On the influence of Si:Al ratio and hierarchical porosity of FAU zeolites in solid acid catalysed esterification pretreatment of bio-oil

Abstract:
A family of faujasite (FAU) zeolites with different Si:Al ratio, and/or hierarchical porosity introduced via postsynthetic alkaline desilication treatment, have been evaluated as solid acid catalysts for esterification pretreatments of pyrolysis bio-oil components. Acetic acid esterification with aliphatic and aromatic alcohols including methanol, anisyl alcohol, benzyl alcohol, p-cresol and n-butanol was first selected as a model reaction to identify the optimum zeolite properties. Materials were fully characterised using N2 porosimetry, ICP, XRD, XPS, FT-IR, pyridine adsorption, NH3 TPD, In-situ ATR and inverse gas chromatography (IGC). IGC demonstrates that the surface polarity and hence hydrophobicity of FAU decreases with increased Si:Al ratio. Despite possessing a higher acid site loading and acetic acid adsorption capacity, high Al-content FAU possess weaker acidity than more siliceous catalysts. Esterification activity increases with acid strength and decreasing surface polarity following the order FAU30>FAU6>FAU2.6. The introduction of mesoporosity through synthesis of a hierarchical HFAU30 material further enhances esterification activity through improved acid site accessibility and hydrophobicity. Methanol was the most reactive alcohol for esterification, and evaluated with HFAU30 for the pretreatment of a real pyrolysis bio-oil, reducing the acid content by 76% under mild conditions.


Reference:
OSATIASHTIANI, Amin; PUÉRTOLAS, Begoña; OLIVEIRA, Caio César Spíndola; MANAUIL, Jinesh C.; BARBERO, Brunella; ISAACS, Mark; MICHAILOF, Crysoula; HERACLEOUS, Eleni; PÉREZ-RAMíREZ, Javier; LEE, Ada F.; WILSON, Karen. On the influence of Si:Al ratio and hierarchical porosity of FAU zeolites in solid acid catalysed esterification pretreatment of bio-oil. Biomass Conversion and Biorefinery, v.7, p. 1-12, 2017. DOI 10.1007/s13399-017-0254-x.


Article access to the site:
https://link.springer.com/article/10.1007/s13399-017-0254-x

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