Architecture controlled PtNi@mSiO2 and Pt–NiO@mSiO2 mesoporous core–shell nanocatalysts for enhanced p-chloronitrobenzene hydrogenation selectivity

Abstract

Architecture controlled PtNi@mSiO₂ and Pt–NiO@mSiO₂ mesoporous core–shell nanocatalysts were synthesized for selective p-chloronitrobenzene hydrogenation to p-chloroaniline. Tetradecyl trimethyl ammonium bromide (TTAB) capped PtNi nanoparticles (NPs) were coated by SiO₂ through the hydrolysis of tetraethylorthosilicate. The resultant PtNi@SiO₂ core–shell NPs were calcined to remove TTAB to obtain mesoporous Pt–NiO@SiO₂ core–shell nanocatalysts (Pt–NiO@mSiO₂), which were subsequently reduced by hydrogen to form mesoporous PtNi@SiO₂ core–shell nanocatalysts (PtNi@mSiO₂). The relevant characterizations such as XRD, TEM, H₂-TPR, and BET confirm that the PtNi@mSiO₂ NPs consist of PtNi alloy nanoparticle cores and mesoporous SiO₂ shells while the Pt–NiO@mSiO₂ NPs contain Pt–NiO heteroaggregate nanoparticle cores and mesoporous SiO₂ shells. The catalytic results for selective hydrogenation of p-chloronitrobenzene show that the selectivity of p-chloroaniline formation over the PtNi@mSiO₂ and Pt–NiO@mSiO₂ nanocatalysts is significantly improved relative to that of control Pt@mSiO₂ nanocatalysts. Moreover, the PtNi@mSiO₂ and Pt–NiO@mSiO₂ nanocatalysts demonstrate high stability during multiple cycles of catalytic hydrogenation reactions. The enhanced catalytic performance is ascribed to the metal–metal interaction for the PtNi@mSiO₂ catalysts and metal–oxide interaction for the Pt–NiO@mSiO₂ catalysts.