Cross ketonization of Cuphea sp. oil with acetic acid over a composite oxide of Fe, Ce, and Al

The objective of this work was to demonstrate the viability of the cross ketonization reaction with the triacylglycerol from Cuphea sp. and acetic acid in a fixed-bed plug-flow reactor. The seed oil from Cuphea sp. contains up to 71% decanoic acid and the reaction of this fatty acid residue with acetic acid yields the fragrance compound and insect repellent 2-undecanone. To this end, we screened several ketonization catalysts taken from the literature including CeO2, CeO2/Al2O3, CeO2/ZrO2, MnOx/Al2O3. The catalysts were characterized by N2 adsorption/desorption, H2-TPH, CO2-TPD, and XRD. Each of these catalysts affected the conversion but the highest yield was found with a new coprecipitated mixed metal oxide of empirical formula Fe0.5Ce0.2Al0.3Ox. In a flow reactor, Fe0.5Ce0.2Al0.3Ox gave 2-undecanone at 91% theoretical yield with reaction conditions of 400 °C, weight hourly space velocity of 2, molar ratio of acetic acid to Cuphea oil of 23, and N2 carrier gas flow of 125 ml/min at 2.4 bar. This high yield is attributed to the low rate of coke formation on the mixed metal catalyst. In the absence of acetic acid, coupling of the decanoic acid residues gives 10-ketononadecane.

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► New ketonization catalyst consisting of a mixed metal oxide.
► Effectively converts Cuphea spp. oil to 2-undecanone upon reaction with acetic acid.
► Selectivity of 90% in a plug flow reactor.
► Leads to a sustainable source of a fragrance compound which is also an effective insect repellent.