A study of the formation of microporous material SAPO-37

The crystallizatio n of mic roporous material SAPO-37 was studied under hydrothermal synthesis (HTS) and dry gel conversion (DGC) conditions. The evolution of the intermediate phases as a function of crystallization time was followed by several techniques including PXRD , SEM, AFM, and solid-state NMR. For DGC, SAPO-37 crystallizes from a semi-crysta lline layered precursor containing large pores and sodalite cages, whose structure is held by weak nonbo nding interactio ns. Si atoms are only incorporated in the later stage of the crystallization via the formation of aluminosilicate species. Under HTS conditions, the crystallization pathway of SAPO-37 is somewhat similar to that for DGC. The AFM data suggest that the crystal growth mechanism is ‘‘birth and spread’’, and the final SAPO-37 crystals have rough (111) surfaces terminated by different structural building units. The findings of the present work provide new physical insights into the formation of SAPO-37. 2013 Elsevier Inc. All rights reserved.