[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40th anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are dee...

Fundamentals and Catalytic Applications of CeO2-Based Materials

Selective catalytic reduction with NH3 (NH3-SCR) is the most efficient technology to reduce the emission of nitrogen oxides (NOx) from coal-fired industries, diesel engines, etc. Although V2O5-WO3(MoO3)/TiO2 and CHA structured zeolite catalysts have been utilized in commercial applications, the increasing requirements for broad working temperature window, strong SO2/alkali/heavy metal-resistance, and high hydrothermal stability have stimulated the development of new-type NH3-SCR catalysts. This review summarizes the latest SCR reaction mechanisms and emerging poison-resistant mechanisms in the beginning and subsequently gives a comprehensive overview of newly developed SCR catalysts, including metal oxide catalysts ranging from VOx, MnOx, CeO2, and Fe2O3 to CuO based catalysts; acidic compound catalysts containing vanadate, phosphate and sulfate catalysts; ion exchanged zeolite catalysts such as Fe, Cu, Mn, etc. exchanged zeolite catalysts; monolith catalysts including extruded, washcoated, and metal-mesh/foam-based monolith catalysts. The challenges and opportunities for each type of catalysts are proposed while the effective strategies are summarized for enhancing the acidity/redox circle and poison-resistance through modification, creating novel nanostructures, exposing specific crystalline planes, constructing protective/sacrificial sites, etc. Some suggestions are given about future research directions that efforts should be made in. Hopefully, this review can bridge the gap between newly developed catalysts and practical requirements to realize their commercial applications in the near future.

Selective Catalytic Reduction of NOx with NH3 by Using Novel Catalysts: State of the Art and Future Prospects.

Catalytic NOx Abatement Systems for Mobile Sources: From Three-Way to Lean Burn after-Treatment Technologies Pascal Granger* and Vasile I. Parvulescu* Unit e de Catalyse et de Chimie du Solide, UMR CNRS 8181, University of Lille 1, 59655 Villeneuve d’Ascq, France Department of Organic Chemistry, Biochemistry and Catalysis, University of Bucharest, Romania, 412 Regina Elisabeta Boulevard, Bucharest 030016, Romania

Catalytic NOx Abatement Systems for Mobile Sources: From Three-Way to Lean Burn after-Treatment Technologies

The review is a summary and analysis of the data characterizing CO adsorption on surface cationic sites of oxides including supported materials and microporous and mesoporous materials. The contributions of various types of CO bonding to the IR frequency shifts of carbon-bonded molecules are analyzed, namely, the increase of the CO stretching frequency in cases of electrostatic and σ bonding and the decrease of the frequency with π bonding. Polycarbonyls, bridging CO, oxygen-bonded CO, and tilted CO are also considered. The main part of the review is a collection of the experimental results characterizing carbonyls of individual metal ions. The spectral behavior of CO bonded to metal atoms is also assessed in the cases when the metal ions are easily reduced to metal (Cu, Ag, Au, Pd, or Pt) or cationic carbonyls are produced after CO adsorption on supported metals (Ru, Rh, Ir, and Os). The interaction of CO with surface OH groups is also considered. It is demonstrated that IR spectroscopy of adsorbed CO is an efficient methodology to characterize cationic surface sites in terms of their nature, oxidation states, coordination environment and coordinative unsaturation, and location at faces, edges or corners of microcrystallites. When applied to materials with surface hydroxyl groups CO undergoes hydrogen bonding and information can be collected on the proton acid strength.

Characterization of oxide surfaces and zeolites by carbon monoxide as an IR probe molecule

The catalytic performances of Ni/CeO2–Al2O3 catalysts for the dry reforming of CH4 (DRM) were investigated. Catalysts with different Ni dispersion and different amount of CeAlO3 species were prepared by different methods and characterized by BET, XRD, XPS, Raman, TPR and TPO techniques. Catalytic activity was studied during time on stream in the range 873–1073 K with a mixture of CH4:CO2:Ar = 40:40:20 vol.% and GHSV 90,000 cm3 g−1 h−1. The intrinsic catalytic activity increased with the increasing of Ni crystallite size. Carbon was deposited as nano-fibres and graphite when catalysts worked at lower temperature, and the largest amount was found on the catalyst with the largest Ni crystallite size. The formation of graphitic deposits is limited by the presence of CeAlO3 species formed during catalyst activation. CA preparation method results particularly attractive because it allows to obtain catalysts with small Ni crystallite size and high content of CeAlO3 species, which both have a role in suppressing the carbon deposition and therefore in obtaining stable catalytic performances.

Ni/CeO2-Al2O3 catalysts for the dry reforming of methane: the effect of CeAlO3 content and nickel crystallite size on catalytic activity and coke resistance

Co and Ni supported on CeO2 as selective bimetallic catalyst for dry reforming of methane

The role of dopants on the catalytic activity for the dry reforming of methane (DRM) was investigated on nickel supported on metal doped ceria (Me-DC) catalysts, Ni/Me0.15Ce0.85O2-δ with Me = Zr4+, La3+ or Sm3+, prepared by citric acid synthetic route. The catalytic activity was in the order Ni/Zr-DC  Zr-DC > CeO2. The extra oxygen vacancies introduced by La3+ and Sm3+ were not capable to split CO2. La-DC and Sm-DC showed significant differences in the numbers and strength of surface basic sites. Therefore, other phenomena rule the formation/removal of carbon on these catalysts. The nature of dopants influenced the Ni-supports interaction and the electronic state of the metal catalyst.

Dry reforming of methane over Ni supported on doped CeO2: New insight on the role of dopants for CO2 activation

The catalytic conversion of carbon dioxide to synthetic CH4 was studied on five Ni/YSZ samples, with the same nickel loading (10 wt%) but different Ni particle size. The catalysts, prepared by different methods, were characterized combining morphological (BET, TEM), structural (XRD, in-operando XAS), electronic (XPS, in-operando XANES) analysis and H2-TPR experiments. The results showed that catalytic activity and CH4 selectivity depended on size and morphology of Ni particles, and that type and amount of deposited carbon strongly depended on Ni0 morphology. The kinetic measurements revealed that both H2 and CO2 reactants were activated on Ni sites, and that YSZ support was not directly involved in the reaction mechanism. The most efficient catalyst was that prepared by wet impregnation with Ni(EDTA)2− complex due to the high Ni0 dispersion.This catalyst showed low amount of carbon and remarkable stability over time on stream. In-operando XAS showed that it did not undergo deactivation by Ni0 → Ni2+ oxidation using high CO2 concentration, thus it is applicable in dynamic conditions like those typical in the energy storage from renewable sources process.

Nickel supported on YSZ: The effect of Ni particle size on the catalytic activity for CO 2 methanation

The paper presents an investigation on the catalytic activity for the ethanol steam reforming of Co3O4 oxidized, reduced and supported on MgO, and of CoO in MgO solid solution. Only samples containing metallic cobalt are found to be active for reforming reaction. H2-TPR characterization of aged samples shows that reaction mixture oxidizes a small fraction of metallic cobalt to Co+2. A distinct role of Co+2 and Co0 in the reaction is enlightened.

Simonetta Tuti

Papers

Ni/CeO2-Al2O3 catalysts for the dry reforming of methane: the effect of CeAlO3 content and nickel crystallite size on catalytic activity and coke resistance

Co and Ni supported on CeO2 as selective bimetallic catalyst for dry reforming of methane

Dry reforming of methane over Ni supported on doped CeO2: New insight on the role of dopants for CO2 activation

Nickel supported on YSZ: The effect of Ni particle size on the catalytic activity for CO 2 methanation

On the Catalytic Activity of Cobalt Oxide for the Steam Reforming of Ethanol