Iron aluminium mixed pillared montmorillonite and the rare earth exchanged analogues as efficient catalysts for phenol oxidation

Iron aluminium mixed pillared montmorillonite prepared by partial hydrolysis method was exchanged with lanthanum, cerium and thorium metal salts. The pillared montmorillonite shows considerable increase in basal spacing and surface area. 27Al and 29Si nuclear magnetic resonance spectra show the presence of iron substituted Keggin cation as the pillaring species. Energy dispersive X-ray analysis shows the presence of about 2% rare earth metals. The prepared systems are excellent catalysts for hydroxylation of phenol underlining the use of eco-friendly clay catalysts for effective removal of pollutants. A detailed study of reaction variables suggests that oxidation of phenol increases with temperature and maximum conversion is obtained at 90 °C. Hydroquinone selectivity increases with phenol concentration and time but decreases with temperature.