The partial oxidation of methanol to formaldehyde with air as oxidant has been studied with supported monometallic and bimetallic catalysts of copper and silver over a range of temperature and contact times. This was done to investigate the influence the bimetallics could possibly have on either the reaction pathways and/or the product(s) selectivity of the oxidation of methanol. Characterisation of these catalysts was performed by nitrogen adsorption and porosity measurements, XRD, and IR spectroscopy of adsorbed methanol and of adsorbed CO. These results indicated no crystalline phases of the loaded metals to be present. CO adsorption showed the presence of small cluster metal atoms on the surface of the catalysts. The reduction peaks from TPR also revealed the presence of partially oxidised and dispersed metal atoms. Infra-red studies of methanol adsorbed on these sample catalysts revealed the presence of intermediate methoxy and formate species which are believed to be formed in the course of the reactions. Results showed the monometallic copper and silver catalyst to be more active than the bimetallics. Although formaldehyde selectivities and yields were generally low, they were highest for the bimetallics supported on the silica catalyst than the monometalics and alumina supported samples. Copper-silver interaction in the bimetallic was proposed to enhance the reduction of the silver that enhanced the selectivity to formaldehyde. In particular under conditions, low conversions of methanol saw highest selectivities to formaldehyde. There was also a pronounced effect of the supports on product distribution and activities with the alumina based samples being more active than the silica supported ones, with the product distributions on the alumina supported significantly showing high yields of DME while the silica showed high yield for methyl formate with COx and CH4 detected in small quantities on all the catalysts within the parameters investigated.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:659064 |
| Date | January 2015 |
| Creators | Leke, Luter |
| 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=227099 |
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