Selective hydrogenation of cinnamaldehyde with PtFe /Al2O3@SBA-15 catalyst: Enhancement in activity and selectivity to unsaturated alcohol by Pt-FeO and Pt-Al2O3@SBA-15 interaction

Selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) was conducted over a series of FeOx-doped Pt catalysts supported on a 15 wt% Al2O3@SBA-15 composite (15AS). It was found that the addition of FeOx to the catalyst greatly improved its performance. With an optimal Fe/Pt molar ratio of 0.25, the PtFe0.25/15AS catalyst reached a maximum reaction rate (defined as moles of converted CAL per gram of Pt per hour) of 13.93 mol gPt−1 h−1 with 76.9% selectivity to COL. Additionally, the PtFe0.25/15AS catalyst afforded the highest TOF value (defined as moles of converted CAL per mole of Pt active sites per second) of 1.54 s−1. X-ray photoelectron spectroscopy analyses and H2 temperature-programmed reduction and CO diffuse-reflectance infrared Fourier-transformation spectroscopy studies reveal that there is strong interaction between Pt nanoparticles and Al2O3@SBA-15 composites and also between Pt and FeOx, resulting in Pt species with a positive charge being dominant in PtFe0.25/15AS catalysts. Therefore, Pt species with positive charges, together with FeOx species, are beneficial for preferential adsorption and activation of carbonyl bonds of CAL, so that the activity and selectivity to COL were improved by PtFex/15AS catalysts (x represents the Fe/Pt molar ratio).