Characterization of AlPO4-14 by magic-angle-spinning nuclear magnetic resonance spectroscopy and thermoanalytical and adsorption measurements

Abstract

AlPO₄-14 has been prepared using piperidine as templating agent. Uniform crystals of tabular habit were obtained. By thermoanalytical measurements of the as-synthesized sample the content of occluded piperidine was determined and its degradation was followed. From the ³¹P MAS NMR spectra it follows that there should exist at least three non-equivalent sites in the framework of calcined AlPO₄-14. Completely reversible changes in the ²⁷Al and ³¹P MAS NMR spectra were found in dehydration/hydration cycles. The relative small pore diameter of AlPO₄-14 (ca. 0.4 nm) prohibits the adsorption of n-alkanes. From the adsorption isotherms of methanol and water the saturation capacities were determined to be 0.17 and 0.27 cm³ g^–1, respectively.