Heterogeneous Catalytic Hydrogenation of N-Benzyl Nicotinamide: A Comparative Study with Nicotinamide Adenine Dinucleotide

Abstract

We report the hydrogenation of N-benzyl nicotinamide (BNA⁺) to 1,4-dihydro-N-benzyl nicotinamide (1,4-BNAH) using a Pt/SiO₂ catalyst under mild conditions (20 °C, 1 atm H₂). A production rate of 1,4-BNAH reaching 170 mmol-1,4-BNAH g-Pt⁻¹ h⁻¹ was achieved, which was approximately 6.8 times higher than that of 1,4-NADH (26 mmol-1,4-NADH g-Pt⁻¹ h⁻¹ or 12 mmol-1,4-NADH mmol-Pt surface active sites⁻¹ h⁻¹). This outcome stands in contrast to the photochemical reduction system, in which 1,4-NADH is formed more rapidly than 1,4-BNAH. Kinetic analysis revealed that both BNA⁺ and NAD⁺ hydrogenation were first-order in H₂ pressure; however, the reaction order with respect to NAD⁺ concentration was 0.14, indicating strong adsorption on Pt surface active sites, whereas that for BNA⁺ was 0.56, suggesting weaker adsorption that contributes to the enhanced 1,4-BNAH production rate. Moreover, the Pt/SiO₂ catalyst exhibited excellent recyclability, retaining its activity over three consecutive cycles without deactivation. This stability is attributed to the weaker adsorption of BNA⁺, mitigating catalyst fouling. Consequently, hydrogenation of BNA⁺ emerges as a promising strategy for cofactor regeneration in biocatalytic processes.