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
  • C25B3/20—Processes
  • C25B3/23—Oxidation
• • 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
  • C25B3/01—Products
  • C25B3/07—Oxygen containing compounds

Definitions

• the present invention relates to a process for the electrochemical production of alkyl-substituted benzaldehydes.
• DE-OS 2 855 508 describes a process in which the electrooxidation of the alkylbenzenes in water and alkanoic acids is carried out.
• the alkyl-substituted benzaldehydes are obtained in good yields.
• the disadvantage of this method is the decrease in the current yields at very high conversions.
• the graphite anodes show a graphite removal in the long-term test.
• the object was therefore to find a process which makes it possible to obtain the benzaldehydes in the electrooxidation of alkylbenzenes for the preparation of the corresponding benzaldehydes, even at high conversions, in good current yields and with improved electrode stability.
• graphite anodes which are mixed with metal oxides such as ruthenium oxide, titanium dioxide, iron oxide, chromium oxide, cobalt oxide, manganese dioxide, nickel oxide or with carbides. such as tungsten carbide. Mixtures of the coating materials mentioned can also be used, such as a mixture of iron oxide and cobalt oxide.
• alkyl radicals R 1 and R 2 in the starting materials of the formula II are, for example, those having 1 to 6, preferably 1 to 4, carbon atoms.
• aryl radicals R 1 phenyl radicals which may be substituted by alkyl, halogen, alkoxy and / or acyloxy groups may be mentioned.
• Starting materials of formula II "are thus methylbenzenes, benzyl alcohols or the alkanoic acid esters of benzyl alcohols which are not substituted or contain the radical R 1 mentioned , such as toluene, p-xylene, p-tert-butyltoluene, p-phenyltoluene, benzyl alcohol, p-methylbenzyl alcohol, p- tert-butylbenzyl alcohol, benzyl acetate, p-methylbenzyl acetate and p-tert-butylbenzyl acetate, of which p-xylene, p-tert-butyltoluene, p-methylbenzyl alcohol, p-tert-butylbenzyl alcohol, p-methylbenzyl acetate and p- tert-Butylbenzyl acetate of particular technical interest.
• Formic acid acetic acid and propionic acid are preferred as alkanoic acids.
• a mixture of the benzene derivative of the formula II, water and the alkanoic acid is used as the electrolyte, which may additionally contain a conductive salt to improve the conductivity.
• the usual salts in organic electrochemistry can be used as the conductive salts, which are soluble in the solution to be electrolyzed and largely stable under the test conditions.
• Examples of conductive salts are tetrafluorobarates, fluorides, hexafluorophosphates, sulfates or sulfonates. The method is preferably carried out in undivided cells.
• the alkylbenzene compound of the formula II is preferably converted to over 80%.
• the current density in the process is, for example, between 1 and 15 A / dm 2 .
• the electrolysis can be carried out batchwise or continuously.
• the electrolysis discharges are preferably worked up by distillation.
• the electrolyte from water-alkanoic acid - conductive salt is expediently returned to the electrolysis.
• the graphite anodes to be used according to the invention can e.g. by coating the electrode base body with the help of thermal spray technology or by thermal decomposition of suitable connections.
• the oxides or carbides are fed directly in powder form to a spraying system, preferably a plasma spraying system, and are applied to the graphite body with the aid thereof.
• the compound is applied to the graphite body in dissolved form and the active layer is produced by baking at elevated temperature.
• a titanium oxide layer by spraying or brushing the electrode with butyl titanate in butanol and then heating to 500 to 600 ° C.
• the coated anodes mentioned surprisingly result in an improvement in the selectivity and an increase in the current yields even at high conversions. This considerably simplifies the processing of the electrolysis discharges. Furthermore, the coated graphite electrodes allow longer running times due to the lower removal.
• Anodes coated graphite anodes (coating see table)
• Electrolyte 16.2% by weight 4-tert. Butyltoluene (TBT) 1.6% by weight NaBF 4 8.2% by weight water 74.0% by weight acetic acid (HOAc)
• the electrolyte is pumped through a heat exchanger during the electrolysis. After the electrolysis has ended, water and acetic acid are distilled off at atmospheric pressure, NaBF 4 is filtered off and the crude 4-tert. Butylbenzaldehyde (TBA) pure distilled at 2 to 20 torr and 40 to 125 ° C.

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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)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)

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• 1981
  • 1981-08-19 DE DE19813132726 patent/DE3132726A1/de not_active Withdrawn
• 1982
  • 1982-07-15 DE DE8282106344T patent/DE3261133D1/de not_active Expired
  • 1982-07-15 EP EP82106344A patent/EP0072914B1/fr not_active Expired
  • 1982-07-22 US US06/400,699 patent/US4411746A/en not_active Expired - Lifetime
  • 1982-08-17 JP JP57141777A patent/JPS5845387A/ja active Pending

Patent Citations (4)

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