Chlor-alkali, chlorine-caustic electrolysis

Salt electrolysis co-produces chlorine and caustic soda: two building blocks on which phosgene (isocyanates), epichlorohydrin (epoxy), methyl chloride (silicones) and the chloride process for TiO2 all depend. China concentrates most of it, about 30 million tonnes of soda in 2024. An electricity-intensive process: its geography follows that of cheap power, and chlorine, dangerous to transport, is consumed near its source.