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
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
  • C01D3/00—Halides of sodium, potassium or alkali metals in general
  • C01D3/04—Chlorides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
  • C01D3/00—Halides of sodium, potassium or alkali metals in general
  • C01D3/04—Chlorides
  • C01D3/06—Preparation by working up brines; seawater or spent lyes
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C68/00—Preparation of esters of carbonic or haloformic acids
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C68/00—Preparation of esters of carbonic or haloformic acids
  • C07C68/02—Preparation of esters of carbonic or haloformic acids from phosgene or haloformates
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
  • C07C69/96—Esters of carbonic or haloformic acids
• • 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
  • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
  • C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
• • 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
  • C25B15/00—Operating or servicing cells
  • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes

Definitions

• the invention relates, in general, to a combined process for the production of diaryl carbonate and electrolysis of alkali chloride-containing process wastewater.
• the invention also relates, more particularly, to processes for the treatment of alkali chloride-containing waste solutions for further use in a diaryl carbonate production process, and even more particularly, a diphenyl carbonate production process (“DPC process”).
• DPC process diphenyl carbonate production process
• diaryl carbonates and more particularly diphenyl carbonates
• the production of diaryl carbonates, and more particularly diphenyl carbonates generally takes place by a continuous process, by the production or introduction of phosgene and subsequent reaction of monophenols and phosgene in an inert solvent in the presence of alkali and a nitrogen catalyst at the reaction interface, according to the following general reaction scheme:
• diaryl carbonates e.g., by interfacial polycondensation
• various literature sources e.g., in “Chemistry and Physics of Polycarbonates”, P OLYMER R EVIEWS , H. Schnell, Vol. 9, John Wiley and Sons, Inc. (1964) pp. 50-51, the entire contents of which are incorporated herein by reference.
• a sodium chloride-containing wastewater stream can be evaporated until all the water has been removed and the remaining salt, together with the organic impurities, can be subjected to a heat treatment as a result of which the organic components are destroyed.
• the use of infrared radiation for such processes can be preferred.
• a disadvantage of such processes is that the water has to be completely evaporated, and so the processes cannot be carried out economically.
• Sodium chloride-containing solutions formed during DPC production typically have a sodium chloride content of 13 to 17 wt. %. Thus, the sodium chloride present in the solutions can never be completely recovered by known processes. With a sodium chloride concentration of 17 wt. %, in a standard sodium chloride electrolysis using a commercial ion exchange membrane having a water transport of 3.5 moles of water per mole of sodium, only approx. 23% of the sodium chloride from the sodium chloride-containing solutions is successfully used. Even by concentrating up to a saturated sodium chloride solution of approx. 25 wt. %, only a recycling quota of 38% of the sodium chloride contained in the sodium chloride-containing solution would be achieved.
• the alkali chloride-containing wastewater solutions forming during the continuous production of diaryl carbonates can be fed directly into an electrochemical oxidation of the alkali chloride obtained to form chlorine, alkali hydroxide solution and optionally hydrogen without costly purification. It has been found that this can be accomplished by introduction of the wastewater solution into an electrochemical oxidation after adjustment of the pH of the solution to a value less than or equal to 8 and simple treatment with an adsorbent, such as activated carbon.
• the chlorine obtained from the electrochemical oxidation can be recycled into the production of phosgene.
• the alkali hydroxide solution can be recycled into the diaryl carbonate production reaction as basic catalyst.
• One embodiment of the present invention includes a process 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 chorine and the alkali hydroxide solution.
• Another embodiment of the present invention includes a process 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 with hydrogen chloride to a value of less than or equal to 7 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; wherein recycling at least a portion of the chlorine comprises feeding the portion to a reaction with carbon monoxide to form at least a portion of the phosgene reacted with the monohydroxyl aryl compound; wherein
• Preferred monohydroxyl aryl compounds which are suitable for use in various embodiments of the processes according to the invention include phenol compounds of the general formula (I): wherein each R independently represents a hydrogen, a halogen or a branched or unbranched C 1 to C 9 alkyl group, alkoxy group, carbonyl group or alkoxycarbonyl group, and n represents an integer of 0 to 5.
• Preferred phenol compounds of the general formula (I) which can be used in processes according to the invention include phenol alkylphenols such as cresols, p-tert.-butylphenol, p-cumylphenol, p-n-octylphenol, p-isooctylphenol, p-n-nonylphenol and p-isononylphenol, halophenols such as p-chlorophenol, 2,4-dichlorophenol, p-bromophenol and 2,4,6-tribromophenol or methyl salicylate are preferred. Phenol is particularly preferred.
• Suitable catalysts for the reaction of phosgene and a monohydroxyl aryl compound to form a phenolate include basic compounds, such as for example, alkali hydroxides.
• Suitable alkali hydroxides include sodium hydroxide, potassium hydroxide and lithium hydroxide.
• Suitable hydroxides, most preferably sodium hydroxide, can be used as a solution, and are preferably used as a 10 to 55 wt. % solution.
• the reaction of phosgene and a monohydroxyl aryl compound can be accelerated by additional catalytic components, such as tertiary amines, N-alkylpiperidines and/or onium salts.
• additional catalytic components such as tertiary amines, N-alkylpiperidines and/or onium salts.
• Tributylamine, triethylamine and N-ethylpiperidine are preferably used.
• the amine catalyst used can be open-chained or cyclic, triethylamine and ethylpiperidine being particularly preferred.
• the amine catalyst is preferably used as a 1 to 55 wt. % solution.
• onium salts refers to compounds such as N 4 X, wherein R can be an alkyl and/or aryl group and/or an H, and X is an anion.
• Phosgene to be reacted with a monohydroxyl aryl compound can be introduced to the reaction in liquid or gaseous form or dissolved in an inert solvent.
• Inert organic solvents that can preferably be used in the processes of the invention include, for example, dichloromethane, toluene, the various dichloroethanes and chloropropane compounds, chlorobenzene and chlorotoluene.
• Dichloromethane is preferably used.
• the reaction of phosgene and a monohydroxyl aryl compound is preferably carried out continuously and particularly preferably in a plug flow without any significant back mixing. This can therefore take place, e.g., in tubular reactors.
• the intermixing of the two phases can be achieved, for example, by inbuilt pipe baffles, static mixers and/or e.g. pumps.
• the reaction of phosgene and a monohydroxyl aryl compound particularly preferably takes place in two stages.
• the reaction is started by bringing together the feedstocks of (i) phosgene, (ii) an inert solvent, which preferably acts first as a solvent for the phosgene, and (iii) a monohydroxyl aryl compound, which is preferably already previously dissolved in the alkali hydroxide solution.
• the residence time in the first stage can typically be 2 seconds to 300 seconds, particularly preferably 4 seconds to 200 seconds.
• the pH during the first stage is preferably adjusted by the alkali lye/monophenol/phosgene ratio such that the pH is 11 to 12, preferably 11.2 to 11.8, particularly preferably 11.4 to 11.6.
• the reaction temperature during the first stage, via cooling is preferably ⁇ 40° C., particularly preferably ⁇ 35° C.
• the reaction to form a diaryl carbonate is completed.
• the residence time in the second stage can typically be 1 minute to 2 hours, preferably 2 minutes to 1 hour, especially preferably 3 minutes to 30 minutes.
• the second stage can be regulated by constant monitoring of the pH value (preferably measured online in the continuous process by known methods) and corresponding adjustment of the pH value by addition of alkali hydroxide.
• the quantity of alkali hydroxide introduced can preferably be adjusted such that the pH of the reaction mixture in the second stage is 7.5 to 10.5, preferably 8 to 9.5, especially preferably 8.2 to 9.3.
• the reaction temperature of the second stage is preferably ⁇ 50° C., particularly preferably ⁇ 40° C., especially preferably ⁇ 35° C., by cooling.
• phosgene can be reacted with a monohydroxyl aryl compound in a molar ratio of phosgene to monohydroxyl aryl compound of 1:2 to 1:2.2.
• Solvent can be mixed into the reaction such that the diaryl carbonate is present in a 5 to 60% solution, preferably a 20 to 45% solution, after the reaction.
• the concentration of amine catalyst is preferably 0.0001 mol to 0.1 mol, based on the monophenol used.
• the organic phase containing the diaryl carbonate is preferably washed, generally with an aqueous liquid and optionally repeatedly, and after each washing operation it is separated as far as possible from the aqueous phase.
• the washing preferably takes place with deionized water.
• the diaryl carbonate solution is generally cloudy after the washing and separation of the washing liquid.
• Aqueous liquids can be used as washing liquid for the separation of the catalyst, e.g., a dilute mineral acid such as HCl or H 3 PO 4 , and deionized water for the further purification.
• the concentration of HCl or H 3 PO 4 in the washing liquid can be, e.g., 0.5 to 1.0 wt. %.
• the organic phase is washed, for example and preferably, twice.
• phase-separating devices for separating the washing liquid from the organic phase, separating vessels, phase separators, centrifuges or coalescers or combinations of these devices that are known in principle can be used.
• the wash liquids separated in the separation of the diaryl carbonate from the solution (b) can, optionally after separating catalyst residues and/or organic solvent residues, be recycled to reaction b) of the process according to the invention.
• the separation and working-up of the diaryl carbonate formed in the reaction of phosgene and monohydroxyl aryl compound can include, as the separation according to (b), preferably at least the following steps:
• wash liquid(s) obtained according to (bb) may possibly be necessary to separate at least one of the wash liquid(s) obtained according to (bb) from catalyst residues and possibly organic solvent residues by adjusting the pH value to at least 9, preferably at least 10, particularly preferably 10 to 11, by adding at least one basic compound, and then extract the solution with at least one inert organic solvent, or preferably subject the solution to a subsequent stripping with stream.
• Suitable basic compounds for the adjustment of the pH value are for example alkali or alkaline earth metal hydroxides or carbonates. The basic compounds may be used in solid form or in the form of their aqueous solutions. Alkali metal hydroxides, particularly preferably sodium hydroxide, are preferably used.
• At least part of the wash liquid(s) from (bb) can be used as a partial replacement of the water for the preparation of the sodium hydroxide for reaction of phosgene and a monohydroxyl aryl compound according to (a), in particular for adjusting the concentration of the sodium hydroxide for reaction of phosgene and a monohydroxyl aryl compound according to (a).
• at least part of the wash liquid(s) from (bb) can be used to dilute the alkali metal hydroxide prepared according to electrochemical oxidation (c), before this is recycled to the production of diaryl carbonate according to reaction of phosgene and a monohydroxyl aryl compound according to (a).
• Such preferred embodiments of the process according to the invention in which the wash liquid separated in separation according to (b) are recycled to the process according to the invention, have the additional advantage of a lower waste water discharge.
• the diaryl carbonate is separated off in the form of its solution in an organic solvent which may be used during the synthesis, e.g. methylene chloride.
• the solvent can be evaporated.
• the evaporation can take place in several evaporator steps. This takes place, e.g., by one or more distillation columns arranged in series, in which the solvent is separated from the diaryl carbonate.
• Such purification of the diaryl carbonate can be carried out continuously, for example, in such a way that the bottom temperature in the distillation is 150° C. to 310° C., preferably 160 to 230° C.
• the pressure applied to perform this distillation is particularly 1 to 1000 mbar, preferably 5 to 100 mbar.
• Diaryl carbonates purified in such a manner can be distinguished by particularly high purities (GC>99.95%) and extremely good transesterification performance, so that a polycarbonate of excellent quality can be produced therefrom.
• diaryl carbonates for the production of aromatic oligo/polycarbonates by the melt transesterification process is known from the literature and is described, e.g., in the Encyclopedia of Polymer Science, Vol. 10 (1969), Chemistry and Physics of Polycarbonates, Polymer Reviews, H. Schnell, Vol. 9, John Wiley and Sons, Inc. (1964) and U.S. Pat. No. 5,340,905, the entire contents of each of which are incorporated herein by reference.
• the remaining aqueous solution, after separation of the diaryl carbonate, can be advantageously freed of highly volatile organic impurities, such as, e.g., residues of the organic solvent used in the synthesis and optionally catalyst, for example by distillation or steam stripping.
• a wastewater solution then remains with a high content of dissolved sodium chloride ( ⁇ 10-20 wt. %) and dissolved sodium carbonates ( ⁇ 0.3-1.5 wt. %).
• the carbonates can form, e.g., by hydrolysis of the phosgene as a secondary reaction of diaryl carbonate production.
• the wastewater can be contaminated with organic compounds, e.g., with phenols (e.g. unsubstituted phenol, and/or alkylphenols).
• the treatment of the previously purified wastewater solution with adsorbents can then preferably take place with activated carbon.
• the adjustment (e.g., lowering) of the pH can be performed with hydrochloric acid or hydrogen chloride.
• the use of less expensive sulfuric acid which is conceivable in principle but less desirable in the present process, can lead to the formation of sodium sulfate during the lowering of the pH, which would then become concentrated in the anolyte circulation in the subsequent electrolysis. Since, e.g., ion exchange membranes can generally only be operated up to a certain sodium sulfate concentration in the anolyte, according to manufacturer's instructions, more anolyte would have to be discharged than when using hydrochloric acid or hydrogen chloride, the reaction product of which is the desired sodium chloride.
• alkali chloride electrochemical oxidation is described in more detail below.
• the following description is provided as an example relating to the electrolysis of sodium chloride, although, as already stated above, in principle any alkali chloride can be used in the process (particularly LiCl, NaCl, KCl).
• the use of sodium is preferred in various embodiments of the processes according to the invention.
• Membrane electrolysis processes can be used for electrochemical oxidation in accordance with the various embodiments of the present invention.
• an electrolytic cell divided into two compartments namely an anode compartment with an anode and a cathode compartment with a cathode, is used.
• the anode and cathode compartments are separated by an ion exchange membrane.
• a sodium chloride-containing solution with a sodium chloride concentration of generally more than 300 g/l is introduced into the anode compartment.
• the chloride ion is oxidized to form chlorine, which is passed out of the cell with the depleted sodium chloride-containing solution (approx. 200 g/l).
• the sodium ions migrate through the ion exchange membrane into the cathode compartment. During this migration, each mole of sodium entrains between 3.5 and 4.5 moles of water, depending on the membrane. This leads to the anolyte becoming depleted of water. In contrast to the anolyte, on the cathode side water is consumed by the electrolysis of water to hydroxide ions and hydrogen.
• the water entering the catholyte with the sodium ions is sufficient to keep the concentration of the sodium hydroxide solution in the discharge at 31-32 wt. %, with an intake concentration of 30% and a current density of 4 kA/m 2 .
• water is electrochemically reduced resulting in the formation of hydroxide ions and hydrogen.
• a gas diffusion electrode can also be used as the cathode, at which oxygen is converted to hydroxide ions with electrons, no hydrogen being formed.
• the hydroxide ions form sodium hydroxide.
• a sodium hydroxide solution with a concentration of 30 wt. % is generally fed into the cathode compartment and a sodium hydroxide solution with a concentration of 31-32 wt. % is discharged.
• the aim is to achieve the highest possible concentration of sodium hydroxide solution, since sodium hydroxide solution is generally stored or transported as a 50 wt. % lye.
• commercial membranes are not at present resistant to a lye with a concentration higher than 32 wt. %, and so the sodium hydroxide solution has to be concentrated by thermal evaporation.
• sodium chloride electrolysis additional water can be introduced into the anolyte by this sodium chloride-containing solution but only water is discharged into the catholyte through the membrane. If more water is introduced by the sodium chloride-containing solution than can be transported to the catholyte, the anolyte is depleted of sodium chloride and the electrolysis cannot be operated continuously. With very low sodium chloride concentrations, the secondary reaction of oxygen formation would start.
• the electrolysis can be operated when a lye concentration of 31 to 43 wt. % and a sodium chloride concentration of 120 to 250 g/l is used.
• the separation of the dialkyl carbonate from the solution includes phase separation, subsequent removal of solvent and optionally used catalyst by stripping with steam, and the separation is followed by the adjustment of the solution pH, and subsequent treatment with activated carbon.
• the alkali chloride-containing wastewater solution i.e., the pH-adjusted, adsorbent-treated solution
• the electrolysis can be fed directly into the electrolysis.
• water can be removed from the alkali chloride-containing wastewater solution by a concentration process.
• a process is therefore preferred, characterised in that the alkali chloride-containing solution is concentrated before the electrolysis by membrane distillation processes or reverse osmosis.
• Reverse osmosis for example or, particularly preferably, membrane distillation or membrane contactors can be used, such as described in MELIN; RAUTENBACH, Membranvon; SPRINGER, BERLIN, 2003, the entire contents of which are incorporated herein by reference.
• Processes according to the invention can also be carried out with an alkali chloride electrolysis in which no hydrogen is produced at the cathode but the cathode is replaced by a gas diffusion electrode at which oxygen is reduced to form hydroxide ions.
• a sodium chloride-containing solution coming from DPC production generally has a sodium chloride content of up to 17 wt. %, in so far as it is the wastewater from the reaction. If the wastewater from the reaction is combined with the washing water, the NaCl concentration is, for example, approx. 13 wt. %. If the electrolysis supplies the chlorine and the sodium hydroxide solution exclusively for DPC production, only a small part of the sodium chloride-containing wastewater can be used in the electrolysis. Thus, with the conventional ion exchange membranes and the standard operating parameters of sodium chloride electrolysis, only a maximum of 26% of the sodium chloride from a 17 wt. % sodium chloride-containing DPC wastewater can be used.
• significantly more than 26% of the sodium chloride from wastewaters formed with a concentration of 17 wt. % can be recycled, in so far as the sodium chloride electrolysis exclusively provides the chlorine and the sodium hydroxide solution for DPC production.
• Sodium chloride electrolyses are generally operated at integrated chemical production sites in connection with a variety of chlorine consumers, such that a sodium chloride-containing wastewater solution is not necessarily available for recycling from each of the various chlorine consumers.
• the proportion of reusable sodium chloride from the wastewater can be increased where the sodium chloride electrolysis is not used exclusively to provide the sodium hydroxide solution and chlorine for diaryl carbonate production.
• Another preferred variant of the processes of the invention is that the wastewater from diaryl carbonate production is concentrated by solid alkali chloride and fed into the alkali chloride electrolysis. As a result, more than 50% of the alkali chloride from the DPC wastewater could be reused.
• An alkali chloride-containing wastewater with a pH of less than 7 is particularly preferably used in or fed to the electrolysis.
• the pH adjustment preferably takes place with hydrochloric acid, but can also take place with gaseous hydrogen chloride.
• the NaCl electrolysis can be operated in such a way that an NaCl solution coming from the electrolysis cell has an NaCl concentration of less than 200 g/l.
• the sodium hydroxide concentration discharged from the cell can be less than 30 wt. %.
• the water transport through the membrane depends not only on the operating parameters but also on the type of membrane used.
• those ion exchange membranes that permit a water transport through the membrane of more than 4.5 moles of water per mole of alkali, preferably sodium, under the conditions of alkali chloride and alkali hydroxide concentration according to the invention are preferably used.
• the current density is calculated based on the area of the membrane and is preferably 2 to 6 kA/m 2 .
• Anodes with a greater surface area are particularly preferably used.
• Anodes with a greater surface area are to be understood as those in which the physical surface area is distinctly larger than the projected surface area.
• Anodes with a greater surface area are, e.g., electrodes with a foam- or felt-like construction.
• the surface area of the anode should preferably be selected such that the local current density based on the physical surface area of the electrode is less than 3 kA/m 2 . The larger the surface area and the lower the local current density, the lower the sodium chloride concentration that can be selected in the brine and the higher the proportion of sodium chloride from the wastewater that can be recycled.
• the pH of the alkali chloride-containing wastewater should preferably be less than 7, particularly preferably from 0.5 to 6, before the electrolysis.
• the alkali chloride electrolysis should be operated in such a way that the alkali chloride concentration of the alkali chloride solution coming from the cell is between 100 and 280 g/l sodium chloride and/or that the concentration of the alkali hydroxide coming from the cell is 13 to 33 wt. %.
• the concentration of the alkali chloride solution coming from the cell should preferably be between 110 and 220 g/l alkali chloride and/or the concentration of the alkali hydroxide coming from the cell should be 20 to 30 wt. %.
• the ion exchange membranes used in the electrolysis should preferably have a water transport per mole of sodium of more than 4.0 moles H 2 O/mole alkali, particularly preferably 5.5 to 6.5 moles H 2 O/mole alkali.
• the process can preferably be operated in such a way that the electrolysis is operated at a temperature of 70 to 100° C., preferably at 80 to 95° C.
• the electrolysis can be operated at an absolute pressure of 1 to 1.4 bar, preferably at a pressure of 1.1 to 1.2 bar.
• the pressure ratios between anode and cathode compartments are preferably selected such that the pressure in the cathode compartment is higher than the pressure in the anode compartment.
• the differential pressure between cathode and anode compartments should preferably be 20 to 150 mbar, more preferably 30 to 100 mbar.
• the coating of the anode can contain, in addition to ruthenium oxide, other precious metal components from subgroups 7 and 8 of the periodic table of elements.
• the anode coating can be doped with palladium compounds. Coatings based on diamond can also be used.
• a mixture of 145.2 kg/h of 14.5% sodium hydroxide solution and 48.3 kg/h of phenol are brought together with a solution of 86.2 kg/h of methylene chloride and 27.5 kg/h of phosgene (8 mole % excess based on phenol) in a vertically standing, cooled tubular reactor.
• This reaction mixture is cooled to a temperature of 33° C. and, after an average residence time of 15 seconds, a pH of 11.5 is measured.
• 5.4 kg/h of 50% NaOH are then metered into this reaction mixture so that the pH of the second reaction step is 8.5 after a further residence time of 5 minutes.
• metering fluctuations that occur are offset by adjusting the additions of NaOH in each case.
• reaction wastewater is continuously mixed by passing through a pipe provided with constrictions. After renewed addition of NaOH, the reaction temperature is adjusted by cooling to 30° C. After separating off the organic from the aqueous phase (reaction wastewater), the DPC solution is washed with 0.6% hydrochloric acid and water. After removing the solvent, 99.9% diphenyl carbonate is obtained.
• the reaction wastewater is not combined with the washing phases here and is freed of solvent residues and catalyst by stripping with steam. After neutralising with hydrochloric acid and treating with activated carbon, the reaction wastewater contains 17% NaCl and ⁇ 2 ppm phenol.
• the electrolysis is performed for example in a laboratory electrolytic cell with an anode area of 0.01 m 2 .
• the current density was 4 kA/m 2 , discharge temperature on the cathode side 88° C. and discharge temperature on the anode side 89° C.
• a Nafion 982 WX ion exchange membrane from DuPont was used.
• the electrolytic voltage was 3.02 V.
• a sodium chloride-containing solution was pumped through the anode compartment at a mass flow rate of 0.98 kg/h.
• the concentration of the solution fed into the anode compartment was 25 wt. % NaCl. A 20 wt.
• % NaCl solution could be removed from the anode compartment. 0.121 kg/h of 17 wt. % reaction wastewater from diphenyl carbonate production and 0.0653 kg/h of solid sodium chloride were added to the NaCl solution removed from the anode compartment. The solution was then fed back into the anode compartment. The water transport through the membrane was 3.5 moles of water per mole of sodium.
• a sodium hydroxide solution was pumped round at a mass flow rate of 1.107 kg/h.
• the concentration of the sodium hydroxide solution fed into the cathode side was 30 wt. % NaOH and the sodium hydroxide solution removed from the cathode side had a concentration of 32% NaOH. 0.188 kg/h of the 31.9% lye were removed from the volume flow and the remainder was topped up with 0.0664 kg/h of water and fed back into the cathode element.
• the wastewater corresponded to the quality of that according to Example 1. Since no hydrogen is required for the production of DPC, the formation of hydrogen during the electrolysis can be omitted.
• the electrolysis was therefore operated with gas diffusion electrodes. The current density was 4 kA/m 2 , cathode side outlet temperature 88° C. and anode side outlet temperature 89° C.
• a Nafion 982 WX ion exchange membrane from DuPont was used.
• the electrolytic voltage was 2.11 V.
• the sodium chloride concentration of the solution removed from the anode compartment was 17 wt. % NaCl. 0.166 kg/h of 17 wt.
• a sodium hydroxide solution was pumped round at a mass flow rate of 0.848 kg/h.
• the concentration of the sodium hydroxide solution fed into the cathode side was 30 wt. % NaOH and the sodium hydroxide solution removed from the cathode side had a concentration of 32 wt. % NaOH. 0.192 kg/h of the 31.2% lye were removed from the volume flow and the remainder was topped up with 0.033 kg/h of water and fed back into the cathode element.
• the proportion of reacted sodium chloride from the DPC reaction wastewater was 32.4%.
• the wastewater corresponded to the quality of that according to Example 1. Since no hydrogen is required for the production of DPC, the formation of hydrogen during the electrolysis can be omitted.
• the electrolysis was therefore operated with gas diffusion electrodes. The current density was 4 kA/m 2 , cathode side outlet temperature 88° C. and anode side outlet temperature 89° C.
• a Nafion 2030 ion exchange membrane from DuPont was used.
• the electrolytic voltage was 1.96 V.
• the sodium chloride concentration of the solution removed from the anode compartment was 15 wt. % NaCl. 0.178 kg/h of 17 wt.
• a sodium hydroxide solution was pumped round at a mass flow rate of 0.295 kg/h.
• the concentration of the sodium hydroxide solution fed into the cathode side was 30 wt. % NaOH and the sodium hydroxide solution removed from the cathode side had a concentration of 32 wt. % NaOH. 0.188 kg/h of the 32% lye were removed from the volume flow and the remainder was topped up with 0.0184 kg/h of water and fed back into the cathode element.
• the proportion of reacted sodium chloride from the DPC reaction wastewater was 34.4%.
• Example 2 The procedure was carried out as in Example 1, with the difference that, after separating the organic phase from the aqueous phase (reaction waste water), the DPC solution was washed with 0.6 wt.-% hydrochloric acid (acid wash), and then once more with water (neutral wash).
• the acidic wash phase from the DPC working-up was adjusted to pH 10 with NaOH and was then freed from solvent residues and catalysts by extraction with methylene chloride or by stripping with steam. After the phase separation an aqueous phase was obtained containing 1.5 wt.-% NaCl, which can be re-used as a partial replacement of the water for the preparation of the 14.5 wt.-% NaOH solution for the DPC production.
• Example 4 The procedure was carried out as in Example 4.
• the neutral wash phase from the DPC working-up can be re-used without further treatment as a partial replacement of the water for the preparation of the 14.5 wt.-% NaOH solution for the DPC production.
• Example 4 The procedure was carried out as in Example 4. The acid and neutral wash phase from the DPC working-up were combined, adjusted to pH 10 with NaOH, and then freed from solvent residues and catalysts by extraction with methylene chloride or by stripping with steam. After phase separation an aqueous phase was obtained containing about 1 wt.-% NaCl, which can be re-used as a partial replacement of the water for the preparation of the 14.5 wt.-% NaOH solution for the DPC production.

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• Materials Engineering (AREA)
• Inorganic Chemistry (AREA)
• Electrochemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Metallurgy (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Water Treatment By Electricity Or Magnetism (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Water Treatment By Sorption (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
• Removal Of Specific Substances (AREA)

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• 2006
  • 2006-09-02 DE DE102006041465A patent/DE102006041465A1/de not_active Withdrawn
• 2007
  • 2007-08-27 EP EP07016720A patent/EP1894914B1/de not_active Expired - Fee Related
  • 2007-08-27 ES ES07016720T patent/ES2335813T3/es active Active
  • 2007-08-27 DE DE502007002159T patent/DE502007002159D1/de active Active
  • 2007-08-30 SG SG200706370-4A patent/SG140577A1/en unknown
  • 2007-08-31 KR KR1020070088036A patent/KR101424808B1/ko not_active IP Right Cessation
  • 2007-08-31 TW TW096132355A patent/TWI422575B/zh not_active IP Right Cessation
  • 2007-08-31 RU RU2007132823/04A patent/RU2484082C2/ru not_active IP Right Cessation
  • 2007-09-03 CN CN2007101821354A patent/CN101139294B/zh not_active Expired - Fee Related
  • 2007-09-03 JP JP2007227482A patent/JP5348865B2/ja not_active Expired - Fee Related
  • 2007-09-04 US US11/849,542 patent/US20080053836A1/en not_active Abandoned

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