InNi2 Intermetallic Catalysts for Enhanced Chemoselective Hydrogenation of Cinnamaldehyde: Electronic Modulation and Mechanistic Insights

Abstract The selective hydrogenation of α,β-unsaturated aldehydes represents a critical transformation in fine chemical manufacturing, requiring precise control of the chemoselectivity between the C═O and C═C bonds. In this work, we synthesized the InNi2 intermetallic compound supported by TiO2. The effects of Ni/In molar ratios and particle sizes on the catalytic hydrogenation performances were systematically investigated in the liquid-phase hydrogenation of cinnamaldehyde. The InNi2 intermetallic compound exhibited excellent activity and selectivity, achieving 98.6% conversion of cinnamaldehyde and 81.9% selectivity toward cinnamyl alcohol. Characterization techniques were carried out, including XRD, H2-TPR, HRTEM, XPS, CO-FTIR, and in situ FTIR spectroscopy and reaction kinetic studies. It revealed that indium incorporation facilitates the formation of InNi2 intermetallic compounds and enhances the electron density on nickel atoms. This electronic modification strengthens the C═O adsorption while increasing the C═C bond activation energy, thereby improving the hydrogenation selectivity. Notably, the 10Ni–In0.5/TiO2-R catalyst also demonstrates promising activity and selectivity to hydrogenate other unsaturated aldehydes (citral, furfural, and 3-methyl-2-butenal) to the corresponding unsaturated alcohols. Recycling experiments confirmed the excellent cyclic stability of the supported InNi2 intermetallic catalyst. This study provides mechanistic insights into the structure–performance relationship of bimetallic catalysts for the selective hydrogenation of aldehydes, offering guidance for the design of efficient catalytic systems for fine chemical synthesis.