THE CRYSTAL MORPHOLOGY OF ZEOLITE-A - THE EFFECTS OF THE SOURCE OF THE REAGENTS

This study investigates the effects of the variation in reagents on th e synthesis of zeolite A. The synthesis was attempted under autogenic conditions and at temperatures of 100 (+/-1)degrees C and 70(+/-1)degr ees C, using various aluminium and silicon sources. Preparation of the gels used silica and aluminium to form mixed systems of organic and i norganic reagent sources. Products formed were analysed and characteri sed instrumentally using X-ray diffraction, X-ray fluorescence, Fourie r transform infrared spectroscopy, thermogravimetric analysis and scan ning electron microscopy. Systems using aluminium isopropoxide consist ently produced uniformly sized crystals, each having deep, chamfered e dges. Sodium reagent sources produced sharp edged crystals. The system using tetraethyl-orthosilicate with aluminium powder produced a hexag onal morphology. The change in the hydroxide concentrations, relative to the systems using sodium silicate and sodium aluminate sources was also monitored, and while it had a marked effect on crystallinity and stability, the crystal morphology remained consistent. (C) 1997 Elsevi er Science B.V.