Hydrothermal synthesis of AlPO4-5: Effect of precursor gel preparation on the morphology of crystals

This paper reports on the effect of precursor gel preparation on the microstructural formation of aluminophosphate-5 (AlPO4-5) molecular sieves in the hydrothermal synthesis. The morphology of AlPO4-5 crystal changed from sphere to ellipse with two symmetrical craters when the aluminophosphate precursor gel was prepared via dropwise addition of acid and TEA under strong stirring, and continuous stirring overnight during the gel aging process. The results also showed that both of well-crystallized spherical and elliptical AlPO4-5 crystals covered by the fibrous crystals could be hydrothermally synthesized at 150 oC for 4 h or longer. The average particle size of spherical AlPO4-5 samples was about 35-45 μm in diameter, whereas the elliptical AlPO4-5 exhibited approximately 13 μm in width and 15 μm in length.