Efficient oxyfunctionalization of n-hexane by aqueous H2O2 over a new TS-PQ™ catalyst

The oxyfunctionalization of n-hexane by aqueous H2O2 was found to proceed substantially faster over a titanium-containing pentasil type catalyst denoted as TS-PQ™ (a trademark of PQ corporation for this titanium silicate material), than over other comparable titanium-containing zeolites. This catalyst has an unprecedented >99% efficiency in utilizing H2O2 in the oxidation of a paraffin. The effect of temperature, stirring rate, pH, solvent, and reactant ratios on the reaction rate, H2O2 efficiency, and product selectivity were evaluated over the TS-PQ™ silicate using a statistically designed catalytic test performed in an atmospheric batch reactor. Accurate reaction times were determined by continuously monitoring H2O2 consumption. Hydrated and in situ dehydrated TS-PQ™ titanium silicate samples were studied in a diffuse reflectance (DRIFT) cell by FT-UV and FT-IR spectroscopy. Unlike TS-1 catalysts that mainly contain isolated Ti4+ ions in tetrahedral lattice positions, TS-PQ™ silicate contains tetrahedral and higher coordination Ti4+ ions. Slightly acidic conditions affect favorably the reaction rate and C2 regioselectivity over the TS-PQ™ catalyst. In contrast to TS-1, applying methanol (MOH) as co-solvent had little or negative effect on the reaction rate and the selectivity of TS-PQ™ catalyst for the oxyfunctionalization of n-hexane.