The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Suljo Linic - One of the best experts on this subject based on the ideXlab platform.
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visible light enhanced Catalytic Oxidation reactions on plasmonic silver nanostructures
Nature Chemistry, 2011Co-Authors: Phillip Christophe, Suljo LinicAbstract:Catalysis plays a critical role in chemical conversion, energy production and pollution mitigation. High activation barriers associated with rate-limiting elementary steps require most commercial heterogeneous Catalytic reactions to be run at relatively high temperatures, which compromises energy efficiency and the long-term stability of the catalyst. Here we show that plasmonic nanostructures of silver can concurrently use low-intensity visible light (on the order of solar intensity) and thermal energy to drive Catalytic Oxidation reactions—such as ethylene epOxidation, CO Oxidation, and NH3 Oxidation—at lower temperatures than their conventional counterparts that use only thermal stimulus. Based on kinetic isotope experiments and density functional calculations, we postulate that excited plasmons on the silver surface act to populate O2 antibonding orbitals and so form a transient negative-ion state, which thereby facilitates the rate-limiting O2-dissociation reaction. The results could assist the design of Catalytic processes that are more energy efficient and robust than current processes. High operating temperatures in heterogeneous Catalytic processes compromise energy efficiency, catalyst lifetime and product selectivity. Plasmonic silver nanoparticles are shown to couple thermal energy and a low-intensity photon flux to drive commercially important Oxidation reactions at lower temperatures than conventional thermal processes.
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Visible-light-enhanced Catalytic Oxidation reactions on plasmonic silver nanostructures
Nature Chemistry, 2011Co-Authors: Phillip Christopher, Hongliang Xin, Suljo LinicAbstract:Catalysis plays a critical role in chemical conversion, energy production and pollution mitigation. High activation barriers associated with rate-limiting elementary steps require most commercial heterogeneous Catalytic reactions to be run at relatively high temperatures, which compromises energy efficiency and the long-term stability of the catalyst. Here we show that plasmonic nanostructures of silver can concurrently use low-intensity visible light (on the order of solar intensity) and thermal energy to drive Catalytic Oxidation reactions—such as ethylene epOxidation, CO Oxidation, and NH3 Oxidation—at lower temperatures than their conventional counterparts that use only thermal stimulus. Based on kinetic isotope experiments and density functional calculations, we postulate that excited plasmons on the silver surface act to populate O2 antibonding orbitals and so form a transient negative-ion state, which thereby facilitates the rate-limiting O2-dissociation reaction. The results could assist the design of Catalytic processes that are more energy efficient and robust than current processes.
Shaobin Wang - One of the best experts on this subject based on the ideXlab platform.
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nanocarbons in different structural dimensions 0 3d for phenol adsorption and metal free Catalytic Oxidation
Applied Catalysis B-environmental, 2015Co-Authors: Stacey Indrawirawan, Xiaoguang Duan, Hongqi Sun, Shaobin WangAbstract:Abstract Metal-free nanocarbon materials in different structural dimensions, such as 0D fullerene (C 60 ), 1D single-walled carbon nanotubes (SWCNTs), 2D graphene nanoplate (GNP), 3D hexagonally-ordered mesoporous carbon (CMK-3) and cubically-ordered mesoporous carbon (CMK-8) were investigated for adsorption and Catalytic Oxidation of phenol in water solutions. A variety of characterisation techniques were used to investigate the properties of the carbon samples. It was found that structural dimension and heat treatment would significantly affect the performance of the nanocarbons in adsorption and catalysis. Both GNP and CMK-3 showed better phenol adsorption with around 40% phenol removal in 500 mL of 20 ppm solutions. The nanocarbons were also used for metal-free activation of peroxymonosulfate (PMS) to produce sulfate radicals for Catalytic phenol Oxidation. Efficient catalysis was observed on CMK-3, CMK-8 and SWCNTs. Thermal treatment of the nanocarbons at 350 °C in nitrogen was conducted to modulate the crystal- and micro-structures and surface functional groups of the different nanocarbons. Enhancements at 2-fold in adsorption on SWCNTs and 7.5-fold in catalysis on CMK-8 were observed after the heat treatments. Mechanisms of adsorption and Catalytic Oxidation of phenol were discussed. This study contributes to the development of green materials for sustainable remediation of aqueous organic pollutants.
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sulfur and nitrogen co doped graphene for metal free Catalytic Oxidation reactions
Small, 2015Co-Authors: Xiaoguang Duan, Kane M Odonnell, Hongqi Sun, Yuxian Wang, Shaobin WangAbstract:S ulfur and nitrogen co-doped reduced graphene oxide (rGO) is synthesized by a facile method and demonstrated remarkably enhanced activities in metal-free activation of peroxymonosulfate (PMS) for Catalytic Oxidation of phenol. Based on fi rst-order kinetic model, S‐N co-doped rGO (SNG) presents an apparent reaction rate constant of 0.043 ± 0.002 min −1 , which is 86.6, 22.8, 19.7, and 4.5-fold as high as that over graphene oxide (GO), rGO, S-doped rGO (S-rGO), and N-doped rGO (N-rGO), respectively. A variety of characterization techniques and density functional theory calculations are employed to investigate the synergistic effect of sulfur and nitrogen co-doping. Co-doping of rGO at an optimal sulfur loading can effectively break the inertness of carbon systems, activate the sp 2 -hybridized carbon lattice and facilitate the electron transfer from covalent graphene sheets for PMS activation. Moreover, both electron paramagnetic resonance (EPR) spectroscopy and classical quenching tests are employed to investigate the generation and evolution of reactive radicals on the SNG sample for phenol Catalytic Oxidation. This study presents a novel metal-free catalyst for green remediation of organic pollutants in water.
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3d hierarchically structured mno2 for Catalytic Oxidation of phenol solutions by activation of peroxymonosulfate structure dependence and mechanism
Applied Catalysis B-environmental, 2015Co-Authors: Yuxian Wang, Moses O Tade, Shaobin WangAbstract:Abstract Hierarchical materials have facilitated fascinating applications in heterogeneous catalysis due to that micro-sized bulk is easily separable and nano-sized sub-blocks can significantly enhance Catalytic performance. In this study, corolla-like δ-MnO2 with sub-blocks of nanosheets, and urchin-shaped α-MnO2 with sub-blocks of nanorods were synthesized by a simple hydrothermal route. The hydrothermal temperature significantly influenced the crystal structure, morphology and textural structure of the obtained three-dimensional (3D) MnO2 catalysts. The Catalytic activities of three samples prepared at 60, 100 and 110 °C (denoted as Mn-60, -100 and -110, respectively) were thoroughly evaluated by activation of peroxymonosulfate (PMS) for Catalytic Oxidation of phenol solutions. Based on first-order kinetics, the rate constants of Mn-60, -100 and -110 catalysts were determined to be 0.062, 0.132, and 0.075 min−1, respectively. The activation energy of Mn-100 in Catalytic Oxidation of phenol solutions was estimated to be 25.3 kJ/mol. The Catalytic stability of Mn-100 was also tested and discussed by monitoring Mn leaching. Electron paramagnetic resonance (EPR), quenching tests, total organic carbon (TOC) analysis and identification of intermediates were applied to illustrate the activation processes of PMS and the mechanism of phenol degradation.
Chung King Law - One of the best experts on this subject based on the ideXlab platform.
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kinetics of Catalytic Oxidation of ethylene over palladium oxide
Proceedings of the Combustion Institute, 2015Co-Authors: Yuxuan Xin, Chung King Law, Hai Wang, Bin Yang, Scott L AndersonAbstract:Abstract Catalytic Oxidation of ethylene was experimentally studied by wire microcalorimetry and mass spectrometry over the temperature range of 400–800 K at atmospheric pressure. The catalyst is a palladium oxide (PdO) surface on a polycrystalline palladium wire. For mixtures containing 0.3–0.6% C 2 H 4 and 3.75% O 2 in N 2 , the heat release rate as well as the mole fractions of gas-phase species were identified. Experimental observation revealed the temperature-dependent channels for the C 2 H 4 Oxidation, with mixed H 2 release and H 2 O production below 580 K and complete Oxidation to CO 2 and H 2 O above 600 K. Analysis of the global reaction kinetics shows that for 620 ⩽ T (K) ⩽ 740 K the surface Catalytic reaction rate is the first order in ethylene concentration and has an activation energy of 48.2 ± 1.4 kJ/mol. A surface chemistry model is proposed and the dissociative adsorption rate constant of C 2 H 4 on PdO surface was determined by fitting the experimental data.
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kinetics of Catalytic Oxidation of methane ethane and propane over palladium oxide
Combustion and Flame, 2014Co-Authors: Yuxuan Xin, Chung King Law, Hai WangAbstract:Catalytic Oxidation of methane, ethane and propane over a palladium oxide (PdO) surface was investigated experimentally by wire microcalorimetry. The Oxidation rate was determined for each reactant at atmospheric pressure in the temperature range of 600–800 K. The apparent kinetic parameters were extracted from the experimental measurements. It is shown that the Oxidation of these hydrocarbons over the PdO surface proceeds with a similar mechanism: they undergo dissociative adsorption followed by the conversion of surface fragments to final products. A detailed surface reaction model is proposed, and the kinetic parameters of the crucial reactions are deduced from the present experimental observations. The Catalytic Oxidation rates are found to increase in the order of methane, ethane and propane. This observation is consistent with density functional theory calculations and may be correlated with the C–H bond energies of the corresponding surface intermediates.
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Catalytic Oxidation of methane over pdo in wire microcalorimetry
Combustion and Flame, 2013Co-Authors: Taichang Zhang, Yuxuan Xin, Zhuyin Ren, Chung King LawAbstract:A two-dimensional model of a weakly buoyant flow over a horizontal wire with surface reaction was developed, using a literature mechanism, to simulate the heat release rate of the Catalytic Oxidation of methane (2 vol.% in air) over a Pd wire with a porous 1-2 mu m PdO surface layer, acquired by wire microcalorimetry over the temperature range of 600-770 K. The experimental and simulation results demonstrate that the Catalytic Oxidation is characterized by a low-temperature, reaction-controlled regime in which the internal pore surface is totally accessible to the reactions, and a high-temperature regime in which finite-rate pore diffusion also affects the overall heat release rate. Furthermore, the controlling reactions are identified to be the oxidative adsorption of methane, desorption of oxygen, and adsorption of oxygen, with the former two being facilitating and the last retarding. The reaction mechanism was modified using the response surface methodology and the experimental data in the low-temperature reaction-controlled regime, yielding satisfactory prediction of the global activation energy and identification of the role of oxygen coverage in the transition of the global activation energy.
Wenfeng Shangguan - One of the best experts on this subject based on the ideXlab platform.
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Catalytic Oxidation of dimethyl phthalate over titania supported noble metal catalysts
Journal of Hazardous Materials, 2021Co-Authors: Yuting Liang, Zhi Jiang, Wenfeng ShangguanAbstract:Abstract Semi-volatile organic compounds (SVOCs) are organic compounds with the boiling point ranging between 240/260 ℃ and 380/400 ℃. Detailed knowledge regarding Catalytic removal of SVOCs from indoor environment is very limited as it remains challenge to explore such reaction due to the viscosity nature of target contaminants. Here, we established a facile methodology to explore the heterogeneous Catalytic Oxidation reaction of dimethyl phthalate (DMP), a model SVOC, over the surface of supported catalyst. DMP was found to be gradually oxidized over the surface of titania supported catalysts including palladium (Pd), platinum and ruthenium with increasing temperature. The cleavage of side chain of DMP occurs at 75 ℃ over the surface of Pd/TiO2, which is significantly lower than that of the other two catalysts. Carbon dioxide was observed as the main product of the Catalytic Oxidation reaction. However, aromatic products and small molecule products were still observed as side-product in different temperature range. Density functional theory calculations further show that DMP can react with reactive oxygen species to form phthalic acid. While the cleavage of the DMP side chain occurs to form products such as methyl benzoate. This work thus provides basic knowledge about indoor SVOCs Catalytic Oxidation removal.
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removal of hexanal in cooking fume by combination of storage and plasma Catalytic Oxidation on alkali modified co mn solid solution
Chemosphere, 2019Co-Authors: Mingxia Chen, Wenfeng ShangguanAbstract:Abstract Cooking oil fumes as an important source of volatile organic compounds in metropolitan areas are poisonous to the environment and human health. In this study, the removal of hexanal (a representative of cooking fume) using “storage-plasma Catalytic Oxidation” at ambient conditions has been investigated. Alkali-modified Co-Mn catalysts were synthesized by coprecipitation method and further characterized by XRD, SEM, N2 adsorption–desorption, H2-TPR, O2-TPD and XPS techniques. It was clearly shown that the Na modification afforded a remarkable enhancement in the hexanal storage capacity, which is ascribed to the formation of surface hydroxyls that resulted in the chemical adsorption. Moreover, the plasma-Catalytic Oxidation results showed 99.4% hexanal removal and 85.7% CO2 selectivity at a GHSV of 47700 h−1. XPS results revealed that Na modification promoted the formation of more abundant Co3+, Mn3+ cations and surface adsorbed oxygen species, thus facilitated the Oxidation process. In-situ FTIR results revealed that Na modification could trigger disproportionation reaction, resulting in the transformation of adsorbed hexanal into alcohol and carboxylic acid thus further speeds up the Oxidation rate. This work provides a low-cost, highly efficient and energy-consuming approach for the removal of gaseous cooking fume by storage and plasma Catalytic Oxidation cycle at room temperature.
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design of 3d mno2 carbon sphere composite for the Catalytic Oxidation and adsorption of elemental mercury
Journal of Hazardous Materials, 2018Co-Authors: Haomiao Xu, Zan Qu, Yong Liao, Wenfeng ShangguanAbstract:Abstract Three-dimensional (3D) MnO2/Carbon Sphere (MnO2/CS) composite was synthesized from zero-dimensional carbon spheres and one-dimensional α-MnO2 using hydrothermal method. The hierarchical MnO2/CS composite was applied for the Catalytic Oxidation and adsorption of elemental mercury (Hg0) from coal-fired flue gas. The characterization results indicated that this composite exhibits a 3D urchin morphology. Carbon spheres act as the core and α-MnO2 nano-rods grew on the surface of carbon spheres. This 3D hierarchical structure benefits the enlargement of surface areas and pore volumes. Hg0 removal experimental results indicated that the MnO2/CS composite has an outstanding Hg0 removal performance due to the higher Catalytic Oxidation and adsorption performance. MnO2/CS composite had higher than 99% Hg0 removal efficiency even after 600 min reaction. In addition, the nano-sized MnO2/CS composite exhibited better SO2 resistance than pure α-MnO2. Moreover, the Hg-TPD results indicated that the adsorbed mercury can release from the surface of MnO2/CS using a thermal decomposition method.
L F Liotta - One of the best experts on this subject based on the ideXlab platform.
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Catalytic Oxidation of volatile organic compounds on supported noble metals
Applied Catalysis B-environmental, 2010Co-Authors: L F LiottaAbstract:Abstract Volatile organic compounds (VOCs) are toxic and mainly contribute to the formation of photochemical smog with a consequent remarkable impact to the air quality. A few techniques are available to reduce VOC emission, among them Catalytic Oxidation is suitable especially for highly diluted VOCs. The development of noble metals and transition metal oxides as catalysts for VOCs Oxidation has been widely reported in the literature and the research field continues to be very active. Selection of Catalytic materials for the abatement of organic pollutants is not easy because the activity depends on the specific molecule, on the reactions conditions and many parameters can affect the catalyst activity and resistance. The present review focus on the most used noble metals catalysts for Oxidation of not halogenated VOC. The effects of metal salt precursor, chlorine poisoning, water inhibition, particle size dependence, nature of the support are discussed. The calculated reaction order with respect to VOC and oxygen as well as the proposed reaction mechanisms are addressed. Examples of the most recent Catalytic systems reported in literature are also included.