Synthesis of pillared clays with Al 13-Fe and Al 13-Fe-Ce polymers in solid state assisted by microwave and ultrasound: Characterization and catalytic activity

Abstract

A new methodology for the synthesis of pillared clays with the Al 13-Fe and Al 13-Fe-Ce polymers in solid state was developed by using microwaves and ultrasound in the aging of the olygomeric solution, in the precipitation of the corresponding sulphates, and in the intercalation of the polymer with the powdered clay. This methodology reduces significantly the water consumption in the intercalation process, and the time for the synthesis of both the polymer in the solid state, and the pillared clay. The resulting polymers were characterized by XRF, XPS, XRD and SEM. The XRF analysis showed that a high percentage of Fe and Ce associated to Al 13-Fe and Al 13-Fe-Ce sulphates, was dissociated during the exchange process with nitrate. Using XPS analyses we established the presence of Ce (III) in the polymers. By means of XRD and SEM we determined that Al 13 and Al 13-Fe sulphates present a monoclinical structure, whereas the Al 13-Fe-Ce sulphates present two crystalline phases, monoclinical and cubical, whose cell parameters are slightly different from those of the sulphates reported in literature. The XRD, XRF and sortometry analyses showed that the pillared clays (synthesized with the proposed methodology), show more intense and remarkably homogenous pillaring signals, and also better textural properties than the clays pillared by the conventional method of synthesis. The catalytic activity was assessed in the phenol oxidation in dilute aqueous medium at 25 °C and at atmospheric pressure. The solids synthesized showed similar catalytic properties than those reported for the solids synthesized by the conventional method.