Fabrication of supported Pd–Ir/Al₂O₃ bimetallic catalysts for 2‐ethylanthraquinone hydrogenation

Abstract

A series of χ wt % Pd‐(1‐χ) wt % Ir (χ = 0.75, 0.50, and 0.25) catalysts supported on γ‐Al2O3 have been prepared by co‐impregnation and calcination‐reduction, and subsequently employed in the hydrogenation of 2‐ethylanthraquinone—a key step in the manufacture of hydrogen peroxide. Detailed studies showed that the size and structure of the bimetallic Pd–Ir particles vary as a function of Pd/Ir ratio. By virtue of its small metal particle size and the strong interaction between Pd and Ir, the 0.75 wt % Pd–0.25 wt % Ir/Al2O3 catalyst afforded the highest yield of H2O2, some 25.4% higher than that obtained with the monometallic 1 wt % Pd catalyst. Moreover, the concentration of the undesired byproduct 2‐ethyl‐5,6,7,8‐tetrahydroanthraquinone (H4eAQ) formed using the Pd–Ir bimetallic catalysts was much lower than that observed with the pure Pd catalyst, which can be assigned to the geometric and electronic effects caused by the introduction of Ir. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3955–3965, 2017

Synthesis of carbon-supported bimetallic palladium–iridium catalysts by microemulsion: characterization and electrocatalytic properties

“…Two iridium states are registered by XPS in our PdIr/C catalysts, similarly to PdIr/TiO 2 [58], PdIr/ Al 2 O 3 [52,53] PdIr/C [30] and PdIr nanoporous aggregates [32]. The lower Ir 4f 7/2 binding energy of 60.8-61.3 eV could be ascribed to the metallic Ir°.…”

“…The Ir 4f 7/2 binding energy of metallic iridium Ir°i n the monometallic Ir catalysts was reported in the range of 60. [51] and Ir/γ-Al 2 O 3 [52,53]. These states were observed at 61.1 and 62.8 eV in series of Ir/SiO 2 [54].…”

“…0.7 H/Pd). No PdH x hydride formation has been observed by the TPR measurements for the Pd-Ir/Al 2 O 3 catalysts [52]. In general, the extent of β-PdH hydride formation was found to be a semiquantitative but very sensitive approach to evaluate the alloying extent in the bimetallic systems like Pd-Ag, Pd-Au, Pd Re, etc.…”

Structurally Disordered Pd−P Nanoparticles as Effective Catalysts for the Production of Hydrogen Peroxide by the Anthraquinone Method

“…Starting from the sixth cycle, the yield of H 2 O 2 decreased from 96.0 % (in the first cycle) to 78 % (in the ninth cycle, on the ninth day). Considering the yield of H 2 O 2 as a characteristic of stability, the PdÀ P/C catalyst is even superior compared with many well-known literary analogues, including Pd monometallic and bimetallic catalysts: 1 wt % Pd/Al 2 O 3 [23] and PdÀ Ir/Al 2 O 3 (0,75 wt % Pd; 0,25 wt % Ir [24] (Table 1)). In terms of H 2 O 2 yield, the initial PdÀ P catalyst nanoparticles (PdÀ P/C) are superior to colloidal Pd/PANI solutions (PANI -polyaniline) (the yield of H 2 O 2 was 85 %).…”

Enhanced catalytic performance of Pd‐Ga bimetallic catalysts for 2‐ethylanthraquinone hydrogenation

“…It has been reported that the support with weak alkalinity possessing high electron density improves the electron density of Pd, which facilitates H 2 activation/dissociation and inhibits the formation of by‐products . In addition, numerous studies have been dedicated to improve the catalytic performance of Pd‐based catalysts by adding promoters, such as Ir, Ni, Co, Ru, La and Zn . Nevertheless, due to the limited catalytic performance of Pd catalysts for 2‐ethylanthraquinone hydrogenation, highly active and stable catalytic materials still need to be developed.…”