Enhanced metal-support interaction over Pd-Au/TiO2 catalysts for vinyl acetate synthesis

The reaction of ethylene and acetic acid to produce vinyl acetate (VAM) was investigated on Pd-Au nanoparticles (NPs) supported on TiO2. Compared with the commercial catalyst Pd-Au/SiO2, Pd-Au/TiO2 exhibited a higher turnover frequency (TOF), likely due to the formation of smaller Pd-Au NPs (similar to 1.9 nm) and metal support interactions (MSI) between TiO2 with Pd-Au NPs. We found that the oxygen vacancies (OVs) of the TiO2 were regulated by adjusting the reduction temperature, facilitating electron transfer from TiO2 to the Pd-Au NPs, leading to enhanced MSI. In situ diffuse reflectance infrared Fourier transform spectroscopy (In situ DRIFTs) and density functional theory (DFT) calculations indicated that the electron-rich Pd-Au NPs of Pd-Au/TiO2 catalyst enhanced O-2 activation for increased TOF, and also promoted AcOH dehydrogenation and the key reaction of ethylene and acetate coupling. Our findings demonstrated that reducible supports could effectively influence the electronic properties of Pd-Au NPs through the construction of MSI, thereby enhancing catalytic activity.