Efficient direct synthesis of 2-ethylhexanal from n-butyraldehyde and hydrogen using palladium modified base catalysts

One-step synthesis of 2-ethylhexanal (2EH) from n-butyraldehyde and hydroge n gas has been studied over palladium modified base catalysts at 1 atm and 130-200 degrees C by using a fixed-bed, integral-flow reactor. The catalyst s were characterized with various techniques: AA, XRD, BET, FT-IR and TPD o f carbon dioxide. The factors affecting the catalytic results were investig ated; these included the catalyst support, the reaction temperature, the pa lladium content, n-butyraldehyde to hydrogen molar ratio (B/H), time-on-str eam and the contact time. The optimum conditions for the synthesis of 2EH w ere 0.5% Pd/KXU, 150 degrees C, B/H 1 and W/F-B 22.2 g.h/mol. The catalytic results were correlated to the catalyst properties; the conversion of n-bu tyraldehyde increases with increasing the catalyst base amount. The main re action path started from self-condensation of n-butyraldehyde to 2-ethyl-3- hydroxyhexanal, followed by dehydration to 2-ethyl-2-hexenal which was then hydrogenated to 2EH. The minor path was direct hydrogenation on the C=O do uble bond of n-butyraldehyde to produce 1-butanol. (C) 1999 Elsevier Scienc e B.V. All rights reserved.