Editing Chloralkali process (section)

{{Short description|Industrial process for electrolysis of sodium chloride}}
[[File:Old drawing of a Chlorine-Caustic Soda Plant (Edgewood, Maryland).JPG|thumb|upright=1.75|Old drawing of a chloralkali process plant ([[Edgewood, Maryland]])]]

The '''chloralkali process''' (also '''chlor-alkali''' and '''chlor [[Alkali#Alkali salts|alkali]]''') is an industrial process for the [[electrolysis]] of [[NaCl|sodium chloride]] (NaCl) solutions. It is the technology used to [[Chlorine production|produce chlorine]] and [[sodium hydroxide]] (caustic soda),<ref name = Du>{{Cite journal | doi = 10.1021/acs.est.8b01195 | title = Sodium hydroxide production from seawater desalination brine: process design and energy efficiency | author = Fengmin Du | author2 = David M Warsinger | author3 = Tamanna I Urmi| author4 = Gregory P Thiel | author5 = Amit Kumar| author6 = John H Lienhard |display-authors=3| journal = Environmental Science & Technology | date = 2018 | pmid = 29669210 | volume = 52 | issue = 10 | pages = 5949–5958 | bibcode = 2018EnST...52.5949D | hdl = 1721.1/123096 | hdl-access = free }}</ref> which are commodity chemicals required by industry. Thirty five million tons of chlorine were prepared by this process in 1987.<ref>{{Greenwood&Earnshaw2nd}}</ref> In 2022, this had increased to about 97 million tonnes. The chlorine and sodium hydroxide produced in this process are widely used in the chemical industry.

Usually the process is conducted on a [[brine]] (an aqueous solution of concentrated NaCl), in which case sodium hydroxide (NaOH), hydrogen, and chlorine result. When using [[calcium chloride]] or [[potassium chloride]], the products contain calcium or potassium instead of sodium. Related processes are known that use molten NaCl to give chlorine and sodium metal or condensed [[hydrogen chloride]] to give hydrogen and chlorine.

The process has a high energy consumption, for example around {{convert|2500|kWh|MJ|abbr=on}} of electricity per tonne of sodium hydroxide produced. Because the process yields [[Equivalent (chemistry)|equivalent]] amounts of chlorine and sodium hydroxide (two moles of sodium hydroxide per mole of chlorine), it is necessary to find a use for these products in the same proportion. For every mole of chlorine produced, one mole of hydrogen is produced. Much of this hydrogen is used to produce [[hydrochloric acid]], [[ammonia]], [[hydrogen peroxide]], or is burned for power and/or steam production.<ref>{{cite book|author1=R. Norris Shreve|author-link=R. Norris Shreve|author2=Joseph Brink|title=Chemical Process Industries|date=1977|page=219|edition=4th|asin=B000OFVCCG}}</ref>