Influence of OH/metal ratio on the stability of AlFe-PILC catalyst for wet peroxide oxidation of phenol

AlFe-pillared clay catalyst with OH/metal = 4; 5 mmol metal/g clay and Al : Fe = 5 : 5 swells intensively in phenol-water solution and has no measurable catalytic activity in phenol removal from water solutions, in contrast to the similar catalyst with OH/metal = 2. The different behavior of two samples can be explained first of all by differences in iron ion distribution in the catalysts as a consequence of applied pillaring solutions prepared at different OH/metal ratios. In the sample with OH/metal = 2 iron ions are uniformly distributed on the AlFe-pillars, while in the sample with OH/metal = 4 iron ions appear not only on the pillars but also as a bulk FeO center dot Fe(2)O3 center dot form. The results obtained by FTIR, SEM, TPR and Mossbauer spectroscopy reveal the differences in acid-base properties, morphology and iron ion distribution in the samples.