scholarly journals Liquid-Phase Ethanol Oxidation and Gas-Phase CO Oxidation Reactions over M Doped (M = Ag, Au, Pd, and Ni) and MM′ Codoped CeO2 Nanoparticles

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Yohan Park ◽  
Yulri Na ◽  
Debabrata Pradhan ◽  
Youngku Sohn
Keyword(s):  
Liquid Phase ◽  
Co Oxidation ◽  
Gas Phase ◽  
Ethanol Oxidation ◽  
Relative Concentration ◽  
Major Product ◽  
Oxidation Reactions ◽  
Visible Absorption ◽  
Potential Applications ◽  
Metal Doped

Transition metal doped metal oxides have been studied extensively for potential applications to environments and chemical industry. Herein, M doped (M = Ag, Au, Pd, and Ni) and MM′ codoped CeO2 nanoparticles (NPs) were prepared by a hydrothermal method and their liquid-phase ethanol and gas-phase CO oxidation performances were examined by UV-visible absorption spectroscopy and temperature programmed mass spectrometry, respectively. The ethanol and CO oxidation performances were enhanced greatly by metal-doping and were dependent on the relative concentration of codoped metals. For ethanol oxidation, the concentration of acetaldehyde became saturated at low levels, while that of ethyl acetate continuously increased to become a final major product. For M doped CeO2 NPs, the ethanol oxidation performance showed an order of Ni < Ag < Pd ≪ Au. For MM′ codoped CeO2 NPs, the activity of Au doped CeO2 deteriorated drastically upon adding other metals (Ag, Ni, and Pd) as a cocatalyst.

scholarly journals Elucidating structure-performance correlations in gas-phase selective ethanol oxidation and CO oxidation over metal-doped γ-MnO2

2020 ◽  
Vol 41 (8) ◽  
pp. 1298-1310 ◽  
Author(s):  
Panpan Wang ◽  
Jiahao Duan ◽  
Jie Wang ◽  
Fuming Mei ◽  
Peng Liu
Keyword(s):  
Co Oxidation ◽  
Gas Phase ◽  
Ethanol Oxidation ◽  
Metal Doped

scholarly journals Uptake and reaction of HOBr on frozen and dry NaCl/NaBr surfaces between 253 and 233 K

2002 ◽  
Vol 2 (1) ◽  
pp. 79-91 ◽  
Author(s):  
J. W. Adams ◽  
N. S. Holmes ◽  
J. N. Crowley
Keyword(s):  
Gas Phase ◽  
Relative Concentration ◽  
Gas Diffusion ◽  
Major Product ◽  
The Arctic ◽  
Sea Spray ◽  
Mixed Salt ◽  
Arctic Boundary Layer ◽  
Similar Composition ◽  
Lower Limits

Abstract. The uptake and reaction of HOBr with frozen salt surfaces of variable NaCl / NaBr composition and temperature were investigated with a coated wall flow tube reactor coupled to a mass spectrometer for gas-phase analysis. HOBr is efficiently taken up onto the frozen surfaces at temperatures between 253 and 233 K where it reacts to form the di-halogens BrCl and Br2, which are subsequently released into the gas-phase. The uptake coefficient for HOBr reacting with a frozen, mixed salt surface of similar composition to sea-spray was <approx> 10-2. The relative concentration of BrCl and Br2 released to the gas-phase was found to be strongly dependent on the ratio of Cl- to Br - in the solution prior to freezing / drying. For a mixed salt surface of similar composition to sea-spray the major product at low conversion of surface reactants (i.e. Br - and Cl-) was Br2. Variation of the pH of the NaCl / NaBr solution used to prepare the frozen surfaces was found to have no significant influence on the results. The observations are explained in terms of initial formation of BrCl in a surface reaction of HOBr with Cl-, and conversion of BrCl to Br2 via reaction of surface Br -. Experiments on the uptake and reaction of BrCl with frozen NaCl / NaBr solutions served to confirm this hypothesis. The kinetics and products of the interactions of BrCl, Br2 and Cl2 with frozen salt surfaces were also investigated, and lower limits to the uptake coefficients of > 0.034, >0.025 and >0.028 respectively, were obtained. The uptake and reaction of HOBr on dry salt surfaces was also investigated and the results closely resemble those obtained for frozen surfaces. During the course of this study the gas diffusion coefficients of HOBr in He and H2O were also measured as (273 ± 1) Torr cm2 s-1 and (51 ± 1) Torr cm2 s-1, respectively, at 255 K. The implications of these results for modelling the chemistry of the Arctic boundary layer in springtime are discussed.

scholarly journals Catalytic CO Oxidation and H2O2 Direct Synthesis over Pd and Pt-Impregnated Titania Nanotubes

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 949
Author(s):  
Lucas Warmuth ◽  
Gülperi Nails ◽  
Maria Casapu ◽  
Sheng Wang ◽  
Silke Behrens ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Co Oxidation ◽  
Gas Phase ◽  
Surface Area ◽  
Heterogeneous Catalysts ◽  
Direct Synthesis ◽  
Pt Nanoparticles ◽  
Titania Nanotubes ◽  
Catalytic Co Oxidation ◽  
H2o2 Direct Synthesis

Titania nanotubes (TNTs) impregnated with Pd and Pt nanoparticles are evaluated as heterogeneous catalysts in different conditions in two reactions: catalytic CO oxidation (gas phase, up to 500 °C) and H2O2 direct synthesis (liquid phase, 30 °C). The TNTs are obtained via oxidation of titanium metal and the intermediate layer-type sodium titanate Na2Ti3O7. Thereafter, the titanate layers are exfoliated and show self-rolling to TNTs, which, finally, are impregnated with Pd or Pt nanoparticles at room temperature by using Pd(ac)2 and Pt(ac)2. The resulting crystalline Pd/TNTs and Pt/TNTs are realized with different lengths (long TNTs: 2.0–2.5 µm, short TNTs: 0.23–0.27 µm) and a specific surface area up to 390 m2/g. The deposited Pd and Pt particles are 2–5 nm in diameter. The TNT-derived catalysts show good thermal (up to 500 °C) and chemical stability (in liquid-phase and gas-phase reactions). The catalytic evaluation results in a low CO oxidation light-out temperature of 150 °C for Pt/TNTs (1 wt-%) and promising H2O2 generation with a productivity of 3240 molH2O2 kgPd−1 h−1 (Pd/TNTs, 5 wt-%, 30 °C). Despite their smaller surface area, long TNTs outperform short TNTs with regard to both CO oxidation and H2O2 formation.

Catalysed liquid phase oxidation of acetals by molecular oxygen

1986 ◽  
Vol 51 (4) ◽  
pp. 847-866 ◽  
Author(s):  
Jaroslav Včelák ◽  
Miroslava Klímová ◽  
Václav Chvalovský
Keyword(s):  
Liquid Phase ◽  
Co Oxidation ◽  
Molecular Oxygen ◽  
Rate Constants ◽  
Radical Mechanism ◽  
Oxidation Reactions ◽  
Dominant Effect ◽  
Autocatalytic Model ◽  
Phase Oxidation ◽  
Effect Of Oxygen

Nine different acetals have been oxidized in the presence of Co(OOCCH3)2.4 H2O under isobaric conditions (0.1 - 0.2 MPa O2 while following the uptake of molecular oxygen. The reactivity of acetals was expressed by the rate constants of the autocatalytic model of oxidation. The main products of the oxidation are alcohols, esters and acids. The distribution of products and the total reactivity of acetals are controlled by the structure of both parts of acetal molecule. The dominant effect on the course of the reaction exerts the type of carbon atoms on which radicals are formed. The oxidation is accompanied by consecutive and co-oxidation reactions, by deactivation of the catalyst and by decarbonylation of intermediate products. The effect of oxygen pressure is reported and the more detailed radical mechanism of the oxidation is proposed.

scholarly journals Uptake and reaction of HOBr on frozen and dry NaCl/NaBr surfaces between 253 and 233K

2002 ◽  
Vol 2 (1) ◽  
pp. 109-145 ◽  
Author(s):  
J. W. Adams ◽  
N. S. Holmes ◽  
J. N. Crowley
Keyword(s):  
Gas Phase ◽  
Relative Concentration ◽  
Gas Diffusion ◽  
Major Product ◽  
The Arctic ◽  
Sea Spray ◽  
Mixed Salt ◽  
Arctic Boundary Layer ◽  
Similar Composition ◽  
Lower Limits

Abstract. The uptake and reaction of HOBr with frozen salt surfaces of variable NaCl / NaBr composition and temperature were investigated with a coated wall flow tube reactor coupled to a mass spectrometer for gas-phase analysis. HOBr is efficiently taken up onto the frozen surfaces at temperatures between 253 and 233 K where it reacts to form the di-halogens BrCl and Br2, which are subsequently released into the gas-phase. The uptake coefficient for HOBr reacting with a frozen, mixed salt surface of similar composition to sea-spray was approx. 10-2. The relative concentration of BrCl and Br2 released to the gas-phase was found to be strongly dependent on the ratio of Cl - to Br - in the solution prior to freezing / drying. For a mixed salt surface of similar composition to sea-spray the major product at low conversion of surface reactants (i.e. Br - and Cl -) was Br2. Variation of the pH of the NaCl / NaBr solution used to prepare the frozen surfaces was found to have no significant influence on the results. The observations are explained in terms of initial formation of BrCl in a surface reaction of HOBr with Cl -, and conversion of BrCl to Br2 via reaction of surface Br -. Experiments on the uptake and reaction of BrCl with frozen NaCl / NaBr solutions served to confirm this hypothesis. The kinetics and products of the interactions of BrCl, Br2 and Cl2 with frozen salt surfaces were also investigated, and lower limits to the uptake coefficients of > 0.034, >0.025 and >0.028 respectively, were obtained. The uptake and reaction of HOBr on dry salt surfaces was also investigated and the results closely resemble those obtained for frozen surfaces. During the course of this study the gas diffusion coefficients of HOBr in He and H2O were also measured as (273 ± 1) Torr cm2 s-1 and (51 ± 1) Torr cm2 s-1, respectively, at 255 K. The implications of these results for modelling the chemistry of the Arctic boundary layer in springtime are discussed.

Tuning the Activities of Cu2O Nanostructures via the Oxide-Metal Interaction

2019 ◽  
Author(s):  
Wugen Huang ◽  
qingfei liu ◽  
Zhiwen Zhou ◽  
Yangsheng Li ◽  
Yong Wang ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Oxidation Catalysis ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Oxidation Reactions ◽  
Tunneling Microscopy ◽  
Temperature Oxidation ◽  
Metal Interaction ◽  
Tremendous Importance ◽  
Oxygen Atoms

Despite tremendous importance in catalysis, the design and improvement of the oxide- metal interface has been hampered by the limited understanding on the nature of interfacial sites, as well as the oxide-metal interaction (OMI). Through the construction of well-defined Cu<sub>2</sub>O-Pt, Cu<sub>2</sub>O-Ag, Cu<sub>2</sub>O-Au interfaces, we found that Cu<sub>2</sub>O Nanostructures (NSs) on Pt exhibit much lower thermal stability than on Ag and Au, although they show the same surface and edge structures, as identified by element-specific scanning tunneling microscopy (ES-STM) images. The activities of the Cu<sub>2</sub>O-Pt and Cu<sub>2</sub>O-Au interfaces for CO oxidation were further compared at the atomic scale and showed in general that the interface with Cu<sub>2</sub>O NSs could annihilate the CO-poisoning problem suffered by Pt group metals and enhance the interaction with O<sub>2</sub>, which is a limiting step for CO oxidation catalysis on group IB metals. While both interfaces could react with CO at room temperature, the OMI was found to determine the reactivity of supported Cu<sub>2</sub>O NSs by 1) tuning the activity of interfacial oxygen atoms and 2) stabilizing oxygen vacancies or vice versa, the dissociated oxygen atoms at the interface. Our study provides new insight for OMI and for the development of Cu-based catalysts for low temperature oxidation reactions.

Tuning the Activities of Cu2O Nanostructures via the Oxide-Metal Interaction

2019 ◽  
Author(s):  
Wugen Huang ◽  
Yangsheng Li ◽  
Yong Wang ◽  
Yunchuan Tu ◽  
Dehui Deng ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Oxidation Catalysis ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Oxidation Reactions ◽  
Tunneling Microscopy ◽  
Temperature Oxidation ◽  
Metal Interaction ◽  
Tremendous Importance ◽  
Oxygen Atoms

Despite tremendous importance in catalysis, the design and improvement of the oxide- metal interface has been hampered by the limited understanding on the nature of interfacial sites, as well as the oxide-metal interaction (OMI). Through the construction of well-defined Cu<sub>2</sub>O-Pt, Cu<sub>2</sub>O-Ag, Cu<sub>2</sub>O-Au interfaces, we found that Cu<sub>2</sub>O Nanostructures (NSs) on Pt exhibit much lower thermal stability than on Ag and Au, although they show the same surface and edge structures, as identified by element-specific scanning tunneling microscopy (ES-STM) images. The activities of the Cu<sub>2</sub>O-Pt and Cu<sub>2</sub>O-Au interfaces for CO oxidation were further compared at the atomic scale and showed in general that the interface with Cu<sub>2</sub>O NSs could annihilate the CO-poisoning problem suffered by Pt group metals and enhance the interaction with O<sub>2</sub>, which is a limiting step for CO oxidation catalysis on group IB metals. While both interfaces could react with CO at room temperature, the OMI was found to determine the reactivity of supported Cu<sub>2</sub>O NSs by 1) tuning the activity of interfacial oxygen atoms and 2) stabilizing oxygen vacancies or vice versa, the dissociated oxygen atoms at the interface. Our study provides new insight for OMI and for the development of Cu-based catalysts for low temperature oxidation reactions.

Application of Disk Aerators to Recarbonation of Alkaline Wastewater from Wet Gasification of Carbide

1991 ◽  
Vol 24 (7) ◽  
pp. 277-284 ◽  
Author(s):  
E. Gomólka ◽  
B. Gomólka
Keyword(s):  
Carbon Dioxide ◽  
Liquid Phase ◽  
Gas Phase ◽  
Flue Gas ◽  
Carbonic Acid ◽  
Low Cost ◽  
Flue Gases ◽  
Carbon Dioxide Content ◽  
Patent Claim ◽  
Phase Dispersion

Whenever possible, neutralization of alkaline wastewater should involve low-cost acid. It is conventional to make use of carbonic acid produced via the reaction of carbon dioxide (contained in flue gases) with water according to the following equation: Carbon dioxide content in the flue gas stream varies from 10% to 15%. The flue gas stream may either be passed to the wastewater contained in the recarbonizers, or. enter the scrubbers (which are continually sprayed with wastewater) from the bottom in oountercurrent. The reactors, in which recarbonation occurs, have the ability to expand the contact surface between gaseous and liquid phase. This can be achieved by gas phase dispersion in the liquid phase (bubbling), by liquid phase dispersion in the gas phase (spraying), or by bubbling and spraying, and mixing. These concurrent operations are carried out during motion of the disk aerator (which is a patent claim). The authors describe the functioning of the disk aerator, the composition of the wastewater produced during wet gasification of carbide, the chemistry of recarbonation and decarbonation, and the concept of applying the disk aerator so as to make the wastewater fit for reuse (after suitable neutralization) as feeding water in acetylene generators.

Modeling of aerated upflow fixed bed reactors for nitrification

1999 ◽  
Vol 39 (4) ◽  
pp. 85-92 ◽  
Author(s):  
J. Behrendt
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Liquid Phase ◽  
Gas Phase ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Bulk Liquid ◽  
Initial Value ◽  
Fixed Bed Reactors ◽  
Number Of Cells

A mathematical model for nitrification in an aerated fixed bed reactor has been developed. This model is based on material balances in the bulk liquid, gas phase and in the biofilm area. The fixed bed is divided into a number of cells according to the reduced remixing behaviour. A fixed bed cell consists of 4 compartments: the support, the gas phase, the bulk liquid phase and the stagnant volume containing the biofilm. In the stagnant volume the biological transmutation of the ammonia is located. The transport phenomena are modelled with mass transfer formulations so that the balances could be formulated as an initial value problem. The results of the simulation and experiments are compared.

Theoretical analysis of counter-current absorption of a poorly soluble gas based on the PDE-AD model

1986 ◽  
Vol 51 (6) ◽  
pp. 1222-1239 ◽  
Author(s):  
Pavel Moravec ◽  
Vladimír Staněk
Keyword(s):  
Experimental Data ◽  
Liquid Phase ◽  
Gas Phase ◽  
Transfer Functions ◽  
Packed Bed ◽  
Packed Bed Column ◽  
Interfacial Transport ◽  
Gaseous Component ◽  
Poorly Soluble ◽  
Counter Current

Expression have been derived in the paper for all four possible transfer functions between the inlet and the outlet gas and liquid steams under the counter-current absorption of a poorly soluble gas in a packed bed column. The transfer functions have been derived for the axially dispersed model with stagnant zone in the liquid phase and the axially dispersed model for the gas phase with interfacial transport of a gaseous component (PDE - AD). calculations with practical values of parameters suggest that only two of these transfer functions are applicable for experimental data evaluation.

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