Solid base catalysts and combined solid base hydrogenation catalysts for the aldol condensation of branched and linear aldehydes

• DOI: 10.1016/j.apcata.2003.12.009
• Publication Date: 2004-04-14T09:27:06Z
• Authors: Christine A. Hami...; S.David Jackson; Gordon J. Kelly
• Keywords: Isobutyraldehyde; Aldol condensation; Base (topology)

Abstract The gas phase condensation reactions of butanal and isobutyraldehyde were studied over a solid base catalyst (4 wt.% Na on SiO 2 ) and combined solid base/hydrogenation catalyst (0.1 wt.% Pd/4 wt.% Na/SiO 2 ). A Pd/Na/SiO 2 catalyst can be used to produce a selectively hydrogenated aldol condensation product 2-ethylhexanal from a butanal feed at high selectivity (maximum 94.9% at 42.4% conversion). Selectivity to the hydrogenated product 2-ethylhexanal increases with time on-line and hydrogen pressure. A dual bed system using a Na/SiO 2 base catalyst followed by a Cu/Zn hydrogenation catalyst can be used to produce a mixture of butanol and 2-ethylhexanol from a butanal feed. 2-Ethylhexanol production in the dual bed system is increased by contact time and hydrogen pressure. The reaction of isobutyraldehyde over a solid base catalyst produces no products and leads to carbon laydown on the catalyst and in the reactor. The reaction of a 1:1 molar mixture of butanal and isobutyraldehyde produces 2-ethylhexenal and a crossed aldol product 2-ethyl-4-methyl-pent-2-enal. The deactivation of the Pd/Na/SiO 2 catalyst with time on-line for the reaction of butanal may be due to the poisoning of base sites by the product 2-ethylhexanal.