Synthesis of AlPO₄-5 large crystals

Effects of cationic surfactant, cetyltrimethylammonium bromide (CTAB), on the synthesis of large and perfect AlPO₄-5 crystals via hydrothermal synthesis were studied. The AlPO₄-5 crystals were obtained by using a gel with tripropylamine as template, pseudoboehmite as aluminum source and phosphoric acid as phosphorus source. Certain amount of HF, isopropanol and CTAB were also added into the initial pregnant gel of the crystal. Large and perfect hexagonal prism shaped AlPO₄-5 crystals with maximum size up to 890μm × 120μm could be formed at 453 K with a crystallization period of 24h by adjusting the added amount of CTAB. Experimental results indicate that the size and the purity of AlPO₄-5 crystals formed are closely related to the adsorption effect between the trimethylammonium cation and the negative ion radicals in the pregnant gel, such as [AlF₆]^3- and [PF₆]^1-.