Bimetallic Pt-Fe catalysts supported on mesoporous TS-1 microspheres for the liquid-phase selective hydrogenation of cinnamaldehyde

Abstract

Mesoporous TS-1 microspheres (MTS-1-MS) were applied to load Pt-Fe bimetallic components with different Fe/Pt molar ratios for the liquid-phase selective hydrogenation of cinnamaldehyde (CAL) to produce cinnamyl alcohol (COL). Combining the XRD and XPS characterization results, Fe dopant co-existed as PtFe fcc alloy or FeOx species, which modified the electronic properties of Pt active sites through the electron transfer from Fe to Pt, therefore, the catalytic performance was improved remarkably with the Fe-doped Pt/MTS-1-MS catalyst. As a result, the PtFe0.25/MTS-1-MS-350 catalyst, which contains Fe amount with a Fe/Pt molar ratio of 0.25 and was calcined at 350 °C before reduction in hydrogen at 400 °C, furnished 95.7% CAL conversion and 89.2% COL selectivity with an initial activity (in terms of TOF value) reaching 19440 h−1, much better than its analogue Pt/MTS-1-MS-350, which only showed 56.6% CAL conversion and 74.4% COL selectivity under the same conditions. To the best of our knowledge, it is one of the most active Pt-Fe bimetallic catalysts up to now. Moreover, the PtFe0.25/MTS-1-MS-350 catalyst can also be cycled for at least 9 times without obvious loss in activity or COL selectivity. Furthermore, theoretical calculations based on several simplified surface models were conducted using the density-functional theory (DFT) to reveal the differences in electronic structures and geometric properties caused by Fe dopant and to explain the reason why CO hydrogenation was preferential on the PtFe0.25/MTS-1-MS-350 catalyst from the perspective of CAL adsorption and COL desorption on/from Pt-Fe surface.