Synthesis of large single crystals of SAPO-47 in the presence of diethylamine using two-step temperature process

By using diethylamine (DEA) as the structure-directing agent (SDA), large single crystals of SAPO-47 have been synthesized with a two-step temperature process. As a typical contaminant, the existence of SAPO-5 introduces a competing phase in the one-step temperature process. But our method shows that an initial temperature of 160 °C can successfully depress the SAPO-5 nuclei, facilitating the synthesis of pure SAPO-47 crystals in the finial crystallization process. Perfect rhombohedral-shaped SAPO-47 crystals with a size 230 × 230 μm are synthesized by optimizing crystallization temperature and duration, molar SiO2/Al2O3 ratio, DEA and HF amount. Single-crystal X-ray diffraction measurement shows that the as-synthesized SAPO-47 crystals are of space group R3¯ symmetry with lattice constants a = b = c = 9.396 Å, α = β = γ = 94.43°, and their unit cell volume is V = 821.7 Å3.

Large single crystals of SAPO-47 (size 230 × 230 μm) have been successfully synthesized using two-step temperature process. These large single crystals have a transparent appearance and very smooth surfaces.Figure optionsDownload as PowerPoint slideHighlights
► Two-step temperature process can successfully restrain the contaminating phase (SAPO-5) and synthesize pure SAPO-47 crystal.
► The molar SiO2/Al2O3 ratio influences not only the average quality and size of SAPO-47 crystals, but also product purity.
► High HF content is found to restrain the nucleation and to slow down the crystal growth, leading to large crystals.
► The content of DEA influences not only the average quality and size of SAPO-47 crystals, but also product purity.