Preparation of nanoporous MgAl ₂O ₄ by combined utilization of sol-gel process and combustion of biorenewable oil

Nanoporous MgAl ₂O ₄ particulates with high porosities were successfully prepared from sol-gel reactions, solvent exchange with castor oil and subsequent combustion and calcination at 700 °C. The products were crystalline and semitransparent. Changes in the metal precursor concentrations allowed control of pore volumes from 0.7 to 1.1 cm ³/g and average pore sizes from 14 to 19 nm. The specific surface areas are about 200 m ²/g regardless of the precursor concentrations. After heating at 1000 °C for 10 hours, the products kept about 70% of their original pore volume and about 60% of the original surface area. Heating at 1100 °C caused a drastic reduction of pore volume and surface area to 40 and 36%, respectively, as the average particle size increased to 23 nm.