Catalytic performance of texturally improved Al–Mg mixed oxides derived from emulsion-synthesized hydrotalcites

Abstract

Mixed oxides of aluminum and magnesium derived from hydrotalcites were prepared by means of a sol–gel method mediated by an emulsified sol as pore template. The emulsion consisted of ethanol as the continuous phase and n-dodecane droplets as the dispersed phase, which was stabilized by the presence of the surfactant Pluronic P123. The use of such an emulsion was essential for obtaining materials with a porous structure that were assessed by mercury intrusion porosimetry and nitrogen physisorption. Additional characterization by NH₃ and CO₂ temperature programmed desorption confirmed that despite the enhancement of their textural properties, the number of acid and base sites was reduced in comparison to a reference and conventionally prepared Al–Mg mixed oxide, as a consequence of the depletion of surface hydroxyls during condensation of the precursors around the nonpolar droplets of the emulsion. Catalytic conversion of 2-propanol under conditions of controlled mass and heat diffusion on the texturally improved Al–Mg mixed oxides evidenced the preparation of a more effective catalyst than the poorly porous reference.