Linear alkylbenzene sulfonic acid, also known as LABSA, has a chemical formula of CH3(CH2)11C6H4SO3H. LABSA exist as a yellow liquid that is soluble in water and non-volatile. It is also bio-degradable and hence easily distinguished from alkylbenzene sulfonate by its linear, straight chain structure. Linear alkylbenzene sulfonic acid is the largest-volume synthetic surfactant because of its relatively low cost and good performance.
The commercial method of manufacturing LABSA is by sulfonating linear alkylbenzene with either oleum (10-25% sulfur trioxide (SO3) in sulfuric acid) or with an SO3-air mixture. The reaction temperature is controlled during the addition of acid and the reaction will go into completion after 30 to 45 minutes. The major product is para-alkylbenzene sulfonic acid. A high temperature and long reaction time would result in an undesirable dark-colored product. Sulphuric acid (H2SO4) is preferred over the use of sulphur trioxide as reaction of pure SO3 is too aggressive as an electrophilic reagent and will form a black char on contact due to its rapid exothermic reaction. Cooling would also be required to prevent the formation of by-products due to the high temperatures. Therefore, H2SO4 and oleum are more commonly used for sulfonation. Sulfonation reaction stops when the concentration of H2SO4 drops to 90%.
LABSA is used in pesticides to enhance the quality of the spray and produce better crops. It is used in numerous industrial applications as a coupling agent and as an emulsifier for agricultural herbicides.
LABSA is commonly used as a synthetic surfactant due to its low cost and effectiveness. It is widely used as an anionic surfactant in a wide range of domestic detergent powder and dish wash cleaner. It is used as an emulsifier and wetting agent due to its high solubility in water, foaming ability and low salt content. It lowers the surface tension of water, allowing stains to be removed easily.
LABSA is used as a degreaser in plating and leather making industry as well as a deinking agent in the paper industry.