Hydrothermal synthesis of SAPO-5 with novel morphologies from hydrogels containing acetic acid and high concentration of triethylamine under neutral or alkaline conditions

SAPO-5 with novel morphologies was hydrothermally synthesized from neutral or alkaline hydrogels containing acetic acid and high concentration of triethylamine (TEA) at 180 °C for 48 h. Bullet-like, pine cone-like and disk-shaped crystals were prepared at the TEA/Al ₂O ₃ molar ratio of 14 and the HAc/Al ₂O ₃ molar ratios of 5-17. All the samples are constructed from flakes with thicknesses ranging from 100 to 300 nm stacked together to form various geometries. Their aspect ratio decreases with increase in the HAc/Al ₂O ₃ molar ratio. Substitution of HCl for HAc results in the formation of SAPO-5 with hexagonal disk flower-like morphology at a TEA/Al ₂O ₃ molar ratio of 14 and HCl/Al ₂O ₃ molar ratio of 4.3. The above SAPO-5 with novel morphologies contains mesopores and exhibits higher ratios of the amounts of the weak acid site to intermediate acid site than those of the conventionally synthesized SAPO-5. The effect of interaction between acetic acid and TEA on formation of the novel morphology is discussed.