Plant oil has the advantages of ① non toxicity, ② excellent biodegradability, ③ renewability, ④ good lubricity, ⑤ high viscosity index, ⑥ lower cost than synthetic oil.

But vegetable oil has poor hydrolysis stability and low-temperature performance, excessive foaming, poor filtration, and especially poor oxidation stability.

Plant oil is mainly composed of triglycerides of fatty acids, as well as a small amount of free fatty acids and some glycerides, 0.1% to 0.5% phospholipids, trace amounts of sterols, tocopherols, and vitamin E. Due to the easy hydrolysis of glyceride groups in plant oil, it has strong biodegradability. The unsaturated double bonds in ester chains are sensitive to high temperatures and prone to oxidation, which is one of the reasons for the poor oxidative stability of vegetable oils.

Generally speaking, the lower the content of linolenic acid and linoleic acid, the higher the content of oleic acid, and the better the oxidation stability of the oil. High oleic acid has a high content of monounsaturated acids. Plant oils with less unsaturated acid content have better oxidation stability than general plant oils.

Plant oils that can be used as green lubricants mainly include castor oil, olive oil, rapeseed oil, soybean oil, palm oil, etc. Rapeseed oil has relatively high oxidation stability, and the output of rapeseed oil in China ranks first in the world, so it is a more realistic way to choose low mustard pickled Chinese cabbage seed oil as the base oil.

Research suggests that adding general antioxidants is difficult to improve the oxidative stability of vegetable oil. Refining and chemical modification can be used to enhance the oxidative stability of vegetable oil. The main modification methods include: ①

The main purpose of chemical and ester exchange is to reduce the double bond content of vegetable oils.

Speaking of ester exchange, as mentioned earlier, vegetable oil is the triglyceride of fatty acids, which is the ester formed by glycerol and fatty acids. If the fatty acids in esters are replaced with nitric acid, it becomes glycerol nitrate ester, also known as nitroglycerin. It is an explosive and an effective emergency medicine for heart disease.

Furthermore, replacing glycerol in esters with methanol or ethanol to form the corresponding fatty acid methyl ester or fatty acid ethyl ester is what we call biodiesel. That is to say, biodiesel is

-Short chain esters of fatty acids are completely different from the hydrocarbons commonly known as diesel.