Classifications

• • 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
  • C25B3/00—Electrolytic production of organic compounds
• • 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
  • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
• • 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
  • C25B11/042—Electrodes formed of a single material
  • C25B11/043—Carbon, e.g. diamond or graphene
• • 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
  • C25B9/70—Assemblies comprising two or more cells
  • C25B9/73—Assemblies comprising two or more cells of the filter-press type

Definitions

• the present invention relates to a novel plate stack cell and a process for the electrolysis of substances.
• Electrolysis cells are used in modern chemistry in a variety of ways Designs used for a variety of tasks. An overview of the design options for electrolysis cells can be found, for example in D. Pletcher, F. Walsh, Industrial Electrochemistry, 2nd edition, 1990, London, pp. 60ff.
• a commonly used form of electrolytic cell is the plate stack cell. A simple arrangement of this is the capillary gap cell. Become frequent the electrodes and corresponding separating elements are arranged like filter presses. In this type of cell, several electrode plates are parallel arranged to each other and by spacing media such as spacers or Diaphragms separated. The spaces are with one or more Electrolyte phases filled.
• a so-called undivided cell usually only contains an electrolyte phase, a divided cell has two or more such Phases on. As a rule, the phases are adjacent to the electrodes liquid. However, so-called solid electrolytes such as ion exchange membranes can also be used be used as electrolyte phases. Will the The electrode is applied directly to the ion exchange membrane, e.g.
• the individual electrodes can be connected in parallel (monopolar) or in series (bipolar). in the Within the scope of the invention, only cells with a bipolar circuit are used considered the stack electrodes.
• the electrolyte is brought up to the electrodes in this way be that an optimal mass transport is achieved.
• the electrolyte fluid be parallel to the electrodes to flow.
• the space-time yield and the selectivity of the electrolysis are related the flow to the electrodes also from the electrode materials used from. These affect the durability, size and weight of the cell essential.
• the electrodes are usually used as massive plates, for example graphite discs.
• Such electrodes have multiple disadvantages resulting from the massive nature of the material result, for example, the reduced compared to a porous material Surface and the associated reduced material turnover, higher Weight and larger space requirements.
• the object of the present invention is therefore to provide a plate stack cell with increased space-time yield, high selectivity, low Weight and space requirements that are as easy to manufacture and operate is.
• Another object of the invention is to provide Electrolysis process with high space-time yield and high selectivity.
• the solution is based on a plate stack cell with a series connection Stack electrodes.
• the plate stack cell is then characterized in that at least one stack electrode made of a graphite felt plate, a carbon felt plate, a fabric with a carbon-covered educt contact surface or a porous solid with a carbon-covered educt contact surface exists or contains such material and that the migration of Electrolysis due to the electrical potential difference due to this carbon-containing Stack electrode is hindered or prevented.
• the process task is performed using an electrolysis process of the plate stack cell defined above.
• a plate stack cell with serial (bipolar) switched stack electrodes provided, at least one stack electrode from a graphite felt plate, a carbon felt plate, a fabric with Carbon-covered educt contact surface or a porous solid with There is carbon-covered educt contact area or such a material contains.
• Felts suitable for use in the present invention are commercially available. Both graphite felts and Carbon felts are used, with both types of felt mainly characterized by Differentiate structure of carbon. Instead of or alongside those described Felting can also be used with other porous materials Contact surfaces with the educt completely or largely with carbon are covered. Contact surfaces are the outer and inner ones Surfaces with which the starting material to be electrolyzed during the electrolysis reaction comes into contact. These materials can be made completely There are carbon such as carbon fabrics, carbon networks or porous carbon solids. But it can also be a carrier from another Materials are used whose contact surface with the educt is entirely or mostly covered with carbon.
• the electrode can be made entirely of the materials mentioned or have one or more additional layers. These layers can be used Example of the stability of the arrangement.
• the plate stack cell in particular the electrodes themselves and the electrolyte, designed so that as little as possible, ideally none Electrolysis due to the electrical potential difference due to the above described carbon-containing stack electrode according to the invention migrate.
• the current inside the electrode should be as exclusive as possible Electrons, not caused by ions.
• Electrolysis conditions especially the electrolyte used, can this migration of electrolytes through the carbonaceous may even be necessary Restrict or prevent stack electrodes through to to achieve a notable electrolysis reaction on these stack electrodes.
• Solid electrolyte can basically be any known for this function Material can be used. Ion exchange membranes are preferred used.
• a liquid electrolyte phase is also created used, which contains the electrolysis products.
• This liquid phase preferably contains no free conduction ions or only a small amount Amounts of it. This becomes exclusive or almost exclusive electronic current reached in the electrode. The ionic current between the electrodes are then completely or largely represented by ions bound in the solid electrolyte, i.e. not because of the potential difference move freely through the carbon-containing stack electrode.
• Electrolyte liquids suitable for use in addition to solid electrolytes contain less than 10% by weight of conductive salts, preferably less than 3% by weight.
• Preferred solvents are organic substances such as methanol, Ethanol, DMF, acetic acid, formic acid or acetonitrile.
• the stack electrodes can also be separated from one another by electrolyte-filled solids be separated.
• electrolyte-filled solid an electrolyte-filled tissue or mesh or a diaphragm is used become.
• This layer is preferably made of graphite cardboard. It can but also metal foils can be used. These measures can be done independently are affected by the nature of the electrolyte, so also in addition to a solid electrolyte.
• the size of the stack electrode in its pore size or in their permeability e.g. by impregnation, so that the Electrolysis should not be allowed to pass at all.
• the plate stack cells according to the invention offer an increased material conversion and improved selectivity. In addition, these stack cells claim only about 20% to 70% of the stacking space of conventional graphite plate stack cells. The space saving is naturally also with a corresponding one Weight savings connected.
• the plays in the cells of the invention Inflow to the individual electrodes only plays a subordinate role. It can thus also on complex measures to improve mass transport on the electrodes can be dispensed with, without the space-time yield in measurable extent would be affected.
• the plate stack cells described can be used in electrolysis processes be used.
• Such an electrolysis process is special for the oxidation of aromatics such as substituted benzenes, substituted Toluene and substituted or unsubstituted naphthalenes are suitable. This Substances are contained in the liquid electrolyte phase of the plate stack cell.
• Processes for the methoxylation of 4-methoxytoluene are particularly preferred, p-xylene, p-tert-butyltoluene, 2-methylnaphthalene, anisole or hydroquinone dimethyl ether. These substances can with the inventive method can also be acyloxylated.
• Another preferred method relates to the anodic dimerization of substituted benzenes, substituted toluenes and substituted or unsubstituted naphthalenes, the substances mentioned being preferably substituted by C 1 - to C 5 -alkyl chains.
• the process according to the invention can also advantageously be used for the methoxylation or hydroxylation of carbonyl compounds, in particular cyclohexanone, acetone, butanone or substituted benzophenones.
• Another preferred method according to the invention is the oxidation of Alcohols or carbonyl compounds to carboxylic acids, e.g. of butynediol to acetylenedicarboxylic acid or from propargyl alcohol to propiolic acid.
• the plate stack cells according to the invention can advantageously also for Functionalization of amides, especially of dimethyl formate to methoxymethyl methyl formamide.
• Furan in particular can form dimethoxydihydrofuran or N-methylpyrrolidone-2 be converted to 5-methoxy-N-methylpyrrolidone-2.
• P-xylene was methoxylated in a plate stack cell according to the invention.
• the electrolytic cell contained a stack of 6 ring disks made of the graphite felt Type RVG 1000 from Deutsche Carbone with a thickness of 3 mm, an inner diameter of 30 mm and an outer diameter of 140 mm.
• This cell was in a circulation apparatus integrated, in which the liquid electrolyte solution, consisting of a mixture 450 g of p-xylene to be methoxylated, 30 g of sodium benzenesulfonate, and 2520 g of methanol was pumped around.
• the electrolysis was carried out at a temperature of about 30 ° C to 40 ° C, a voltage of 5 V to 6 V and a current of about 5 A. carried out until one measured at the hydrogen evolution at the cathode Amount of current of 4.4 F per mol of p-xylene was used.
• the mass conversion was 99%, the electricity yield 74% with one yield of 71% tolylaldehyde dimethyl acetal and 24% tolyl methyl ether.
• the plate stack consisted of 12 graphite felt type washers RVG 2003 from the company Deutsche Carbone with a thickness of 3 mm, one inner diameter of 30 mm and an outer diameter of 140 mm. A 2 mm thick layer was made between the plates Graphite cardboard of the Sigraflex type from Sigri and a filter network Polypropylene arranged. These intermediate layers were also as washers educated.
• the electrolyte consisted of 600 g of cyclohexanone to be electrolyzed, 2259 g methanol, 66 g water, 15 potassium iodide and 60 g potassium hydroxide (43%).
• the electrolysis temperature was 15 ° C to 20 ° C, the current was about 5 A.
• the electrolysis was carried out after a charge transport of 2.2 F canceled per mole of cyclohexanone.
• cyclohexanone was used in a conventional electrolytic cell treated with a plate stack of 11 washers.
• the washers consisted of plane-cut solid graphite with a waviness less than 0.1 mm and had a thickness of 5 mm, an inner diameter of 30 mm and an outer diameter of 140 mm.
• the Electrode disks were spaced 0.5 mm apart in the cell arranged, the plate spacing by radially arranged polypropylene strips which was less than 10% of the electrode area covered.
• the liquid electrolyte solution consisted of a mixture of 675 g of cyclohexanone to be electrolyzed, 1965 g of methanol, 45 g of water, 2 g of NaOCH 3 and 90 g of potassium iodide.
• the electrolysis was carried out at a temperature of about 30 ° C to 40 ° C and a current of about 5 A carried out until a current of 2.2 F per mol of cyclohexanone was used.
• the electrolytic cell according to the invention thus allows for comparable Energy use significantly increased yields while using less of potassium iodide, to a significant extent by the cheaper Potassium hydroxide can be replaced. This in turn leads to a purer one Electrolysis product.
• the electrolysis was carried out at 48 ° C to 55 ° C and a current of about 5 A performed. It was transported at a charge of 7.5 F canceled per mole of p-xylene. With a material turnover of 99% achieved a yield of 86% tolylaldehyde dimethyl acetal.
• Example 3 instead of the electrodes described in Example 3 above, solid electrodes became Graphite plate electrodes are used as described above in the comparative example to Example 2 have been described. The electrolysis conditions corresponded those described in Example 3.
• the yield of tolylaldehyde dimethyl acetal was 77%.
• the modified electrode arrangement according to the invention also offers thus considerable advantages in the space-time yield of the electrolysis process.
• the plate stack consisted of an alternating sequence of 9 RVG 1000 washers Deutsche Carbone and 8 Nafion 117 washers Dupont company, which were arranged as described in Example 1.
• the Nafion 117 was previously swollen in DMF at 110 ° C. for 10 min.
• the electrolyte liquid placed in the apparatus contained 584 g DMF and 2560 g of methanol.
• the electrolysis temperature was 40 ° C to 47 ° C, the cell voltage 5 V to 6 V and the current 3 A to 5 A.
• the endurance test was carried out after one run of 390 hours average current use of 1.66 F per mol DMF an average selectivity achieved by 79%.
• the average electricity yield was just under 90% on DMF consumption.
• Nafion 117 was used as an intermediate layer between the electrodes, which was previously swollen in DMF for 10 min at 110 ° C.
• the electrolysis temperature was 80 ° C.
• the current efficiency was 95% Sales of dimethyl formate only 10%.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)
• Inert Electrodes (AREA)

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Publications (2)

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• 1995
  • 1995-09-12 DE DE19533773A patent/DE19533773A1/de not_active Withdrawn
• 1996
  • 1996-09-10 KR KR10-1998-0701817A patent/KR100441573B1/ko not_active IP Right Cessation
  • 1996-09-10 EP EP96931067A patent/EP0853688B1/de not_active Expired - Lifetime
  • 1996-09-10 CA CA002228748A patent/CA2228748A1/en not_active Abandoned
  • 1996-09-10 US US09/029,824 patent/US6077414A/en not_active Expired - Fee Related
  • 1996-09-10 ES ES96931067T patent/ES2133197T3/es not_active Expired - Lifetime
  • 1996-09-10 JP JP51165197A patent/JP3926387B2/ja not_active Expired - Fee Related
  • 1996-09-10 WO PCT/EP1996/003970 patent/WO1997010370A1/de active IP Right Grant
  • 1996-09-10 DE DE59602191T patent/DE59602191D1/de not_active Expired - Fee Related
  • 1996-09-10 CN CN96196902A patent/CN1092251C/zh not_active Expired - Fee Related
  • 1996-09-11 ZA ZA9607652A patent/ZA967652B/xx unknown

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