Benzenesulfonic Acid Alkyl Derivatives(CAS#27176-87-0)–Anionic Surfactant LABSA

1. Properties:

• Appearance and Physical Form: Alkylbenzenesulfonic acid (C10–C13) is supplied as a brown to off‑white or light yellow to brown viscous liquid with a slight sulfur dioxide odor. The product typically contains 96–98% active matter. Lower active grades may appear as a paste or solid (melting point approx. 10°C).
• Solubility: The acid is readily soluble in water, alcohols, glycol ethers, glycols, esters, ketones, aromatic hydrocarbons, and aliphatic hydrocarbons. Its alkali metal salts are water‑soluble, while its amine salts are oil‑soluble, enabling formulation flexibility across aqueous and non‑aqueous systems.
• Chemical Properties: As a strong anionic surfactant (pKa ~1–2), alkylbenzenesulfonic acid does not dissociate completely in acidic media, allowing it to function effectively as an acid‑stable surfactant. The molecule contains a hydrophobic alkyl tail (C10–C13, >95% linear) and a hydrophilic sulfonic acid head group, imparting exceptional surface activity. The product demonstrates outstanding chemical stability across a wide pH range (acidic to alkaline) and excellent hard water resistance. A unique characteristic is the ability to form various salts—sodium salts are water‑soluble, while amine salts are oil‑soluble. The HLB of its salts typically ranges from about 11 to 14. The product is highly hygroscopic, stable in the presence of acids, alkalis, and some oxidizers such as sodium hypochlorite, but incompatible with strong bases and oxidizing agents.

2. Applications:

Household & Industrial Detergents (Primary):

• Laundry Powders & Liquids: As the most widely used anionic surfactant globally, LABSA is the key raw material for laundry powders and liquid detergents. It provides excellent detergency, foam generation, and soil suspension even in hard water conditions.
• Dishwashing Liquids: Used in hand dishwashing detergents to generate stable, creamy foam while effectively cutting grease.
• Hard Surface Cleaners: Incorporated into bathroom, kitchen, and general‑purpose cleaners, especially acidic formulations for limescale removal from sanitary installations.
• Industrial & Institutional (I&I) Cleaners: Applied in heavy‑duty industrial degreasers, floor cleaners, carwash formulations (both automatic and hand), dairy cleaners, aluminum cleaners, and bottle wash detergents.

Textile Industry:

• Wetting & Mercerizing Agent: Functions as an efficient wetting agent and mercerizing assistant in textile processing, improving fiber wettability and dye penetration.
• Degreasing & Scouring: Applied in de‑fatting, de‑waxing, degumming, and de‑oiling of natural fibers such as cotton, ramie, wool, and silk.
• Dyeing Auxiliary: Enhances level dyeing and acts as a dispersant to prevent uneven coloration.

Agrochemicals:

• Emulsifiable Concentrates (EC): Serves as an emulsifier in pesticide and herbicide formulations, including emulsifiable concentrates, concentrated emulsions, and suspoemulsions, improving active ingredient dispersion and stability.
• Wetting Agent for Agricultural Adjuvants: Enhances spray coverage and leaf penetration of crop protection products.

Leather Processing:

• Degreasing Agent: Used to remove natural fats and oils from hides during leather tanning and processing.
• Emulsifier: Facilitates emulsification of leather treatment oils and finishes.

Paper Industry:

• De‑inking Agent: Applied in paper recycling processes to remove ink from waste paper pulp.
• Dispersant: Improves dispersion of fillers and pigments in paper coating formulations.

Metalworking & Electroplating:

• Degreasing & Metal Cleaning: Used in metal cleaning formulations to remove oils, grease, and soils from metal surfaces before electroplating or finishing operations.
• Pickling Inhibitor Component: Serves as a surfactant in acid pickling baths for steel and metal processing.

Other Industrial Applications:

• Biodiesel Production Catalyst: Dodecylbenzenesulfonic acid acts as an effective acid catalyst for the esterification of fatty acids (e.g., oleic acid) to produce biodiesel.
• Conductive Polymer Dopant: Used as a dopant for conductive polymers such as polyaniline and as a strong acid catalyst for amino‑crosslinked coatings.
• Personal Care (Limited): In small quantities, LABSA can be used as a foaming and emulsifying agent in toilet soaps in combination with other milder surfactants.
• Construction Chemicals: Increases the surface area of distempers and improves performance in certain construction material additives.

3. Preparation Method:

• Laboratory Method: Alkylbenzenesulfonic acid can be prepared by reacting linear alkylbenzene (LAB) with concentrated sulfuric acid or chlorosulfonic acid under controlled conditions. The sulfonic acid group is introduced onto the aromatic ring, typically at the para position relative to the alkyl chain.
• Industrial Process: Industrial production of high‑quality LABSA follows a continuous falling‑film sulfonation process using gaseous sulfur trioxide (SO₃) as the sulfonating agent. The key steps include: 1) Air drying to remove moisture, 2) Sulfur melting and combustion to produce SO₂, then oxidation to SO₃, 3) Continuous falling‑film sulfonation of linear alkylbenzene (C10–C13) with SO₃ in a multi‑tube falling‑film reactor, 4) Digestion/hydrolysis of the resulting sulfonation mixture, and 5) Optional bleaching to improve color. The reaction is highly exothermic and requires precise control of temperature and reactant ratios. The final product is typically obtained at 96–98% active matter with residual free oil (<2.5%) and sulfuric acid (<0.75%). Alternative sulfonating agents include oleum (fuming sulfuric acid) in batch reactors, but falling‑film SO₃ sulfonation is preferred for its efficiency, product quality, and reduced waste generation.

4. Safety Information:

• Hazard Classification: Alkylbenzenesulfonic acid is classified as a corrosive substance. According to CLP Regulation (EC) No 1272/2008 and GHS, the product carries the following hazard statements: H302 (Harmful if swallowed), H312 (Harmful in contact with skin), H314 (Causes severe skin burns and eye damage), H371 (May cause damage to organs), H373 (May cause damage to organs through prolonged or repeated exposure), and H412 (Harmful to aquatic life with long‑lasting effects).
• Health Hazards: The substance is corrosive to skin, eyes, and mucous membranes. Eye contact may cause permanent damage and potential blindness. Skin contact may cause permanent injury. Thermal decomposition can release irritating and toxic gases including sulfur oxides.
• Personal Protection: When handling concentrated solutions, wear chemical‑resistant gloves (nitrile or neoprene), protective clothing, chemical splash goggles, and a face shield. Use in well‑ventilated areas. Avoid breathing mists or vapors. Wash exposed skin thoroughly after handling. Do not eat, drink, or smoke while using the product.
• First Aid Measures:
  • Eye Contact: Immediately rinse with plenty of water for at least 15 minutes while keeping eyelids open. Seek immediate medical attention.
  • Skin Contact: Wash immediately with plenty of soap and water. Remove contaminated clothing. Seek medical attention if irritation persists.
  • Inhalation: Move victim to fresh air. Keep at rest in a position comfortable for breathing. If symptoms persist, seek medical advice.
  • Ingestion: Rinse mouth immediately. Do NOT induce vomiting. Seek immediate medical attention.
• Fire & Reactivity Hazards: The product is not flammable, but thermal decomposition may produce toxic and corrosive fumes including sulfur oxides. Incompatible with strong bases, oxidizing agents, and metals. Use water spray, foam, dry powder, or CO₂ as extinguishing media appropriate for surrounding fire.
• Environmental Precautions: Harmful to aquatic life with long‑lasting effects (H412). Avoid direct release into natural water bodies, drains, or the environment. Large spills should be contained and prevented from entering waterways.
• Storage & Stability: Store in sealed, corrosion‑resistant containers (plastic or lined drums) below 30°C in a cool, dry, well‑ventilated area. Protect from direct sunlight, moisture, strong bases, oxidizing agents, and metals. The product is hygroscopic—avoid exposure to atmospheric moisture. Prolonged storage may cause darkening of color; however, this does not typically affect performance. Long‑term storage temperature should not exceed 45°C, and handling/blending temperature should not exceed 65°C. Shelf life is typically 12–24 months in tightly closed original containers. For improved storage stability, stabilizers such as small amounts of triethanolamine or glycols may be added.
• Regulatory Compliance: LABSA is listed on EINECS (248-289-4), TSCA, DSL, and other regional chemical inventories. It meets OECD SIDS criteria and is widely approved for use in consumer, industrial, and commercial detergents and cleaners. Always consult the Safety Data Sheet (SDS) for complete safety and regulatory information specific to each product grade.