Highly dispersed NiCu alloy nanoparticles supported on carbon-doped silica (NiCu/C@SiO2) were first prepared through the one-step impregnation with a mixed solution of nickel nitrate, cupric nitrate and glucose, followed by...

Highly dispersed Pt nanoparticles (∼2.5 nm) on phosphorus-doped activated coconut shell carbon (Pt/P-ACC) were synthesized by a two-step impregnation route. Pt/P-ACC showed a high activity, chemoselectivity, and reusability toward the hydrogenation of nitrobenzene to p -aminophenol, with hydrogen as the reducing agent in sulfuric acid. The effects of P species on the catalyst structure, surface properties, and catalytic performance were investigated. It was found that the Pt/P-ACC catalyst had an excellent catalytic activity due to its smaller Pt nanoparticles and higher content of surface-active metal compared with Pt/ACC. Besides, the experimental results and in situ infrared studies demonstrated that the interaction effect between the Pt and P species imbued the surface of Pt with an electron-rich feature, which decreased the adsorption of electron-rich substrates (that is, phenylhydroxylamine) and prevented their full hydrogenation, leading to enhanced selectivity during the hydrogenation of nitrobenzene to p -aminophenol.

Highly-dispersed Pt nanoparticles supported on nitrogen-modified CMK-3 mesoporous carbon (Pt/N-CMK-3) were first fabricated by a two-step impregnation route. The influences of N content on the catalyst porous structure, Pt nanoparticle size, surface properties, and interaction between Pt species and the support were investigated in detail using N2 sorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS). The N species acted as anchoring sites for the stabilization of Pt particles. Benefiting from the formation of ultrafine metal nanoparticles, the Pt/N-CMK-3 exhibited excellent catalytic activity and selectivity for the selective hydrogenation of nitro aromatics to the corresponding anilines with hydrogen. The Pt/N-CMK-3 catalyst could be reused eight times and keep its catalytic performance.

Carbon doped silica-supported NiCu alloy nanoparticles (Ni 1 Cu x /C@SiO 2 ) with different Cu/Ni molar ratio (x = 0.12, 0.24, 0.36) were fabricated via one-step impregnation, following in situ carbonization reduction. Effects of Cu content on catalyst structure, surface properties and particle sizes were investigated by Brunauer-Emmett-Teller (BET), inductively coupled plasma (ICP), Raman, X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The surface Ni 0 content increased with increasing Cu content, but showed a maximum at 0.24 of Cu/Ni molar ratio, because the smaller NiCu alloy nanoparticle formed and the segregation of antioxidative Cu atoms on the surface protected the metallic Ni from oxidation. The Ni 1 Cu x /C@SiO 2 were investigated for nitrobenzene hydrogenation with H 2 . The optimal Ni 1 Cu 0.24 /C@SiO 2 catalyst with the highest Ni 0 content showed markedly improved catalytic activity compared to monometallic Ni/C@SiO 2 . The Ni 0 species were the active sites for the hydrogenation of nitrobenzene. The Ni 1 Cu 0.24 /C@SiO 2 could transform various substituted nitroarenes to corresponding aromatic amines. Moreover, the Ni 1 Cu 0.24 /C@SiO 2 could be recycled for 8 times without decrease in catalytic performance, exhibiting superior anti-oxidation and anti-leaching abilities.

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