Macroporous Magnetic Iron Oxides and Their Composites for Liquid-Phase Catalytic Oxidation

A novel synthetic approach is proposed to the production of macroporous magnetic iron oxides and their iron aluminate composites for liquid-phase catalytic oxidation. The materials were prepared by sol-gel synthesis where metal precursors were mixed with a colloidal template solution based on siloxane-acrylate latex. The pore structure and magnetic properties of the composites were studied as functions of temperature and magnetic field. The effects of the heat treatment schedule on the phase composition, porosity, and catalytic properties of the materials were elucidated. The results are supported by scanning electron microscopy, X-ray powder diffraction analysis, nuclear gamma resonance, and low-temperature nitrogen adsorption. The addition of aluminum ions in the course of sol-gel (template) synthesis allows the materials to preserve their pore structure upon high-temperature treatment, thereby improving the catalytic properties and significantly affecting the magnetic characteristics of the resulting magnetic composites.