IMMOBILIZATION OF THE HETEROPOLY ACID (HPA) H4SIW12O40 (SIW12) ON MESOPOROUS MOLECULAR-SIEVES (HMS AND MCM-41) AND THEIR CATALYTIC BEHAVIOR

Supported catalysts, consisting of SiW12 immobilized on hexagonal meso porous silica (HMS) and its aluminum-substituted derivative (MCM-41) w ith different loadings and calcination temperatures, have been prepare d and characterized by X-ray diffraction, FT-IR and NH3-temperature pr ogrammed desorption. It is shown that SiW12 retains the Keggin structu re on the mesoporous molecular sieves and no HPA crystal phase is deve loped, even at SiW12 loadings as high as 50 wt%. In the esterification of acetic acid by n-butanol, supported catalysts exhibit a higher cat alytic activity and stability and held some promise of practical appli cation. In addition, experimental results indicate that the loaded amo unt of SiW12 and the calcination temperatures have a significant influ ence on the catalytic activity, and the existence of aluminum has also an effect on the properties of supported catalysts.