Direct ring C H bond activation to produce cresols from toluene and hydrogen peroxide catalyzed by framework titanium in TS-1

A series of TS-1 samples with varying Ti content was prepared and applied in the partial oxidation of toluene with H2O2 as oxidant. The TS-1 samples and relevant systems were characterized by XRD, FT-IR, in situ FT-IR, nitrogen adsorption/desorption, DR UV–vis, XPS, ICP-AES, EPR, SEM, TEM and TG. The results showed that the framework Ti species was responsible for the selective ring CH bond activation, resulting in toluene hydroxylation; while the extra-framework Ti species was advantageous to the formation of side chain oxidation products and to the deep oxidation of both kinds of the products formed. Under the optimized reaction conditions, the toluene conversion reached 38.9% with 84.3% selectivity to cresols (TOF, 2.66 h−1), while, the selectivity of para-cresol was 66.8%, which might be caused by the pore structure and steric hindrance of methyl group. The catalyst regenerated by calcination exhibited stable activity and selectivity after the second run.