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1.
This paper reports work on the scale-up of a perforated bipole trickle-bed electrochemical reactor for the electro-synthesis of alkaline peroxide. The reactor uses a relatively simple cell configuration in which a single electrolyte flows with oxygen gas in a flow-by graphite felt cathode, sandwiched between a microporous polyolefin diaphragm and a nickel mesh/perforated Grafoil anode/bipole. Both one and two-cell reactors are scaled-up from cathode dimensions 120 mm high by 25 mm wide and 3.2 mm thick (reactor-A) to 630 mm high by 40 mm wide and 3.2 mm thick (reactor-B). The scale-up is achieved by the use of constrictions that prevent segregation of the 2-phase flow in the larger cell, combined with switching from a polypropylene to a polyethylene diaphragm with improved transport properties and raising the electrolyte feed concentration from 1 to 2 M NaOH.For the one-cell reactor-B with a polypropylene diaphragm, operating on a feed of 1 M NaOH and oxygen at 900 kPa(abs)/20 °C, the peroxide current efficiency at a superficial current density of 5 kA m−2 increases from 27% (un-constricted cathode) to 57% with a constricted cathode. The corresponding current efficiencies at 3–5 kAm−2 for reactor-A and the constricted reactor-B are respectively 69–64% and 66–57%. Under similar conditions at 3–5 kA m−2 the one-cell constricted reactor-B with a polyethylene diaphragm gives current efficiencies of 88–64%, and changing to an electrolyte of 2 M NaOH raises this range to 90–80%. At 3–5 kA m−2 the equivalent two-cell (bipolar) constricted reactor-B shows current efficiencies of 82–74% and at 5 kA m−2 obtains 0.6 M peroxide in 2 M NaOH with specific energy 6.5 kWh per kg H2O2. 相似文献
2.
Soybean oil has been hydrogenated electrocatalytically on Raney nickel powder catalyst at atmospheric pressure and moderate temperatures in a novel undivided packed bed radial flow-through reactor. The reactor consisted of a single anode/cathode tubular element, where Raney nickel catalyst powder was contained in the annular space between two concentric porous ceramic tubes and the flow of the reaction medium (a dispersion of oil in a water/t-butanol/tetraethylammonium p-toluenesulfonate electrolyte) was either in the inward or outward radial direction. The innovative design of this reactor allows for a thin nickel bed and a high anode/cathode interfacial area without the normal problems associated with electrolyte flow distribution. The total size of the reactor can be increased without changing the relative anode/cathode position and the electrolyte flow pattern by simply increasing the length and/or number of anode/cathode elements in a single common shell (similar to a shell-and-tube heat exchanger). For the brush hydrogenation of soybean oil, current efficiencies of 90–100% were achieved with a single element reactor when the electrolyte oil content was 10 or 25 wt/vol %, the apparent current density was 10 or 15 mA cm–2, the temperature was 75 °C, and the electrolyte flowed in the inward radial direction. The electrohydrogenated oil product was characterized by a high stearic acid content and low concentrations of linolenic acid and trans fatty acid isomers, as compared to the traditional high temperature chemical catalytic oil hydrogenation route with hydrogen gas. 相似文献
3.
Characterisation of a laboratory electrochemical ozonation system and its application in advanced oxidation processes 总被引:1,自引:0,他引:1
Leonardo M. Da Silva Débora V. Franco Juliane C. Forti Wilson F. Jardim Julien F.C. Boodts 《Journal of Applied Electrochemistry》2006,36(5):523-530
An electrochemical reactor for oxygen/ozone production was developed using perforated planar electrodes. An electroformed
-PbO2 coating, deposited on a platinised titanium substrate, was employed as anode while the cathode was a platinised titanium substrate. The electrodes were pressed against a solid polymer electrolyte to minimise ohmic drop and avoid mixing of the gaseous products (H2 and O2/O3). Electrochemical ozone production (EOP) was investigated as function of current density, temperature and electrolyte composition. Electrochemical characterisation demonstrated ozone current efficiency, ΦEOP, ozone production rate (g h−1),
, and grams of O3 per total energy demand (g h−1 W−1), increase on decreasing electrolyte temperature and increasing current density. The best reactor performance for EOP was obtained with the base electrolyte (H2SO4 3.0 mol dm−3) containing 0.03 mol dm−3 KPF6. Degradation of reactive dyes used in the textile industry (Reactive Yellow 143 and Reactive Blue 264) with electrochemically-generated ozone was investigated in alkaline medium as function of ozone load (mg h−1) and ozonation time. This investigation revealed ozonation presents very good efficiency for both solution decolouration and total organic carbon (TOC) removal. 相似文献
4.
G. Psofogiannakis Y. Bourgault B. E. Conway M. Ternan 《Journal of Applied Electrochemistry》2006,36(1):115-130
A mathematical model was developed and used to predict the performance of direct propane phosphoric acid (PPAFC) fuel cells,
utilizing both Pt/C state-of the-art electrodes and older Pt black electrodes. It was found that the overpotential caused
by surface processes on the platinum catalyst in the anode is much greater than the potential losses caused by either ohmic
resistance or propane diffusion in gas-filled and liquid-filled pores. In one comparison, the anode overpotential (0.5 V)
was larger than the cathode overpotential (0.3 V) at a current density of 0.4 A cm−2 for Pt loadings 4 mg Pt cm−2. The need for sufficient water concentration at the anode, where water is a reactant, was indicated by the large effect of
H3PO4 concentration. In another comparison, the model predicted that at 0.2 A cm−2, modern carbon supported Pt catalysts would produce 0.35 V compared to 0.1 V for unsupported Pt black catalysts that were
used several decades ago, when the majority of the research on direct hydrocarbon fuel cells was performed. The propane anode
and oxygen cathode catalyst layers were modeled as agglomerates of spherical catalyst particles having their interior spaces
filled with liquid electrolyte and being surrounded by gas-filled pores. The Tafel equation was used to describe the electrochemical
reactions. The model incorporated gas and liquid-phase diffusion equations for the reactants in the anode and cathode and
ionic transport in the electrolyte. Experimental data were used for propane and oxygen diffusivities, and for their solubilities
in the electrolyte. The accuracy of the predicted electrical potentials and polarization curves were normally within ±0.02 V
of values reported in experimental investigations of temperature and electrolyte concentration. Polarization curves were predicted
as a function of temperature, pressure, electrolyte concentration, and Pt loading. A performance of 0.45 V at 0.5 A cm−2 was predicted at some conditions. 相似文献
5.
A positive-electrolyte-negative (PEN) assembly solid oxide fuel cell (SOFC) with a thin electrolyte film for intermediate
temperature operation was fabricated. Instead of the traditional screen-printing method, both anode and cathode catalysts
were pressed simultaneously and formed with the fabrication of nano-composite electrolyte by press method. This design offered
some advantageous configurations that diminished ohmic resistance between electrolyte and electrodes. It also increased the
proton-conducting rate and improved the performance of SOFCs due to the reduction of membrane thickness and good contact between
electrolyte and electrodes. The fabricated PEN cell generated electricity between 600°C and 680°C using H2S as fuel feed and air as oxidant. Maximum power densities 40 mW·cm−2 and 130 mW·cm−2 for the PEN configuration with a Mo-Ni-S-based composite anode, nano-composite electrolyte (Li2SO4+Al2O3) film and a NiO-based composite cathode were achieved at 600°C and 680°C, respectively. 相似文献
6.
Ju Hee Kim Young Min Park Taejin Kim Haekyoung Kim 《Korean Journal of Chemical Engineering》2012,29(3):349-355
Composite cathodes with La0.6Sr0.4Co0.2Fe0.8O3−δ
(LSCF) and Ce0.9Gd0.1O1.95 (GDC) are investigated to assess for solid oxide fuel cell (SOFC) applications at relatively low operating temperatures (650–800
°C). LSCF with a high surface area of 55 m2g−1 is synthesized via a complex method involving inorganic nano-dispersants. The fuel cell performances of anode-supported SOFCs
are characterized as a function of compositions of GDC with a surface area of 5 m2g−1. The SOFCs consist of the following: LSCF-GDC composites as a cathode, GDC as an interlayer, yttrium stabilized zirconia
(YSZ) as an electrolyte, Ni-YSZ (50: 50 wt%) as an anode functional layer, and Ni-YSZ (50: 50 wt%) for support. The cathodes
are prepared for 6LSCF-4GDC (60: 40 wt%), 5LSCF-5GDC (50: 50 wt%), and 4LSCF-6GDC (40: 60 wt%). The 5LSCF-5GDC cathode shows
1.29 Wcm−2, 0.97 Wcm−2, and 0.47 Wcm−2 at 780 °C, 730 °C, and 680 °C, respectively. The 6LSCF-4GDC shows 0.92 Wcm−2, 0.71 Wcm−2, and 0.54 Wcm−2 at 780 °C, 730 °C, and 680 °C, respectively. At 780 °C, the highest fuel cell performance is achieved by the 5LSCF-5GDC,
while at 680 °C the 6LSCF-4GDC shows the highest performance. The best composition of the porous composite cathodes with LSCF
(55 m2g−1) and GDC (5 m2g−1) needs to be considered with a function of temperature. 相似文献
7.
Subramanyan Vasudevan 《Korean Journal of Chemical Engineering》2009,26(5):1246-1251
The electrochemical preparation of strontium perchlorate, Sr(ClO4)2, from strontium chlorate employing platinum anode and a rotating stainless steel cathode is described. The effect of electrolyte
concentration, current density, pH and temperature of the electrolyte and cathode rotation on current efficiency for the preparation
of strontium perchlorate was studied. A maximum current efficiency of 42% was achieved corresponding to an energy consumption
of 6.1 kWh. kg−1. 相似文献
8.
N. Droushiotis A. Torabi M. H. D. Othman T. H. Etsell G. H. Kelsall 《Journal of Applied Electrochemistry》2012,42(7):517-526
Single layer La0.6Sr0.4Co0.2Fe0.8O3 hollow fibre (HF) precursors (<1 mm ID) produced by phase inversion (PI) were sintered at 1,200, 1,350 and 1,400 °C. The increase in sintering temperature resulted in microstructural changes in the LSCF fibres, reflected in their electrical conductivities. LSCF-based cathodes with different designs were brushed onto co-extruded nickel–gadolinium-doped ceria (CGO) anode/CGO electrolyte dual-layer HFs (<1 mm ID) fabricated by PI. The effect of cathode layers on the overall performance of the fuel cells (FCs) was assessed using nearly identical anode and electrolyte compositions, thicknesses, and microstructures. Cathode microstructure design caused cells to perform differently producing peak power densities of 0.35–0.7 W cm−2 at 600 °C. Impedance spectroscopy analysis at 600 °C on the FCs produced 0.12–0.24 Ω cm2 confirming the cathode’s structural effect on the overall area-specific resistance of the FCs. The best performing FC with a brush-deposited cathode was compared to a similar FC where cathode was deposited by dip coating; at 600 °C the first produced 0.6 W cm−2 while the second cell 0.7 W cm−2. Co-extruding anodes and electrolytes by using PI and combining dip coating for cathode deposition could lead to the fabrication of FCs with enhanced microstructures and improved performances. 相似文献
9.
Yuta Suga Rie YoshinagaNaoki Matsunaga Yoshihiro HirataSoichiro Sameshima 《Ceramics International》2012
This paper reports on the composition and flow rate of outlet gas and current density during the reforming of CH4 with CO2 using three different electrochemical cells: cell A, with Ni−GDC (Gd-doped ceria: Ce0.8Gd0.2O1.9) cathode/porous GDC electrolyte/Cu−GDC anode, cell B, with Cu−GDC cathode/ porous GDC electrolyte/Cu−GDC anode and cell C, with Ru−GDC cathode/ porous GDC electrolyte/ Cu−GDC anode. In the cathode, CO2 reacts with supplied electrons to form CO fuel and O2− ions (CO2+2e−→CO+O2−). Too low affinity of Cu cathode to CO2 in cell B reduced the reactivity of the CO2 with electrons. The CO fuel, O2− ions and CH4 gas were transported to the anode through the porous GDC mixed conductor of O2− ions and electrons. In the anode, CH4 reacts with O2− ions to produce CO and H2 fuels (CH4+O2−→2 H2+CO+2e−). The reforming efficiency at 700−800 °C was lowest in cell B and highest in cell A. The Cu anode in cells A and C worked well to oxidize CH4 with O2− ions (2Cu+O2−→Cu2O+2e−, Cu2O+CH4→2Cu+CO+2H2). However, a blockage of the outlet gas occurred in all the cells at 700−800 °C. The gas flow is inhibited due to a reduction in pore size in the cermet cathode, as well as sintering and grain growth of Cu metal in the anode during the reforming. 相似文献
10.
A novel perforated bipole trickle-bed electrochemical reactor is investigated for the electro-synthesis of alkaline peroxide.
The process uses a relatively simple cell configuration in which a single electrolyte flows with oxygen gas in a flow-by graphite
felt cathode, sandwiched between a micro-porous diaphragm and a perforated bipolar electrode plate. The graphite felt cathodes
are 120 mm high by 25 mm wide and have a thickness of 3.2 mm. The reactor is operated at current densities in the range 1–5 kA m−2, ca. 800 kPa (abs) pressure and temperature (In/Out) 20–45 °C with one and two-cells. The reactor shows good performance
(current efficiency ∼78% at 2 kA m−2 and a specific energy of 5 kWh per kg of peroxide generated) with peroxide concentrations from 0.02 to 0.15 M in 1 M NaOH. 相似文献
11.
N. Duteanu G. Vlachogiannopoulos M. R. Shivhare E. H. Yu Keith Scott 《Journal of Applied Electrochemistry》2007,37(9):1085-1091
Data on the performance of a direct borohydride fuel cell (DBFC) equipped with an anion exchange membrane, a Pt–Ru/C anode
and a Pt/C cathode are reported. The effect of oxidant (air or oxygen), borohydride and electrolyte concentrations, temperature
and anode solution flow rate is described. The DBFC gives power densities of 200 and 145 mW cm−2 using ambient oxygen and air cathodes respectively at medium temperatures (60 °C). The performance of the DBFC is very good
at low temperatures (ca. 30 °C) using modest catalyst loadings of 1 mg cm−2 for anode and cathode. Preliminary data indicate that the cell will be stable over significant operating times. 相似文献
12.
A. K. Sahu G. Selvarani S. Pitchumani P. Sridhar A. K. Shukla 《Journal of Applied Electrochemistry》2007,37(8):913-919
Incorporation of silica particles through a sol-gel process into the anode-catalyst layer with a sol-gel modified Nafion-silica
composite membrane renders easy retention of back-diffused water from the cathode to anode through the composite membrane
electrolyte, increases the catalyst-layer wettability and improves the performance of the Polymer Electrolyte Fuel Cell (PEFC)
while operating under relative humidity (RH) values ranging between 18% and 100% with gaseous hydrogen and oxygen reactants
at atmospheric pressure. A peak power density of 300 mW cm−2 is achieved at a load current-density value of 1200 mA cm−2 for the PEFC employing a sol-gel modified Nafion-silica composite membrane and operating at 18% RH. Under similar operating
conditions, the PEFC with a Membrane Electrode Assembly (MEA) comprising Nafion-silica composite membrane with silica in the
anode-catalyst layer delivers a peak power density of 375 mW cm−2. By comparison, the PEFC employing commercial Nafion membrane fails to deliver satisfactory performance at 18% RH due to
the limited availability of water at its anode, acerbated electro-osmotic drag of water from anode to cathode and insufficient
water back diffusion from cathode to anode causing the MEA to dehydrate. 相似文献
13.
Weidong An Jin Ki Hong Peter N. Pintauro Kathleen Warner William Neff 《Journal of the American Oil Chemists' Society》1998,75(8):917-925
A new electrochemical method has been devised and tested for the moderate temperature/atmospheric pressure hydrogenation of
edible oils, fatty acids, and fatty acid methyl esters. The method employed a solid polymer electrolyte (SPE) reactor, similar
to that used in H2/O2 fuel cells, with water as the source of hydrogen. The key component of the reactor was a membrane-electrode-assembly, composed
of a RuO2 powder anode and either a Pt-black or Pd-black powder cathode that were hot-pressed as thin films onto the opposing surfaces
of a Nafion cation-exchange membrane. During reactor operation at a constant applied current, water was back-fed to the RuO2 anode, where it was oxidized electrochemically to O2 and H+. Protons migrated through the Nafion membrane under the influence of the applied electric field and contacted the Pt or Pd
cathode, where they were reduced to atomic and molecular hydrogen. Oil was circulated past the back side of the cathode and
unsaturated triglycerides reacted with the electrogenerated hydrogen species. The SPE reactor was operated successfully at
a constant applied current density of 0.10 A/cm2 and a temperature between 50 and 80°C with soybean, canola, and cottonseed oils and with mixtures of fatty acids and fatty
acid methyl esters. Reaction products with iodine values in the range of 60–105 were characterized by a higher stearic acid
content and a lower percentage of trans isomers than those produced in a traditional hydrogenation process. 相似文献
14.
Electrostatic spray deposition (ESD) was applied to fabricate a thin-layer of yttria-stabilized zirconia (YSZ) electrolyte
on a solid oxide fuel cell (SOFC) anode substrate consisting of nickel-YSZ cermet. A colloidal solution of 8 mol% YSZ in ethanol
was sprayed onto the substrate anode surface at 250–300 °C by ESD. After sintering the deposited layer at 1250–1400 °C for
1–2 h depending on temperature, the cathode layer, consisting of lanthanum strontium manganate (LSM), was sprayed or brush
coated onto the electrolyte layer. Performance tests and AC impedance measurements of the complete cell were carried out at
800 °C to evaluate the density and conductance of the electrolyte layer formed by ESD. With a 97% H2/3% H2O mixture and air as fuel and oxidant gas, respectively, the open-circuit voltage (OCV) was close to theoretical and electrolyte
impedance was about 0.23Ω cm2. A power density of 0.45 W cm−2 at 0.62 V was obtained. No abnormal degradation was observed after 170 h operation. The electrolyte sintering temperature
and time did not significantly affect the electrolyte impedance.
on leave from 相似文献
15.
In the first part of this study, the characteristics of a La0.5Sr0.5CoO3?δ cathode are described, including its chemical bulk diffusion coefficient (Dchem), and electrical conductivity relaxation experiments are performed to obtain experimental Dchem measurements of this cathode. The second part of this study describes two methods to improve the single‐cell performance of solid oxide fuel cells. One method uses a composite cathode, i.e., a mix of 30 wt% electrolyte and 70 wt% cathode; the other method uses an electrolyte‐infiltrated cathode, i.e., an active ionic‐conductive electrolyte with nano‐sized particles is deposited onto a porous cathode surface using the infiltration method. In this work, 0.2M Ce0.8Sm0.2O1.9 (SDC)‐infiltrated La0.5Sr0.5CoO3?δ exhibits a maximum peak power density of 1221 mW/cm2 at an operating temperature of 700°C with a thick‐film SDC electrolyte (30 μm), a NiO + SDC anode (1 mm) and a La0.5Sr0.5CoO3?δ cathode (10 μm). The enhancement in electrochemical performances using the electrolyte‐infiltrated cathode is attributed to the creation of electrolyte/cathode phase boundaries, which considerably increases the number of electrochemical sites available for the oxygen reduction reaction. 相似文献
16.
A new occluded corrosion cavity (OCC) simulation cell was designed to study the underscale corrosion behavior of carbon steel
(N80) in 0.2 mol L−1 NaCl solution. The chemical components of the solution in the OCC were measured and the electrochemical behavior of the occluded
anode and the bulk cathode were studied by electrochemical impedance spectroscopy (EIS). The newly designed OCC cell can easily
simulate the auto-catalyzing acidification process and may be used to study the mechanism of underscale corrosion. The corrosion
scale exacerbates the underscale corrosion and the area ratio of the bulk cathode to the occluded anode (R = Sc/Sa) determines the development of simulated localized corrosion in the OCC cell. When R was within a certain range, the corrosion rate in the OCC could be kept at a persistently high level. The pH of the solution
in the OCC decreased and the chloride ions (Cl−) concentrated as the local corrosion developed. The anodic process on the occluded anode was controlled by irreversible charge
transfer and the cathodic process on the bulk cathode was controlled mainly by oxygen diffusion. 相似文献
17.
This paper describes the mathematical modelling and experimental work performed to evaluate porous cathodes for the electrochemical reduction of nitrates and nitrites in alkaline waste streams. A dynamic model of a batch process was developed that included a divided cell with a porous cathode, a cation-selective separator, a planar anode, and reservoirs for electrolyte recirculation and gas–liquid separation. Constant current experiments were done using a divided cell with nickel foam as the porous cathode. The experiments were performed with a catholyte feed of either 0.6 M NaNO2 or 1.95 M NaNO3, both supported by a 1.33 M NaOH solution, a current density of 0.25 A cm–2 and a solution temperature of 32 C. The experimental results showed that the ammonia production reaction is the dominant cathodic reaction (80% of the current). Estimates of the kinetic parameters were obtained using the experimental data and the model. The model was then used to simulate and study the performance of the porous electrode compared to the planar electrode for a range of operating currents. The results showed that at the optimum current density for a planar electrode of 0.25 A cm–2, use of a porous cathode results in one-third the energy costs and time required to achieve 95% destruction of nitrate and nitrite compared to a planar cathode. At 0.40 A cm–2, the energy and time required to achieve 95% destruction was an order-of-magnitude less for the porous electrode. 相似文献
18.
Sankar Namboothiri Mark P. Taylor John J.J. Chen Margaret M. Hyland Mark A. Cooksey 《Electrochimica acta》2011,(9):3192
Laboratory scale electrolysis experiments were conducted to investigate the electrowinning of aluminium using hydrogen diffusion anodes. A potassium-based electrolyte (KF–AlF3–Al2O3), porous nickel alloy anode and molybdenum disk cathode were used in experiments at 750 °C. Hydrogen gas was supplied to the anode/electrolyte interface through the porous anode. Experiments were conducted in potentiostatic, galvanostatic and galvanodynamic modes. There was a measurable depolarisation of the anode potential and also anode reaction of hydrogen and oxygen ions in the bath to form water vapour was confirmed by the water vapour condensate found at the electrolysis exit gas pipe. Metallic aluminium was found on the spent cathode. The experiments conducted in the galvanodynamic mode suggested that the rate limiter for hydrogen oxidation was the availability of surface hydrogen at the anode/electrolyte interface. The anode surface corroded during electrolysis and impurities were found both in the molten bath and on the cathode. 相似文献
19.
U. S. Mohanty B. C. Tripathy P. Singh S. C. Das V. N. Misra 《Journal of Applied Electrochemistry》2008,38(2):239-244
The effect of Mo6+ on the current efficiency, deposit quality, surface morphology, crystallographic orientations and polarisation behaviour
of the cathode during electrodeposition of nickel from sulfate solutions was investigated. Mo6+ did not have a significant effect on current efficiency over the concentration range 2–100 mg dm−3. However; a decrease in current efficiency by a magnitude of more than 20% was seen at 500 mg dm−3. The quality of the nickel deposit with reference to the visual appearance and contamination level varied with varying concentration
of Mo6+; this was also reflected in the morphology and crystallographic orientations of the deposits. Addition of Mo6+ to the electrolyte introduced two new crystal planes i.e., (220) and (311). Depolarisation of the cathode was noted at lower
concentrations of Mo6+ (2–40 mg dm−3) whereas polarisation of the cathode was observed at Mo6+ concentration >40 mg dm−3 .The effect of Mo6+ on parameters such as Tafel slope (b), transfer coefficient (α) and exchange current density (i
0) were also determined. 相似文献
20.
S. P. Gabuda S. G. Kozlova Yu. V. Mironov V. E. Fedorov 《Nanoscale research letters》2009,4(9):1110-1114
An abrupt change in internuclear Re–Re distances between {Re6} subunits in the carbon-centered [Re12μ6-CS17(CN)6]
n− complexes caused by the change of the oxidation state (n = 6, 8) is first theoretically shown to be possibly controlled by an external electric field. 13C NMR signal is shown to change over ~400 ppm (~37G) for μ6-C atom together with n. Thereby, the metal cluster [Re12μ6-CS17(CN)6]
n− can be considered as a perspective model of a molecular switch. 相似文献