Construction of a Respiratory-like Microenvironment on the Ultrafine Platinum Particles to Promote the Selective Hydrogenation of Nitroaromatics

Continuous technology is the future development direction of selective hydrogenation synthesis for fine chemicals. To achieve high hydrogenation performance at atmospheric pressure, it is necessary to construct a suitable microenvironment on the surface of the catalyst to achieve effective mass transfer at the gas–liquid–solid three-phase interface. Ultrafine metal clusters were obtained using Dicyandiamide (DICY) in the hydrothermal process. Subsequently, the alkylsilane was added to construct a respiratory-like microenvironment. (The microenvironment is similar to the respiratory channels, which regulate the entry and exit of substances rhythmically and dynamically, ensuring the continuous and efficient catalytic reaction). The continuous selective hydrogenation of nitroaromatics over Pt-AC(DICY)-C8 in a fixed-bed microreactor showed excellent hydrogenation ability, with the conversion of 2-chloro-4-nitrotoluene reaching 100% and the 3-chloro-4-methylaniline selectivity exceeding 99% within 80 h. The excellent hydrogenation performance is attributed to the highly dispersed Pt clusters, which increase the active sites. The respiratory-like microenvironment promotes the mass transfer of H2 and hydrophobic reactants, increasing the H2 concentration surrounding the Pt active site and the enrichment of reactants. Simultaneously, the respiratory-like microenvironment is conducive to the rapid diffusion of hydrophilic products and prevents excessive hydrogenation. This strategy shows the potential to improve the efficiency and stability of the continuous catalytic hydrogenation reaction.