Formation of microporous material AlPO4-18 under dry-gel conversion conditions

The formation of microporous molecular sieve AlPO4-18 under the dry gel conversion (DGC) conditions was examined. The evolution of the dry gel was monitored by powder XRD, SEM and, in particular, solid-state NMR techniques. The results show that the aluminophosphate (AlPO) amorphous dry gel is first converted to a layered AlPO phase. The layered intermediate has some resemblances to AlPO4-18 and is held together by very weak non-bonding interactions. Continuous heating results in the transformation of this layered phase into AlPO4-18 via reorganizations and condensations of P and Al sites. Three non-equivalent P sites of AlPO4-18 develop at different rates during the evolution.

Graphical abstractCrystallization of AlPO4-18 was examined by steam-assisted conversion.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Formation of AlPO4-18 examined under dry gel conversion conditions. ► Evolution of dry gel phase followed by powder XRD, SEM and solid-state NMR. ► New insight into crystallization at a molecular level obtained.