Preparation of SiO2 and NiO/Al2O3 aerogels by supercritical CO2 drying and their catalytic activity

Aerogels of SiO2 and NiO/Al2O3 were prepared by means of sol-gel method followed by supercritical CO2 drying. Aerogels were characterized in terms of BET surface area, pore size distribution by both nitrogen adsorption and mercury porosimetry, and TEM microscope observation in comparison with xerogels that were prepared by ambient drying of alcogel. Aerogels had higher surface area and pores in meso- and macropore size region. TEM microscopy revealed that aerogels had large pores and a highly divided state of NiO on Al2O3 matrix. Catalytic activity of NiO/Al2O3 aerogels was measured for partial oxidation of iso-butylene. Aerogel catalyst was selective to methylacrolein over acetone, whereas xerogel catalyst was not selective.