Selective Hydrogenation over Supported Metal Catalysts: From Nanoparticles to Single Atoms

Abstract

Selective catalytic hydrogenation has wide applications in both petrochemical and fine chemical industries, however, it remains challenging when two or multiple functional groups coexist in the substrate. To tackle this challenge, the “active site isolation” strategy has been proved effective, and various approaches to the site isolation have been developed. In this review, we have summarized these approaches, including adsorption/grafting of N/S-containing organic molecules on the metal surface, partial covering of active metal surface by metal oxides either via doping or through strong metal–support interaction, confinement of active metal nanoparticles in micro- or mesopores of the supports, formation of bimetallic alloys or intermetallics or core@shell structures with a relatively inert metal (IB and IIB) or nonmetal element (B, C, S, etc.), and construction of single-atom catalysts on reducible oxides or inert metals. Both advantages and disadvantages of each approach toward the site isolation have been discussed for three types of chemoselective hydrogenation reactions, including alkynes/dienes to monoenes, α,β-unsaturated aldehydes/ketones to the unsaturated alcohols, and substituted nitroarenes to the corresponding anilines. The key factors affecting the catalytic activity/selectivity, in particular, the geometric and electronic structure of the active sites, are discussed with the aim to extract fundamental principles for the development of efficient and selective catalysts in hydrogenation as well as other transformations.

Gold catalysts containing interstitial carbon atoms boost hydrogenation activity

“…Gold is among the least active metals toward molecules at a solid–liquid or solid–gas interface. For example, it has the highest energy barrier for the dissociation of H 2 and the least stable chemisorption state 1 – 3 . This inertness has been attributed to the full filling of the antibonding d state on adsorption and the small orbital overlap with the adsorbate according to the d -band model 1 , 4 .…”

Strong metal-support interaction promoted scalable production of thermally stable single-atom catalysts

“…I n recent years, single-atom catalysts (SACs) have attracted considerable attention as a means by which to maximize precious metal utilization and generate well-defined, uniform active sites [1][2][3][4][5][6][7][8][9] . SACs exhibit superior catalytic performance (activity and/or selectivity) for thermal oxidation 1,10-12 and hydrogenation 9,[13][14][15][16][17] , electrochemistry [18][19][20][21][22][23] , and industrially important processes such as the water-gas shift reaction, C-C coupling, C-H activation, and methanol reforming 11,[24][25][26][27] . Counter-intuitively, SACs were recently reported to exhibit better stability than their nanoparticle (NP) counterparts, highlighting their potential for commercial applications 28,29 .…”

Direct Transformation of Glycerol to Propanal using Zirconium Phosphate‐Supported Bimetallic Catalysts

“…It has been known that as the homolytic dissociation of H 2 normally requires the denotation of d-electrons of metal to H 2 , and therefore a high electron density of the Ru sites is beneficial for the H dissociation. [59] The dissociated hydrogen atoms could diffuse into the adjacent unsaturated Co sites and facilitate hydrogenation reaction. It has been reported that the selective hydrogenation of C=C bonds could be improved by the metalÀ support/promoter interaction to modulate the electronic properties of metal active site.…”