Effect of Pt/Co Ratio of Pt–Co Nanoparticles on Ionic Liquid-Modified SBA-15 for Selective Hydrogenation of Cinnamaldehyde

A series of Pt–Co bimetallic nanoparticles with different Pt/Co atomic ratios were prepared on ionic liquid-modified SBA-15 for selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) under solvent-free reaction conditions. The addition of Co significantly modified the electronic properties of Pt and affected the activity of the prepared bimetallic nanoparticles. Removal of Cl from Pt in NaBH4 solution was more effective with higher amounts of Co, which promoted the formation of a Pt–Co alloy in the sample and further increased the charge density of Pt due to charge transfer from Co to Pt on the nanoparticles, as revealed by XAFS. The presence of Ptδ− and Coδ+ in the bimetallic nanoparticles promotes hydrogen dissociation and CAL adsorption via C═O. The activity and COL selectivity of bimetallic catalysts gradually improved when the Pt/Co ratios decreased from 3:1 to 1:3. The highest performance was achieved over PtCo3/IL-SBA-15 (Pt/Co═ 1:3) with a COL selectivity of 98.2%. The catalyst was very stable, with no significant decrease in activity at the fifth recycling run. This work highlights the effect of Co addition on the formation of Pt–Co alloys and their compositions prepared via chemical reduction and provides an understanding of CAL activation on the nanoparticles with different surface compositions.