The preparation of catalysts by the adsorption and subsequent decomposition of volatile metal carbonyl species, namely Mo(CO)6, within zeolites could result in the Mo species being in a more highly dispersed state thoughout the zeolite than can generally be achieved with the conventional wetness impregnation method. The uptake and decomposition of metal carbonyls in various zeolites has been studied thermogravimetrically, using a vacuum microbalance. This gave information on the amount of Mo(CO)6 that can be uptaken into the zeolite pores, the relative amounts remaining during decarbonylation and final weight loadings of Mo within the zeolite. Zeolites tested were HUSY, HBeta, HZSM-5, HMordenite and HMCM-22 of varying Si/Al ratio. Thermal and photo activated decarbonylations of Mo(CO)6, both with and without the presence of O2, gave a range of Mo/zeolite catalysts with tuneable metal weight loading. This could be anywhere between 0 and 15 wt%, depending on zeolite. The as-synthesised and used catalysts were analysed by a range of techniques, such as X-Ray Photoelectron Spectroscopy, IR Spectroscopy, X-ray Diffraction, 27Al Nuclear Magnetic Resonance and High Resolution Transmission Electron Microscopy. The prepared Mo/Zeolite catalysts were assessed for their suitability in the methane dehydroaromatisation reaction and compared to catalysts prepared by the conventional wetness impregnation technique (using an aqueous solution of (NH4)6Mo7O24). Catalysts were tested on a custom built microreactor with online GC analysis. The use of two GC systems (GC-FID and GC-TCD) allowed for the analysis of all major products. Testing was carried out over an 8 hour period using a methane space velocity of 3000 ml g-1 h-1. Reaction profiles were constructed using the carbon balancing method.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:569618 |
| Date | January 2012 |
| Creators | Shepherd, Ashley |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=192269 |
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