Efficient adjustment of product selectivity using controllable Pd nanoparticles in nitroarene hydrogenation

Abstract

Product selectivity adjustment is a much-studied topic in mesoscience that is critical for industrial processes and strongly related to reaction intermediates formed by interactions between catalytic active sites and reactants. Herein, we report efficient adjustment of the product selectivity in the hydrogenation of substituted nitroarenes via rational reaction intermediates achieved using controllable Pd nanoparticles. Pd nanoparticles fixed within zeolite Beta crystals (Pd@Beta) afforded rational Pd–NO2 interactions, in which the Pd nanoparticle-adsorbed substituted nitroarenes, such as nitrobenzaldehyde, were reasonably hydrogenated into the corresponding aminobenzaldehyde. However, for Pd nanoparticles supported on the external surfaces of zeolite beta crystals, various side products were obtained owing to the coexistence of PdNO2 and PdCO interactions. When Pd nanoparticles were artificially controlled in various positions in a fixed-bed reactor, the product selectivity was significantly affected. These results demonstrate the importance of molecular adsorption and diffusion processes in adjusting product selectivity in catalytic reactions.