10.1016/S0021-9517(03)00192-1
The research presented in the "Journal of Catalysis" focused on the aldol condensation of acetaldehyde and heptanal using hydrotalcite-type catalysts to produce 2-nonenal, a higher molecular weight aldehyde. The study explored the effects of various reaction parameters, including temperature, acetaldehyde to heptanal molar ratio, and the nature of the solvent (hexane, toluene, ethanol). The catalysts tested were MgO with strong Lewis basic sites, Mg(Al)O mixed oxides derived from hydrotalcite precursors with acid–base pairs of the Lewis type, and rehydrated Mg(Al)O mixed oxides with Br?nsted basic sites. The optimal reaction conditions were determined to be a temperature of 373 K, an acetaldehyde/heptanal molar ratio of 2/1, and an ethanol/reactants molar ratio of 5/1. The experiments involved the synthesis of Mg–Al hydrotalcite followed by its calcination at various temperatures to produce Mg(Al)O mixed oxides. The rehydrated form of these calcined materials was also tested. Characterization of the catalysts was performed using chemical analysis, XRD, BET specific surface area measurements, and basicity was studied by CO2 adsorption followed by calorimetry and gravimetry. The acidity was estimated from temperature-programmed desorption of NH3 (NH3-TPD). Catalytic tests were carried out in a stainless-steel autoclave, and the reaction products were analyzed by gas chromatography and mass spectrometry. The results provided insights into the influence of catalyst properties on the selectivity and conversion of reactants.
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