Four categories include: lubricating oil additives, fuel additives, composite additives and other additives.
petroleum products additive
In the early 1980s, the total output of petroleum product additives in Europe and America was 2Mt (excluding tetraethyl lead antiknock agent), of which about 80% was used for lubricating oil.
Lubricating oil additives As early as 1930s, the United States used additives in lubricating oil. With the development of machinery industry, especially the upgrading of internal combustion engine, lubricating oil additives have also been developed, and the corresponding additive product series has been formed. The function of lubricating oil additives can be summarized in three aspects: ① reducing the corrosion and wear of metal parts; (2) Restrain the formation of sludge and paint film inside the parts when the engine is running; ③ Improve the physical properties of base oil. Lubricating oil additives mainly include metal detergent, ashless dispersant, antioxidant, viscosity index improver, pour point depressant, extreme pressure antiwear agent, antirust agent, metal passivator and defoamer. Additives can be added to the engine oil alone, or they can be mixed into composite additives and then added to the engine oil.
Metal detergent is mainly used for internal combustion engine oil and marine cylinder oil. Its function is to inhibit the formation of carbon deposit in the piston ring groove of the cylinder, reduce the adhesion of the paint film on the piston skirt and neutralize the corrosion and wear of metal parts caused by acidic substances (including oxidation products of lubricating oil itself) produced after fuel combustion. Commonly used are organometallic salts, such as sulfonates, alkylphenolates, alkylsalicylates, thiophosphonates, etc. These salts are made into low alkali, medium alkali and high alkali respectively, and most of them are high alkali.
Ashless dispersant is a kind of lubricating oil additive which has developed fastest since 1960s. Its outstanding performance is that when the crankcase works at a low temperature, it can inhibit the gasoline engine oil from producing sludge, thus avoiding the blockage of the internal oil circuit of the gasoline engine and the corrosion and wear of parts. The representative compound is polyisobutylene succinimide. When ashless dispersant and metal detergent are used together, a small amount of antioxidant and corrosion inhibitor can be added to prepare various internal combustion engine oils.
Antioxidants According to the different application conditions of oil products, antioxidants can be roughly divided into: ① Anti-oxidation and anti-corrosion agents, mainly used in internal combustion engine oil, which can not only inhibit the oxidation of oil products, but also prevent the corrosion of crankcase bearings. Zinc dialkyl dithiophosphate is widely used, and it is also an effective extreme pressure antiwear agent, which is mostly used in industrial lubricants such as gear oil and antiwear hydraulic oil. ② Antioxidant additives, mainly shielding phenols (such as 2,6-di-tert-butyl-p-cresol) and aromatic amines. The former is mostly used for industrial lubricants such as turbine oil and hydraulic oil; The latter is widely used to synthesize lubricating oil. The role of antioxidants is to delay the oxidation of oil products and prolong their service life.
Viscosity index improver is also called tackifier. It is used to improve the viscosity of oil products and the viscosity-temperature characteristics to meet the viscosity requirements of oil products in a wide temperature range. Mainly used for blending multi-stage internal combustion engine oil, automatic transmission oil and low-temperature hydraulic oil. Its main varieties are polymethacrylate, polyisobutylene, ethylene propylene polymer, styrene and diene polymer. Polymethacrylate has a good effect on improving the low temperature performance of oil products, and is mostly used in gasoline engine oil; Ethylene propylene copolymer has good shear stability and thermal stability, and is suitable for supercharged diesel engine oil and gasoline engine oil.
Pour point depressant is used to lower the freezing point of oil products, improve the state of paraffin crystallization in oil products, and prevent particles from bonding with each other to form a network structure, thus maintaining the fluidity of oil products at low temperature. Commonly used are polymethacrylate (containing long alkyl chain), polyalphaolefin and alkylnaphthalene.
Extreme pressure antiwear agent is used to prevent wear and scrape between metal surfaces under boundary lubrication and extreme pressure (high load condition). It is an organic compound containing sulfur, phosphorus and chlorine, and the others are their metal salts or amine salts. These compounds have strong chemical activity, and under certain conditions, they can react with metal surfaces to form a reaction film with low melting point and low shear strength, thus reducing the wear between metal surfaces and preventing scratches. Commonly used extreme pressure antiwear agents: sulfides include sulfurized isobutylene and dibenzyl disulfide; Phosphate includes tricresyl phosphate, amine phosphate, etc. Mainly used for gear oil.
Oily agent is mainly used to improve the lubricity of oil products and enhance their anti-wear ability. Animal and vegetable oils, higher fatty acids, higher fatty alcohols and their esters and salts all belong to this category. It is mostly used for guide rail oil, hydraulic guide rail oil and metalworking oil.
Rust inhibitors are used to improve the ability of preventing metal parts from rusting when oil products come into contact with moisture and air. Commonly used rust inhibitors include petroleum sulfonate, alkenyl succinic acid, lanolin and its magnesium salt.
Metal passivator is a compound that can form a protective film on the metal surface and reduce the catalytic activity of metal on oil oxidation. Generally, it is often used in combination with antioxidant additives to effectively prolong the service life of oil products. Commonly used metal passivators are derivatives of thiadiazole and benzotriazole.
Defoamer is a kind of compound that can change the surface tension of oil and gas and make the foam formed in oil escape quickly, such as methyl silicone oil and ester compounds.
Lubricating grease additives Antioxidants, anti-compression and anti-wear agents, oiliness agents, rust inhibitors and metal passivators used in lubricating grease are basically the same as those used in lubricating oil.
Petroleum fuel additives include additives used in gasoline, jet fuel, diesel oil and other petroleum products. There are many varieties, and the following are commonly used:
Antiknock agents are mainly used to improve the combustion characteristics of gasoline and increase its octane number. For a long time, the most effective and economical antiknock agents are tetraethyl lead and tetramethyl lead. Tetraethyl lead was found to be an antiknock agent in 192 1 and put into practical use in 1923, but no other more suitable antiknock agent was found, so tetraethyl lead has been used up to now despite its certain toxicity. After 1970s, in order to reduce lead poisoning pollution, European and American countries restricted the lead content in gasoline and developed and used unleaded gasoline. As a high octane number component, methyl tert-butyl ether (MTBE) has been applied in the development of non-toxic antiknock agent.
Antioxidants are mainly used in gasoline and diesel oil containing secondary processing components to improve the oxidation stability of these oils. N, N ′-di-sec-butyl-p-phenylenediamine and shielding phenol are commonly used antioxidants in gasoline. The composition of diesel oil is complex, so the application of antioxidants must be determined by experiments.
Anti-icing agent is mostly used in jet fuel to prevent trace water in engine oil from freezing at low temperature. Because of the difficulty in transporting engine oil, it will affect the normal operation of the engine. Effective anti-icing agents include ethylene glycol monomethyl ether and so on.
Antistatic agents are used to improve the conductivity of jet fuel and other oil products, and to prevent fires caused by friction and electrification during high-speed pump transportation and filtration. Usually, it consists of metal salts of organic acids and polymerized nitrogen-containing compounds.
Fluidity improver is used to change the crystal form of paraffin in diesel oil, thus improving the low-temperature fluidity of oil and making diesel oil meet the requirements of wide temperature range. Commonly used flow improvers such as polymers of ethylene and vinyl acetate.
Additives for petroleum asphalt and petroleum wax Some additives should also be used in asphalt and petroleum wax products. Emulsified asphalt should be mixed with various nonionic or ionic emulsifiers to improve construction conditions and improve paving efficiency; Polyisobutylene, oleamide and polyethylene oxide should be added to various special asphalt to improve the heat resistance, load resistance, skid resistance and crack resistance of asphalt pavement.
In petroleum wax, polyisobutylene or polyethylene is sometimes added to improve the toughness and adhesion of wax, and ultraviolet absorber such as UV-53 1 is added to improve the photochemical stability of deeply refined white wax.