Browsing by Author "Roberts, Stephen"

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    Performance of gold catalysts for low temperature water gas shift
    (2001) Roberts, Stephen; Fletcher, Jack
    The ultimate objective of the study was to investigate the performance of suitably prepared gold catalysts for low temperature water gas shift (LTS) - and more specifically to investigate the performance of these catalysts at temperatures below those traditionally utilised. As opposed to the research undertaken to-date on gold catalysed water gas shift, the reaction was performed, as far as possible, under conditions resembling those found industrially, viz. conditions of temperature, pressure, WHSV and dry feed gas composition typical of those applicable to industrial LTS units. Important to this study was therefore the generation of a comprehensive performance benchmark for the commercially available LTS catalyst, a copper-based material, against which to compare the performance of the gold deposited catalysts. The gold catalysts were prepared by deposition-precipitation, a preparation procedure found to yield nano-sized gold particles, suggested in literature as being crucial for activity, on the metal oxide support. Using this procedure, gold promoted low (copper) and high (iron oxide) temperature shift catalysts and commercial zinc oxide supports were prepared and tested. A wide spectrum of Au particle sizes were prepared on the supports, ranging from approximately 3-500 nm. The gold promoted LTS catalyst was found to exhibit slightly higher activity than the commercially available catalyst at temperatures below the conventional LTS range. It would appear as if gold promotion is advantageous to the industrial catalyst and could impact greatly on LTS catalyst life. Even though substantially less active than the commercial copper catalyst was found, the gold promoted commercial zinc oxide catalyst exhibited significantly higher activity than that previously quoted in literature and better performance than the iron oxide supported catalysts of this study. Consequently, the Au/ZnO system exhibits good potential for further developments in terms of water gas shift conversion.
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    Platinum group metals catalyzed steam methane reforming via micro-channel reactor
    (2014) Zhou, Yi; Fletcher, Jack; Roberts, Stephen
    Steam methane reforming is a well-established industrial process used for generating hydrogen and synthesis gas. By performing this reaction in micro-channel reactors it is possible to take advantage of increased heat and mass transfer rates, allowing equipment size and residence times to be decreased by an order of magnitude which, in turn, leads to the possible utilisation of small scale steam reformers for portable fuel cell power systems. In this study, two commercial steam reforming catalysts, namely catalysts YR and XR, and a single in-house synthesised Rh/Al2O3 catalyst were studied in both packed bed and microchannel reactor configurations. All these catalysts exhibited stable activity in the packed bed reactor experiments.