Further studies on aluminophosphate molecular sieves. Part 1.—AlPO4-H2: a hydrated aluminophosphate molecular sieve

Abstract

Pure, highly crystalline AlPO4-H2 is synthesized from an aluminophosphate gel containing dipentylamine and characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetry and solid-state nuclear magnetic resonance spectroscopy. The AlPO4-H2 structure has orthorhombic symmetry with cell parameters of a= 16.184(5)Å, b= 9.914(3)Å, and c= 8.134(4)Å. It is constructed exclusively from hydrated triple crankshaft chains that also build the 18-membered ring VPl-5. AlPO4-H2 is a microporous, hydrated aluminophosphate with highly elliptical 10-ring channels (2.9 Å by 7.6 Å). One third of the framework Al atoms are octahedrally coordinated to two water molecules and four framework oxygens. Since AlPO4-H2 and VPl-5 share the same structural building unit, some of their physicochemical properties are similar. The existence of AlPO4-H2 and VPl-5 suggests that other molecular sieves with the same type of building unit can be synthesized.