Lubricating oil oxidation process, influencing factors and improvement methods


During the storage and use of lubricating oil, in the p […]

During the storage and use of lubricating oil, in the presence of oxygen and the catalytic action of heat, light and metal, the least structural carbon-hydrogen bond in the oil molecule is destroyed, and a radical chain reaction occurs to form an oxide and peroxidize. Things, water, etc. Then, it is further polymerized and condensed to form a colloid, a sludge, a paint film, etc., so that the performance of the lubricating oil is deteriorated and the service life is shortened.

Factors affecting the oxidation of lubricating oil

(1) Effect of chemical composition of lubricating oil on oxidation

Among the various types of hydrocarbons contained in lubricating oils, aromatic hydrocarbons are the least susceptible to oxidation, and naphthenes are the second. The cyclic hydrocarbons are most susceptible to oxidation, and the aromatic hydrocarbons and cycloalkanes with side chains are more susceptible to oxidation than the corresponding side-chain-free room maps and naphthenes. The aromatic hydrocarbon is oxidized to form phenol, and phenol is an antioxidant, which can hinder the oxidation of hydrocarbons, and thus the content of aromatic hydrocarbons in the lubricating oil has a great influence on its oxidation stability.

(2) The effect of temperature

At normal temperature and pressure, the oxidation process of the lubricating oil is very slow, so the lubricating oil in storage is not easily oxidized and deteriorated. Various mechanical equipment also generates heat, which is the temperature rise of the equipment in operation. When the temperature rises to 50-60 degrees, the oxidation speed is approximately doubled.

(3) The pressure of maintenance

Lubricating oil should be in contact with air during use. Increasing the pressure of the nutrient can accelerate the oxidation of the lubricating oil. The speed of the oxidation reaction is proportional to the increase in pressure.

(4) Effects of metals and metal salts

Various metal materials in the equipment, such as copper and iron, will catalyze the oxidative deterioration of the oil, promote the viscosity of the lubricating oil, and generate acidic substances to corrode mechanical parts. In particular, the influence of copper and lead is large, and the influence of metal salt depends on the ion type and concentration of the metal salt.

Ways to improve the oxidation resistance of lubricating oil

At present, there are two ways to provide anti-oxidation and corrosion resistance of lubricating oil: one is reasonable refining, and the other is to add anti-oxidant anti-corrosion agent. For the purpose of rational refining, the sulfur-containing, nitrogen-containing heterocyclic compound of the unsaturated hydrocarbon is removed. However, the process of improving its anti-oxidation and anti-corrosion properties by refining is limited, because even high-temperature conditions, even stable aromatics are also oxidized, so an effective method must be added by adding an antioxidant or an anti-oxidation anti-corrosion agent. The antioxidant properties of lubricating oils.