PROCESS FOR PREPARING DIARYL CARBONATE

Making diaryl carbonate comprises (a) producing phosgene by reacting chlorine with carbon monoxide; (b) reacting phosgene with monophenol in presence of e.g. sodium-containing base, to give a reaction wastewater solution containing diaryl carbonate and alkali chloride-containing, preferably sodium chloride; (c) separating and processing the diaryl carbonate; (d) optionally separating the residual solvent and optionally residual catalyst of the residual alkali chloride-containing solution; and (e) concentrating and oxidizing a part of residual alkali chloride-containing solution. Producing diaryl carbonate comprises (a) producing phosgene by reacting chlorine with carbon monoxide; (b) reacting the formed phosgene with at least one monophenol in the presence of an aqueous alkali-containing base, preferably sodium-containing base, optionally a nitrogen catalyst to a reaction wastewater solution containing diaryl carbonate and an alkali chloride, preferably sodium chloride; (c) separating and processing the formed diaryl carbonate; (d) optionally separating the residual solvent, and optionally residual catalyst of the residual alkali chloride-containing solution; (e) concentrating at least one part of the residual alkali chloride-containing solution by osmotic membrane distillation; and (f) electrochemically oxidizing at least one part of the alkali chloride-containing solution to form chlorine, aqueous alkali solution and optionally hydrogen.