Structural studies of high dispersion H3PW12O40/SiO2 solid acid catalysts

Andrew D. Newman, D. Robert Brown, Prem Siril, Adam F. Lee, Karen Wilson

Research output: Contribution to journalArticlepeer-review

Abstract

Highly dispersed H3PW12O40/SiO2 catalysts with loadings between 3.6 and 62.5 wt% have been synthesised and characterised. The formation of a chemically distinct interfacial HPW species is identified by XPS, attributed to pertubation of W atoms within the Keggin cage in direct contact with the SiO2 surface. EXAFS confirms the Keggin unit remains intact for all loadings, while NH3 adsorption calorimetery reveals the acid strength >0.14 monolayers of HPW is loading invariant with initial ΔHads = −164 kJ mol−1. Lower loading catalysts exhibit weaker acidity which is attributed to an inability of highly dispersed clusters to form crystalline water. For reactions involving non-polar hydrocarbons the interfacial species where the accessible tungstate is highest confer the greatest reactivity, while polar chemistry is favoured by higher loadings which can take advantage of the H3PW12O40 pseudo-liquid phase available within supported multilayers.
Original languageEnglish
Pages (from-to)2893-2902
Number of pages10
JournalPhysical Chemistry Chemical Physics
Volume8
Issue number24
Early online date22 May 2006
DOIs
Publication statusPublished - 2006

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