Ionothermal synthesis of AlPO_4 molecular sieves in the presence of quaternary ammonium cation

摘要

Several aluminophosphate molecular sieves were synthesized ionothermally, in ionic liquid 1-butyl-3-methyl imidazolium bromide ([BMIm]Br) with adding various quaternary ammonium cation (quats, including tetramethyl ammonium (TMA~+), choline, tetraethyl ammonium (TEA~+), tetrapropyl ammonium (TPA~+) and tetrabutyl ammonium (TBA~+)). These products were characterized by X-ray diffraction (XRD), ~(13)C nuclear magnetic resonance (NMR) and scanning electron microscope (SEM). The result indicates that the crystallization pathway is changed by adding these quats. AlPO_4-42 (IZA code LTA) crystallizes when TMA~+ is added in the system, AlPO_4-5 (AFI) crystallizes when choline or TEA~+ is added, and the AIPO_4-11 (AEL) crystallizes when TPA~+ or TBA~+ is added. ~(13)C NMR analysis indicates that these introduced quats may either replace the [BMlm]~+ to act as template alone, or direct structures cooperatively with the [BMIm], or in some cases they cannot change the original structure directing effect of [BMIm]~+.