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

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: College of Engineering & Physical Sciences > School of Infrastructure and Sustainable Engineering > Chemical Engineering & Applied Chemistry
College of Engineering & Physical Sciences > Energy and Bioproducts 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
Publication ISSN: 0039-6028
Full Text Link:
Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Special issue
Published Date: 2016-04
Published Online Date: 2015-07-14
Accepted Date: 2015-07-13
Authors: Montero, J.M.
Isaacs, M.A.
Lee, A.F. (ORCID Profile 0000-0002-2153-1391)
Lynam, J.M.
Wilson, K. (ORCID Profile 0000-0003-4873-708X)

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