In Situ High Temperature High Pressure MAS NMR Study on the Crystallization of AlPO4‑5
journal contributionposted on 28.01.2016, 00:00 by Zhenchao Zhao, Suochang Xu, Mary Y. Hu, Xinhe Bao, Jian Zhi Hu
A damped oscillating crystallization process of AlPO4-5 at the presence of small amount of water is demonstrated by in situ high temperature high pressure multinuclear MAS NMR. Crystalline AlPO4-5 is formed from an intermediate semicrystalline phase via continuous rearrangement of the local structure of amorphous precursor gel. Activated water catalyzes the rearrangement via repeatedly hydrolysis and condensation reaction. Strong interactions between organic template and inorganic species facilitate the ordered rearrangement. During the crystallization process, excess water, phosphate, and aluminums are expelled from the precursor. The oscillating crystallization reflects mass transportation between the solid and liquid phase during the crystallization process. This crystallization process is also applicable to AlPO4-5 crystallized in the presence of a relatively large amount of water.