Technology development for the production of biobased products from biorefinery carbohydrates—the US Department of Energy’s “Top 10” revisited

2.2. MOFs with Metal Active Sites 4614 2.2.1. Early Studies 4614 2.2.2. Hydrogenation Reactions 4618 2.2.3. Oxidation of Organic Substrates 4620 2.2.4. CO Oxidation to CO2 4626 2.2.5. Phototocatalysis by MOFs 4627 2.2.6. Carbonyl Cyanosilylation 4630 2.2.7. Hydrodesulfurization 4631 2.2.8. Other Reactions 4632 2.3. MOFs with Reactive Functional Groups 4634 2.4. MOFs as Host Matrices or Nanometric Reaction Cavities 4636

Engineering Metal Organic Frameworks for Heterogeneous Catalysis

Supported metal nanostructures are the most widely used type of heterogeneous catalyst in industrial processes. The size of metal particles is a key factor in determining the performance of such catalysts. In particular, because low-coordinated metal atoms often function as the catalytically active sites, the specific activity per metal atom usually increases with decreasing size of the metal particles. However, the surface free energy of metals increases significantly with decreasing particle size, promoting aggregation of small clusters. Using an appropriate support material that strongly interacts with the metal species prevents this aggregation, creating stable, finely dispersed metal clusters with a high catalytic activity, an approach industry has used for a long time. Nevertheless, practical supported metal catalysts are inhomogeneous and usually consist of a mixture of sizes from nanoparticles to subnanometer clusters. Such heterogeneity not only reduces the metal atom efficiency but also frequent...

Single-atom catalysts: a new frontier in heterogeneous catalysis.

Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

Single-atom catalysis has arguably become the most active new frontier in heterogeneous catalysis. Aided by recent advances in practical synthetic methodologies, characterization techniques and computational modelling, we now have a large number of single-atom catalysts (SACs) that exhibit distinctive performances for a wide variety of chemical reactions. This Perspective summarizes recent experimental and computational efforts aimed at understanding the bonding in SACs and how this relates to catalytic performance. The examples described here illustrate the utility of SACs in a broad scope of industrially important reactions and highlight the advantages these catalysts have over those presently used. SACs have well-defined active centres, such that unique opportunities exist for the rational design of new catalysts with high activities, selectivities and stabilities. Indeed, given a certain practical application, we can often design a suitable SAC; thus, the field has developed very rapidly and afforded promising catalyst leads. Moreover, the control we have over certain SAC structures paves the way for designing base metal catalysts with the activities of noble metal catalysts. It appears that we are entering a new era of heterogeneous catalysis in which we have control over well-dispersed single-atom active sites whose properties we can readily tune. Single-atom catalysts are heterogeneous materials featuring active metals sites atomically dispersed on a surface. This Review describes methods by which we prepare and characterize these materials, as well as how we can tune their catalytic performance in a variety of important reactions.

Heterogeneous single-atom catalysis

Sustainable production of acrolein: investigation of solid acid–base catalysts for gas-phase dehydration of glycerol

In recent years, there has been an increasing interest in catalysis by nanosized gold catalysts, which are active in reactions such as CO oxidation, propylene epoxidation, hydrogenation of unsaturated compounds, vinyl chloride synthesis, and others. 5,11] Despite such a diverse spectrum of reactions, efforts have been mainly devoted to elucidating the catalytically active sites in the oxidation reactions. Little attention has been paid to the nature of active gold, especially cationic gold species, in the other reactions such as hydrogenation of unsaturated compounds. This is surprising, since catalytic hydrogenation is one category of the best studied and industrially most important reactions on conventional transition metal catalysts, 19] and Au ions in solution can activate carbon– carbon double and triple bonds and are finding applications as efficient homogeneous catalysts in many organic reactions. 21] Hydrogenation of 1,3-butadiene has long been a model reaction for the study of active sites on conventional metal catalysts. 19] A few preliminary investigations on the hydrogenation of 1,3-butadiene with supported gold catalysts showed that small gold nanoparticles were active in the reaction, although theoretical calculations seem to suggest that the surface of metallic gold is chemically inert for hydrogen activation. By using Au/ZrO2 catalysts with very low loadings of Au (< 0.1%), we have now discovered that isolated surface-type Au ions are actually the active sites for the selective hydrogenation of 1,3-butadiene. The activity and selectivity of these Au ions are comparable to those of conventional precious transition metals such as Pd and Pt. This finding that low loadings of Au ions are more active for the hydrogenation reaction than high loadings of Au nanoparticles could raise intensive interest in exploring the potential of surface-type Au ions in heterogeneous catalytic reactions. The use of isolated and heterogenized Au ions in catalysis and related materials may be the key to using the noble gold in areas usually reserved for conventional precious metal catalysts, for example, to significantly improve the economics and reduce the use of other precious metals. Figure 1 shows the effect of gold loading on 1,3-butadiene conversion over Au/ZrO2 catalysts calcined at 200 8C. No butane (i.e., the product of complete hydrogenation) but only butenes were detected as the hydrogenation products over all

Catalysis by Gold: Isolated Surface Au3+ Ions are Active Sites for Selective Hydrogenation of 1,3‐Butadiene over Au/ZrO2 Catalysts

Sustainable production of acrolein: Gas-phase dehydration of glycerol over Nb2O5 catalyst

Onewaytolowercostsistomakethemostefficientuseofthenoblemetalssothateverymetalatomisusedinthecatalyticprocess.Becausecatalysisattheelectrodeofafuelcellisasurfacephenomenon,theutilizationofPtinelectrocatalystscanbedefinedasthedispersionorexposedpercentageofPtatoms in the catalyst, which is approximately equal to thereciprocalofthePtparticlesizeinnanometers.

http://www.wiley-vch.de/contents/jc_2002/2006/z600155_s.pdf

Enhancement of Pt Utilization in Electrocatalysts by Using Gold Nanoparticles

CO2 reforming of CH4 was studied at 1030 K over Ni/ZrO2 catalysts with different preparations. It was shown that catalytic stability depends greatly on the preparation method of the support precursor. The catalyst prepared by impregnation of ultra-fine Zr(OH)4 (6 nm) particles with nickel nitrate showed high and extremely stable activity for syngas production. In contrast, the nickel catalyst prepared using bigger Zr(OH)4 particles deactivated rapidly. Also, the nickel catalyst made from co-precipitation of ultra-fine nickel–zirconium hydroxide (7 nm) was not resistant to coke deposition during the reaction.

Bo-Qing Xu

Papers

Sustainable production of acrolein: investigation of solid acid–base catalysts for gas-phase dehydration of glycerol

Catalysis by Gold: Isolated Surface Au3+ Ions are Active Sites for Selective Hydrogenation of 1,3‐Butadiene over Au/ZrO2 Catalysts

Sustainable production of acrolein: Gas-phase dehydration of glycerol over Nb2O5 catalyst

Enhancement of Pt Utilization in Electrocatalysts by Using Gold Nanoparticles

Highly active and stable Ni/ZrO2 catalyst for syngas production by CO2 reforming of methane