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

SURFACE SCIENCE

卷:646

Article

Montero, J. M.²  Isaacs, M. A.¹  Lee, A. F.¹  Lynam, J. M.²  Wilson, K.¹ 

[1] Aston Univ, European Bioenergy Res Inst, Birmingham B4 7ET, W Midlands, England

[2] Univ York, Dept Chem, York YO10 5DD, N Yorkshire, England

关键词: Solid base;    In-situ XPS;    Nanoparticulate MgO;    Methanol;    Ester;    Biodiesel synthesis;   

DOI  :  10.1016/j.susc.2015.07.011

来源: Elsevier

【 摘 要 】

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. (C) 2015 Published by Elsevier B.V.

【 授权许可】

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