Design of Effective Catalysts for Selective Alkyne Hydrogenation by Doping of Ceria with a Single-Atom Promotor

Abstract

Since the discovery that ceria is an active catalyst for selective hydrogenation of alkynes, there has been much debate on the catalytic mechanism. In this work, we propose, based on density functional theory (DFT) investigations, a mechanism that involves the heterolytic dissociation of H at oxygen vacancies of CeO(111), facilitated by frustrated Lewis pairs consisting of spatially separated O and Ce sites. The resulting O-H and Ce-H species effectively catalyze the hydrogenation of acetylene, avoiding the overstabilization of the CH* intermediate in a previously proposed mechanism. On the basis of our mechanism, we propose the doping of ceria by Ni as a means to create oxygen vacancies. Interestingly, the Ni dopant is not directly involved in the catalytic reaction, but serves as a single-atom promoter. Experimental studies confirm the design principles and demonstrate much higher activity for Ni-doped ceria in selective hydrogenation of acetylene. The combined results from DFT calculations and experiment provide a basis to further develop selective hydrogenation catalysts based on earth-abundant materials.

Water‐Assisted Homolytic Dissociation of Propyne on a Reduced Ceria Surface

“…[2,3] These counterintuitive findings triggered numerous experimental and theoretical investigations into the mechanism of the selective hydrogenation of alkynes by ceria. [4] Hydrogen activation on ceria is generally considered to be the main rate-limiting step since the optimal reaction conditions require a large H 2 /alkyne ratio (30:1) and the conversion of alkyne increases as the H 2 partial pressure increases. [2][3][4] Extensive studies on the interaction of H 2 and ceria show that the dissociation of H 2 proceeds through a hydride intermediate.…”

Rh Doping in Pd Nanocubes Optimizes the Adsorption of 3‐Nitrostyrene towards Selective Hydrogenation of Vinyl Group

“…For example, doping of reduced grapheme oxides supported Pd catalyst with N dopants boosted the interaction between carbonyl (C=O) group and support, which prevented the C=O group from approaching Pd and hence improving the active and selective for hydrogenation of C=C group in cinnamaldehyde . Besides, the dispersion of Pd atoms over bimetallic nanoparticle surfaces was both disrupted formation of the β‐hydride phase and weakened ethylene adsorption, thereby demonstrating higher active and selective in hydrogenation of acetylene . Moreover, the incorporation of Fe into Pt‐based zigzag nanowires lowered electron density of the surface Pt atoms, which resulted in highly activity and unsaturated alcohol selectivity during the hydrogenation of α, β‐unsaturated aldehyde .…”

“…[15] Besides, the dispersion of Pd atoms over bimetallic nanoparticle surfaces was both disrupted formation of the β-hydride phase and weakened ethylene adsorption, thereby demonstrating higher active and selective in hydrogenation of acetylene. [16] Moreover, the incorporation of Fe into Pt-based zigzag nanowires lowered electron density of the surface Pt atoms, which resulted in highly activity and unsaturated alcohol selectivity during the hydrogenation of α, β-unsaturated aldehyde. [17] Furthermore, the doping of Co atoms into Ru catalysts compressed the Ru lattice strain, improving the selectivity for hydrogenation of 4nitrostyrene to 4-aminostyren without influence upon the conversion.…”

Wasserunterstützte homolytische Dissoziation von Propin auf reduzierter Ceroxidoberfläche

“…[2,3] Diese kontraintuitiven Erkenntnisse haben zahlreiche experimentelle und theoretische Untersuchungen zum besseren Verständnis des Mechanismus der selektiven Alkinhydrierung durch Ceroxid inspiriert. [4] Die Aktivierung von Wasserstoff auf Ceroxid wird allgemein als der wichtigste geschwindigkeitslimitierende Schritt der Reaktion angesehen, da die optimalen Reaktionsbedingungen ein deutlich unproportionales H 2 /Alkin-Verhältnis (30:1) erfordern und der Umsetzungsgrad des Alkins mit steigendem H 2 -Partialdruck zunimmt. [2][3][4] Umfangreiche Untersuchungen zur Wechselwirkung von H 2 und Ceroxid zeigen, dass die Dissoziation von H 2 über ein Hydrid-Intermediat verläuft.…”

“…[4] Die Aktivierung von Wasserstoff auf Ceroxid wird allgemein als der wichtigste geschwindigkeitslimitierende Schritt der Reaktion angesehen, da die optimalen Reaktionsbedingungen ein deutlich unproportionales H 2 /Alkin-Verhältnis (30:1) erfordern und der Umsetzungsgrad des Alkins mit steigendem H 2 -Partialdruck zunimmt. [2][3][4] Umfangreiche Untersuchungen zur Wechselwirkung von H 2 und Ceroxid zeigen, dass die Dissoziation von H 2 über ein Hydrid-Intermediat verläuft. [5] Sowohl die Anwesenheit von Sauerstoff-Leerstellen als auch die Oberflächenterminierung von Ceroxid spielen eine entscheidende Rolle bei der H 2 -Aktivierung.…”