Synthesis of pillared clays with Al–Fe and Al–Fe–Ce starting from concentrated suspensions of clay using microwaves or ultrasound, and their catalytic activity in the phenol oxidation reaction

A new methodology for the synthesis of pillared clays with Al–Fe and Al–Fe–Ce was developed, in which the clay is added directly to the pillaring solution, and microwaves or ultrasound are used in the synthesis of the pillaring solution as well as in the intercalation process. That methodology allows the volumes of water and the processing time to decrease significantly compared to the conventional method of synthesis of pillared clays. The analysis of XRD, XRF and adsorption–desorption isotherms show that the synthesized solids present more intense and homogeneous signals of pillaring and better texture properties than the clay pillared using the conventional method of synthesis. The XPS analysis shows that the Fe and Ce species are located preferably in the inner parts of the pillared clays. The catalytic activity of the pillared clays was evaluated in the phenol oxidation reaction in a diluted aqueous medium where the synthesized materials showed catalytic properties comparable to those of the materials synthesized through the conventional method reported in the literature.