US2795541A - Electrolytic production of percompounds - Google Patents

Electrolytic production of percompounds Download PDF

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Publication number
US2795541A
US2795541A US327221A US32722152A US2795541A US 2795541 A US2795541 A US 2795541A US 327221 A US327221 A US 327221A US 32722152 A US32722152 A US 32722152A US 2795541 A US2795541 A US 2795541A
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Prior art keywords
anode
anolyte
tube
diaphragm
production
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US327221A
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Muller Josef
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Evonik Operations GmbH
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Degussa GmbH
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    • 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
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • 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
    • C25B1/28—Per-compounds
    • C25B1/29—Persulfates
    • 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

Definitions

  • the present invention relates to an improved process and apparatus for carrying out .electrolyses in cells of the diaphragm type and more particularly to an improved process and apparatus especially adapted for the anodic production of persulfuric acid and salts thereof.
  • electrolytic processes in which the anode and cathode are separated by a porous diaphragm can be materially improved by suitable shaping .of the diaphragm employed to enclose the anode or cathode which not only permit the use of especially 'highcurrent densities, without the necessity of providing special cooling of the electrodes involved whereby not only high yields of easily decomposed compounds such as persulfuric acid and its salts can be obtained, but also whereby high current efliciencies are obtainable.
  • the diaphragms are so constructed that they notonly uniformly surround the entirely effective length of the electrode contained therein, but also that the volume of the electrode compartment bears a certain relationship to the inner surface area of the diaphragm so that whenexpressed in centimeters, the ratio of the volume of the electrode compartment to the inner surface of the diaphragm is at least 1 :4, that is so that at least 4 cm. of i phragm surface are provi d or ea h cm?
  • While the process and apparatus according to the invention is of general applicabilityto electrolyses of aqueous liquids wherein diaphragms are employed such as, for example, anodic oxidation processes such as the production of perchloric acid, perchlorates, .perborates, perphosphoric acid and perphosphates, as Well as the oxidation of organic compounds and cathodic reduction processes such as the Production of hydrosulfite and hydrazobenzene, it will be described in the following with par- 2. ticular reference to the production of persulfuric acid for which the process and apparatus have been found particularly adapted.
  • the diaphragms employed according to the invention I are in the form of relatively narrow tubular elements of uniform cross-section in order to provide the required compartment volume to diaphragm area ratio.
  • these are circular in cross-section and are mounted concentrically with respect ,to the electrode enclosed thereby, but those of oval or rectangular cross-section can also be employed provided the necessary volume to diaphragm area ratio is provided.
  • porous inert ceramic tubes having, for example, an inner diameter of about 6 mm. are admirably suitable as the diaphragms for the electrolytic cells according to the invention.
  • the use of the relatively narrow tubular diaphragms according to the invention permits the use of extremely high current densities without provisions for cooling the electrode within the diaphragm.
  • current densities of at least 500 amps. per liter of anolyte and preferably between 1000 and 2000 amps. per liter of anolyte are employed in the anodic production of persulfuric acid.
  • a further advantage of the relatively narrow tubular diaphragms resides in the fact that they provide a very simple way to achieve a very rapid flow of the electrolyte through the c ls i h s been found ac o d to h invention that rapid flow of the electrolyte through the space surrounded by the diaphragm produces high current efficiencies and according to the invention it was found in the production of pfirsulfuric acid that the anolyte should only be permitted to remain within the anode cell or cells at most for fifteen minutes and preferably only 4 to 8 minutes.
  • the relatively narrow tubular diaphragms surrounding the anode have. been found particularly suitable for this, as the gases formed at the anode are sufiicient to cause the anolyte to flow through the anode compartment, as because of the relatively small cross-section of the tubular diaphragm, such gases carry along the anolyte to the outlet. It was found that the pumping elfect of the gases is. so energetic that further measures need not be taken to convey the anolyte even when the electrolysis is carried out Within a plurality of the tubular diaphragms conectedin series. Consequently, according to the invention, it is no longer necessary to transport the anolyte from one cell unit to the .next by a cascading arrangement whereby a considerable saving in space is obtained.
  • the electrolyte be sup-- plied to the lower end of the tubular diaphragm or diaphragms through an appropirate feeding tube especially when a plurality thereof are to be connected in series without providing gradientsin height.
  • the electrolyte which is expelled from the upper open end of the diaphragm tubes is collected and supplied to diaphragm tubes next in the series through appropriate tubular connections so that connection of aplurality of cell units in series is easily and expediently effected.
  • the pumping action of the anode gases in the narrow tubes employed according to the invention can in some instances be so great that the resulting flow can only be completely utilized when a plurality of the diaphragm tubes are connected in series.
  • the conveyance of the electrolyte by the pumping action of the anode gases according to the invention provides a further advantage in that it renders it possible to alter the velocity of the flow in each step of an electrolytic process carried out with a plurality of cell units connected in series simply by selecting an appropriate number of parallelly connected tubes for each cell unit.
  • a further advantage of the process according to the invention is that it can be carried out with countercurrent flow of the anolyte and catholyte. For example, it is possible thereby to avoid the disadvantages of the previous processes for the production of persulfuric acid which are occasioned by the fact that in the latter part of the process the cathode acidis the weakest at the point at which the H504- ion requirements are the highest in the anode space.
  • the diaphragms employed according to the invention are rather narrow porous tubes preferably of ceramic. These narrow tubes render possible, even with rather long tubes surrounding an anode of about 1 meter long, an advantageous reduction in the thickness of the walls without danger of mechanical failure.
  • the reduction in the thickness of the diaphragm substantially improves'the heat exchange between the anolyte and the cooled catholyte so that even with the high current densities employed according to the invention in the production of persulfuric compounds, no special cooling means need be provided in the anode space.
  • a further result of the thinner diaphragms is that a lower voltage loss occurs in the diaphragm. It has, for example, been found in practical use that only 27% of the voltage is used for the diaphragms according to the invention.
  • the electrodes employed within the narrow tubular diaphragms according to the invention are advantageously in the form of wires and especially clad wires which have a core of a good conducting metal such as copper, silver or aluminum coated with, for example, platinum. It was found that anodes formed of clad wires having a good conductor as a core such as, for example, silver coated with a dense tantalum coating and wound with fine platinum wire or otherwisecoated with platinum proved especially advantageous. For example, a silver wire coated with tantalum 100 microns thick having a total diameter of 1.3 mm. and 1 meter long having its lower portion 90 cm. wound with meters of platinum wire 0.15 mm. in
  • anode for the production of persulfuric acid or other compounds through electrolytic oxidation.
  • Such an electrode only requires 10 g. of Ag, 6.3 g. of Ta and 3.78 g. of Pt.
  • the clad anode can be U shaped so that the ends do not dip into the electrolyte and need not be clad.
  • the dimensions of the electrodes employed in the narrow tubular diaphragms according to the invention are advantageously such that the distance thereof from the inner wall of the diaphragm is between 0.5 to 3 mm., preferably about 2 mm. With such spacing the optimum conditions with respect to a low voltage loss and conveyance of the electrolyte by the anode gases is achieved.
  • the anolyte be passed through the narrow tubular diaphragms containing the anodes with a velocity of 0.5 to 2 meters per minute and preferably between about 1.0 and 1.6 meters per minute.
  • a velocity of 0.5 to 2 meters per minute and preferably between about 1.0 and 1.6 meters per minute.
  • seven cell units connected in series in which the tubular diaphragms and anodes each were about 1 meter long gave very excellent results in the production of persulfuric acid of high concentration.
  • the specific current load with reference to the area of the inner surface of the diaphragms employed according to the invention for the production of persulfuric acid advantageously amounts to 0.1 to 0.15, preferably 0.12 to 0.14 amps. per cm. and the porosity of the diaphragm is selected so that such current density is obtained with a cell voltage of at most 4.0 to 4.5 volts.
  • the crosssection of the diaphragms for the anodes is advantageously selected Within the requirement of the proper volume to diaphragm area ratio according to the invention so that the current taken up for 1 meter length of anode cells is between 20 to 30 and preferably about 25 amps.
  • the process according to the invention renders it possible in the production of persulfuric acid, especially when high current densities are employed, rapidly to achieve a high end concentration, which is of advantage as it lowers the amount of steam required for the distillation thereof when it is employed in the production of hydrogen peroxide. Also, the increased rate of formation of the persulfuric acid and the relatively short time it remains in the anode compartments is of special significance with respect to the unfavorable influence of Caro acid.
  • the positive anolyte flow which is obtained according to the invention produces an extraordinarily low temperature sensitivity of the electrolyte, especially when a plurality of anode systems are connected in series and, furthermore, renders it possible to regulate the supply of the anolyte and the effluent persulfuric acid formed only at one point which substantially simplifies the operation of a plant operating according to the invention. Furthermore, it may be pointed out that in an electrolytic plant employing a plurality of anodes, the frequent degasification of the anolyte is advantageous and that the increase of the quantity of anolyte flow permits a more exact and less sensitive dosing of the electrolytes.
  • the cell voltages of 4.5 and less which can be employed are extraordinarily low. This factor coupled with the fact that, as has been mentioned before, the process provides high current efiiciencies, give energy savings of 20 to 30% in comparison with the previously known processes for the production of persulfuric acid which operate at substantially lower current densities and in some instances, operate with special anode cooling.
  • a persulfuric acid containing 350 to 400 g./l. of free persulfuric acid can be obtained with current yields of over 70%.
  • the current requirements, calculated upon 1 kg. of H202 lies under 12 kwh. and normally is about 11 kwh.
  • the previously known processes in comparison require at least 18 kwh.
  • Fig. 1 diagrammatically shows a single cell provided with a tubular anode compartment according to the invention
  • Fig. 2 is an enlarged diagrammatic view of a preferred form of anode employed according to the invention.
  • Fig. 3 diagrammatically shows an electrolytic apparatus wherein a plurality of anodic compartments are connected in a series of units.
  • Fig. 4 diagrammatically shows a top view of one of the distributing pipes for feeding the anolyte to the anode compartments of one unitof the series shown in Fig. 3.
  • Fig. 1, 1 designates the wire electrode which is surrounded by porous diaphragm tube 2 to provide an elongated narrow anode compartment.
  • the cathode 3 which, for example, can be of lead, is provided with lead cooling coils 4.
  • the electrodes are supported in a vessel 5 which serves to hold the catholyte.
  • the anolyte is supplied to the bottom end of the porous diaphragm 2 through leveling tube 6 so that it will be. carried upwardly through the relatively narrow anode compartment by the anode gases formed during electrolysis.
  • the flow of the anolyte to the anode compartment is regulated by regulating valve 15, whereas overflow 17 serves to maintain the proper catholyte level in vessel 5.
  • the catholyte is supplied to the vessel through opening 16.
  • the top of the electrolysing vessel closes with a cover 7 which carries a bell 8 of porcelain or inert plastic to collect the hydrogen produced at the cathode and permit its withdrawal through outlet 12.
  • the upper end of diaphragm tube passes through cover 7 and is attached thereto by a fluid and gas tight seal 9, preferably of nonmetallic material such as a plastic.
  • Compartment 10 which is carried on top of the cover serves to collect the anolyte thrown up from the open end of the diaphragm tube 2 by the action of the anode gases and serves to separate the anolyte from the gases.
  • the anode gases are withdrawn from such compartment through outlet 13, whereas the degasified anolyte is withdrawn through outlet 11.
  • the anode wire 1 is preferably attached to a cooled bus bar 14 by soldering to insure good electrical contact.
  • a cooled bus bar 14 As the free upper portion of the anode wire merely serves as a conductor for the electrolysing current and not the electrolysis itself, but still is in contact with the anode products, it is of significance that this portion be maintained as cool as possible. It was found that the use of a bus bar cooled with a circulating cooling fluid effects cooling of a considerable portion of the free upper portion of the anode wire attached thereto so that heating thereof by the joulean effect is largely avoided and undesirable effects upon the anode products are also largely avoided.
  • FIG. 2 A preferred form of the anode 2 is shown in Fig. 2 in which a clad wire composed of a conducting metal core 18, such as copper, silver or aluminum and tantalum cladding 19 is wound with a thin platinum wire 20.
  • a conducting metal core 18, such as copper, silver or aluminum and tantalum cladding 19 is wound with a thin platinum wire 20.
  • FIGs. 3 and 4 show by way of example, an electrolytic apparatus for the practical production of persulfuric acid.
  • seven serially connected units of anode compartments according to the invention are provided within vessel 25 serving to hold the catholyte.
  • Each unit is composed of forty parallelly connected porous diaphragms 22 about 1 meter long and having an internal diameter of about 6 mm. which serve as the anode compartments for anodes 21.
  • the anode compartments of each unit are arranged between cathodes 23 which are cooled by cooling coils 24.
  • the catholyte is supplied to vessel 25 through feed line 116 and is withdrawn therefrom through overflow 117.
  • the anolyte is supplied to the anode compartments of the first unit in the series through feed line 26 which is connected to the bottom ends of the anode compartments of such unit through line 30 and distributory line 31.
  • the upper ends of the porous diaphragms 22 pass through cover 27 and open into compartment 100 which serves to collect the anolyte thrown up from the open ends of the porous diaphragms by the anode gases and serves to separate the anolyte from such gases.
  • the separated anode gases are withdrawn through outlet 113, whereas the anolyte is supplied to anode compartments of the succeeding unit through lines 26', 30 and distributing line 31.
  • the succeeding anode compartment units are similarly constructed and the anolyte collected in compartments 100 is supplied to the next unit in the series in a similar manner except that in the last unit the anolyte containing persulfuric acid is withdrawn from the apparatus through line 111 ifgroworlging up in any desired manner, for example, to
  • a bell 2 8 is attached to the lower side of cover 27 to collect the hydrogen evolved from the cathodes associated with the anode compartment units.
  • the collected hydrogen is withdrawn from the apparatus through line 112.
  • the electrolysing current is supplied to the anodes through cooled bus bars 114.
  • the process of the invention is not limited to. the particular form of apparatus described, as numerous variations are possible as long as provisions are made for the various critical features of the invention, namely, a ratio between the electrode compartment volume and the diaphragm area within the limits described, the use of high current densities, rapid positive flow of the electrolyte through the electrode compartment so that the electrolyte remains Within the electrode compartment or compartments for only a short period of time which renders it possible to avoid the use of special additional anode cooling.
  • the electrodes and tubular electrode compartments be absolutely vertical, as they can be more or less inclined and can even be of angular shape.
  • Example An electrolytic apparatus With seven cathodes and seven serially connected anode units composed of 40 parallelly connected porous dia-' phragms (porous porcelain tubes 9/6 mm. diameter, about one meter long) provided with 40 anode wires (platinum silver clad wire 1.2 mm. diameter with a 60 mm. platinum cladding about one meter long) is filled with 40% sulfuric acid.
  • the cooling coils at the cathodes the cooling water passes with a velocity of 50 liters per minute with a temperature of about 10 C.
  • the load After turning on of the current the load is slowly regulated to about 7000 amps. whereby 0.9 liter per minute of sulfuric acid of 41.5% are supplied to the cathode compartment.
  • 0.9 liter per minute of sulfuric acid of 41.5% are supplied to the cathode compartment.
  • the conveyance of the electrolyte through the cathode compartment is regulated by the ionic flow through the diaphragms which permits a running oli of only 0.7 liter acid per minute of the efiluent 0.9 liter of acid.
  • This quantity with the potential value increasing addition is supplied to the anode units through a special feed line.
  • From the seventh anode unit persulfuric acid with 340345 grs. HzSzOs per liter runs off with a velocity of 0.9 liter per minute.
  • Thrs acid is recovered with a value of 36 B. and a current efliciency of 74 to 75%. At a temperature of about 19 C. the acid contains but 2 to 4 grs. of Caro acid.
  • the voltage of the electrolytic apparatus is about 4.2 volt with a current requirement of about 1.55 to 1.60 kwh. per one kg. H2S2Oa. Calculated upon 1 kg. of hydrogen peroxide only about 10 kwh. are needed or 3.5 kwh. for one kg. of 35 vol. percent of hydrogen peroxide respectively.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
US327221A 1951-12-22 1952-12-22 Electrolytic production of percompounds Expired - Lifetime US2795541A (en)

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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2904478A (en) * 1954-12-08 1959-09-15 Degussa Production of hydrogen peroxide
US2929769A (en) * 1955-07-07 1960-03-22 Isaac L Newell Electroplating anode
US3038849A (en) * 1958-10-07 1962-06-12 Herman S Preiser Insoluble trailing anode for cathodic protection of ships
US3102086A (en) * 1957-07-26 1963-08-27 Ici Ltd Method of improving the corrosion resistance of titanium metals
US3104220A (en) * 1960-04-27 1963-09-17 Herman S Preiser Flexible trailing anode
US3133872A (en) * 1959-03-10 1964-05-19 Chemionics Engineering Lab Inc Anode for electrochemical applications
US3278404A (en) * 1957-07-17 1966-10-11 Ici Ltd Method and apparatus for cathodic protection
US3297560A (en) * 1962-08-16 1967-01-10 Metallgesellschaft Ag Apparatus for alkali chloride electrolysis having a corrosion assistant anode
US3313721A (en) * 1958-12-31 1967-04-11 Englehard Ind Inc Dish-shaped anode
US3409530A (en) * 1965-10-20 1968-11-05 Continental Oil Co Helical electrode
US3880721A (en) * 1972-03-02 1975-04-29 Lockheed Aircraft Corp Method for reducing (pseudo-) ohmic overpotential at gas-evolving electrodes
US3972306A (en) * 1973-10-05 1976-08-03 Sharp Kabushiki Kaisha Coil shaped developing electrode for a copying machine
US4105534A (en) * 1977-08-29 1978-08-08 John L. Raymond Apparatus for removing impurities from electrolyte solutions
US4626326A (en) * 1985-06-06 1986-12-02 Fmc Corporation Electrolytic process for manufacturing pure potassium peroxydiphosphate

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US981900A (en) * 1910-02-08 1911-01-17 Consortium Elektrochem Ind Process for production of compounds of persulfuric acid.
US1059809A (en) * 1910-10-06 1913-04-22 Gustav Adolph Manufacture of persulfates.
US1104754A (en) * 1912-11-06 1914-07-21 Davis Bournonville Co Electrolytic cell.
US1342378A (en) * 1920-06-01 gerstle
US1477099A (en) * 1922-07-07 1923-12-11 Firm Of Chem Fab Weissenstein Anode for forming percompounds
US1937621A (en) * 1927-01-03 1933-12-05 Du Pont Electrolytic apparatus
US2331320A (en) * 1936-01-18 1943-10-12 Forest H Hartzell Electrode for electrometallurgical purposes
US2349998A (en) * 1938-02-01 1944-05-30 Trinius Werner Apparatus for obtaining persalts by electrolysis

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE560583C (de) * 1926-01-28 1932-10-05 Oesterr Chem Werke Gewinnung von UEberschwefelsaeure und ihren loeslichen Salzen durch Elektrolyse von Schwefelsaeure
BE373771A (ro) * 1930-02-20
DE737917C (de) * 1938-02-01 1943-07-29 Giesler & Trinius Verfahren zur Gewinnung von Persalzen durch Elektrolyse
FR848739A (fr) * 1938-02-01 1939-11-06 Giesler & Trinius Procédé de fabrication de persels, tels que les persulfates, par électrolyse

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1342378A (en) * 1920-06-01 gerstle
US981900A (en) * 1910-02-08 1911-01-17 Consortium Elektrochem Ind Process for production of compounds of persulfuric acid.
US1059809A (en) * 1910-10-06 1913-04-22 Gustav Adolph Manufacture of persulfates.
US1104754A (en) * 1912-11-06 1914-07-21 Davis Bournonville Co Electrolytic cell.
US1477099A (en) * 1922-07-07 1923-12-11 Firm Of Chem Fab Weissenstein Anode for forming percompounds
US1937621A (en) * 1927-01-03 1933-12-05 Du Pont Electrolytic apparatus
US2331320A (en) * 1936-01-18 1943-10-12 Forest H Hartzell Electrode for electrometallurgical purposes
US2349998A (en) * 1938-02-01 1944-05-30 Trinius Werner Apparatus for obtaining persalts by electrolysis

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2904478A (en) * 1954-12-08 1959-09-15 Degussa Production of hydrogen peroxide
US2929769A (en) * 1955-07-07 1960-03-22 Isaac L Newell Electroplating anode
US3278404A (en) * 1957-07-17 1966-10-11 Ici Ltd Method and apparatus for cathodic protection
US3102086A (en) * 1957-07-26 1963-08-27 Ici Ltd Method of improving the corrosion resistance of titanium metals
US3038849A (en) * 1958-10-07 1962-06-12 Herman S Preiser Insoluble trailing anode for cathodic protection of ships
US3313721A (en) * 1958-12-31 1967-04-11 Englehard Ind Inc Dish-shaped anode
US3133872A (en) * 1959-03-10 1964-05-19 Chemionics Engineering Lab Inc Anode for electrochemical applications
US3104220A (en) * 1960-04-27 1963-09-17 Herman S Preiser Flexible trailing anode
US3297560A (en) * 1962-08-16 1967-01-10 Metallgesellschaft Ag Apparatus for alkali chloride electrolysis having a corrosion assistant anode
US3409530A (en) * 1965-10-20 1968-11-05 Continental Oil Co Helical electrode
US3880721A (en) * 1972-03-02 1975-04-29 Lockheed Aircraft Corp Method for reducing (pseudo-) ohmic overpotential at gas-evolving electrodes
US3972306A (en) * 1973-10-05 1976-08-03 Sharp Kabushiki Kaisha Coil shaped developing electrode for a copying machine
US4105534A (en) * 1977-08-29 1978-08-08 John L. Raymond Apparatus for removing impurities from electrolyte solutions
US4626326A (en) * 1985-06-06 1986-12-02 Fmc Corporation Electrolytic process for manufacturing pure potassium peroxydiphosphate

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NL92567C (ro)

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