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

The hydrothermal synthesis of cobalt-substituted microporous alumino-phosph ates from an r[Pr2NH] . [CoxAl1-xP1]O-4 . y[H2O] gel is described. A well-d efined set of experiments, based on an experimental design, was carried out in order to rationalize the influence of the crystallization time/temperat ure, and r, x and y of the initial gel on the isomorphous substitution of C o2+ . CoAPO-11, CoAPO-44, CoAPO-46 were the main crystalline materials obta ined. These solids were characterized by X-ray diffraction (XRD), thermogra vimetrical analysis (TGA), scanning electron microscopy (SEM), electron mic roscope microprobe analysis (EMMA) and diffuse reflectance spectra (DRS), w hich resulted in a quantitative model relating the synthesis conditions wit h the overall crystallinity. In addition, a relation between the overall cr ystallinity and the degree of isomorphous substitution has been established . (C) 1999 Elsevier Science B.V. All rights reserved.