Chlorine - Production

Production

In industry, elemental chlorine is usually produced by the electrolysis of sodium chloride dissolved in water. This method, the chloralkali process industrialized in 1892, now provides essentially all industrial chlorine gas. Along with chlorine, the method yields hydrogen gas and sodium hydroxide (with sodium hydroxide actually being the most crucial of the three industrial products produced by the process). The process proceeds according to the following chemical equation:

2 NaCl + 2 H2O → Cl2 + H2 + 2 NaOH

The electrolysis of chloride solutions all proceed according to the following equations:

Cathode: 2 H+ (aq) + 2 e− → H2 (g)
Anode: 2 Cl− (aq) → Cl2 (g) + 2 e−

Overall process: 2 NaCl (or KCl) + 2 H2O → Cl2 + H2 + 2 NaOH (or KOH)

In diaphragm cell electrolysis, an asbestos (or polymer-fiber) diaphragm separates a cathode and an anode, preventing the chlorine forming at the anode from re-mixing with the sodium hydroxide and the hydrogen formed at the cathode. The salt solution (brine) is continuously fed to the anode compartment and flows through the diaphragm to the cathode compartment, where the caustic alkali is produced and the brine is partially depleted. Diaphragm methods produce dilute and slightly impure alkali but they are not burdened with the problem of preventing mercury discharge into the environment and they are more energy efficient. Membrane cell electrolysis employ permeable membrane as an ion exchanger. Saturated sodium (or potassium) chloride solution is passed through the anode compartment, leaving at a lower concentration. This method is more efficient than the diaphragm cell and produces very pure sodium (or potassium) hydroxide at about 32% concentration, but requires very pure brine.

Read more about this topic:  Chlorine

Famous quotes containing the word production:

    “In the production of the necessaries of life Nature is ready enough to assist man.”
    —Henry David Thoreau (1817–1862)

    “From the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”
    —Charles Darwin (1809–1882)

    “The production of obscurity in Paris compares to the production of motor cars in Detroit in the great period of American industry.”
    —Ernest Gellner (b. 1925)