Heteropoly compounds as catalysts for hydrogenation of propanoic acid

Benaissa, H., Davey, P. N., Khimyak, Y. Z. and Kozhevnikov, I. V. (2008) Heteropoly compounds as catalysts for hydrogenation of propanoic acid. Journal of Catalysis, 253 (2). pp. 244-252.

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Abstract

Bulk Keggin heteropoly acids (HPAs) H3+n[PMo12-nVnO40] (n=0–2) and their Cs+ salts catalyse the vapour-phase hydrogenation of propanoic acid at 350?°C and 1 bar H2 pressure, yielding propanal together with 3-pentanone and propane as the main products. Catalyst acidity (controlled by Cs substitution) has crucial effect on the reaction selectivity. As the Cs content increases, the selectivity to propanal passes a maximum (74–76%). At the same time, the selectivity to propane sharply decreases, whereas 3-pentanone selectivity increases monotonously. This indicates that 3-pentanone is likely to form via Cs propanoate intermediate. Partial substitution of Mo(VI) by V(V) in the PMo12O3-40 anion has a small effect on the catalyst performance. Initially crystalline, the catalysts become amorphous after reaction, with their surface area significantly reduced. As evidenced by FTIR, H4[PMo11VO40] and its Cs salts, possessing a higher thermal stability, retain the Keggin structure in their bulk after reaction, whereas less stable H3[PMo12O40] and H5[PMo10V2O40] derivatives undergo decomposition. This shows that the as-made crystalline heteropoly compounds are catalyst precursors rather than the true catalysts. The reaction over Cs2.4H1.6[PMo11VO40] is zero order in propanoic acid with an activation energy of 85 kJ/mol. The formation of propanal is suggested to occur via a Mars–Van Krevelen mechanism.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Pharmacy (former - to 2024)
UEA Research Groups:	Faculty of Science > Research Groups > Pharmaceutical Materials and Soft Matter Faculty of Science > Research Groups > Drug Delivery and Pharmaceutical Materials (former - to 2017)
Depositing User:	Rhiannon Harvey
Date Deposited:	31 Jan 2012 13:01
Last Modified:	06 Feb 2025 02:28
URI:	https://ueaeprints.uea.ac.uk/id/eprint/36629
DOI:	10.1016/j.jcat.2007.11.011

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