Lubrication Oxidation Stability

HalogenatedFluids. Chlorocarbons, fluorocarbons, or combinations of the two are used to form lubricating fluids (see Chlorocarbons and CHLOROHYDROCARBONS Fluorine COMPOUNDS, ORGANIC). Generally, these fluids are chemically inert, essentially nonflammable, and often show excellent resistance to solvents. Some have outstanding thermal and oxidation stability, because they are completely unreactive even in Hquid oxygen, and extremely low volatility. 

Lube oil extraction plants often use phenol as solvent. Phenol is used because of its solvent power with a wide range of feed stocks and its ease of recovery. Phenol preferentially dissolves aromatic-type hydrocarbons from the feed stock and improves its oxidation stability and to some extent its color. Phenol extraction can be used over the entire viscosity range of lube distillates and deasphalted oils. The phenol solvent extraction separation is primarily by molecular type or composition. In order to accomplish a separation by solvent extraction, it is necessary that two liquid phases be present. In phenol solvent extraction of lubricating oils these two phases are an oil-rich phase and a phenol-rich phase. Tne oil-rich phase or raffinate solution consists of the "treated" oil from which undesirable naphthenic and aromatic components have been removed plus some dissolved phenol. The phenol-rich phase or extract solution consists mainly of the bulk of the phenol plus the undesirable components removed from the oil feed. The oil materials remaining... 

An ATE requires high lubrication performance, high levels of oxidation stability to withstand the locally high operating temperatures, a degree of fluidity that ensures... 

Steam-turbine lubricants Lubricants in steam turbines are not exposed to such arduous conditions as those in engines. The main requirement is for high oxidation stability. However, they may be exposed to aqueous condensate or, in the case of marine installations, to sea water contamination, so they have to be able to separate from water easily and to form a rustpreventing film on ferrous surfaces, and it is usual to employ rust inhibitors. The problem of tin oxide formation on white-metal bearings is associated with the presence of electrically conducting water in lubricants and can be over-come by keeping the lubricant dry . 

Early refiners utilized simple batch distillation to prepare kerosenes and lubricating oils. As the demand for these materials expanded and new crude oils were found, certain desirable and undesirable characteristics became apparent. Crude oils were selected from which products possessing desirable characteristics could be distilled—for example, oxidation stability, low smoke tendency, low carbon-forming tendency, small viscosity change with change in temperature (high viscosity index), light color, and attractive appearance were more likely to be found in petroleum of the paraffinic or Pennsylvania type. 

Stability—In petroleum products, the resistance to chemical change. Gum stability in gasoline means resistance to gum formation while in storage. Oxidation stability in lubricating oils and other products means resistance to oxidation to form sludge or gum in use. 

Lubricants are formulated products composed of a base stock, which is either a mineral or synthetic oil, and various specialty additives designed for specific performance needs. Additive levels in lubricants range from 1 to 25% depending on the application. Synthetic base stocks are oligomers of small molecules, synthesized to a defined molecular weight. Important performance indicators include viscosity index which measures the viscosity index behavior over a temperature range, oxidative stability, and pour point. The performance of synthetic and mineral oils (Morse, 1998 Shubkin, 1993) is summarized in Table 2.7. 

Similarly to bis(octylphenoxy)dithiophosphate, one can obtain other bis(alkylphenoxy)derivatives of dithiophosphoric acid. As mentioned above, these ethers are veiy efficient additives for lubricant oils used in intensive operation engines. An addition of 1-5% of these substances greatly increases thermal oxidative stability and anticorrosion properties of lubricant oils and reduce varnish formation in engines. 

Stavinoha and Kline (2001) adapted ASTM method D 6186 (Oxidation Induction Time of Lubricating Oils by Pressure Differential Scanning Calorimetry [P-DSC]) for analyzing the oxidative stability of SME treated with antioxidants. This report concluded that isothermal P-DSC analysis is suitable for screening the effectiveness of antioxidants for treating biodiesel. 

Sharma, B. K., and Stipanovic, A. J. 2003. Development of a New Oxidation Stability Test Method for Lubricating Oils Using High-Pressure Differential Scanning Calorimetry. Thermochim. Acta, 402,1-18. 

Dithiocarbamate and dithiophosphinate complexes have important uses. The former are used as fungicides and for solvent extraction and the latter as high pressure lubricants. Dithiocarbamates stabilize high oxidation states as in [FeIV(dtc)3]+ or [NiIV(dtc)3]+. Although dithiocarbamates are usually made from sodium salts such as NaS2CNMe2 or by oxidations using thiuram disulfides, they can also be made by insertion reactions of CS2 with dialkylamides, for example,... 

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