Selective formation of AlPO4-21 and AlPO4-12 molecular sieves by microwave technique

AlPO₄-12 Molecular Sieves (MS) were also synthesized through the Microwave Technique (MT), using Trimethylamine (TMA) rather than Dimethylamine (DMA) as the template in the presence of Hydrofluoric acid (HF). XRD, SEM, MAS NMR and TG-DSC were used to characterize the products synthesized in different conditions. The results indicated that the MT accelerated the crystallization of AlPO₄-12 MS, particularly owing to the release of aluminum species from AlF _n complexes and dissolving the impurity. The structural directing effect of the TMA was changed through ion pairing with fluoride ions, leading to the crystallization of AlPO₄-12 rather than AlPO₄-21 MS.