Sustainable formation of tricarballylic acid from citric acid over highly stable Pd/Nb2O5·nH2O catalysts
2022
Stuyck, Wouter | Bugaev, Aram L. | Nelis, Tom | de Oliveira-Silva, Rodrigo | Smolders, Simon | Usoltsev, Oleg A. | Arenas Esteban, Daniel | Bals, Sara | Sakellariou, Dimitrios | De Vos, Dirk
Recently, a reaction sequence was developed for the production of tricarballylic acid, an interesting plasticiser precursor, from citric acid by using a H-Beta zeolite and Pd/C catalyst. Although yields of 85% of tricarballylic acid were obtained, citric acid elicited Al leaching from the zeolite framework, resulting in loss of activity. In this work, Nb₂O₅·nH₂O was found to be a stable and performant catalyst for this reaction, and a strong involvement of the hydroxyl group of citric acid with the Nb₂O₅·nH₂O surface was observed by ¹³C MAS NMR. Next, Pd/Nb₂O₅·nH₂O catalysts were synthesized via a low temperature reduction method to preserve the acidity of the Nb₂O₅·nH₂O support; the nature of the Pd phase was examined by XAS. In presence of a 0.6 wt% Pd/Nb₂O₅·nH₂O catalyst, yields over 90% of tricarballylic acid were obtained over multiple runs. Finally, this catalyst was also suitable for the dehydration-hydrogenation of other monohydroxy carboxylic acids.
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