Unsupported Nanoporous Platinum–Iron Bimetallic Catalyst for the Chemoselective Hydrogenation of Halonitrobenzenes to Haloanilines

Abstract

An unsupported nanoporous platinum−iron bimetallic catalyst (PtFeNPore) was prepared with an electrochemical dealloying technique. Its structure and composition were characterized through various measurement methods, such as X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). An intermetallic compound and iron oxide species were both found in the PtFeNPore catalyst. The nanoporous structure and Lewis acidity (caused by iron oxide species) of the PtFeNPore catalyst resulted in superior catalytic activity and high selectivity. The PtFeNPore-catalyzed hydrogenation of various halonitrobenzenes proceeded successfully under mild reaction conditions and produced good to excellent yields of the corresponding haloanilines with high selectivity. PtFeNPore can be recycled through magnetic separation easily and reused five times without significant deactivation.

Recent Advances in Hydrogenation Reactions Using Bimetallic Nanocatalysts: A Review

“…[161,168,170,171] Y. Geng et al employed an unsupported nanoporous PtÀ Fe bimetallic catalyst prepared via electrochemical dealloying technique in the chemoselective hydrogenation of halonitrobenzene to haloaniline. [172] It was seen that p-chloro, p-bromo, and p-fluoro compounds gave about 88% selectivity to phaloaniline in methanol at room temperature in a hydrogen balloon atmosphere. However, p-iodo compound required a higher temperature and reported a yield of 86%.…”

“…In the presence of Pt−Fe catalyst, the NO 2 group was selectively adsorbed which induced further polarization of N=O and easy hydride attack by Pt−H. Hence NO 2 was exclusively reduced, preventing dehalogenation [172] …”

“…In the presence of PtÀ Fe catalyst, the NO 2 group was selectively adsorbed which induced further polarization of N=O and easy hydride attack by PtÀ H. Hence NO 2 was exclusively reduced, preventing dehalogenation. [172] In another study, Ir was doped with Fe via reverse microemulsion technique, and hydrogenation of nitrostyrene at 3 bar H 2 and 40 °C were carried out (Scheme 10). [170] IrFe/Fe 2 O 3 showed 86% conversion and 96% selectivity to 3-amino styrene at 195 min.…”

Synthesis of palladium‐chelated poly(triazine imide) heterogeneous nanocatalysts for reduction of p‐nitrophenol to p‐aminophenol

“…Although the high‐surface area and high‐surface‐to‐volume of small size Pd NPs provide rapid catalytic reactions in practical applications, unsupported‐Pd NPs have the tendency to easily aggregate in solutions, which reduces their high efficiency 28–31 . Hence, the way to overcome or minimize all these drawbacks is the immobilization of metal NPs on a variety of less expensive solid supports, including zeolite, metal oxides, surfactants, polymers and carbon materials, including graphene, graphene oxide, carbon nanotubes, and mesoporous carbon 2,25,32–41 …”

“…[24][25][26][27] Although the high-surface area and high-surface-tovolume of small size Pd NPs provide rapid catalytic reactions in practical applications, unsupported-Pd NPs have the tendency to easily aggregate in solutions, which reduces their high efficiency. [28][29][30][31] Hence, the way to overcome or minimize all these drawbacks is the immobilization of metal NPs on a variety of less expensive solid supports, including zeolite, metal oxides, surfactants, polymers and carbon materials, including graphene, graphene oxide, carbon nanotubes, and mesoporous carbon. 2,25,[32][33][34][35][36][37][38][39][40][41] Recently, graphitic-carbon nitride (g-C 3 N 4 ) materials have attracted numerous interests, arising from not only their ability to provide a valuable extension of carbon in novel material applications but also their exceptional chemical stability and outstanding properties.…”