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.

Owing to the increasing emissions of carbon dioxide (CO2), human life and the ecological environment have been affected by global warming and climate changes. To mitigate the concentration of CO2 in the atmosphere various strategies have been implemented such as separation, storage, and utilization of CO2. Although it has been explored for many years, hydrogenation reaction, an important representative among chemical conversions of CO2, offers challenging opportunities for sustainable development in energy and the environment. Indeed, the hydrogenation of CO2 not only reduces the increasing CO2 buildup but also produces fuels and chemicals. In this critical review we discuss recent developments in this area, with emphases on catalytic reactivity, reactor innovation, and reaction mechanism. We also provide an overview regarding the challenges and opportunities for future research in the field (319 references).

Recent advances in catalytic hydrogenation of carbon dioxide

Unlike homogeneous catalysts, heterogeneous catalysts that have been optimized through decades are typically so complex and hard to characterize that the nature of the catalytically active site is not known. This is one of the main stumbling blocks in developing rational catalyst design strategies in heterogeneous catalysis. We show here how to identify the crucial atomic structure motif for the industrial Cu/ZnO/Al{sub 2}O{sub 3} methanol synthesis catalyst. Using a combination of experimental evidence from bulk-, surface-sensitive and imaging methods collected on real high-performance catalytic systems in combination with DFT calculations. We show that the active site consists of Cu steps peppered with Zn atoms, all stabilized by a series of well defined bulk defects and surface species that need jointly to be present for the system to work.

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The Active Site of Methanol Synthesis over Cu/ZnO/Al2O3 Industrial Catalysts

Global challenges and strategies for control, conversion and utilization of CO2 for sustainable development involving energy, catalysis, adsorption and chemical processing

Liquid hydrocarbon fuels play an essential part in the global energy chain, owing to their high energy density and easy transportability. Olefins play a similar role in the production of consumer goods. In a post-oil society, fuel and olefin production will rely on alternative carbon sources, such as biomass, coal, natural gas, and CO(2). The methanol-to-hydrocarbons (MTH) process is a key step in such routes, and can be tuned into production of gasoline-rich (methanol to gasoline; MTG) or olefin-rich (methanol to olefins; MTO) product mixtures by proper choice of catalyst and reaction conditions. This Review presents several commercial MTH projects that have recently been realized, and also fundamental research into the synthesis of microporous materials for the targeted variation of selectivity and lifetime of the catalysts.

Conversion of Methanol to Hydrocarbons: How Zeolite Cavity and Pore Size Controls Product Selectivity

The role of metal oxides such as Ga 2 O 3 , Al 2 O 3 , ZrO 2 and Cr 2 O 3 contained in Cu/ZnO-based ternary catalysts for methanol synthesis from CO 2 and H 2 was classified into two categories: to improve the Cu dispersion and to increase the specific activity The Cu/ZnO-based multicomponent catalysts developed on the basis of the role of metal oxides were highly active and stable for a long period in a continuous methanol synthesis operation

Development of copper/zinc oxide-based multicomponent catalysts for methanol synthesis from carbon dioxide and hydrogen

Hydrogen dissociation by gold clusters.

Epoxidation of propylene with H2 and O2 in the explosive regime in a packed-bed catalytic membrane reactor

We have carried out a project to clarify the active site and the role of ZnO in Cu/ZnO-based catalysts for methanol synthesis from CO 2 and H 2 using both classical catalytic and surface science techniques. The active site model in which Zn species present on the Cu surface promote the methanol synthesis had been initially proposed based on the results of the powder catalysts such as a physical mixture of Cu/SiO 2 and ZnO/SiO 2 . The promotion of Zn has then been proved by a model catalyst of a Zn-deposited Cu(1 1 1) surface. The mechanism and kinetics of the methanol synthesis over Zn/Cu(1 1 1) as well as the structure of the active site have been studied on the atomic level by surface science techniques, such as XPS, AES, LEED, IRAS, and STM. A metallic Cu–Zn surface alloy is a catalytically active species for the methanol synthesis from CO 2 and H 2 .

Tadahiro Fujitani

Papers

Development of copper/zinc oxide-based multicomponent catalysts for methanol synthesis from carbon dioxide and hydrogen

Hydrogen dissociation by gold clusters.

Epoxidation of propylene with H2 and O2 in the explosive regime in a packed-bed catalytic membrane reactor

The chemical modification seen in the Cu/ZnO methanol synthesis catalysts

Propene epoxidation with dioxygen catalyzed by gold clusters.