EFFECT OF MALIC-ACID ON STRUCTURE OF SILICON ALKOXIDE-DERIVED SILICA

The effect of malic acid on specific surface area, pore size distribut ion and gel structure of sol-gel derived silica gels was investigated. Tetraethoxysilane (TEOS) used as starting material was modified with malic acid prior to hydrolysis. The specific surface area of calcined gels increased and the pore size distribution shifted to smaller value s and became sharper with an increase in malic acid. Malic acid affect ed particle size and the extent of condensation due to its acidity and condensation hindrance. Under high malic acid concentrations particul ate gels were formed, Malic acid chemically bonded or adsorbed to sili ca polymers prevented particle growth and condensation among particles , Gels obtained at above malic acid/TEOS=1.17 (mol/mol) and calcined a t 450 degrees C for 3 h showed high specific surface areas about 1000 m(2) g(-1). The gel had uniform mesopores with around 2 nm radius.