Crystal morphology control of AFI type molecular sieves with microwave irradiation

Abstract

AFI type molecular sieves with various morphologies such as aggregated sphere, plate, rod, prism and barrel were synthesized under varying reaction conditions under microwave irradiation. Hexagonal plate-like crystals with an aspect ratio of about 0.2 were obtained in the presence of silica under alkaline conditions. Rod-like crystals with an aspect ratio of about 40 were obtained with the addition of fluoride and an increase of template and water concentrations. The addition of silica to an alkaline precursor gel hindered the crystal growth in the c-direction and the presence of fluoride ions retarded the nucleation and crystal growth.