Efficient Pt–FeOx/TiO2@SBA-15 catalysts for selective hydrogenation of cinnamaldehyde to cinnamyl alcohol

Abstract

TiO₂ was coated onto mesoporous silica SBA-15 by hydrolysis of tetrabutyl titanate to prepare 15 wt% TiO₂@SBA-15 composites (15TS). The 15TS composites retain the mesostructure of the SBA-15 host, and TiO₂ was highly dispersed and uniformly coated. 5 wt% Pt nanoparticles supported on 15TS were employed for liquid-phase selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL). Compared with the Pt catalyst supported on pristine SBA-15, the Pt/15TS catalyst afforded higher activity and selectivity to COL. Furthermore, the modification of the Pt/15TS catalyst by FeO_x can greatly improve the activity and selectivity to COL. As a result, the Pt–FeO_x/15TS catalyst displayed excellent selectivity to COL (around 84.5%) at nearly complete CAL conversion. Of particular note is that further calcination of the Pt–FeO_x/15TS catalyst precursor in air at 773 K before reduction would greatly enhance the catalytic performance. Consequently, the TOF reached 3.06 s⁻¹ with a selectivity to COL of 86.4% over the Pt–FeO_x/15TS-773 catalyst. Moreover, the Pt–FeO_x/15TS-773 catalyst can also be reused about eight times without distinct loss in activity or selectivity. Based on characterization by XPS and H₂-TPR, the important promotion effect of FeO_x and strong metal–support interaction played key roles in preferential adsorption and activation of CO bonds in CAL.