Direct Benzyl Alcohol and Benzaldehyde Synthesis from Toluene over Keggin-Type Polyoxometalates Catalysts: Kinetic and Mechanistic Studies

Abstract EN

The catalytic activity of various Keggin polyoxometalate catalysts has been investigated in the gas-phase partial oxidation of toluene to produce benzyl alcohol and benzaldehyde.

The catalyst systems HPMo12O40, HPMo11VO40, FePMo12O40, and PMo11FeO39 were prepared and characterized by FT-IR, UV-visible, SEM, XRD, TGA, and cyclic voltammetry.

The acid/base properties were evaluated using the decomposition of isopropanol.

Catalytic studies were carried under atmospheric pressure and over the temperature range 200°C–350°C, using carbon dioxide as a mild oxidant.

Toluene conversion and product distribution depend mainly on the catalyst composition and operating conditions.

In addition to benzaldehyde, benzyl alcohol is obtained with a high selectivity on the PMo11FeO39 catalyst.

The kinetic data show that the reoxidation of the reduced catalyst is the rate-limiting step for the partial oxidation reaction of toluene.