Detergent additives
Time：
2025-11-06
What are the detergent additives?
Detergent additives
Detergent additives, also known as TBN boosters. Detergent additives are the lubricant additive that clean and keep engine parts clean. They are important additives in internal combustion engine oils and one of the five major additives in modern lubricants (detergents, dispersants, antioxidants, extreme pressure anti-wear additives, and viscosity index improvers).
Detergent additives
Detergent additives can inhibit the oxidation and deterioration of lubricating oil under high-temperature conditions or reduce the formation of high-temperature deposits on the piston ring surface, keeping the engine interior (combustion chamber and crankcase) clean and extending the service life of the lubricating oil.
Detergent additives are generally classified according to their organic acid functional groups, and can be divided into sulfonates, salicylates, phenolates, and naphthenates. Sulfonates, salicylates, and phenolates are all alkyl aryl groups, mainly alkylbenzenes, such as commonly used alkylbenzene calcium sulfonate, alkyl salicylate calcium, and sulfide alkylphenol calcium.
In addition, the total base number (TBN) of detergents is also an important data. TBN indicates the detergent's ability to neutralize acids; TBN 300 is considered high base number, and TBN 400 is considered super-high base number.
Preparation process of detergent
Formation of normal salts: Organic acids react with metal oxides in the presence of water or a accelerator to form organic acid normal salts.
Overalkalinization (also known as carbonation): This involves reacting excess metal oxides with carbon dioxide to obtain overalkaline organic acid salts.
Separation and purification: The solvent is evaporated and the mixture is centrifuged to remove impurities by filtration.
The role of Detergents
Detergents maintain the cleanliness of lubricating oils primarily through solubilization, colloidalization, acid neutralization, and cleaning:
Solubilization:
As the name suggests, this involves using the action of detergents (which are surfactants) to dissolve normally insoluble substances. It mainly dissolves impurities produced by lubricating oil oxidation and incomplete fuel combustion, inhibiting deposit formation. Dispersants have a stronger solubilizing effect than detergents.
Colloidalization:
- Also known as dispersing, colloidalization occurs when detergents, being oil-soluble surfactants, adsorb polar substances (such as soot, sludge, and resin impurities) in the oil, while the oily groups form a colloidal state, suspending these polar substances in the oil and preventing them from agglomerating into larger impurities.
Acid neutralization:
- High-alkalinity or ultra-high-alkalinity detergents contain a large amount of inorganic alkaline components (such as high-alkalinity calcium sulfonate, ultra-high-alkalinity calcium sulfonate, ultra-high-alkalinity magnesium sulfonate, etc.), possessing a large alkaline reserve. They can continuously neutralize acidic impurities produced by lubricating oil oxidation and incomplete fuel combustion. They can also neutralize sulfur dioxide, sulfur trioxide, sulfuric acid, and sulfurous acid produced by fuel combustion, inhibit corrosion, and slow down lubricating oil oxidation (acidic impurities accelerate oxidation).
Cleaning action:
- Detergents can remove impurities generated in the above processes, removing them from the surface of parts and maintaining the cleanliness of metal components.
Types of Detergents
Detergents are mainly classified into sulfonates, salicylates, phenolates, and naphthenates, etc.
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Sulfonate detergents：
- Based on raw materials, sulfonates can be divided into petroleum sulfonates and synthetic sulfonates.
- Based on total base number (TBN), sulfonates can be classified into low base number, medium base number, high base number, and ultra-high base number sulfonates.
- Based on the type of metal salt, they can also be classified into calcium salts, magnesium salts, barium salts, and sodium salts. Calcium sulfonate is the most widely used due to its excellent high-temperature detergency, high TBC, and strong acid neutralization ability, making it the primary additive in internal combustion engine oil formulation. Magnesium sulfonate is the next most common, possessing low ash content and excellent rust prevention properties. It works even better when used with calcium sulfonate and is suitable for high-grade gasoline engine oils. Sodium sulfonate has good rust prevention and hydrophilicity; its emulsifying ability can be adjusted by changing its molecular weight. Barium sulfonate has the best rust prevention properties, but barium is a heavy metal.
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Salicylates:
- It is typically alkyl salicylate calcium, which possesses excellent high-temperature detergency, acid neutralization ability, and antioxidant capacity.
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Phenolates:
- The most widely used alkylphenol salt is calcium alkylphenolate, second only to calcium sulfonate. The advantages of calcium alkylphenolate are its excellent acid neutralization ability, good antioxidant properties, and good high-temperature detergency. It is particularly effective in inhibiting carbon deposits in the piston ring grooves of turbocharged diesel engine oils and is one of the indispensable additives for turbocharged diesel engine oils. The synergistic effect of calcium alkylphenolate and calcium sulfonate is even better when they are combined, and they complement each other's shortcomings.
In lubricating oils, detergents are rarely used alone; they are usually used in combination with other detergents, dispersants (polyisobutylene succinimide), antioxidants and corrosion inhibitors (ZDDP), and antioxidants.
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