O2 consumption under standard conditions. Switching off H2O2 hydrogenation was concluded to be due to an increase in Pd2+, isolating active Pd0 species. Secondly, active catalysts to both the synthesis and hydrogenation of H2O2 have been produced with no halide; the addition of halide has been shown to decrease hydrogenation activity while maintaining synthesis activity. Finally, a biphasic solvent system and a constant flow of gases through the reaction medium have been examined in order to produce higher H2O2 concentrations. In the former case H2O2 is extracted in-situ from an immiscible organic phase. The production of a 3 wt% H2O2 solution highlights the potential of such a system. In the latter case a semi-continuous flow reactor is utilised increasing the H2O2 concentration up to ca. 1 wt% (from ca. 0.2 wt%). The reactor allowed H2 selectivity and H2O concentration to be measured as a function of time, thus providing greater insight into catalyst activity.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:573624 |
| Date | January 2013 |
| Creators | Shaw, Greg |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/47738/ |
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