Abstract
Cerium oxide-based catalysts proved superior in activity, selectivity, and stability to several other oxides for the condensation of two carboxylic acids to produce non-symmetric ketones. The effects of CeO 2 loading on the catalysts and the addition of more basic or acidic oxides to CeO 2 were also studied. The catalysts were characterized by surface area, XRD, and redox behavior using TGA. CeO 2-based catalysts began deactivating after >12 h operation at WHSV∼4, but could be completely regenerated by high temperature air. The optimum temperature range for methylcyclopropylketone (MCPK) production from acetic and cyclopropanecarboxylic acids (CCA) were 690–730 K, and 670–680 K for methylnonylketone (MNK) production from acetic and decanoic acids. The optimal loadings of CeO 2 on supports approached a monolayer, but the maximum yield appeared almost independent of support. Both acidic and basic oxide additives to CeO 2 increased the rates to isomers of both CCA and MCPK, and to aldol condensation products. Catalyst performance improved with respect to time on stream and the number of regeneration cycles. This behavior resulted from the gradual dispersion of CeO 2 on the support during reduction/oxidation cycles. Acetic acid/air could also be used to activate the catalysts prior to feeding the second acid.
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