The surface chemistry of nanocrystalline MgO catalysts for FAME production:an in situ XPS study of H2O, CH3OH and CH3OAc adsorption

Montero, J.M., Isaacs, M.A., Lee, A.F., Lynam, J.M. and Wilson, K. (2016). The surface chemistry of nanocrystalline MgO catalysts for FAME production:an in situ XPS study of H2O, CH3OH and CH3OAc adsorption. Surface science, 646 , pp. 170-178.

Abstract

An in situ XPS study of water, methanol and methyl acetate adsorption over as-synthesised and calcined MgO nanocatalysts is reported with a view to gaining insight into the surface adsorption of key components relevant to fatty acid methyl esters (biodiesel) production during the transesterification of triglycerides with methanol. High temperature calcined NanoMgO-700 adsorbed all three species more readily than the parent material due to the higher density of electron-rich (111) and (110) facets exposed over the larger crystallites. Water and methanol chemisorb over the NanoMgO-700 through the conversion of surface O2 − sites to OH− and coincident creation of Mg-OH or Mg-OCH3 moieties respectively. A model is proposed in which the dissociative chemisorption of methanol occurs preferentially over defect and edge sites of NanoMgO-700, with higher methanol coverages resulting in physisorption over weakly basic (100) facets. Methyl acetate undergoes more complex surface chemistry over NanoMgO-700, with C–H dissociation and ester cleavage forming surface hydroxyl and acetate species even at extremely low coverages, indicative of preferential adsorption at defects. Comparison of C 1s spectra with spent catalysts from tributyrin transesterification suggest that ester hydrolysis plays a key factor in the deactivation of MgO catalysts for biodiesel production.

Publication DOI: https://doi.org/10.1016/j.susc.2015.07.011
Divisions: Engineering & Applied Sciences > Chemical engineering & applied chemistry
Engineering & Applied Sciences > European Bioenergy Research Institute (EBRI)
Additional Information: -© 2015, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ Funding: EPSRC (EP/F063423/1; EP/K000616/1; and Leadership Fellowship EP/G007594/4); and Royal Society for an Industry Fellowship (IF100206).
Uncontrolled Keywords: biodiesel synthesis,ester,in-situ XPS,methanol,nanoparticulate MgO,solid base,Surfaces and Interfaces,Condensed Matter Physics,Materials Chemistry,Surfaces, Coatings and Films
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
Published Date: 2016-04
Authors: Montero, J.M.
Isaacs, M.A.
Lee, A.F. ( 0000-0002-2153-1391)
Lynam, J.M.
Wilson, K. ( 0000-0003-4873-708X)

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