Kinetics of fatty acid ketonization in liquid phase with anatase and rutile TiO2 catalysts

Catalytic ketonization of carboxylic acids is promising for the synthesis of renewable products. Despite its potential, fatty acid ketonization and its kinetics in the liquid phase are less investigated. This work encompasses kinetic evaluation of two TiO 2 catalysts (anatase and rutile) for C-C coupling of C 12 -C 18 fatty acids in inert dodecane solvent. The rutile catalyst, with higher Lewis acid density, showed higher intrinsic activity and more favorable activation energy barriers. Unfortunately, this material suffers from stronger product inhibition by ketone, water and carbon dioxide compared to anatase. Langmuir-Hinshelwood kinetic models were developed and validated against the experimental data, supporting that C-C coupling of adsorbed species is rate determining in the ketonization mechanism. The Lewis acid site density and distance between active Ti species at the surface were invoked to explain the activity patterns. The impacts of substrate chain length, solvent and liquid phase purging on the ketonization kinetics were investigated, showcasing potential for future improvements. • Kinetic study of fatty acid ketonization with anatase and rutile TiO 2 in liquid phase. • Rutile TiO 2 , with higher Lewis acid site density, showed higher intrinsic activity for ketonization. • More active rutile catalyst was more prone to product inhibition by ketone, H 2 O and CO 2 . • Power laws and Langmuir-Hinshelwood kinetic models were developed for both catalysts. • The impact of substrate carbon chain length, solvent and reactor purging on kinetics was shown.