Abstract: The present invention relates to a gas diffusion electrode that includes an electrically conductive carrier, and a porous coating based on an electrochemically active catalyst and a hydrophobic material, wherein the electrode has a first side facing an oxygen-containing gas and a second side facing an alkaline electrolyte, wherein the catalyst comprises a noble metal as a catalytically active component, wherein the hydrophobic material comprises a hydrophobic polymer, and wherein the coating comprising the catalyst has a pore volume from 10 to 500 mm3/g, and a pore diameter in the range from 100 to 10,000 nm.

Abstract: The present invention relates to a process for the continuous preparation of diaryl carbonates from phosgene and at least one monohydroxy compound (monophenol) in the presence of catalysts, and also the use thereof for preparing polycarbonates. The hydrogen chloride formed in the reaction is converted by electrochemical oxidation into chlorine, with the chlorine being recirculated to the preparation of phosgene. In particular, the process comprises utilization of the hydrogen chloride formed for the process for preparing diphenyl carbonate (DPC process).

Abstract: The present invention relates to a process for the continuous preparation of diaryl carbonates from phosgene and at least one monohydroxy compound (monophenol) in the presence of catalysts, and also the use thereof for preparing polycarbonates. The hydrogen chloride formed in the reaction is converted by thermal oxidation into chlorine, with the chlorine being recirculated to the preparation of phosgene. In particular, the process comprises utilization of the hydrogen chloride formed for the process for preparing diphenyl carbonate (DPC process).

Abstract: The invention relates to a process for production of diaryl carbonate combined with the electrolysis of the resultant alkali metal chloride-containing process wastewater. The process according to the invention makes possible, inter alia, improved utilization in electrolysis of the alkali metal chloride-containing solution obtained in the production of diaryl carbonate.

Abstract: The present invention describes an electrochemical cell, comprising at least an anode half-cell with an anode, a cathode half-cell with a cathode, and an ion exchange membrane arranged between the anode half-cell and the cathode half-cell, the anode and/or the cathode is a gas diffusion electrode. And a gap is provided between the gas diffusion electrode and the ion exchange membrane, and the half-cell with the gas diffusion electrode has an electrolyte feed and an electrolyte discharge as well as a gas inlet and a gas outlet. The electrochemical cell preferably has an electrolyte feed that is hermetically connected to the gap.

Abstract: The invention describes an electrode and an electrode coating which are based on a catalyst containing finely divided carbon modifications and noble metal (oxide)s.

Abstract: A combined process for the preparation of polycarbonate from bisphenols and diaryl carbonates, the monophenol liberated being reacted again for the preparation of the diaryl carbonate and the alkali metal halide forming in the preparation of the diaryl carbonate being converted by electrochemical oxidation, optionally over a gas diffusion electrode, into chlorine and alkali hydroxide solution, the chlorine being recycled into the preparation of the phosgene and the alkali hydroxide solution being recycled into the preparation of the diaryl carbonate.

Abstract: The invention relates to a combined process for the preparation of polycarbonate by the phase boundary process and downstream electrolysis of sodium chloride-containing process wastewater.

Abstract: A process is described for producing polycarbonate and utilizing at least some of the process waste water by concentrating the sodium chloride-containing waste water phases for the electrolysis using osmotic membrane distillation, if appropriate with simultaneous dilution of the sodium hydroxide solution obtained from the electrolysis for the polycarbonate production process.

Abstract: A process for preparing diaryl carbonate and utilizing at least part of the process wastewater by increasing the concentration of the wastewater phases containing sodium chloride for the electrolysis by means of osmotic membrane distillation with simultaneous dilution of the sodium hydroxide solution obtained from the electrolysis for the diaryl carbonate production process (diphenyl carbonate process) is described.

Abstract: The invention describes an electrochemical cell for the electrolysis of an aqueous solution of hydrogen chloride, comprising at least an anode half-cell with an anode, a cathode half-cell with a gas diffusion electrode as cathode and an ion exchange membrane arranged between the anode half-cell and the cathode half-cell, the membrane consisting of at least a perfluorosulfonic acid polymer, wherein the gas diffusion electrode and the ion exchange membrane are adjacent to each other, characterised in that the gas diffusion electrode and the ion exchange membrane, under a pressure of 250 g/cm2 and at a temperature of 60° C., have a contact area of at least 50%, with respect to the geometric area.

Abstract: The present invention describes an electrochemical half-cell, comprising a gas space, an electrolyte space and a gas diffusion electrode in the form of a cathode or anode. The gas diffusion electrode separates the gas space from the electrolyte space and comprises an electrically conductive substrate and an electrochemically active coating. The gas diffusion electrode includes a coating-free edge region and is connected to a support structure in the coating-free edge region via an electrically conductive plate, which covers at least the coating-free edge region as well as a coated edge region.

Abstract: Processes which include: (a) providing a gas phase comprising hydrogen chloride; (b) oxidizing the hydrogen chloride in a reactor to form a product gas comprising chlorine, unreacted hydrogen chloride and water, the reactor having structural parts with inner surfaces that are contacted during oxidation by one or both of the gas phase and the product gas; (c) cooling the process gas; (d) separating the unreacted hydrogen chloride and water from the product gas; (e) drying the product gas; and (f) separating the chlorine from the product gas; wherein the inner surfaces of the reactor structural parts that are contacted during oxidation by one or both of the gas phase and the product gas are comprised of a nickel material having a nickel content of at least 60 wt. %, are described.

Abstract: The invention relates to a process for preparing methylenediphenyl diisocyanates which comprises at least the steps: A) reaction of aniline with formaldehyde in the presence of hydrochloric acid as catalyst to give a mixture of diamines and polyamines of the diphenylmethane series (MDA) and subsequent at least partial neutralization of the hydrochloric acid by means of alkali metal hydroxide, B) reaction of the mixture of diamines and polyamines of the diphenylmethane series obtained in step A) with phosgene to give a mixture of diisocyanates and polyisocyanates of the diphenylmethane series (MDI) and hydrogen chloride, wherein C) the hydrochloric acid which has been neutralized in step A) is separated off in the form of a solution containing alkali metal chloride and is subsequently at least partly fed to an electrochemical oxidation to form chlorine, alkali metal hydroxide and optionally hydrogen and D) at least part of the chlorine produced in step C) is used for preparing the phosgene used in step B).

Abstract: The invention relates to a combined process for the preparation of polycarbonate by the phase boundary process and downstream electrolysis of sodium chloride-containing process wastewater.

Abstract: The invention relates to a process for production of diaryl carbonate combined with the electrolysis of the resultant alkali metal chloride-containing process wastewater. The process according to the invention makes possible, inter alia, improved utilization in electrolysis of the alkali metal chloride-containing solution obtained in the production of diaryl carbonate.

Abstract: An isocyanate is produced by: (a) reacting chlorine with carbon monoxide to form phosgene, (b) reacting the phosgene with an organic amine to form an isocyanate and hydrogen chloride, (c) separating the isocyanate and hydrogen chloride, (d) optionally, purifying the hydrogen chloride, (e) preparing an aqueous solution of the hydrogen chloride, (f) optionally, purifying the aqueous solution of hydrogen chloride, (g) subjecting the aqueous hydrogen chloride solution to electrochemical oxidation to form chlorine, and (h) returning at least a portion of the chlorine produced in (g) to (a).

Abstract: The present invention describes an electrochemical half-cell, comprising a gas space, an electrolyte space and a gas diffusion electrode in the form of a cathode or anode. The gas diffusion electrode separates the gas space from the electrolyte space and comprises an electrically conductive substrate and an electrochemically active coating. The gas diffusion electrode includes a coating-free edge region and is connected to a support structure in the coating-free edge region via an electrically conductive plate, which covers at least the coating-free edge region as well as a coated edge region.

Abstract: The invention relates to a method for improving the performance of nickel electrodes in alkali chloride electrolysis by adding water-soluble platinum compounds to the catolyte.

Abstract: Processes comprising: (a) reacting phosgene and a monohydroxyl aryl compound in the presence of a suitable catalyst to form a diaryl carbonate and a solution comprising an alkali chloride; (b) separating the diaryl carbonate from the solution; (c) adjusting the pH of the solution to a value of less than or equal to 8 to form a pH-adjusted solution; (d) treating the pH-adjusted solution with an adsorbent to form a treated solution; (e) subjecting at least a portion of the treated solution to electrochemical oxidation to form chlorine and an alkali hydroxide solution; and (f) recycling at least a portion of one or both of the chlorine and the alkali hydroxide solution.