As one of the largest electrochemical operations in the world, the chlor-alkali industry is responsible for producing five major chemicals —— chlorine (Cl2), hydrogen (H2), sodium hydroxide (NaoH), sodium hypochlorite (NaClO) and vinyl chloride monomer (CHCl) —— all of which are integral to a staggering amount of day-to-day life.
The process makes use of the electrolysis of brine in a membrane cells with positive and negatively charged electrodes. The anode oxidizes the chloride ion (Cl-), which loses an electron to become free chlorine gas. The hydrogen ions (H+) are pulled at the cathode and form hydrogen gas. The ion-selective membrane of the cell allows the sodium ions (Na+) to freely flow across and react with water to produce sodium hydroxide, but prevents hydroxide (OH−) and chloride from diffusing across.
Due to the corrosive nature of chlorine production, mixed metal oxide clad titanium anodes have been employed as the commercial non-reactive anode material for efficient and economical production of chlorine gas, caustic soda, and hydrogen fuels.