Titanium (IV) oxide, an efficient and structure-sensitive heterogeneous catalyst for the preparation of azoxybenzenes in the presence of hydrogen peroxide

The titanium (IV) oxide is used as the catalyst in the heterogeneous liquid phase reaction for the oxidation of aniline and substituted anilines using dilute hydrogen peroxide as an oxidizing agent with different solvent conditions. Titanium (IV) oxide samples have been prepared under different experimental conditions by the sol-gel method. Experimental data showed that anatase form was an efficient catalyst for the title reaction and exhibited excellent selectivity (100%) and good yield (>90%) for the oxidation of aniline and substituted anilines, whereas the rutile form was found to be totally inactive. A high percentage of selectivity and good yields were achieved under mild reaction conditions. The recovered catalyst was used several times for the oxidation reaction with virtually no loss of activity. Overall a good catalytic activity and structure relationship was observed. (C) 2008 Elsevier B.V. All rights reserved.