Transition Metal Oxide-Modified Ir Nanoparticles Supported on SBA-15 Silica for Selective Hydrogenation of Substituted Nitroaromatics

Abstract

Modification of active metals with metal oxide modifiers has attracted considerable attention in heterogeneous catalysis due to their synergistic effect. However, a controllable synthesis of highly reactive and stable metal–metal oxide hybrid nanocatalysts is difficult. To solve this problem, presynthesized IrM (M = Fe, Co, and Ni) bimetallic nanoparticles were initially confined in the mesopores of SBA-15 and were then in situ transformed to Ir-MO x hybrids. The obtained Ir-MO x /SBA-15 nanocatalysts show superior activity and selectivity in the hydrogenation of substituted nitroaromatics to corresponding aromatic amines compared to Ir/SBA-15. Among these Ir-based catalysts, Ir-FeO x /SBA-15 exhibits the highest activity and selectivity and has a wider substrate scope due to the interaction between Ir and FeO x . Therefore, our research provides a way to design reactive and stable hydrogenation catalysts.

Adsorption and Catalytic Activity of Gold Nanoparticles in Mesoporous Silica: Effect of Pore Size and Dispersion Salinity

“… 12 , 13 Recent studies have proposed to overcome such a limitation by immobilizing catalytic NPs within an inert porous matrix. 14 − 16 Here, the NPs are either synthesized within the confined pore space or the presynthesized NPs are physically/chemically adsorbed onto the pore walls. The immobilization of NPs in porous material is anticipated to preserve the NP stability in extreme environments such as high salinity media while retaining the catalytic activity, albeit reduced due to mass transport limitations (discussed later).…”

“…The stability and spatial distribution of metallic nanoparticles (NPs) in aqueous solution is the key in harvesting their unusual properties in the fields of pharmaceuticals, biosensors, and catalysis. − Due to the high surface energy and large surface area-to-volume ratio, the dispersed state of metallic NPs in aqueous solution is thermodynamically unfavorable leading to their spontaneous aggregation. − A common strategy to stabilize NPs in aqueous medium is via physical/chemical adsorption of surfactants or ligands onto NPs imparting a kinetic barrier against the aggregation. − However, the surfactants or ligands can significantly alter the physical and chemical properties of the NPs, especially their catalytic performance in aqueous media. , Recent studies have proposed to overcome such a limitation by immobilizing catalytic NPs within an inert porous matrix. − Here, the NPs are either synthesized within the confined pore space or the presynthesized NPs are physically/chemically adsorbed onto the pore walls. The immobilization of NPs in porous material is anticipated to preserve the NP stability in extreme environments such as high salinity media while retaining the catalytic activity, albeit reduced due to mass transport limitations (discussed later).…”

Tailoring the activity and selectivity of Rh/SiO2 for the selective hydrogenation of phenol by CoOx promotion

“…34 However, inducing such SMSI effects need reducible support and high-temperature H 2 reduction, which greatly hindered its application. 35 Recently, promoting noble metal NPs with nanosized transition metal oxide is a new strategy to regulate the catalytic activity and selectivity in various hydrogenation reactions. [35][36][37] Compared to the traditional SMSI structure, this metal-metal oxide hybrid structure and its catalytic performance could be more precisely controlled.…”

“…35 Recently, promoting noble metal NPs with nanosized transition metal oxide is a new strategy to regulate the catalytic activity and selectivity in various hydrogenation reactions. [35][36][37] Compared to the traditional SMSI structure, this metal-metal oxide hybrid structure and its catalytic performance could be more precisely controlled. For example, Xu et al developed MoO x promoted Ir/TUD-1 catalysts with precise control of the coverage of metal oxides for the selective hydrogenation of crotonaldehyde to produce protocol.…”

“…34 However, inducing such SMSI effects need reducible support and high-temperature H 2 reduction, which greatly hindered its application. 35…”