The hydroxylation of benzene to phenol with hydrogen peroxide was investigated using different solvents and a series of catalysts, obtained by modification of titanium silicalite (TS-1). The best results were obtained after post-synthesis treatment of TS-1 with NH 4 HF 2 and H 2 O 2 . The new catalyst (TS-1B), used in the presence of a particular co-solvent (sulfolane) is able to protect the produced phenol from over-oxidation and dramatically enhanced the selectivity of the reaction.