A mild solution chemistry method to synthesize hydrotalcite-supported platinum nanocrystals for selective hydrogenation of cinnamaldehyde in neat water

Abstract

Hydrotalcite-supported platinum nanocrystals (Pt NCs) were synthesized by a facile solution chemistry method, and then applied as an efficient catalyst for the selective hydrogenation of cinnamaldehyde (CMA) in neat water. The reduction of metal precursor ions was achieved in an aqueous solution at a low temperature (323 K), simultaneously accompanied by the crystallization of the hydrotalcite support. The size of the Pt NCs can be delicately tuned by the relative ratio of surfactant to metal precursor ions, and characterized by HRTEM and CO-adsorption infrared spectroscopy. The Pt particle sizes are closely associated with the hydrogenation selectivity toward cinnamyl alcohol (CMO), with a higher selectivity up to 85% over the larger-sized Pt in an aqueous medium. The effects of alkali (NaOH) on the catalytic performance were explored. The findings indicated that the addition of alkali enhances the selectivity toward CMO (to 90%). The catalysts showed high stability with a marginal decrease in activity and selectivity after repeated use. The hydrogenation products could be easily separated from the solvent by simple extraction, which is a greener and more convenient process than those using organic solvents.