Supported Catalysts Weiting Yu,† Marc D. Porosoff,† and Jingguang G. Chen*,†,‡,§ †Catalysis Center for Energy Innovation, Department of Chemical and Bimolecular Engineering, University of Delaware, Newark, Delaware 19716, United States ‡Department of Chemical Engineering, Columbia University, New York, New York 10027, United States Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, United States

Review of Pt-based bimetallic catalysis: from model surfaces to supported catalysts.

Alkynes can be selectively hydrogenated into alkenes on solid palladium catalysts. This process requires a strong modification of the near-surface region of palladium, in which carbon (from fragmented feed molecules) occupies interstitial lattice sites. In situ x-ray photoelectron spectroscopic measurements under reaction conditions indicated that much less carbon was dissolved in palladium during unselective, total hydrogenation. Additional studies of hydrogen content using in situ prompt gamma activation analysis, which allowed us to follow the hydrogen content of palladium during catalysis, indicated that unselective hydrogenation proceeds on hydrogen-saturated β-hydride, whereas selective hydrogenation was only possible after decoupling bulk properties from the surface events. Thus, the population of subsurface sites of palladium, by either hydrogen or carbon, governs the hydrogenation events on the surface.

https://science.sciencemag.org/content/sci/320/5872/86.full.pdf

The roles of subsurface carbon and hydrogen in palladium-catalyzed alkyne hydrogenation.

/pdf/chemicals-from-alkynes-with-palladium-catalysts-2z3b447mxh.pdf

Chemicals from Alkynes with Palladium Catalysts

Selective oxidation of primary carbon-hydrogen bonds with oxygen is of crucial importance for the sustainable exploitation of available feedstocks. To date, heterogeneous catalysts have either shown low activity and/or selectivity or have required activated oxygen donors. We report here that supported gold-palladium (Au-Pd) nanoparticles on carbon or TiO2 are active for the oxidation of the primary carbon-hydrogen bonds in toluene and related molecules, giving high selectivities to benzyl benzoate under mild solvent-free conditions. Differences between the catalytic activity of the Au-Pd nanoparticles on carbon and TiO2 supports are rationalized in terms of the particle/support wetting behavior and the availability of exposed corner/edge sites.

https://science.sciencemag.org/content/sci/331/6014/195.full.pdf

Solvent-Free Oxidation of Primary Carbon-Hydrogen Bonds in Toluene Using Au-Pd Alloy Nanoparticles

Two-dimensional materials and single-atom catalysts are two frontier research fields in catalysis. A new category of catalysts with the integration of both aspects has been rapidly developed in recent years, and significant advantages were established to make it an independent research field. In this Review, we will focus on the concept of two-dimensional materials confining single atoms for catalysis. The new electronic states via the integration lead to their mutual benefits in activity, that is, two-dimensional materials with unique geometric and electronic structures can modulate the catalytic performance of the confined single atoms, and in other cases the confined single atoms can in turn affect the intrinsic activity of two-dimensional materials. Three typical two-dimensional materials are mainly involved here, i.e., graphene, g-C3N4, and MoS2, and the confined single atoms include both metal and nonmetal atoms. First, we systematically introduce and discuss the classic synthesis methods, advanced ...

Catalysis with Two-Dimensional Materials Confining Single Atoms: Concept, Design, and Applications.

The effect of various changes to the palladium catalyst during its stabilization in the course of the selective hydrogenation of ethyne‐ethene mixtures (formation of hydride and carbide phases and of carbonaceous deposits) was reviewed. The deposits in the form of a carbonaceous overlayer on the palladium surface create sites at which selective ethyne hydrogenation to ethene can occur. The carbonaceous deposit on the support increases the selectivity to ethane formation by increasing the rate of ethene hydrogenation on support sites (spillover of hydrogen from metal to the support surface) and by decreasing the effective diffusivity of ethyne in the pores.

Selective Hydrogenation of Ethyne in Ethene‐Rich Streams on Palladium Catalysts. Part 1. Effect of Changes to the Catalyst During Reaction

Developments in the last three decades of kinetics of selective hydrogenation of ethyne in ethene‐rich streams on palladium catalysts are reviewed. Most of the studies can be described comprehensively by a model that assumes carbonaceous deposits (i) create irreversibly on the palladium surface small A types of active site (selective to ethene) and large E types of active site (selective to ethane), and (ii) are involved in hydrogenation of ethene on E s sites on the support. The relative importance of these sites, with varying (i) reaction conditions, (ii) palladium dispersion, (iii) process modifiers, and (iv) promoters, is discussed.

Selective Hydrogenation of Ethyne in Ethene‐Rich Streams on Palladium Catalysts, Part 2: Steady‐State Kinetics and Effects of Palladium Particle Size, Carbon Monoxide, and Promoters

Universal mathematical relations between the mean relative size of metallic crystallites (drel(VS)) and their dispersion (FE) in supported metal catalysts have been developed. The relations are:  drel(VS) = 5.01/FE for FE 0.2 the commonly used definition of dVS should be modified. The developed relations apply well to various thermodynamically probable crystallite shapes including fcc cubooctahedra of varying geometry, icosahedra, surface-reconstructed cubooctahedra, bcc rhombic dodecahedra, and hcp truncated bipyramids. The new relations are more precise than the commonly used equation dVS = a/FE, where a is a constant specific to a given metal.

Relation between Crystallite Size and Dispersion on Supported Metal Catalysts

The kinetics of hydrogenation reactions of acetylene–ethylene mixtures over a Pd/α-Al 2 O 3 commercial catalyst was studied. Reaction rates were measured by using a gradientless reactor. The kinetic expressions derived, based upon a mechanism involving two types of active sites produced on the palladium surface by carbonaceous deposits, were used for the interpretation of experimental results. The kinetic parameters in these equations and in recently published kinetic expressions were estimated by using multiresponse technique. Statistical analysis of regression showed that the proposed kinetic model describes the process more adequately than do the competitive models.

The kinetic model of hydrogenation of acetylene–ethylene mixtures over palladium surface covered by carbonaceous deposits

Palladium nanocrystals supported on helical carbon nanofibers for highly efficient electro-oxidation of formic acid, methanol and ethanol in alkaline electrolytes

Andrzej Borodzinski

Papers

Selective Hydrogenation of Ethyne in Ethene‐Rich Streams on Palladium Catalysts. Part 1. Effect of Changes to the Catalyst During Reaction

Selective Hydrogenation of Ethyne in Ethene‐Rich Streams on Palladium Catalysts, Part 2: Steady‐State Kinetics and Effects of Palladium Particle Size, Carbon Monoxide, and Promoters

Relation between Crystallite Size and Dispersion on Supported Metal Catalysts

The kinetic model of hydrogenation of acetylene–ethylene mixtures over palladium surface covered by carbonaceous deposits

Palladium nanocrystals supported on helical carbon nanofibers for highly efficient electro-oxidation of formic acid, methanol and ethanol in alkaline electrolytes