| Abstract |
Carboxylic acids and esters are common intermediate products formed in biomass conversion processes. Reaction kinetics studies for upgrading mixtures containing carboxylic acids and esters by ketonization reactions (to achieve C-C coupling) over a ceria zirconia catalyst have been carried out using butanoic acid, pentanoic acid, and hexanoic acid at temperatures of 548, 573, 598, and 623 K. The results from these experimental studies have been consolidated and described using kinetic models. For the ketonization of hexanoic acid, a kinetic model, previously developed for hexanoic acid, has been modified and extended to describe a wider and more applicable concentration range, between 2.5 and 75 mol %. Furthermore, the homo- and the cross-ketonization of butanoic acid, pentanoic acid, and hexanoic acid have been studied, showing that the rate of cross-ketonization is faster than the rate of homo-ketonization. Because esters are common side products of biomass conversion processes, formed by the esterification of acids with primary and second alcohols, the reaction kinetics for the direct ketonization of esters has also been studied, showing that ester ketonization is slower than ketonization of the corresponding acid. Finally, a kinetic model has been developed to describe the experimentally observed product distribution obtained by reacting a mixture of different biomass-derived species over a ceria zirconia catalyst. The model includes the ketonization of acids and the ketonization of esters as well as the esterification of acids with primary and secondary alcohols. |
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