Highly Efficient Hydrogenation of Nitrobenzene to Aniline over Pt/CeO₂ Catalysts: The Shape Effect of the Support and Key Role of Additional Ce³⁺ Sites

Abstract

Pt/CeO 2 catalysts with different support shapes and prereduction temperatures were prepared and tested in the liquidphase hydrogenation of nitrobenzene. Detailed characterizations reveal that the support shape effect of Pt/CeO 2 catalysts on nitrobenzene hydrogenation originates from the exposed crystal planes on CeO 2 with different reducibilities. A high-energy surface is readily reduced to generate more Ce 3+ surface sites and oxygen vacancies, not only favoring the dispersion and stabilization of Pt species due to stronger metal−support interaction but also providing more adsorption sites for reactants and intermediates. Reduction treatment at high temperatures has been proved to be an effective way to improve the performance of Pt/CeO 2 catalysts by providing additional Ce 3+ surface sites and high H-spillover capability. The additional Ce 3+ far away from Pt, derived from a high-temperature reduction, can adsorb the N-phenylhydroxylamine intermediate more effectively due to its stronger electron-donating ability and in turn promote aniline formation. It is also found that Na ions with suitable content facilitate the generation and stabilization of surface Ce 3+ by charge transfer and help Pt particles to maintain a smaller size. Consequently, a 0.25 wt % Pt catalyst, supported on Na-containing CeO 2 nanorods and reduced at 600 °C, displays a high level of aniline productivity of 40.8 mol AN /g Pt /h and excellent stability in nitrobenzene hydrogenation at room temperature. A pathway of nitrobenzene hydrogenation catalyzed by Pt/CeO 2 is also proposed.

A Magnetically Separable Pd Single‐Atom Catalyst for Efficient Selective Hydrogenation of Phenylacetylene

“…To investigate whether activated H * was spilled to the carbon shell, WO 3 as an indicator was mixed with Pd 1 /Ni@G physically to conduct the phenylacetylene semi‐hydrogenation reaction, because the spilled‐over hydrogen migrates and readily reacts with the yellow WO 3 to form dark blue H x WO 3 . [ 39,47–49 ] As seen in Figure S20, Supporting Information, the WO 3 alone in the reaction system exhibited an unchanged color under the same hydrogenation conditions. In contrast, WO 3 was reduced visibly as the mixture solution of catalyst and substrate changed its color from grey into light green, indicating the occurrence of hydrogen spillover (Figure S20, Supporting Information).…”

Highly-efficient RuNi single-atom alloy catalysts toward chemoselective hydrogenation of nitroarenes

“…5b ). The FT-IR spectra of gaseous 4-NS shows three characteristic peaks located at 1603, 1528, and 1356 cm –1 , attributing to ν (C=C), ν as (NO 2 ), and ν s (NO 2 ), respectively 46 – 48 . In the presence of monometallic Ni, a red-shift of all these three bands is observed: v (C=C) (1595 cm –1 ), ν as (NO 2 ) (1520 cm –1 ), and ν s (NO 2 ) (1351 cm –1 ), indicating both C=C and −NO 2 groups undergo chemisorption on the surface of Ni (most likely parallel adsorption configuration).…”

Dual Modification of Carbon Support Enables Robust Anchoring of Ruthenium Nanoclusters for Efficient Hydrogen Evolution and Aromatic Nitroreduction

“…To solve this challenge, various catalyst supports have been designed and developed for dispersing and anchoring metallic nanocatalysts. [5][6][7][8][9][10][11][12] Besides, as suggested by previous studies, [1] catalyst support may also play essential roles in tuning the size and intrinsic activity of catalyst. Thus, an ideal catalyst support should have large specific surface area, high electrical conductivity, strong cohesion to catalyst, and good resistance toward severe reaction condition.…”