How is LABSA used in detergent manufacturing?

LABSA is the acid form of the most widely used detergent surfactant. Detergent makers neutralise it with an alkali, usually caustic soda or soda ash, to make sodium linear alkylbenzene sulphonate (LAS). LAS does the cleaning in most laundry powders, many laundry liquids and a large share of dishwashing liquids. LABSA itself is the raw material, not the finished surfactant.

What is LABSA?

LABSA stands for linear alkylbenzene sulphonic acid. It is made by sulphonating linear alkylbenzene (LAB), a benzene ring carrying a straight alkyl chain of roughly 10 to 13 carbons, usually with sulphur trioxide. The product is a viscous, brown liquid and a strong acid.

The "linear" part matters. Earlier detergents used branched alkylbenzene sulphonates, which broke down slowly in the environment and caused persistent foam on rivers and in sewage works. The industry moved to the linear form, which biodegrades readily under aerobic conditions. LAS remains one of the most studied surfactants for that reason.

Why does LABSA need to be neutralised?

The acid is corrosive and is not the useful surfactant. Neutralising it converts the sulphonic acid group into its sodium salt, which is the active cleaning agent:

LABSA + NaOH → sodium LAS + water

The reaction releases heat, so the alkali is added under control with stirring and, in larger plants, cooling. Adding acid and alkali too quickly can cause local hot spots and spattering.

How much alkali does it take?

Stoichiometry gives a starting point. With an average molecular weight of about 320 to 330 for the acid, 100 kg of pure LABSA needs roughly 12 to 13 kg of sodium hydroxide to neutralise. Commercial LABSA also carries a small amount of free sulphuric acid, which consumes extra alkali.

In practice, work from the acid value on the certificate of analysis and finish by measuring pH. Most detergent liquids aim for a mildly alkaline pH, and the exact target depends on the formulation.

The alkali you choose depends on the process:

• Liquid caustic soda is convenient for liquid detergents because it doses easily and adds water you need anyway.
• Caustic soda flakes suit plants that prefer to make up their own solution or need to control water content.
• Soda ash (sodium carbonate) is common in dry-neutralisation powder plants, where it also acts as a builder.

How is LABSA used in laundry powders?

There are two main routes.

Spray drying. LABSA is neutralised in a slurry with caustic soda, then mixed with builders, fillers and other ingredients. The slurry is sprayed into a hot tower, where it dries into hollow, free-flowing granules. This gives a light, quick-dissolving powder but uses a lot of energy.

Dry neutralisation. LABSA is sprayed onto soda ash and other powders in a mixer, and the acid reacts with the carbonate in place. This needs far less energy and simpler equipment, which is why it is widely used in smaller and mid-size plants.

In both routes, LAS works alongside builders that soften the water. LAS is sensitive to hardness, because calcium and magnesium ions form insoluble salts with it and reduce its cleaning power. Builders bind those ions so the surfactant can do its job.

How is LABSA used in liquid detergents?

For laundry and multi-purpose liquids, LABSA is neutralised in water with caustic soda or with an organic amine such as triethanolamine. Amine salts are more soluble and can help make clearer, more concentrated liquids.

LAS is rarely used alone in liquids. It is commonly blended with:

• SLES, such as SLES 70%, which adds foam, mildness and tolerance to hard water.
• Non-ionic surfactants, such as alcohol ethoxylates, which are strong on oily soils and help at lower wash temperatures.

The balance between anionic and non-ionic surfactants is one of the main levers a formulator has for cost, foam and cleaning on different soils.

How is LABSA used in dishwashing products?

Hand dishwashing liquids often use LAS and SLES together. LAS gives strong grease cutting at low cost, and SLES improves foam stability and feel on the hands. Salt is commonly used to raise the viscosity of these blends. Dishwash bars and pastes, popular in several markets, often use LAS with fillers such as calcite.

What should you watch when handling LABSA?

LABSA is corrosive and causes severe skin burns and eye damage. Treat it as a strong acid:

• Use chemical-resistant gloves, eye and face protection, and protective clothing.
• Store it in compatible containers, such as stainless steel or suitable plastics, away from alkalis and oxidisers.
• Keep containers closed, because the acid absorbs moisture.
• Neutralise in a controlled way, adding one reagent gradually to the other with stirring.

The SDS for the grade you buy has the specific guidance. It is available on request for every product on this site.

How is LABSA classified for trade?

Under HS 2022, linear alkylbenzene sulphonic acids and their salts have their own subheading, 340231, within heading 3402 for organic surface-active agents. Older references may still show 340211. Our article on HSN codes for chemical exports explains how the digits and editions work.

Where do you start?

If you are setting up or scaling a detergent line, list the products you make, the neutralising route your plant uses and the volumes you need. Then compare quotes for LABSA and the matching alkali on active content and delivered cost. A single quote request can cover the acid, the caustic soda and any co-surfactants together.