Abstracts Book - IMRC 2018

• SF3-O048
CERIUM AND ZIRCONIUM OXIDES AS ACTIVE CATALYSTS FOR
THE SYNTHESIS OF KETONES FROM ALDEHYDES: HYDROGEN
PRODUCTION AND MECHANISTICAL INSIGHTS
Lina M. Orozco 1,2 , Michael Renz 1 , Avelino Corma 1
1 Universidad Politécnica de Valencia, Instituto de Tecnología Química, Spain. 2 Universidad
Tecnológica de Pereira, Grupo Polifenoles, Facultad de Tecnologías. Grupo Infección e
Inmunidad, Facultad de Ciencias de la Salud, Colombia.
Introduction. Ketones are important fine chemicals and a classical way to
synthesize them is the ketonic decarboxylation of carboxylic acids. A less known
possibility is the connection of two molecules of aldehyde to form a ketone,
without synthesis of the carboxylic acid. The reaction mechanism of this
ketonization is still under debate and many aspects of the reaction need still
further study, especially the reaction mechanism. The catalytic conversion of
heptanal as model compound into 7-tridecanone was studied over m-ZrO 2 and
CeO 2 . Combining this reaction with a subsequent hydrodeoxygenation step,
diesel fuel can be prepared from heptanal. Experimental. The reactions were
carried out in a fixed-bed continuous-flow reactor over CeO 2 or m-ZrO 2 .
Typically, temperatures were between 350 to 450 °C and atmospheric pressure
was employed. The cascade reaction was carried out coupling ketonization
(CeO 2 , 450 ºC) and hydrodeoxygenation (Pt/Al 2 O 3 , 300 ºC) in two different
reactors under hydrogen pressure. Results and discussion. When we studied
the heptanal ketonic decarboxylation over m-ZrO 2 and CeO 2 , we found that the
carboxylic acid is a reaction intermediate. Curiously, hydrogen is co-produced
and water acts as “oxidant” It is proposed that the dehydrogenation of the
aldehyde occurs by a hydride transfer to the oxide surface when the aldehyde
is stabilized as a hydrate, which is formed with surface hydroxy groups. This has
been supported by a labelling experiment with a 1D-aldehyde. For the concept
of the combination of ketonization and hydrodeoxygenation processes, an
advantage can be exploited from the hydrogen production, designing a
sustainable process for converting two molecules of aldehyde into a long chain
alkane. No further reagents are needed and the only by-product is one molecule
of carbon dioxide. Starting from heptanal, a diesel fraction with almost 90%
selectivity of alkanes was obtained. Conclusion. Ketonization of aldehydes has a
big potential for biorefinery processes. Thereby, it is of paramount interest to
understand the mechanism of the reaction for optimization purposes.
Mechanistic studies have clarified the mechanism for both reactions. Thus, it can