Synthesis and characterization of CAM-1, a novel aluminophosphate molecular sieve precursor

Abstract

A new aluminophosphate molecular sieve precursor was synthesized hydrothermally in a non-aqueous system, Al₂O₃–P₂O₅–triethylamine–triethylene glycol, and characterized by powder X-ray diffraction, ²⁷Al and ³¹P magic-angle-spinning NMR with cross-polarization, scanning electron microscopy, energy-dispersive X-ray analysis, IR spectroscopy, thermogravimetric analysis and elemental analysis. The material has molar composition 3.0 Al₂O₃:3.0 P₂O₅:2.0 N(C₂H₅)₃:3 H₂O. NMR reveals the presence of at least two crystallographic sites for phosphorus in a population ratio of 2:1 and three inequivalent sites for aluminium. The chemical shift anisotropy and hydrophilicity of the phosphorous resonating at –23.6 ppm are much greater than that of phosphorus at –30.3 ppm. IR spectroscopy monitors very strong interactions between the organic template and the aluminophosphate framework. Upon calcination at 200 °C the material transforms into the dense-phase AlPO₄-tridymite, while the sample loses 21% of its weight as a result of the decomposition of the template.