On the synthesis of CoAPO-46, -11 and -44 molecular sieves from a Co(Ac)2 · 4H2O· Al(iPrO)3·H3PO4 · Pr2NH·H2O gel via experimental design

Abstract

The hydrothermal synthesis of cobalt-substituted microporous alumino-phosphates from an r[Pr2NH] ·[CoxAl1−xP1]O4 · y[H2O] gel is described. A well-defined set of experiments, based on an experimental design, was carried out in order to rationalize the influence of the crystallization time/temperature, and r, x and y of the initial gel on the isomorphous substitution of Co2+. CoAPO-11, CoAPO-44, CoAPO-46 were the main crystalline materials obtained. These solids were characterized by X-ray diffraction (XRD), thermogravimetrical analysis (TGA), scanning electron microscopy (SEM), electron microscope microprobe analysis (EMMA) and diffuse reflectance spectra (DRS), which resulted in a quantitative model relating the synthesis conditions with the overall crystallinity. In addition, a relation between the overall crystallinity and the degree of isomorphous substitution has been established.