Investigation into the role of MgO in the synthesis of MAPO-11 large single crystals

MgO was introduced into the reaction system of AlPO4-11 and large MAPO-11 single crystals were obtained by using di-iso-propylamine as the template and HF as the mineralizer. The crystal size of MAPO-11 is about eight times that of AlPO4-11. Compared with that of AlPO4-11, the crystallization time of MAPO-11 is shortened greatly while the crystallinity is increased. We followed the crystallization process of AlPO4-11 and MAPO-11 single crystals and elucidated the role of MgO in the crystallization process. To obtain useful information on understanding the crystallization and growth mechanism of molecular sieve single crystals, we monitored the evolution of the gel phases as a function of crystallization time through XRD, IR, and 27Al Magic Angle Spinning (MAS) NMR. 31P Magic Angle Spinning (MAS) NMR and 1H-31P CP MAS NMR measurements were conducted to reveal the different sites of phosphorus in the final products. IR spectroscopy also provided insight into the interactions between the organic template and the inorganic gel species.