Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
  • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
  • H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/02—Hydrogen or oxygen
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
  • C25B11/097—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds comprising two or more noble metals or noble metal alloys
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B5/00—Electrogenerative processes, i.e. processes for producing compounds in which electricity is generated simultaneously
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/90—Selection of catalytic material
  • H01M4/92—Metals of platinum group
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/90—Selection of catalytic material
  • H01M4/92—Metals of platinum group
  • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
  • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/08—Fuel cells with aqueous electrolytes
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
  • C01B2203/06—Integration with other chemical processes
  • C01B2203/066—Integration with other chemical processes with fuel cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• Hydrogen is expected to be a primary energy source in the 21st century for electricity generation, fuel and other applications. It is an environmentally clean energy source since it generates no pollutants. Fossil fuels and water are the major sources for the manufacture of hydrogen. However, these processes are highly energy intensive consuming nearly twice as much as energy from these sources and not always environment-friendly. Moreover, the fossil-fuel (mainly petroleum) reserves of the world are depleting at an alarming rate. The electrolysis of water so far is the cleanest way but the theoretical over-potential required to oxidize water is -1.23 V versus SHE (standard hydrogen electrode).
• the electrolyte solution for the cathode compartment was H 2 SO 4 , and LiClO 4 was used for the anode compartment.
• the authors do not present an explanation of why they used LiClO 4 .
• the solutions were deoxygenated with N 2 prior to use. All of the slurries were 2% weight concentration. The authors ⁇ found much lower currents than the ones reported by Coughlin and Farooque 1' ⁇ (10 times lower) and they attributed this behavior to the types of coal utilized, coal slurry concentration, electrode area, and reaction temperature employed. However, the electrolyte that they used is different and this may have affected their results. An important finding by the authors is that they reported that the activity of the system is in the extracted solution and not in the slurry. This finding is in some sense contradictory with what Coughlin and
• Electrodes comprising electrocatalysts comprising noble metals electrodeposited on carbon substrates.
• the carbon substrates may comprise many different carbon materials, including but not limited to carbon nano-tubes, carbon fibers, and so forth. Also provided are methods of using the electrocatalysts provided herein for the electrolysis of coal in acidic medium.
• electrolytic cells for the production of hydrogen from coal slurries in acidic media.
• the electrolytic cells uses the electrodes described herein as the anode.
• the electrolytic cells uses the electrodes described herein as the cathode.
• the electrolytic cells utilizes the electrodes provided herein as both the anode and the cathode.
• coal/petroleum fuel cells and coke/char slurry fuel that utilize the electrocatalysts provided herein as the anode.
• electrochemical treatment processes where iron-contaminated effluents are purified in the presence of coal slurries using the electrocatalysts described herein.
• catalytic additives for the electro-oxidation of coal comprising iron salts, i.e., Fe +2 and Fe +3 .
• an electrolytic cell for the production of hydrogen from coal slurries containing iron salts in acidic media using the developed catalyst as anode or cathode are also provided.
• electrochemical treatment process where iron-contaminated effluents are purified in the presence of coal slurries using the developed catalyst.
• Figure 1 is a schematic representation of the Glass cell for electro-oxidation studies of Ohio coal.
• Figure 2 shows the current densities under potentiostatic conditions for different electrodes (anode) at 40 C, for Pittsburgh No. 8 slurry with concentration 0.12 g/ml in IM H2SO4.
• Figure 3 shows the XRD spectrum for purified graphite and Pittsburgh Seam No.8 identifying the main components.
• Coal contains iron, oxygen, and sulfur.
• Figure 4 shows current densities under potentiostatic conditions for Pittsburgh No. 8 and graphite slurries with concentration 0.12 g/ml in IM H2SO4 at 40 oC.
• Pt-Ir 80:20 was used as anode. The currents developed in the coal are higher than the ones observed in graphite.
• " • ' Figure 1 5 shows" tM effect of Iron (HI) on the electrolysis of graphite and coal on a Pt-Ir (80 20) electrode at 40 oC, IM H2SO4, concentration of coal or graphite was kept constant at 0.12 g/ml
• Figure 6 shows current densities under potentiostatic conditions for Pittsburgh No 8 slurries with concentration 0 12 g/ml in IM H 2 SO 4 at 40 0 C at different Fe +3 concentrations.
• Pt-Ir (80 20) was used as anode
• the Fe +3 concentration in solution has a positive effect on the current densities developed in the cell.
• Figure 7 shows current densities under potentiostatic conditions for Pt-Ir electrodes (anode) at 40 °C, with Pittsburgh No 8 concentration 0.12 g/ml, 1 M H2SO4 and 80 mM Fe+3 concentration.
• Figure 8 shows a proposed Mechanism for the Oxidation of Coal in the Presence of Fe+2/Fe+3
• Figure 9 shows current densities under potentiostatic conditions for different electrode materials at 40 0 C, with Pittsburgh No 8 concentration 0 12 g/ml, 1 M H2SO4 and 100 mM Fe+3/100 mM Fe+2 concentrations.
• Figure 10 shows galvanostatic expe ⁇ ments performed at 60° C in a compact continuous bench scale coal electrolytic cell using Pt-Rh plated on carbon fibers as anode and Pt plated on carbon fibers as the cathode The applied current was 50 mA.
• FIG 11 shows galvanostatic performance of the coal electrolytic cell at 60 oC and 100 mA (25 mA/cm2) with different solutions. The results indicate that the electrolysis of coal is enhanced in the presence of Fe+2/Fe+3
• Figure 12 shows Cell Voltage with Pt-Rh/carbon fiber anode electrode for 3 runs at 100mA, IM H 2 SO 4 , and coal concentration 0 12g/ml operating at 60 0 C.
• Figure 13 shows SEM pictures of (a) unreacted coal before testl (Original coal) , (b) reacted coal after test 1, (c) acetone washed coal and (d) acetone washed coal heat to 25O 0 C for 6-8 hours
• Figure 14 shows Cell Voltage with Pt-Ir-Rh/carbon fiber anode electrode for 3 runs at 100mA, IM H2SO4, and coal concentration 0 12g/ml operating at 60 0 C.
• Figure 15 shows Cell Voltage with Pt-Rh-Ir/carbon fiber electrode at 100mA, IM H2SO4, and coal concentration 0 12g/ml operating at 60 0 C with 10 mM Fe2+ and 100 mM Fe3+
• Figure 16 shows a batch test, effect of tme on CO 2 evolution
• Figure 17 shows a batch test, effect of temperature on CO 2 evolution.
• Figure 18 shows a process for preparing carbon fiber for electrodeposition procedure [002 ⁇ "FTgWFlSf shWs'SEMfhotographs of the carbon fibers before plating and after plating.
• Figure 20 shows the effect of pressure and temperature on the thermodynamics potential of the Coal electrolytic cell.
• An electrocatalyst made of electrodeposited noble metals (by layers) on supported carbon fibers (nano-tubes or carbon fibers) has been developed for electrolysis of coal in acidic medium. Described herein are: an electrolytic cell for the production of hydrogen from coal slurries in acidic media using the developed catalyst as anode or cathode; coal/petroleum coke/char slurry fuel cell using the developed catalyst as anode; and an electrochemical treatment process where iron-contaminated effluents are purified in the presence of coal slurries using the developed catalyst.
• Additives The catalytic effect of iron salts (Fe +2 and Fe +3 ) on the electro-oxidation of coal is also described herein. Further described herein are: an electrolytic cell for the production of hydrogen from coal slurries containing iron salts in acidic media using the developed catalyst as anode or cathode; coal/petroleum coke/char slurry containing iron salts fuel cell using the developed catalyst as anode; an electrochemical treatment process where iron-contaminated effluents are purified in the presence of coal slurries using the developed catalyst.
• a continuous coal electrolytic cell for the production of pure hydrogen without the need of separated purification units.
• the cell can be integrated into a power generation system comprised by coal electrolytic cell/proton exchange membrane fuel cell.
• Fuels The electrolytic cell, additives, and electrocatalysts can use solid fuels such as: petroleum coke, all ranges of coal, and chars.
• the energy consumption for the electrolysis of coal at 60 0 C is 22.5 W-h/g H 2
• for water electrolysis at the same operating conditions in our cell is 42 W-h/g H 2 (46.5% lower energy consumption for the electrolysis of coal).
• the soldered part and most of the length of the copper wire was coated with a polymer (PTFE) which is stable at higher temperatures (120 0 C) and resistant to the coal-water slurry in which it was tested. This coating was done twice and heated for 15-20 minutes in an oven at 200 0 C to ensure uniform distribution of the coating and finally air dried.
• PTFE polymer
• Pt, Pt-Ir, Pt-Ru, Pt-Rh obtained form Alfa Aesar were used for the evaluation. Before the electrodes were used for testing they were cleaned properly with a strong base and with acetone to remove any dust particles (as well as grease) on the surface and finally with distilled water.
• Counter electrode was made of Pt-Ru with thrice as much as the area of the working electrodes.
• the surface area of the counter electrode (cathode) was kept much larger than that of the working electrode (anode) in order to keep the anodic reaction limiting.
• a digitally controlled impeller was used to mix the slurries in order to maintain their homogeneity. All the experiments were carried out at 4O 0 C. Once the cell was set, an ARBIN potentiostat was used to perform the experiments under potentiostatic conditions at different voltages (0.4, 0.6, 0.8 and IV) in order to examine the reaction rate. The tests were run for at least 100 minutes with each electrode.
• Pt-Ir is one of the best electrodes for the electrolysis of water in acidic medium. This is because there is a stable film formation on the surface of the Pt-Ir electrode whose electrical conductivity is very high compared to the film formed on the surface of the pure Pt. This could be the possible reason for the better performance of Pt-Ir. But the optimum amount of Ir content in Pt-Ir depends on the process you are dealing with. From figure 2 it can also be seen that there is no difference in the current densities between Pt and Platinized Pt electrode. There was no exfoliation of the platinized electrode material due to the coal particles. This means that to achieve the same current densities at lower cost it is better to use Platinized Pt electrode.
• FIG. 7 shows the performance of two different electrode compositions: Pt-Ir 80:20 and Pt-Ir 60:40.
• the experiments were performed using the experimental set up shown in Figure 1.. AU the experiments were carried out under potentiostatic conditions (at 0.4, 0.6, 0.8 and IV) at 40 0 C, with a Pittsburgh No 8 coal concentration of 0.12 g/ml, 1 M H 2 SO 4 and 80 mM iron concentration. The most important observation was that, the currents generated in our experiments were relatively high compared to the literature values.
• Fe +3 oxidizes the coal according to the reaction proposed by Coughlm and Faroquee, ⁇ Eq. (4). That is, Fe +3 is reduced at the surface of the coal to Fe +2 according to a chemical reaction (see stages 1, 2, and 3 in Figure S). On the other hand, Fe +2 gets oxidized back to Fe +3 at the surface of the anode of the electrolytic cell according to Eq. (5), (see stage 4.a of Figure 8). Coal needs to contact the anode of the electrolytic cell to transport the Fe +2 to the surface of the anode (if there is no contact between the coal and the anode the process does not precede in time).
• the electro-oxidation of coal should be enhanced by the synergistic effect of Fe (III) and Fe (II) present in solution. If the hypothesis is correct the current densities observed should be improved by the presence Of Fe +2 in solution simultaneously with Fe +3 .
• the effect of Fe +2 /Fe +3 in solution is shown in Figure 9. As demonstrated, the presence Of Fe +2 increases the current density of the cell. Again Pt-Ir seems to be the best electrode for the reaction (highest current at the lowest voltage). It can also be seen that the Pt-Ir electrode approaches concentration limitations faster than the other electrode materials.
• Electrocatalysts for the electro-oxidation of solid fuels in acidic medium (example shown for bituminous coal slurries): The results from Section I indicated that Pt-Ir is a suitable catalysts for the electro-oxidation of coal. This section describes the development of a large surface area electrode. The electrodes were fabricated by plating Pt-Ir-Rh on carbon fibers.
• Titanium gauze obtained from Alfa Aesar was cut into a rectangular shape of known area.
• the cut foils were hooked to a titanium wire (diameter 0.5mm) of suitable length on to the center of one of the edges of the rectangular foil.
• the reason for choosing titanium is due to its stability and low cost.
• the carbon fibers (approximate diameter of 5 mm) were wound uniformly on the surface of the gauze and the two ends of the fibers were tied to the titanium wire with a small piece of titanium foil to ensure proper electrical contact.
• the solution was heated (close to 60°C-70°C) and mixed using ultrasonic water bath.
• the Pt-Rh was pulse deposited under galvanostatic conditions for at least 1 - 2 hours and the iridium salt was deposited for 5-6 hours.
• Rhodium was basically plated first to improve the conductivity of the electrode material so that other materials can be plated on the fibers easily. Intermittently after each pulsing the electrode was weighed to ensure if there was proper plating.
• the loadings of the nobel metals were kept between 2-4 mg/cm of fiber bundle (6000 fibers per bundle).
• FIG 11 shows the performance of the coal electrolytic cell at 60 0 C operating at 100 mA (25 mA/cm 2 ) with different solutions: coal with Fe +3 , sulfuric acid with Fe +3 /Fe +2 , sulfuric acid with Fe +2 , and coal with Fe +2 /Fe +3 .
• the fact that the cell can operate for longer times in the presence of Fe +2 /Fe +3 indicates that Fe +3 enhances the oxidation of coal and at the same time the coal helps in reducing Fe +3 to Fe +2 which in turn allows a close loop.
• coal gets oxidized with a sudden increase in the cell voltage. The formation of films on the surface of the coal was observed. At the end of the experiments the coal particles agglomerated.
• Electrochemical performance measurement in continuous coal electrolytic cell All the experiments were performed at 60 0 C using Pt-Rh and Pt-Rh-Ir plated on carbon fibers as anodes and Pt plated on carbon fibers as cathode. Polarization experiments were carried out using the system described above containing 0.12 g/ml Pittsburgh No. 8 coal suspended in 1 M sulfuric acid with the above mentioned different working electrodes of known geometric areas. The coal used was previously stored in ah Argon ' " filled G ' tove ' b " bx"t ⁇ ” ' keep it from exposing to the oxygen which would otherwise form a film on the surface of the coal particles and could possibly lead to the increase in the overpotential for the electro-oxidation of the coal.
• the particle size of the coal used was ranging from 74 - 105 ⁇ m.
• the coal slurry was made by mixing the above coal dust with a specified concentration of 1 M sulfuric acid which acts as electrolyte. Moreover in all the galvanostatic experiments the above parameters (concentration of coal slurry: 0.12 g/ml, concentration Of H 2 SO 4 : 1 M, temperature 60 0 C, Concentration OfFe 2+ , Fe 3+ : 100 mM each) were kept constant to make a comparative study of only the effect of anodic materials on the electro-oxidation of Ohio coal. A constant current of 100 niA was applied and tests were performed until the potential reached 1.2 V.
• Figure 12 shows the polarization performance of Pt-Rh anode for coal water slurry solution (0.12 g/ml) containing each of 100 mM Fe +2 and Fe +3 at 100 mA supplied constantly.
• the curves indicate that as time passed the cell potential increased gradually reaching the maximum set potential (1.2 V) for the cell.
• the first run (test 1) lasted for 62 hours. This showed that at this potential the coal almost got deactivated. The deactivation is caused because coal was recycled in the system. This does not mean that the coal lost all its calorific value. But the coal was just deactivated possibly due to the films formed on the surface of the coal. This is in agreement with what other researchers reported previously.- ⁇ ? Other researchers described that these films are formed due to surface functional groups such as carboxyl, carbonyl and hydroxyl oxygen which act as intermediates accumulating on
• the acetone-filtrate was light brown in color, indicating some amount of tar like compounds were extracted from coal, at the same time acetone aided in removing the surface films.
• the acetone washed coal was dried in an oven at 25O 0 C for 6 hours. The dried coal was cooled to room temperature and about 2 g of the sample was collected for the analysis. Reactivated coal was mixed back with the initially collected coal filtrate containing iron. The coal slurry was re- polarized to check the activity regained after washing with acetone. It was observed that the electro- oxidation of coal lasted for 10.5 hours during the second run (test 2 as shown in figure 12). Similarly two other runs were performed (by filtering water and acetone washed) until the coal almost lost its activity. During the tests 3 and 4 the polarization lasted for 8 hours and 2 hours respectively (see figure 12).
• Ga* collection experiments The gas collection experiments were performed using Pt-Ir- Rh/carbon fiber electrode. The experimental conditions were slightly different and they are explained as follows: Temperature- 80 0 C, coal slurry concentration - 0.04 g/ml, H 2 SO 4 concentration - 1.5 M, concentration of Fe +2 and Fe +3 - 100 mM each, current 300 mA. The experimental conditions were intensified to enhance the oxidation of coal. The experiments were performed in two setups: a) batch system and b) continuous circulation system. The batch system was mainly used to evaluate the rate of generation of CO 2 due to chemical oxidation and also the effect of temperature on the evolution rate of CO 2 . These two tests were studied both in the absence and presence of iron content. All the results were reported based on the compositions recorded by SRI Gas chromatography.
• Figure 16 shows the effect of time, it can be seen that initially the percent cumulative CO 2 evolution was 20 % for coal slurry containing iron while for the coal slurry in the absence of iron content it was negligible. As time passed there was gradual increase in CO 2 evolution for the first 100 minutes in both cases and then there was a rapid increase for the next 100 minutes with a very steep slope in case of coal containing iron while in case of bare coal also the CO 2 evolution increased but with a lesser slope. After 200 minutes the CO 2 evolution stabilized in both the cases. These results indicate that the presence of Fe salts is very important for the complete oxidation of coal.
• the continuous system was also used to electrolyze water in the cell in order to compare the energy consumed during water electrolysis with the energy consumed during coal electrolysis.
• the energy consumption for the electrolysis of coal at 60 0 C was 22.5 W-h/g H 2
• for water electrolysis at the same operating conditions in our cell was 42 W-h/g H 2 (46.5% lower energy consumption for the electrolysis of coal).
• the continuous system was also used to electrolyze water in the cell in order to compare the energy consumed during water electrolysis with the energy consumed during coal electrolysis.
• the energy consumption for the electrolysis of coal at 60 0 C was 22.5 W-h/g H 2
• for water electrolysis at the same operating conditions in our cell was 42 W-h/g H 2 (46.5% lower energy consumption for the electrolysis of coal).
• a planar bench-scale coal electrolytic cell was built using the novel electrodes.
• the cell has operated galvanostatically at 300 niA (75 mA/cm 2 ) at 80 0 C with a cell voltage of 0.7-0.9 V without significant detrimental performance when the Pt/Tr electrodes are used for up to 36 hours (starts as low as 0.7).
• the slight increase in the cell voltage with time is because the coal is getting oxidized seems it is recycled to the cell (that is fresh coal is not continuously pumped).
• FIGde preparation shows a schematic representation of the procedure used to increase the electronic conductivity of the carbon fibers during plating (and also during the operation of the electrode).
• the fibers were wrapped on a titanium gauze, therefore, there were in electric contact with the metal at different points. This improvement allowed an easy and homogenous plating of the fibers at any point.
• the electronic conductivity at any point in the fiber was the same as the electronic conductivity of the Ti gauze (which is really high).
• Figure 19 shows a Scanning Electron Microscope photograph of the electrode before plating and after plating.
• a first layer of Rh was deposited on the electrode to increase the electronic conductivity of the fibers.
• a second layer consisted of Pt was plated on the electrode. The Pt layer did not cover all the Rh sites, leaving Rh surface to act as a preferred H adsorbent.
• Electrodes The schematic for the construction of the electrode is shown if Figure 18. The plating procedure consists into two steps: 1. First layer plating and 2. Second layer plating
• First layer plating This step consists on plating the carbon fiber ' s or the carbon nanotubes with materials that show a strong affinity for OH or H. Examples include: Rh, Ru, and Pd. Rh is the prefer material.
• the first layer coverage is preferably about 2 mg/cm or greater of fiber to guarantee a complete plating of the fiber.
• Second layer plating This step consists on plating the electrode with materials that have a strong affinity for the oxidation of coal, petroleum coke, and char. Examples include: Pt and Ir. Monometallic deposition and/or bimetallic deposition of these materials can be performed. Ratios of Pt:Ir can range from 100% Pt-0% Ir to 80% Pt-20% Jr.
• Table 4 summarizes the plating conditions for the anode and the cathode of the electrolytic cell.
• the electrode is weighted. The weight corresponds to the Rhodium loading.
• the Platinum is deposited on top of the Rhodium.
• the electrode is measure again. The measurement will correspond to the total loading.
• the Platinum loading is oMineH ⁇ ⁇ sutfiractirig ⁇ ihe ⁇ tdlaf 1 loading from the Rhodium previous measurement.
• the relation Platinum/Rhodium is then calculated so as the percentage of fixed loading. Because the loading depends on the length of the fiber, another measurement have to be calculated. It is known that 10 cm of fiber bundle (6000 fibers per bundle) weights 39.1 mg, and because it is know the weight of fiber (calculated in step 1), then by proportionality it can be known the length of the total fiber that is being used in each electrode.
• Table 5 summarizes the general conditions of the plating bath. During the whole plating procedure, the solution was mixed to enhance the transport of the species to the fibers and or nanotubes.
• Table 6 shows examples of some electrodes compositions, lengths, and loadings of noble metals.
• the electrodes consist of a carbon fiber and/or carbon nanotubes substrates which were plated with a first layer of noble metal. This metal had a strong affinity for OH and H. Then after, the electrode was plated (single deposition and/or bimetallic deposition) with a noble metal that has a strong affinity for coal/petroleum coke/char oxidation.
• Electrolytic Cell The anode of the electrolytic cell was constructed using the procedure described in section I. It consists of carbon fibers plated with two layers of materials. The first layer is made of a metal that has affinity for OH and H, while the second layer is made of a metal or metals that have affinity for coal, petroleum coke, and char. The cathode was made similar to the anode.
• the fibers are rested (be wrapped) on a metal gauze.
• Any inert material for the acidic deposition bath as well as the acidic medium of the solution could be used. The best choice seems to be titanium.
• fO08 ' 4] ⁇ f ' UhI"" cell' 1 *" can be made of any nonconductive polymer. Examples include: polypropylene, acrylic, stainless steel, titanium, etc. The choice for the material depends on temperature and pressure.
• the gaskets of the cell were made of Teflon.
• the choice for the gasket depend on the temperature, concentration of sulfuric acid, and pressure of the cell.
• the electrodes in the cell need to be separated by a membrane or separator that stands the strong acidic conditions of the medium.
• a membrane or separator that stands the strong acidic conditions of the medium. Examples include: polyethylene and Naf ⁇ o. The best choice seems to be polyethylene.
• Additives Fe +2 and Fe +3 has a catalytic effect on the electro-oxidation of coal.
• Other salts can also be used, for example Ce +4 .
• Ce +4 The best choice seems to be iron salts seems they are already present in the coal and they are less expensive than Ce +4 .
• the range for the concentration of Fe +2 and F +3 goes from 1O mM to IM.
• Temperature The temperature can vary from 25 0 C to 160 0 C. Higher temperatures require an increased in pressure to keep the water in liquid phase. The higher the temperature the faster the rate of electro-oxidation of coal.
• Figure 20 shows the thermodynamics effect of increasing temperature and pressure on the cell voltage. The results indicate that pressure does not significantly increase the voltage of the cell according to the thermodynamics as long as the temperature is increased.
• Particle size The particle size can be allowed to vary from between 210-250 ⁇ m to less than 44 ⁇ m. The smaller the particles size the faster the electro-oxidation rate.
• Slurry concentration and fuel type The slurry concentration can be varied between 0.04 to 0.4 kg/dm 3 .
• the system described herein may use solid fuels such as: petroleum coke, all ranges of coal, and chars. Low bituminous coal oxidize faster.
• Iron concentration Fe +3 /Fe +2 .
• the iron content can be changed from the original value presented in the coal slurry to up to 1 M.
• Electrolyte and electrolyte concentration The electrolyte used in the cell can be any acid; examples include phosphoric acid, acetic acid, trifluoromethanesulfonic acid, and sulfuric acid. The preferred choice is sulfuric acid.
• the electrolyte concentration can vary from 0.1 to 5 M.
• the anode and cathode materials described herein, and the additives described can be used for the production of hydrogen in-situ from the electrolysis of solid fuels such as petroleum coke; all range's of coal, and chars. Because the anode and cathode are separated by a membrane, pure hydrogen is produced at the cathode compartment and pure CO 2 is produced at the anode compartment. Therefore, purification of hydrogen is not needed and it can be directly used in any type of fuel cell. Because of the purity of the hydrogen and the low operating temperature of the fuel cell, it is anticipated that the coal electrolytic cell can be easily coupled with a proton exchange membrane (PEM) fuel cell.
• PEM proton exchange membrane
• the electrolytic cell can use electric energy from renewable (wind, solar energy) and traditional sources (coal or natural gas).
• the electrochemical gasification of coal produces hydrogen directly from coal without NO x , SO x pollution, or subsequent downstream gas separation or purification.
• the immediate anticipated benefits of the technology are: 1. Production of hydrogen at lower cost than the current technology (natural gas reforming) for distributed power, 2. Fuel flexibility, 3. Enhancement of the national security in the United States through less reliance on foreign fuel, and 4. Zero hazardous environmental emissions.
• the storage of coal/water slurries is commercially feasible; therefore, the electrolysis of coal/water slurries helps solve the problem of hydrogen storage.
• Low temperature solid fuel cell _
• the developed anode with the presence of the additives can be used for the electro-oxidation of solid slurries (e.g., coal, petroleum coke, and chars) that couple with a cathode electrode in which the reduction of oxygen takes place constitute a direct low temperature solid slurries fuel cell.
• solid slurries e.g., coal, petroleum coke, and chars
• Remediation process The developed electrode materials as well as the electrolytic cell can be used to treat acid waters with high content of iron. At the anode of the cell the oxidation of the slurry takes place while at the cathode hydrogen is produced. If the hydrogen is used to power a fuel cell, clean water is returned into the process. Acidic waters with high content of iron are usually found in rivers and lakes near coal mining.

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• 2006
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