Issue 7, 2023

WOx/ZrOx functionalised periodic mesoporous organosilicas as water-tolerant catalysts for carboxylic acid esterification

Abstract

Catalyst hydrophobicity is an oft-neglected property despite its significance in aqueous phase reactions and those wherein water is a by-product, such as condensation and esterification. Here we synthesise WOx/ZrOx impregnated periodic mesoporous organosilicas (PMOs) of varying organic framework content, through the stepwise substitution of bis(triethoxysilyl)benzene (BTSB) for tetraethyl orthosilicate (TEOS), followed by tungsten and zirconium co-grafting. Incorporation of phenyl groups into the framework of mesoporous SBA-15 silica imparts surface hydrophobicity and tunes the solid acidity, while preserving the textural properties of the parent silica. The resulting WOx/ZrOx/PMO catalysts exhibit excellent turnover frequencies (TOFs) for the esterification of C3–C16 carboxylic acids in methanol at 60 °C, with TOFs inversely proportional to fatty acid chain length. The superior activity and stability (water tolerance up to 50 mol%) of WOx/ZrOx/PMO versus WOx/ZrOx/SBA-15 is attributed to the displacement of water from in-pore active sites, mitigating the reverse ester hydrolysis reaction. Such hydrophobic, solid acid catalysts are anticipated to find widespread application in aqueous phase synthesis, particularly of biorefinery output streams.

Graphical abstract: WOx/ZrOx functionalised periodic mesoporous organosilicas as water-tolerant catalysts for carboxylic acid esterification

Associated articles

Supplementary files

Article information

Article type
Paper
Submitted
14 dec 2022
Accepted
25 feb 2023
First published
27 feb 2023

Sustainable Energy Fuels, 2023,7, 1677-1686

WOx/ZrOx functionalised periodic mesoporous organosilicas as water-tolerant catalysts for carboxylic acid esterification

V. C. dos Santos-Durndell, L. J. Durndell, M. A. Isaacs, A. F. Lee and K. Wilson, Sustainable Energy Fuels, 2023, 7, 1677 DOI: 10.1039/D2SE01724E

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