Basic Process for Synthetic Ester Lubricants
Release time:
2023-04-21
Author:
Goncord Oil
Synthetic lubricants, including synthetic lubricating oils and synthetic greases, offer superior performance compared with petroleum-based lubricants in terms of high- and low-temperature resistance, high-vacuum stability, chemical stability, flame retardancy, and radiation resistance. They are employed in demanding lubrication applications for both military and civilian equipment.
Synthetic lubricants, including synthetic lubricating oils and synthetic greases, exhibit superior performance compared to petroleum-based lubricants in terms of high- and low-temperature resistance, high-vacuum stability, chemical stability, flame retardancy, and radiation resistance. They are employed in demanding lubrication applications for both military and civilian equipment. However, their cost—typically 3 to 10 times higher than that of petroleum-based lubricants—limits their widespread use. In the early 1980s, synthetic lubricants accounted for only about 2% of global lubricant production. Ester oils represent one of the earliest and most well‑rounded categories of synthetic lubricants. Today, nearly all jet engine lubricants worldwide are based on ester oils, making them a critically important class of synthetic lubricants. The defining molecular feature of ester oils is the presence of ester functional groups—COOR—within their structure. Depending on the number and positioning of these ester groups, ester oils are further classified into diesters, polyol esters, and complex esters. Diesters are produced by reacting a dicarboxylic acid with a monohydric alcohol, or a dihydric alcohol with a monocarboxylic acid; they contain two ester linkages. Common dicarboxylic acids include adipic acid, azelaic acid, and sebacic acid, while typical primary alcohols include iso‑octanol, iso‑nonanol, iso‑decanol, and iso‑tridecanol. Polyol Esters: Neopentyl polyol esters are synthesized by reacting neopentyl polyols with one or more monocarboxylic acids, resulting in molecules that possess two or more ester linkages.
Common polyol esters include trimethylolpropane and pentaerythritol esters of C5–C9 fatty acids. A shared characteristic of neopentyl polyol esters is that the β‑carbon atom in their molecular structure lacks hydrogen, resulting in superior thermal stability compared with other esters. The length of the R’‑group carbon chain determines their viscosity and low‑temperature fluidity: longer chains yield higher viscosity and poorer low‑temperature flow. Complex esters, as the name suggests, have a more intricate structure. They are formed by esterifying dicarboxylic acids with diols (or polyols) to create long‑chain molecules, followed by further esterification of the terminal groups with monofunctional alcohols or monocarboxylic acids. The average molecular weight of complex esters typically ranges from 800 to 1,500. Their viscosity is generally higher than that of diesters and polyol esters, but their thermal stability is inferior to that of polyol esters.
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