Electrochemical and Photocatalytic Oxidation of Hydrocarbons

Electrochemical and Photocatalytic Oxidation of Hydrocarbons PDF Author: Azadeh Rismanchian
Publisher:
ISBN:
Category : Anodes
Languages : en
Pages : 169

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Book Description
This study demonstrates the development of a stable anode for electrochemical oxidation of hydrocarbons in solid oxide fuel cell (SOFC) and a highly active TiO2 based catalyst for photocatalytic reactions. The Ni/YSZ anode of SOFC was modified by Cu electroless plating. The catalytic activity toward H2 and CH4 oxidation were compared by the Faraday resistance (RF) obtained from the impedance spectroscopy. The RF ratio of Cu-Ni/YSZ in CH4 to H2 was greater than that of Ni/YSZ, indicating low catalytic activity of Cu-Ni/YSZ toward CH4 oxidation. The addition of Cu decreased the catalytic activity, but increased stability to 138 h in dry CH4. Characterization of the carbon type with Raman spectroscopy and temperature programmed oxidation showed that Cu formed disordered carbon rather than graphitic carbon which is the precursor to coking. Addition of CO2 to CH4 was studied as another approach to prevent coking. Electrochemical performance and mass spectrometry of the reactor effluent showed that the CH4-CO2 SOFC generated electricity from CO and H2, products of dry reforming reaction, with CO as the major contributor to current generation. CH4-CO2 decreased the activation polarization but showed a limiting current due to the fuel depletion at the interlayer-electrolyte interface. Anode interlayer was modified by reducing the particle size to 2 μm. The fine microstructure increased the three phase boundary length and reduced the activation polarization. The pore loss in the fine microstructure resulted in diffusion limitation and a limiting current in CH4 which was eliminated by adding 4 wt% of pore former at interlayer. Further addition of pore former lowered the performance by creating discontinuity at electrolyte-interlayer interface. The photocatalytic oxidation of ethanol on TiO2 and TiO2 modified with Ag and Au nanoparticles was studied by in-situ IR spectroscopy. Au and Ag increased the surface hydroxyl groups, which further served as active species to oxidize ethanol. Higher rate of electron transfer to Au than to Ag, evidenced by IR spectroscopy, resulted in higher rate of oxidation in Au-TiO2. This resulted in formation of formate (HCOO) on Au-TiO2 and acetate (CH3COO) on Ag-TiO2 as the major intermediate during the initial period of the photocatalytic oxidation.

Electrochemical and Photocatalytic Oxidation of Hydrocarbons

Electrochemical and Photocatalytic Oxidation of Hydrocarbons PDF Author: Azadeh Rismanchian
Publisher:
ISBN:
Category : Anodes
Languages : en
Pages : 169

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Book Description
This study demonstrates the development of a stable anode for electrochemical oxidation of hydrocarbons in solid oxide fuel cell (SOFC) and a highly active TiO2 based catalyst for photocatalytic reactions. The Ni/YSZ anode of SOFC was modified by Cu electroless plating. The catalytic activity toward H2 and CH4 oxidation were compared by the Faraday resistance (RF) obtained from the impedance spectroscopy. The RF ratio of Cu-Ni/YSZ in CH4 to H2 was greater than that of Ni/YSZ, indicating low catalytic activity of Cu-Ni/YSZ toward CH4 oxidation. The addition of Cu decreased the catalytic activity, but increased stability to 138 h in dry CH4. Characterization of the carbon type with Raman spectroscopy and temperature programmed oxidation showed that Cu formed disordered carbon rather than graphitic carbon which is the precursor to coking. Addition of CO2 to CH4 was studied as another approach to prevent coking. Electrochemical performance and mass spectrometry of the reactor effluent showed that the CH4-CO2 SOFC generated electricity from CO and H2, products of dry reforming reaction, with CO as the major contributor to current generation. CH4-CO2 decreased the activation polarization but showed a limiting current due to the fuel depletion at the interlayer-electrolyte interface. Anode interlayer was modified by reducing the particle size to 2 μm. The fine microstructure increased the three phase boundary length and reduced the activation polarization. The pore loss in the fine microstructure resulted in diffusion limitation and a limiting current in CH4 which was eliminated by adding 4 wt% of pore former at interlayer. Further addition of pore former lowered the performance by creating discontinuity at electrolyte-interlayer interface. The photocatalytic oxidation of ethanol on TiO2 and TiO2 modified with Ag and Au nanoparticles was studied by in-situ IR spectroscopy. Au and Ag increased the surface hydroxyl groups, which further served as active species to oxidize ethanol. Higher rate of electron transfer to Au than to Ag, evidenced by IR spectroscopy, resulted in higher rate of oxidation in Au-TiO2. This resulted in formation of formate (HCOO) on Au-TiO2 and acetate (CH3COO) on Ag-TiO2 as the major intermediate during the initial period of the photocatalytic oxidation.

Electrochemical and Photocatalytic Oxidation of Carbon and Hydrocarbons

Electrochemical and Photocatalytic Oxidation of Carbon and Hydrocarbons PDF Author: Felipe Guzman Montanez
Publisher:
ISBN:
Category : Carbon
Languages : en
Pages : 154

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Book Description
"Development of novel technologies for the conversion and storage of energy has been actively investigated in recent years. The use of a combined approach consisting of direct electrochemical and photocatalytic oxidation reactions could allow the efficient utilization of energy resources. Direct electrochemcial oxidation in a fuel cell could offer significant advantages over conventional combustion technologies, in light of their increased energy efficiency, reduction in emission of toxic pollutants, and overall process simplicity. The majority of fuel cell research has focused on the use of hydrogen, an environmentally friendly fuel characterized by high energy density and production of H2O byproduct. Despite these advantages, commercialization of hydrogen powered fuel cells is currently limited by difficulties in hydrogen production and storage. The high operation temperature of the solid oxide fuel cell (700-1000 °C) facilitates the direct use of hydrocarbon and carbon fuels, avoiding the complex and expensive reforming processes for the generation of concentrated H2 fuel. Exposure of gaseous hydrocarbons to the fuel cell at these high temperatures provides a thermodynamically favorable pathway for formation of carbon deposits (i.e., coking) which can lead to rapid and irreversible anode electrode degradation. This dissertation presents a study of the use of a novel Cu/Ni-YSZ anode electrode that reduces the formation of coke deposits and allows the energy efficient operation of the solid oxide fuel cell in hydrocarbon and carbon fuels. The microstructure of the Cu/Ni-YSZ anode electrode is extensively characterized by scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The performance of the Cu/Ni-YSZ anode and the energy efficiency during the operation on carbon (i.e., coke, a devolatized form of coal) is experimentally measured with the aid of in situ electrochemical analysis and, mas spectrometry (MS) and gas chromatograph (GC) demonstrating higher energy efficiencies compared with combustion technologies. Photocatalytic reactions over semiconductor catalysts such as TiO2 have received significant attention due to their potential applications for conversion and storage of solar energy to chemicals and the degradation of harmful pollutants present in air streams and wastewaters. Excitation of photocatalysts by exposure to light of appropriate energy causes promotion of electrons from the valence band to the conduction band, resulting in the generation of electron/hole pairs that can initiate redox reactions with species adsorbed on the surface of the photocatalyst. Hydrogen can be produced by the photocatalytic reduction of water (i.e. splitting reaction). Addition of alcohol molecules have been shown to improve the photocatalytic evolution of H2 from H2O due to hole scavenging oxidation reactions that limit electron/hole recombination. Detail knowledge of the mechanisms governing the photocatalytic oxidation of alcohols could facilitate the development of highly efficient photocatalysts for water splitting and degradation of volatile organic compounds (VOC). The photocatalytic evolution of H2 from aqueous solutions containing menthanol (CH3OH) hole scavenging reagents was studied by tracing the reaction of D2O over a Cu/S-TiO2 catalyst under UV illumination. Use of D2O/CH3OH produced higher formation rates of HD and D2 than that of H2. The low H2 formation rates indicate that the direct reaction of CH3OH with photogenerated holes does not proceed to an appreciable extent in the presence of high concentrations of D2O. The role of CH3OH in accelerating hydrogen formation can be attributed to its ability to produce an electron donor, injecting its electrons to the conduction band. The photocatalytic oxidation of alcohols was further studied at 30 °C and 1 atm by in situ infrared methods, using ethanol as a model compound. Results from these studies have shown ethanol adsorbs on TiO2 in the presence of high contents of water as molecularly adsorbed theanol (CH3CH2OHad), which exhibit a lower initial C-H scission and CO2 formation rate than ethoxy CH3CH2Oad produced from ethanol adsorbed low water content TiO2 catalysts. CH3CH2OHad photooxidation produced formic acid (HCOOHad) and formate (HCOO−ad) species, whereas CH3CH2Oad reactions proceed via formation of acetaldehyde (CH3CHOad) and acetate (CH3COO−ad). CH3CHOad was found to react on TiO2 via hydrogen abstraction of the [alpha]-Carbon producing CH3COO−ad species on the TiO2 surface. In the presence of excess H2O, weakly adsorbed species (i.e., acetic acid CH3COOHad) can be redistributed in the surface and dissociated producing acetate."--Abstract.

Electrochemical and Photocatalytic Oxidation of Organic Pollutants from Waste Water Using Efficient Nano-catalytic Coatings Prepared by Electrodeposition

Electrochemical and Photocatalytic Oxidation of Organic Pollutants from Waste Water Using Efficient Nano-catalytic Coatings Prepared by Electrodeposition PDF Author: Syed Zohaib Javaid Zaidi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Study of the Mechanism of the Electrochemical Oxidation of Hydrocarbons by Experimental Separation of Reaction Steps

Study of the Mechanism of the Electrochemical Oxidation of Hydrocarbons by Experimental Separation of Reaction Steps PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 26

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Electrochemical Oxidation of Saturated Hydrocarbons

Electrochemical Oxidation of Saturated Hydrocarbons PDF Author: A. C. Makrides
Publisher:
ISBN:
Category :
Languages : en
Pages : 52

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Book Description
A study of the behavior under N2 and propane gases, of smooth Pt electrodes in concentrated phosphoric acid electrolytes was carried out. The adsorption of propane on Pt from concentrated H3PO4 at 80C. was studied with anodic and cathodic charging curves. Neither of these by itself was found to give a reliable estimate of the adsorbate concentration, but together they provided an insight into the character of the adsorbed species. Initial adsorption is probably on a single site but substantial further material is adsorbed on 3 sites, except at low potentials. The stoichiometry of this 3 site adsorbate corresponds to direct adsorption of propane. At longer times of adsorption, the propane degrades and is partially oxidized. This adsorbed product releases about two electrons per Pt surface site atom during its oxidation at high potentials. Coverage with this species is high at some potentials, and is potentialdependent. The rate of adsorption is probably controlled by the rate of diffusion of propane to the electrode. Current potential curves for the oxidation of C3H8 on smooth Pt, from 85% H3PO4, at 130C, were also studied. The oxidation rate, at low potentials, is activationcontrolled, with a Tafel slope of about 2.3 RT/F. At higher potentials, the oxidation rate is controlled by diffusion of propane.

Ammonia-nitrogen Removal by Breakpoint Chlorination

Ammonia-nitrogen Removal by Breakpoint Chlorination PDF Author: Thomas A. Pressley
Publisher:
ISBN:
Category : Ammonia
Languages : en
Pages : 60

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The Electrochemical Oxidation of Some Terpene Hydrocarbons

The Electrochemical Oxidation of Some Terpene Hydrocarbons PDF Author: Harry E. Stanley
Publisher:
ISBN:
Category : Hydrocarbons
Languages : en
Pages : 108

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Electrochemical Oxidation of Saturated Hydrocarbons

Electrochemical Oxidation of Saturated Hydrocarbons PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
A study of the behavior under N2 and propane gases, of smooth Pt electrodes in concentrated phosphoric acid electrolytes was carried out. The adsorption of propane on Pt from concentrated H3PO4 at 80C. was studied with anodic and cathodic charging curves. Neither of these by itself was found to give a reliable estimate of the adsorbate concentration, but together they provided an insight into the character of the adsorbed species. Initial adsorption is probably on a single site but substantial further material is adsorbed on 3 sites, except at low potentials. The stoichiometry of this 3 site adsorbate corresponds to direct adsorption of propane. At longer times of adsorption, the propane degrades and is partially oxidized. This adsorbed product releases about two electrons per Pt surface site atom during its oxidation at high potentials. Coverage with this species is high at some potentials, and is potentialdependent. The rate of adsorption is probably controlled by the rate of diffusion of propane to the electrode. Current potential curves for the oxidation of C3H8 on smooth Pt, from 85% H3PO4, at 130C, were also studied. The oxidation rate, at low potentials, is activationcontrolled, with a Tafel slope of about 2.3 RT/F. At higher potentials, the oxidation rate is controlled by diffusion of propane.

Electrochemical Oxidation of Saturated Hydrocarbons. Appendix: Size Determination and Structural Study on Unsupported Platinum Catalysts

Electrochemical Oxidation of Saturated Hydrocarbons. Appendix: Size Determination and Structural Study on Unsupported Platinum Catalysts PDF Author: B. N. Das
Publisher:
ISBN:
Category :
Languages : en
Pages : 35

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Book Description
The average particle size of platinum black samples was determined by X-ray diffraction, adsorption (BET), and electron microscopic techniques. Stacking faults, twinning, locked-in strain, and stored energy were obtained by the Warren-Averbach method. Particle size distribution was measured by two electron microscopic methods and found to conform to a log-normal distribution. Results obtained by the various methods are compared. (Author).

The Oxidation of Hydrocarbons in the Liquid Phase

The Oxidation of Hydrocarbons in the Liquid Phase PDF Author: N. M. Emanuel'
Publisher: Elsevier
ISBN: 1483149250
Category : Science
Languages : en
Pages : 425

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Book Description
Approx.424 pages