A Predictable Catalyst Model for Highly Active and Selective Catalysis of Hydrogenation of Nitroarenes: Comprehension of Various Precious Metal Nanoparticles

Abstract

Various precious metal catalysts have been commonly used in catalytic reactions, but the differences and likeness between their catalytic performances are rarely systematically studied. Therefore, we have prepared the Pd, Pt, Rh, Ru, Au, and Ag/ Fe 3 O 4 catalysts, and the similarities and differences of various catalysts are analyzed by XRD, FT-IR, TEM, HR-TEM, XPS, BET, and VSM characterizations. Besides that platinum is the best catalyst component, the Pd and Rh/Fe 3 O 4 catalysts also exhibit excellent catalytic activity and chemoselectivity, but the Ru, Au, Ag-containing catalysts show poor catalytic performance for hydrogenation of 4-nitrophenol. According to the kinetic study, we have demonstrated that the reaction orders for Pd, Pt, and Rh are 0.8, 0.8, and 1.5, respectively. This result reveals that the activity of Pd, Pt, and Rh-containing catalysts can be precisely predicted. Moreover, our catalytic system is fascinating with many advantages such as environmental friendliness, mild reaction conditions, and the magnetic separability.[a] Dr. differences in their catalytic activity. Moreover, the TOF of the Pd, Pt, and Rh-containing catalysts is precisely predicable with the palladium, platinum, and rhodium content, and their predictable activity models can be built. Our catalytic system has unparalleled advantages with environmentally friendly, mild reaction conditions (low temperature and atmospheric H 2 pressure), and the magnetic separability. Furthermore, all of the Pd, Pt, and Rh-containing catalysts show outstanding reusability with at least 5 cycles. 2 3 4 5 6 7 8

Hydrogenation of Nitroarenes by Onsite-Generated Surface Hydroxyl from Water

“…Hydrogenation of nitroarenes to anilines (HNA) is a fundamentally important process for the synthesis of agrochemicals, dyes, pigments, pharmaceuticals, as well as polymers. − A molecular hydrogen (H 2 )-based hydrogenation pattern, in contrast to catalytic transfer hydrogenation by an organic hydrogen source, such as formic acid, NaBH 4 , N 2 H 4 , and NH 3 BH 3 , , has been the most widely used industrial pattern because of its readily scalable production and environmental-friendliness with water as the sole byproduct. However, it has been widely accepted that the conventional H 2 -based hydrogenation pattern typically requires noble metals (e.g., Rh, , Ru, Pd, Pt, − Au, , and Ir) as catalysts under relatively rigorous reaction conditions of above 100 °C and 10–50 bar. Moreover, the current production of high-purity H 2 is mainly from multistep and energy-intensive industries involving coal gasification or steam methane reforming (SMR) water–gas shift (WGS), etc. , From an overall perspective, the conventional H 2 -based hydrogenation pattern is essentially a multistep roundabout process that includes first the H 2 formation from surface hydrogen-containing species in the SMR or WGS and then the activation and dissociation of H 2 back to surface hydrogen species for the hydrogenation of unsaturated compounds in the hydrogenation reaction.…”

“…1−3 A molecular hydrogen (H 2 )-based hydrogenation pattern, in contrast to catalytic transfer hydrogenation by an organic hydrogen source, such as formic acid, 4 NaBH 4 , 5 N 2 H 4 , 6 and NH 3 BH 3 , 7,8 has been the most widely used industrial pattern because of its readily scalable production and environmental-friendliness with water as the sole byproduct. However, it has been widely accepted that the conventional H 2 -based hydrogenation pattern typically requires noble metals (e.g., Rh, 9,10 Ru, 11 Pd, 12 Pt, 13−15 Au, 16,17 and Ir 18 ) as catalysts under relatively rigorous reaction conditions of above 100 °C and 10−50 bar. Moreover, the current production of highpurity H 2 is mainly from multistep and energy-intensive industries involving coal gasification or steam methane reforming (SMR) water−gas shift (WGS), etc.…”

Encapsulating Electron-Rich Pd NPs with Lewis Acidic MOF: Reconciling the Electron-Preference Conflict of the Catalyst for Cascade Condensation via Nitro Reduction

“…In this study, we focus our exploration on the combination of UiO-66 and noble-metal nanoparticles to find a promising catalyst for the cascade reaction via nitro reduction. Noble-metal nanoparticles have been widely used in nitro reduction as the active catalyst. , When poly­(vinylpyrrolidone) (PVP) is used as a stabilizer of metal nanoparticles, Pd NPs become electron-rich because of the N-coordination of PVP as the ligand, so it is a good candidate for constructing the inner layer. UiO-66, which was developed by Lillerud and co-workers in 2008, has a Zr cluster center node with rich acid sites.…”

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

“…Under such a circumstance, great efforts have been made by the scientific community. Various heterogeneous catalysts based on different metals, including precious metals (Au, Pt, Pd, Rh, and Ru) and base metals (Fe, Zn, Co, Mo, and Ni), have been exploited for the selective hydrogenation of HNBs over the past years. Pt nanoparticles have attracted considerable attention because they exhibit good catalytic activity for reduction of nitro groups and a moderate degree of chemoselectivity .…”