Surface engineering of TeOx modification on MoVTeNbO creates a high-performance catalyst for oxidation of toluene homologues to aldehydes

Abstract

The heterogeneous catalytic oxidation of toluene by O₂ is an inherently safe and green route for production of benzaldehyde, but after more than fifty years of effort, it remains a great challenge. Here, we report the best heterogeneous catalyst, TeO_x/MoVTeNbO, up to now for the green oxidation of toluene by O₂ to benzaldehyde, balancing the catalyst activity, selectivity, and stability. The deposition of TeO_x endows the MoVTeNbO composite oxide with entirely new property for toluene oxidation and the surface engineering mechanism has been fully explained. The discrete TeO_x clusters on the surface, shielding the nonselective oxidation sites that interact strongly with the benzene ring of toluene molecule, allows toluene molecule to chemically adsorb to the surface perpendicularly and the methyl is then prone to oxidation to aldehyde on the reshaped selective oxidation sites, where V=O is the main active species responsible for continuously extracting hydrogen from methyl and implanting oxygen to form benzaldehyde. The TeO_x clusters participate in this reaction through variable valences and stabilize benzaldehyde by couple interaction with the –CHO group of benzaldehyde, thereby achieving high selectivity to benzaldehyde (>95%). The extended works indicate that the catalytic mechanism is effective in a series of selective oxidation of toluene homologues to corresponding aldehydes.