Solvent effect in selective hydrogenation of cinnamaldehyde over Pd–Ni nanoclusters encapsulated within siliceous zeolite

Abstract

Selective hydrogenation of unsaturated-organic compounds derived from biomass sources is a key step for producing chemicals and fuels, but it faces challenges in enhancing product selectivity and energy efficiency. Metal nanoparticles (NPs) encapsulated in zeolite crystals (metal@zeolite) are desirable and robust materials that can control catalytic activity and selectivity by tuning their structure. However, the solvent effect on selective hydrogenation over metal@zeolite has been unexplored, which plays a significant role in the reaction process. Here, the solvent effect on the selective hydrogenation of cinnamaldehyde (CAL), a representative substrate, over Pd–Ni bimetallic clusters encapsulated inside S-1 zeolite (Pd0.6Ni@S-1) was first reported. The results showed that Pd0.6Ni@S-1 effectively converted CAL into hydrocinnamaldehyde (HCAL) under mild conditions and that the product distribution was solvent-dependent by correlating the selectivity with solvent properties. The polarity of polar solvents affected the solvent-CAL interaction and thus the hydrogenation pathway. Our study reveals the importance of solvent engineering for selective hydrogenation over metal@zeolite catalysts and provides insights for designing efficient and robust materials for biomass conversion.