Crystal engineering of SAPO-11 sieves by forming intermediate phases

Abstract

Using XRD, ²⁷Al and ³¹P MAS NMR, Raman spectroscopy, SEM, TEM, N₂ adsorption–desorption, and IR spectroscopy with pyridine adsorption, we studied the influence of the aluminum source and the aging temperature of the gel with the following composition: 1.0Al₂O₃·1.0P₂O₅·0.2SiO₂·1.5DPA·30H₂O, on the properties of the formed intermediate phases and the products of their subsequent crystallization in SAPO-11 molecular sieves. It has been established that by changing the nature of the aluminum source and the gel aging temperature, it is possible to synthesize various intermediate silicoaluminophosphates (amorphous, layered, AlPO₄·2H₂O) and control the morphology and size of the crystals formed during further crystallization of the SAPO-11 molecular sieves. The high stability and selectivity of the synthesized SAPO-11 nanoscale sample in the reaction of vapor-phase isomerization of cyclohexanone oxime to caprolactam were shown.