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Relationship between Acid–Base Properties and the Activity of ZrO 2 ‐Based Catalysts for the Cannizzaro Reaction of Pyruvaldehyde to Lactic Acid
Author(s) -
Albuquerque Elise M.,
Borges Luiz E. P.,
Fraga Marco A.,
Sievers Carsten
Publication year - 2017
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201700305
Subject(s) - catalysis , chemistry , monoclinic crystal system , lewis acids and bases , reaction mechanism , reaction rate , dissociation (chemistry) , base (topology) , lactic acid , polymer chemistry , molecule , organic chemistry , bacteria , mathematical analysis , mathematics , biology , genetics
The Cannizzaro reaction of pyruvaldehyde to lactic acid is investigated in a flow reactor with ZrO 2 catalysts with different structures and acid–base properties. The results show that a difference in the crystalline structures of two ZrO 2 polymorphs strongly affects the conversion of pyruvaldehyde. The monoclinic phase of zirconia is the most active for this reaction. A good correlation is observed between the reaction rate and the concentration of Lewis acid sites of sufficient strength, which shows that these sites play a major role in the reaction. A reaction mechanism is proposed involving coordinatively unsaturated Zr 4+ cations as sites for activating pyruvaldehyde molecules, whereas Zr 4+ −O 2− pairs generate terminal OH groups through water dissociation.