Lubricant Base Stocks

Lubricant Base Stocks
Petroleum-based Oils
Synthetic Oils

Lubricant Base Stocks:


A lubricant usually consists of a base fluid, generally of petroleum origin, combined with additive chemicals that enhance the various desirable properties of the base fluid. Base fluids are essentially obtained from two main sources: the refining of petroleum crude oil and the synthesis of relatively pure compounds with properties that are suitable for lubricants. (Lubrizol)
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Petroleum-Based Oils:


Crude oils are found in a variety of types, ranging from light-colored oils (consisting mainly of gasoline) to black, nearly solid asphalts. These crudes are highly complex mixtures containing many hydrocarbons, ranging from methane -- the main constituent of natural gas, with one carbon atom -- to compounds containing fifty or more carbon atoms. The heavier asphaltic materials cannot be vaporized because they decompose when heated above normal distillation temperatures, and their molecules either "crack" to form gas, gasoline and lighter fuels, or unite to form higher molecular weight molecules. These latter materials result in carbonaceous residues called "coke." Crude oils also contain varying amounts of compounds like sulfur, nitrogen, and oxygen; metals such as vanadium and nickel; water; and salts. All of these materials can cause problems in refining or subsequent product applications. Their reduction or removal increases refining cost appreciably. (Lubrizol)
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Synthetic-based Oils:


Lubricant base fluids can also be synthetic. Synthetics are prepared by the chemical reaction of lower molecular weight materials to produce a fluid of higher molecular weight designed to provide certain predictable properties. This is in contrast to refined petroleum oils, which are composed of many compounds of varying chemical composition, depending on the refining method and the crude stock source.

Among the advantages claimed for synthetic lubricants over comparable petroleum-based fluids are improved thermal and oxidative stability, more desirable viscosity/temperature characteristics, improved low-temperature properties, superior volatility characteristics, and preferred frictional properties.

Commercial synthetic fluids are not confined to a single chemical type. Among those of current commercial interest are olefin oligomers, automotive and industrial applications Neopentyl polyol esters, automotive and aircraft applications esters of dibasic acids, automotive and aircraft applications, alkylated aromatics, automotive and industrial applications. These four types have found use in automotive lubricants, either alone or in combination with petroleum base oils.

Synthetic materials, in general, can be used over a wider temperature range than petroleum base fluids in the same viscosity range. Certain synthetic lubricant base stocks can be blended with petroleum oils to obtain necessary high-temperature volatility and low-temperature viscosity characteristics when the proper petroleum base oils are unavailable. (Lubrizol)
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