Facile synthesis of FeAlPO-5 molecular sieve in eutectic mixture via a microwave-assisted process

Abstract

FeAlPO-5 molecular sieve with AFI topology was ionothermally prepared under microwave irradiation in a three-component eutectic mixture and characterized by various techniques. N 2 adsorption/desorption measurements implied that the resultant samples exhibited a mesopore characteristic. Electron spin resonance (ESR) and diffuse reflectance UV–Visible spectra (DR UV–Vis) results revealed that various iron species coexisted on the mesoporous FeAlPO-5 molecular sieve. CHN elemental analysis, thermogravimetry–differential thermal analysis (TG–DTA) and the results of Fourier transform infrared spectra (FT-IR) suggested that tetraethylammonium bromide acted as the structure-directing agent in the synthetic process of FeAlPO-5 molecular sieve. In addition, the factors affecting the crystallization of FeAlPO-5 molecular sieve were investigated in detail. Contrary to the effect of the composition of the eutectic mixture, the types of iron and aluminum sources, as well as the addition of water, did not have major influences on the phase selectivity of the crystallization reaction. Relatively low P 2O 5/Al 2O 3 ratio, the addition of appropriate amount of HF, a longer time and higher temperature favored the crystallization of FeAlPO-5 molecular sieve.