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
  • C25B13/00—Diaphragms; Spacing elements
  • C25B13/04—Diaphragms; Spacing elements characterised by the material
  • C25B13/08—Diaphragms; Spacing elements characterised by the material based on organic materials
• • 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

Definitions

• This invention relates to a process for the preparation of olefine oxides.
• the process is carried out in that the electrolyte is transferred from the anode chamher into the cathode chamber through a diaphragm and olifine halohydrin is formed by electrochemical action from the olefine introduced into the anode chamber, and this olfine halohydrin, dissolved in the electrolyte, is transported through the diaphragm and is converted into olefine oxide in the cathode chamber due to the alkalinity in the cathode chamber.
• Several of the aforesaid systems consisting of an anode, a diaphragm and a cathode can be combined to form a cell aggregate.
• the diaphragm which separates the anode chamber from the cathode chamber may be made of an inert permeable or porous material such as asbestos, Teflon, polyethylene etc.
• the web may be made exclusively from monofils or it may be made from yarns produced from endless filaments or staple fibres.
• Different forms of polyacrylonitrile fibres may be used in the warp and weft, e.g. the warp may be made of monofils and the weft of yarn spun from fibres.
• Suitable thicknesses for the fabric of the diaphragm are for example 0.1 to 1.5 mm., especially 0.2 to 1 mm. It may be advantageous to shrink the fabric by heat before it is used in accordance with the invention.
• the fabric may be subjected to a swelling process before it is used, for example with the use of organic solvents, e.g. those formed in the course of the electrochemical process.
• the fabrics used according to the invention may be made of pure polyacrylonitrile or of copolymers containing at least of bound acrylonitrile.
• the remaining constitutents may consist of the usual components used for copolymerisation, e.g. vinyl acetate or methyl acrylate.
• the cathode is a wire mesh and the polyacrylonitrile fabric is adhered to it.
• these polyacrylonitrile fabrics are distinguished by great stability, both as regards the constancy of the operating results and as regards the chemical and mechanical resistance.
• the polyacrylonitrile fabric can be produced very uniformly and hence provides a diaphragm which is uniform in its permeability over its whole surface. This factor also contributes to the advantageous effect.
• abestos may be used as a diaphragm for the process of the invention.
• the asbestos proves to be unsatisfying since the asbestos fibers can be used only for a short period of time since the separation of the cathode chamber and anode chamber is insufiicient after a few days. This causes a recirculation between both chambers which leads to a formation of by-products such as glycol.
• diaphragm materials e.g. materials from polyethylene or fiuor hydrocarbons the na similar effect is noticed since these materials are insufficient to withstand the mechanical stress to which they are subjected. Furthermore these materials have the disadvantages that they are not sufficiently wettable which is of importance for the passage of current.
• the polyacrylonitrile fiber materials could be used for the process of the invention since it was to be expected that the nitrilo groups would be saponified in the very strong alkaline medium which occurs at the cathode. It has been found that very surprisingly the diaphragms of the invention are very durable for long reaction times.
• Suitable materials for use in the preparation of the olefine oxides are in particular gaseous Inonoolefines such as ethylene, propylene and butylene as well as halogenated monoolefines, for example allyl chloride.
• gaseous Inonoolefines such as ethylene, propylene and butylene as well as halogenated monoolefines, for example allyl chloride.
• Aqueous solutions of sodium chloride or potassium chloride or mixtures thereof may for example be used as electrolyte.
• the concentration of the salts in the electrolytes may be, for example, 2 to 20% and preferably 3 to 15%.
• the anodes and cathodes may be rectangular and placed parallel to each other.
• the anode should preferably be porous so that the gaseous raw material introduced can pass through the pores of the anode into the anode chamber.
• the gaseous olefines may be introduced through a frit or similar distributor means arranged below the anode.
• Other methods of introducing the olefines may also be employed provided they ensure fine distribution of the gas in the anolyte.
• a suitable material for the anode is, for example, graphite, but platinum-plated titanium may also be used.
• the aqueous electrolyte is introduced into the anode chamber and transferred through the diaphragm and the cathode into the cathode chamber, the electrolyte being transferred at a rate of between and 100 cc./min. through 1 square decimetre of the cathode surface.
• the catholyte leaving the cathode chamber may be freed from the olefine oxide contained in it, e.g. by distillation, and returned to the anode chamber, thereby completing the cycle.
• the process may be carried out e.g. with current densities of 2 to 50 amp/100 cm. of electrode surface, voltages of 3.2 to 5 volts and temperatures of to 90 C. It is advantageous to work at ordinary pressure but a slightly elevated pressure may be employed.
• the rate of throughput of olefine through the anode chamber is preferably so chosen that 5 to 95% of the olefine is converted in a single passage through the chamber.
• anolyte charged with halohydrin is reacted outside the cell with the catholyte to form the olefine oxide and that the reacted mixture of anolyte and catholyte is reintroduced into the anode and cathode chamber respectively.
• EXAMPLE 1 An electrolytic cell containing a porous graphite anode having an area of 150 cm. and a wire mesh cathode of the same surface area arranged opposite it is used. A cloth of polyacrylonitrile fabric made from threads of a thickness of 0.2 mm. was applied to the cathode on the side facing the anode. The entire thickness of the cloth was 0.5 mm. The electrolyte was a 9.3% solution of common salt. This was passed from the anode chamber into the cathode chamber through the diaphragm at a rate of 2 l. per hour. The temperature of the electrolyte was 52 C. The operation was carried out at ordinary pressure and a voltage of 3.5 volts between anode and cathode.
• Propylene was passed through the porous anode at the rate of l. per hour. 20% of this propylene was converted and 80% left the anode chamber in a gaseous state.
• the electrolyte passed through the diaphragm and the cathode, and the propylene chlorohydrin formed in the anode chamber and dissolved in the electrolyte was converted into propylene oxide in the cathode chamber.
• the catholyte contained 0.35% of propylene oxide.
• the propylene oxide dissolved in the catholyte can easily be recovered from the electrolyte by distillation before the electrolyte is returned to the anode chamber.
• EXAMPLE 2 An electrolytic cell having an anode of 175 cm. of
• anode was a wire mesh cathode of the same surface area. On the side of the cathode facing the anode was applied a cloth of polyacrylonitrile fabric made from threads of 0.2 mm. in thickness. The total thickness of the cloth was 0.5 mm.
• a frit plate of ceramic material was arranged below the anode, through which plate the olefine that was to be reacted was introduced in a finely divided form into the anode chamber.
• the electrolyte was a 5% aqueous potassium chloride solution.
• EXAMPLE 3 The electrolytic cell described in Example 2 was used. The current density was 11.1 amp./ cm. The electrolyte was a 5% aqueous potassium chloride solution. This was passed at the rate of 4.1 per hour from the anode chamber to the cathode chamber through the diaphragm. The temperature of the electrolyte was 52 C. Ordinary pressure was employed. Ethylene was charged through the frit at the rate of 45 l. per hour. 20% of this ethylene was converted and 80% left the anode chamber in a gaseous state.
• the electrolyte passed through the diaphragm and the cathode, and the conversion of the ethylene chlorohydrin formed in the anode chamber and dissolved in the electrolyte into ethylene oxide took place in the cathode chamber.
• the catholyte contained 0.3% of ethylene oxide. 82% of the total current yield was ethylene oxide, 8% ethylene chlorohydrin and 6% dichloroethane.
• EXAMPLE 4 The electrolytic cell described in Example 2 was used under the experimental conditions described in Example 3. A gaseous mixture consisting of 50% allyl chloride and 50% nitrogen was introduced into the anode chamber through the frit at the rate of 45 l. per hour. 40% of the allyl chloride was converted, 60% left the anode chamber in the gaseous state. The electrolyte passed through the diaphragm and the cathode, and in the cathode chamber the propylene-dichlorohydrin formed in the anode chamber and dissolved in the electrolyte was converted into epichlorohydrin. The catholyte contained 0.55% of epichlorohydrin and the total current yield of epichlorohydrin was 70% What we claim is:
• electrolyte is an aqueous solution of a chloride selected from the group consisting of sodium chloride, potassium chloride, and mixtures thereof.
• olefin is selected from the group consisting of a gaseous monoolefin and a halogenated monoolefin.
• Colunm 4, line 28, hl" should read 4 l.

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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)
• Cell Separators (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)

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Citations (3)

• 1965
  • 1965-03-04 DE DEF45416A patent/DE1243170B/de active Pending
• 1966
  • 1966-02-22 AT AT162366A patent/AT262246B/de active
  • 1966-03-01 US US530788A patent/US3451905A/en not_active Expired - Lifetime
  • 1966-03-01 NL NL6602654A patent/NL6602654A/xx unknown
  • 1966-03-03 BE BE677299D patent/BE677299A/xx unknown
  • 1966-03-03 GB GB9402/66A patent/GB1090006A/en not_active Expired
  • 1966-03-04 ES ES0323793A patent/ES323793A1/es not_active Expired

Patent Citations (3)

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