Aldol condensation of benzaldehyde and heptanal: a comparative study of laboratory and industrially prepared Mg–Al mixed oxides

Abstract

AbstractBACKGROUNDSeveral layered double hydroxides (with Mg:Al ratio varying from 2:1 to 4:1) were prepared by a co‐precipitation method at constant pH value. The activity of laboratory prepared samples was compared with that of industrially prepared layered double hydroxides with the same Mg/Al ratio in aldol condensation of benzaldehyde with heptanal.RESULTSCharacterization of all solid catalysts was performed using different techniques (ICP‐MS, thermogravimetry, X‐ray diffraction, DRIFT spectroscopy, nitrogen physisorption method, scanning electron microscopy). Acido‐basic properties of prepared materials were investigated using ammonia (carbon dioxide, respectively) temperature programmed desorption. Heptanal conversion and selectivity to two main products, i.e. 2‐pentylcinnamylaldehyde (jasmine aldehyde) and 2‐pentylnon‐2‐enal, were monitored. All catalysts resulted in heptanal conversions higher than 95%.CONCLUSIONThe highest selectivity to jasmine aldehyde (66% at 70% heptanal conversion, 46% theoretical yield) was obtained using ESM 3:1 catalyst (100°C, heptanal:benzaldehyde = 1:2 molar, solvent‐free synthesis). © 2017 Society of Chemical Industry