n-Butyraldehyde self-condensation catalyzed by Ce-modified γ-Al2O3?

RSC Advances Pub Date: 2015-11-27 DOI: 10.1039/C5RA21125E

Abstract

Self-condensation of n-butyraldehyde is an important process for the industrial production of 2-ethylhexanol. The catalytic performance of some solid acids such as γ-Al2O3 and molecular sieves for the self-condensation of n-butyraldehyde was investigated and the results showed that γ-Al2O3 was the best one. Then the effect of preparation conditions on the catalytic performance of γ-Al2O3 and the effect of reaction conditions on the self-condensation of n-butyraldehyde were discussed. In order to improve the catalytic performance, γ-Al2O3 was modified by different substances and Ce–Al2O3 was found to show the best catalytic performance; the conversion of n-butyraldehyde and the yield of 2-ethyl-2-hexenal could reach 93.8% and 88.6%, respectively. Moreover, the Ce–Al2O3 catalyst had excellent reusability. The XPS analysis of Ce3d demonstrated that the valence state of cerium affected the catalytic performance of Ce–Al2O3 to some extent but not predominantly. Instead the acid–base property of Ce–Al2O3 played a dominant role in the catalytic performance. The reaction components formed over the Ce–Al2O3 catalyst were identified by GC-MS and then some side-reactions were speculated and a reaction network for n-butyraldehyde self-condensation catalyzed by Ce–Al2O3 was proposed. Subsequently, the research on the intrinsic kinetics of n-butyraldehyde self-condensation catalyzed by Ce–Al2O3 showed that both the forward and backward reactions are second order and the corresponding activation energy is separately 79.60 kJ mol?1 and 74.30 kJ mol?1, which is higher than that of the reaction catalyzed by an aqueous base or acid.

Graphical abstract: n-Butyraldehyde self-condensation catalyzed by Ce-modified γ-Al2O3
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