Can surface energy measurements predict the impact of catalyst hydrophobicity upon fatty acid esterification over sulfonic acid functionalised periodic mesoporous organosilicas?

Cyril Pirez, Adam F. Lee, Christopher Jones, Karen Wilson

Research output: Contribution to journalSpecial issue

Abstract

Sulfonic acid functionalised periodic mesoporous organosilicas (PrSO3 H-PMOs) with tunable hydrophobicity were synthesised via a surfactant-templating route, and characterised by porosimetry, TEM, XRD, XPS, inverse gas chromatography (IGC) and ammonia pulse chemisorption. IGC reveals that incorporation of ethyl or benzyl moieties into a mesoporous SBA-15 silica framework significantly increases the non-specific dispersive surface energy of adsorption for alkane adsorption, while decreasing the free energy of adsorption of methanol, reflecting increased surface hydrophobicity. The non-specific dispersive surface energy of adsorption of PMO-SO3H materials is strongly correlated with their activity towards palmitic acid esterification with methanol, demonstrating the power of IGC as an analytical tool for identifying promising solid acid catalysts for the esterification of free fatty acids. A new parameter [-ΔGCNP-P], defined as the per carbon difference in Gibbs free energy of adsorption between alkane and polar probe molecules, provides a simple predictor of surface hydrophobicity and corresponding catalyst activity in fatty acid esterification.

Original languageEnglish
Pages (from-to)167-173
Number of pages7
JournalCatalysis Today
Volume234
Early online date23 Feb 2014
DOIs
Publication statusPublished - 1 Oct 2014
Event2nd international congress on Catalysis for Biorefineries - Dalian, China
Duration: 22 Sep 201325 Sep 2013

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Bibliographical note

Funding: EPSRC (EP/K000616/1, EP/F063423/1 and EP/G007594/3) and a Leadership Fellowship; and the Royal Society for the award of an Industry Fellowship.

Keywords

  • solid acid
  • free fatty acid esterification
  • periodic mesoporous organic materials
  • inverse gas chromatography
  • hydrophobicity
  • biodiesel

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