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•OSC is classified into two categories: total and dynamic.•Elemental doping, active component loading, geometrical, and environmental conditions that affect OSC are ...reviewed.•Measuring techniques and conditions that affect the OSC amount are also discussed.•Typical catalytically reactions related to the role of OSC in automotive emissions control are focused.
CeO2 is widely used as a catalyst support component due to its redox property of oxygen storage and release. This unique feature, which is usually referred to as “oxygen storage capacity” (OSC), can be quantitatively evaluated by different methods and techniques. Since the oxygen release benefits oxidation reactions, catalytic activity can be correlated with OSC. The measured amount of OSC can be influenced by a number of factors, such as the nature of the reducing agent, the conditions of reducing gas flow and operation temperature, the aging, the composition, and physical and geometric properties of CeO2-based materials, and the type of analytical technique used. Therefore, these influencing factors include, but are not limited to, the use of H2 or CO as reducing agent, continuous or pulsed feed of reducing agent, the presence of other elements in the CeO2 structure, particle size and surface area, supported catalyst components and aging, etc. This review paper focuses on the measurement of OSC, the effect of influencing factors, and the role of OSC in the typical reactions that occur in automotive emission control like oxidation, NO reduction, water gas shift, and reforming reactions. Furthermore, this review addresses the reactions in which the catalytic activity can be correlated with OSC.
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▶ Biomass is a promising alternative for the sustainable supply of chemicals. ▶ Furan derivatives can be produced through catalytic conversion of sugars. ▶ 5-Hydroxymethylfurfural, ...2,5-furandicarboxylic acid and dimethylfuran are useful. ▶ The catalyst design and catalytic pathways are discussed.
Recently, the production of furan derivatives from sugars has become exciting in chemistry and in catalysis studies, because it aids one of the major routes for achieving sustainable energy supply and chemicals production. 5-Hydroxymethylfurfural (5-HMF), 2,5-furan-dicarboxylic acid (2,5-FDCA) and 2,5-dimethylfuran (2,5-DMF) have been called the “sleeping giants” of renewable intermediate chemicals. 5-HMF is a dehydration product of hexoses and a potential substitute of petroleum-based building blocks of various polymers. 2,5-FDCA is derived from oxidative dehydration of hexoses and is considered as one of the top 12 compounds made from a sugar into a value-added chemical T. Werpy, G. Petersen, Top Value Added Chemicals From Biomass, 2004. Available electronically at
http://www.osti.gov/bridge. 2,5-DMF is produced through hydrogenation of HMF and is less volatile and of 40% higher energy density than ethanol. This review discusses mainly the catalytic routes for the synthesis of 5-HMF, 2,5-FDCA, 2,5-DMF and other furanic derivatives from sugars. Meanwhile, the possible reaction mechanism for the conversion of hexoses is discussed, and furthermore, some promising research orientations and advantageous catalysts are suggested based on the major problems encountered in the recent research.
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•Overview of research on lignin monomers.•Overview of research on lignin dimers.•Numerous examples utilizing homogenous catalysts and heterogeneous catalysts.•Selective cleavage of CO ...and CC bonds.
Biomass-based energy fulfills the future need of sustainable humanity. The utilization of lignin which is a primary constituent of biomass still remains the world most difficult problem due to its highly aromatic polymeric structure. Investigations on lignin model compounds renew the knowledge on CC and CO bond cleavage chemistry and indicate directions for lignin deconstruction. This review is to present the state of the art of the chemical transformation of lignin model compounds including monomers and dimers based on catalyst classifications, with emphasis on the fundamental catalytic chemistry in different processes. Moreover, how ideas derived from concepts transform to strategies for controlling the reaction pathways is also discussed.
The dehydration of D‐fructose and glucose has been studied with acidic ionic liquids as catalysts. A series of Brønsted‐acidic ionic liquids has been synthesized and tested in the dehydration of ...D‐fructose. The results showed that N‐methyl‐2‐pyrrolidonium methyl sulfonate NMP+CH3SO3− and N‐methyl‐2‐pyrrolidonium hydrogen sulfate NMP+HSO4− have high catalytic activity. Highly efficient and selective dehydration of D‐fructose to 5‐hydroxymethylfurfural (HMF) was achieved in dimethyl sulfoxide (DMSO) under mild conditions. For example, a 72.3 % yield of HMF with 87.2 % selectivity were obtained for 2 h at 90 °C in the presence of 7.5 mol % NMP+CH3SO3−. The effects of the reaction temperature, time, and solvent were investigated in detail. The catalyst and solvent can be recycled for the dehydration of D‐fructose. The Hammett method was used to determine the acidities of these ionic liquids, which indicated that the acidity and molecular structure have strong effects on the catalytic activity of ionic liquids. Based on the experimental results, a possible reaction mechanism for the dehydration of D‐fructose is proposed.
Highly efficient dehydration of fructose to 5‐hydroxymethylfurfural (HMF) is developed in the presence of catalytic amounts of Brønsted‐acidic ionic liquids (ILs). For example, a yield of 72.3 % HMF and selectivity of 87.2 % selectivity are obtained with NMP+CH3SO3− as a catalyst under mild conditions.
A Review on the Pd-Based Three-Way Catalyst Wang, Jihui; Chen, Hong; Hu, Zhicheng ...
Catalysis reviews. Science and engineering,
01/2015, Letnik:
57, Številka:
1
Journal Article
Recenzirano
The application of Pd in three-way catalyst represents a significant technology breakthrough for the removal of pollutants from gasoline powered vehicle exhaust gas. Pd shows superior catalytic ...activity for hydrocarbon (HCs) oxidation and thermal stability to the conventional Pt/Rh catalyst. However, Pd catalysts are more susceptible to chemical poisoning. This work summarizes the progress of the Pd-based three-way catalyst and its related technologies. The state of Pd in the reaction, the support and oxygen storage material, the promoters, and preparation methods on the catalytic performance are reviewed. The process and catalyst configurations, e.g., close-couple (CCC), dual bricks, layered, and zone-coated catalysts, are described and compared. The advances in the understanding of the reaction and deactivation mechanisms in the three-way catalysis systems are also discussed.
An all-iron non-aqueous redox flow battery (NARFB) based on iron acetylacetonate (Fe(acac)3) anolyte and N-(ferrocenylmethyl)-N,N-dimethyl -N-ethylammonium bis(trifluoromethane-sulfonyl)imide ...(Fc1N112-TFSI) catholyte with an open circuit voltage of 1.34 V is designed. Due to the high electrochemical activity of the active species, the resultant battery demonstrates fairly high cycling performance and rate capability with anion exchange membrane FAP-375-PP. The Coulombic efficiency (CE) of 98.7%, voltage efficiency (VE) of 84.5%, and energy efficiency (EE) of 83.4% are achieved over 100 cycles at the current density of 10 mA cm−2. VE and EE can be further enhanced by employing mixed-reactant electrolyte as both anolyte and catholyte, which are 89.2% and 85.2%, respectively. The underlying reasons for the capacity decay are discussed for future optimization.
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•An all-iron non-aqueous RFB based on Fc1N112-TFSI and Fe(acac)3 is proposed.•The anion exchange membrane FAP-375-PP is preferable for this battery system.•The iron-based RFB shows high rate capability.•The factors for capacity decay during cycling are analyzed.
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•Anodization time has an effect on the anodic TiO2 nanotube film thickness.•The distortion of Ti metal phase in the growth of TiO2 form Ti is monitored.•The sequence of the appearance ...of the anatase TiO2 peaks are revealed with time.•A SRichard model has a fidelity of R2 = 0.999 for fitting the anodic TNT film growth.
Anodic TiO2 nanotube (TNT) films show promises for photon-driven catalytic, electricity storage and chemical processes. The film thickness of anodic TNT is known to affect its performance in optical and electronic applications. Also, factors affecting the morphology and dimensions of anodic TNT films are rather well-known. However, the knowledge on phase transition and composition in the growth of anodic TiO2 from the titanium metal is very limited. In this work, the anodization time is controlled in intervals of 10, 60, 300, 1000, 2000 and 5000 s to investigate its effect on phase composition and transition, and the morphology of the anodic TNT during the growth process. Even though the mechanism of anodic TNT formation is still under debate, the scanning electron microscope results support bottom-up tube growth with evidence of a compact layer. It was also found that the Richards growth model is applicable to correlate growth time and film thickness. Finally, the phase transition, crystal orientation and pore formation during the anodic process are further discussed.
NASICON-type solid-state electrolyte is characterized by high electrical conductivity but its application in all-solid-state battery is limited by the high sintering temperature and poor interface ...contact with the electrodes. Here, solid-state reactive sintering, without intermediate calcination and ball-milling steps and no sintering additive, is proposed to prepare dense and highly conductive NASICON at lower temperatures. The samples sintered at 950 and 1000 °C achieve relative density of ~90% and high ion conductivity of 8.43 × 10−4 and 1.48 × 10−3 S cm−1 at room temperature, respectively. The reasonable interface contact between sodium metal and 950 °C-sintered electrolyte affords the symmetric sodium battery to cycle stably at 0.05 mA cm−2 for ~1000 h and full battery at 0.1C (0.02 mA cm−2) at room temperature. This work provides a new strategy to prepare NASICON solid-state electrolyte, which can be extended to prepare other solid-state electrolytes and thus promote the development of all-solid-state battery.
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•950 °C-sintered NASICON electrolyte has relative density of 91.9%.•950 °C-sintered sample shows electrical conductivity of 8.43 × 10−4 S cm−1 at RT.•Symmetric sodium and full batteries cycle stably at room temperature.
Biochar obtained from the pyrolysis of corn cob is used as the fuel of a direct carbon fuel cell (DCFC) employing a composite electrolyte composed of a samarium doped ceria (SDC) and a eutectic ...carbonate phase. An anode layer made of NiO and SDC is utilized to suppress the cathode corrosion by the molten carbonate and improves the whole cell stability. The anode off-gas of the fuel cell is analyzed with a gas chromatograph. The effect of working temperature on the cell resistance and power output is examined. The maximum power output achieves 185 mW cm−2 at a current density of 340 mA cm−2 and 750 °C. An anode reaction scheme including the Boudouard reaction is proposed.
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•Corn cob biochar is prepared with a pyrolysis process.•Electrochemical performance of the biochar is examined in DCFC.•Boudouard reaction takes part in the anode mechanism.•Biochar is suitable for DCFC.
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