Controlling the porosity and crystallinity of MgO catalysts by addition of surfactant in the sol-gel synthesis

Abstract

Abstract This study presents an easy route to induce pore formation, increase the specific surface area and control the crystallite size of magnesium oxides obtained using the sol-gel method with addition of Pluronic P123 surfactant. The structural characteristics of the materials were evaluated using X-ray diffraction, N2 physisorption isotherms, mercury intrusion porosimetry, scanning electron microscopy and CO2 temperature programmed desorption. The catalytic properties were assessed using the Knoevenagel condensation reaction. The results showed a systematic decrease of the magnesium oxide crystallinity with increased concentration of the surfactant used in the synthesis. This was associated with increase of the magnesium oxide BET area from 2 m2/g to over 50 m2/g, as well as the formation of pores in the macropore region, as confirmed by microscopy images. In addition, the surface modification resulted in CO2 chemisorption increasing from 378 μmol/g, for the pristine MgO sample, to 1529 μmol/g, for the porous sample, accompanied by an increase in the concentration of strong basic sites. The most porous sample presented the highest catalytic activity in the Knoevenagel condensation reaction.