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The environmental and economic challenges currently faced by the wax market may be addressed by the use of sustainable bio-based alternatives. Hereto, ketonization of vegetable oils and animal fats is...

TiO2 is one of the most promising catalysts for liquid-phase ketonization of carboxylic acids. As recently reported, its use significantly contributes to the overall environmental impact of the fatty acid ketonization process. Therefore, postsynthetic modifications such as metal addition and thermal treatment under inert and reducing atmospheres were studied to enhance the catalytic activity of anatase TiO2 for the ketonization of lauric acid. Although more active surfaces can be generated by the additional metal through hydrogen spillover effects, its presence led to substantial decarboxylation rather than ketonization. Interestingly, metal-free anatase TiO2 is also substantially activated after thermal treatment in nitrogen or hydrogen gas, while maintaining its full ketonization selectivity. Ascertained by X-ray analysis, this was not related to polymorphism but due to a higher content of Lewis acid sites, of which the hydrogen-treated catalysts possessed the largest density. A quadratic relationship appears between the ketonization rate and surface acid site density, a defining characteristic of rate-determining bimolecular C–C coupling in the ketonization mechanism. In contrast to studies on short-chain carboxylic acids, this liquid-phase study renders hydrogenated TiO2 as the most promising catalyst, while metal addition is less suitable for selectivity reasons. Although less essential for bio-oil upgrading, high selectivity is of utmost importance for on-purpose fatty acid ketonization.