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Acids get most of the attention in industrial chemistry, but bases are just as essential. Every soap bar, every sheet of paper, every aluminium can, every bag of cement and most of the world’s fertiliser depends on a small group of bases produced by the hundreds of millions of tonnes each year.
Here are the most important industrial bases, how they’re made and why they matter. Production figures are rounded estimates.
1. Ammonia, NH₃
Production: about 180–190 million tonnes per year, making it one of the most produced chemicals in the world.
How it’s made: the Haber process
N₂ + 3H₂ ⇌ 2NH₃ ΔH = −92 kJ/mol
- Nitrogen comes from the air; hydrogen mostly from natural gas (by steam reforming), though “green” hydrogen from electrolysis is growing.
- Conditions: iron catalyst, about 400–450 °C, 150–250 atmospheres.
- These are compromise conditions: lower temperatures would give a better yield but too slow a rate; higher pressures would improve the yield but cost more.
The Haber process uses about 1–2% of the world’s total energy supply and is responsible for a significant share of global CO₂ emissions, which is why cleaner production methods are a major research area.
Main uses:
- Fertilisers (about 70–80%): directly, or converted into urea, ammonium nitrate, ammonium sulfate and ammonium phosphates.
- Making nitric acid (via the Ostwald process), nylon, plastics, dyes and explosives.
- Refrigeration (as a refrigerant in large industrial plants).
- Household cleaners (as dilute aqueous ammonia).
It has been estimated that nitrogen fertiliser made from Haber process ammonia supports the food supply of roughly half the world’s population.
2. Sodium hydroxide, NaOH (caustic soda)
Production: about 80–90 million tonnes per year.
How it’s made: the chlor-alkali process
Electrolysis of concentrated brine (sodium chloride solution):
2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂
Modern plants use membrane cells, where an ion-exchange membrane lets sodium ions through but keeps the chlorine and hydroxide apart. Every tonne of chlorine produced comes with about 1.1 tonnes of sodium hydroxide, so the two products’ markets are closely linked.
Main uses:
- Pulp and paper: breaking down lignin in wood (the kraft process).
- Aluminium: dissolving aluminium oxide from bauxite (the Bayer process).
- Soap and detergents: saponifying fats.
- Chemicals: making hundreds of other compounds, and neutralising acids.
- Textiles: treating cotton (mercerisation gives it strength and lustre).
- Water treatment: raising pH and removing metals.
- Food: peeling fruit and vegetables, curing olives, making pretzels their brown crust.
3. Lime: calcium oxide and calcium hydroxide
Production: about 400 million tonnes of lime per year.
How it’s made: limestone (calcium carbonate) is heated in a kiln at about 900–1000 °C:
CaCO₃ → CaO + CO₂
This gives quicklime, calcium oxide. Adding water gives slaked lime (hydrated lime), calcium hydroxide, in a very exothermic reaction:
CaO + H₂O → Ca(OH)₂
Main uses:
- Steelmaking: combining with acidic impurities (silica, phosphorus oxides) to form slag.
- Construction: mortar, plaster and soil stabilisation.
- Water and wastewater treatment: softening water and adjusting pH.
- Flue-gas desulfurisation: capturing sulfur dioxide from power stations.
- Agriculture: neutralising acidic soils (though ground limestone is more common for this).
- Sugar refining: purifying sugar cane and beet juice.
Making lime releases CO₂ in two ways: from the chemical decomposition of limestone and from burning fuel to heat the kiln. The same is true of cement, which is one of the largest industrial sources of CO₂.
4. Sodium carbonate, Na₂CO₃ (soda ash)
Production: about 60–65 million tonnes per year.
How it’s made:
- The Solvay process (developed in the 1860s): brine, limestone and ammonia are combined in a clever cycle that recycles the ammonia. The overall reaction is 2NaCl + CaCO₃ → Na₂CO₃ + CaCl₂.
- Natural deposits: large deposits of the mineral trona (a sodium carbonate–hydrogencarbonate mineral), especially in the United States, are mined and processed.
Main uses:
- Glass-making (about half): sodium carbonate lowers the melting point of silica.
- Detergents and washing soda.
- Chemicals, including sodium hydrogencarbonate (baking soda).
- Water softening and pH control.
- Increasingly, lithium processing for batteries.
5. Potassium hydroxide, KOH (caustic potash)
Production: a few million tonnes per year.
How it’s made: electrolysis of potassium chloride solution, similar to the chlor-alkali process.
Main uses:
- Soft and liquid soaps (potassium soaps are softer and more soluble than sodium soaps).
- Alkaline batteries (as the electrolyte).
- Making potassium carbonate and other potassium compounds, including fertilisers.
- Biodiesel production (as a catalyst).
- Food processing.
6. Other important industrial bases
| Base | Main uses |
|---|---|
| Magnesium oxide and hydroxide | refractory bricks for furnaces, antacids, wastewater treatment, flame retardants |
| Sodium hydrogencarbonate | baking, fire extinguishers, antacids, flue-gas treatment |
| Aluminium hydroxide | flame retardant in plastics, antacid, source of pure alumina |
| Amines (e.g. monoethanolamine) | removing CO₂ and H₂S from natural gas; carbon capture |
| Lithium hydroxide | lithium-ion battery cathodes, lubricating greases, CO₂ scrubbers |
A worked example: the Bayer process
Sodium hydroxide’s role in aluminium production shows how a base can purify an ore. Bauxite contains aluminium oxide mixed with iron oxides and silica. Hot, concentrated sodium hydroxide dissolves the amphoteric aluminium oxide but leaves the basic iron oxides behind:
Al₂O₃ + 2NaOH + 3H₂O → 2Na[Al(OH)₄]
The insoluble iron-rich residue (“red mud”) is filtered off. Cooling and seeding the solution precipitates pure aluminium hydroxide, which is heated to give pure aluminium oxide for electrolysis. The sodium hydroxide is recycled. Every aluminium drinks can starts with this acid–base separation.
Why bases matter so much
Three themes run through the list:
- Feeding the world: ammonia for fertilisers.
- Processing raw materials: sodium hydroxide for aluminium and paper, lime for steel, sodium carbonate for glass.
- Neutralising and cleaning: bases remove acidic pollutants, adjust pH in water treatment and turn fats into soap.
Bases and acids also depend on each other. The chlor-alkali process gives both sodium hydroxide and chlorine (used to make hydrochloric acid and PVC). Ammonia is the raw material for nitric acid. And much industrial chemistry is simply neutralising the acid made in one step with the base made in another. See the most important industrial acids.
Safety
Industrial bases are highly corrosive, especially sodium and potassium hydroxide and quicklime. Workers use face shields, gloves and protective clothing, and plants have emergency eyewash and shower stations. Ammonia gas is toxic and its release is a serious hazard. Quicklime reacts violently with water, generating heat. Spilled quicklime should never be hosed down in bulk; it’s swept up dry and handled with care.
Key takeaways
- Ammonia (Haber process) is mostly used for fertilisers and underpins global food supply.
- Sodium hydroxide (chlor-alkali electrolysis) is essential for paper, aluminium, soap and chemicals.
- Lime (from heating limestone) is vital for steel, construction and pollution control.
- Sodium carbonate (Solvay process or natural trona) is used mainly in glass-making.
- Industrial acids and bases are made in linked processes and often neutralise each other; learn more about individual bases in the strong bases.
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