Petroleum oil

The base lubricant is usually a petroleum oil while the thickener usually consists of a soap or soap mixture. In addition they may contain small amounts of free alkali, free fatty acid, glycerine, anti-oxidant, extreme-pressure agent, graphite or molybdenum disulphide. 

Asphaltenes have high concentrations of heteroelements sulfur, nitrogen, nickel and vanadium. Their content varies widely in petroleum oils (Table 1.5). They cause a number of problems throughout the petroleum industry. 

Demulsibility of petroleum oils and synthetic fluids NFT 60-125 ISO 6614 ASTM D 1401 Time necessary for separation of phases... 

Gas bubble separation time of petroleum oils NFT 60-149 ASTM D 3427 Time for air liberation after supersaturation (measurement of density)... 

Chemists make compounds and strive to understand their reactions. My own interest lies in the chemistry of the compounds of the elements carbon and hydrogen, called hydrocarbons. These make up petroleum oil and natural gas and thus are in many ways essential for everyday life. They generate energy and heat our houses, fuel our cars and airplanes and are raw materials for most manmade materials ranging from plastics to pharmaceuticals. Many of the chemical reactions essential to hydrocarbons are catalyzed by acids and proceed through positive ion intermediates, called carbocations. 

Another area of my post-Nobel research that turned into a major continuing effort evolved from the realization that our hydrocarbon resources, the marvelous gift of nature in the form of petroleum oil and natural gas, are finite and not renewable. 

Synthetic fluids are safe, noncorrosive, essentially nontoxic, and thermally stable when operated under conditions recommended by the manufacturers. Generally, these fluids are more expensive than petroleum oils, but the synthetics can usually be reprocessed to remove degradation products. There are several classes of chemicals offered permitting a wide temperature range of appHcation. Any heat-transfer fluid in use should be examined periodically to monitor degradation or contamination. 

Therminol Heat-Transfer Fluids. Monsanto Chemical Co. manufactures a series of synthetic heat-transfer fluids that offer a wide operating temperature range. AH of these fluids, except for Therminol VP-1 and Therminol LT, are intended for Hquid-phase operation only. Monsanto also offers the two natural petroleum oil-based heat-transfer fluids discussed. 

Hydrocarbons, compounds of carbon and hydrogen, are stmcturally classified as aromatic and aliphatic the latter includes alkanes (paraffins), alkenes (olefins), alkynes (acetylenes), and cycloparaffins. An example of a low molecular weight paraffin is methane [74-82-8], of an olefin, ethylene [74-85-1], of a cycloparaffin, cyclopentane [287-92-3], and of an aromatic, benzene [71-43-2]. Cmde petroleum oils [8002-05-9], which span a range of molecular weights of these compounds, excluding the very reactive olefins, have been classified according to their content as paraffinic, cycloparaffinic (naphthenic), or aromatic. The hydrocarbon class of terpenes is not discussed here. Terpenes, such as turpentine [8006-64-2] are found widely distributed in plants, and consist of repeating isoprene [78-79-5] units (see Isoprene Terpenoids). 

Rya.nia., The root and stem of the plant yania speciosa family Flacourtiaceae, native to South America, contain from 0.16—0.2% of iasecticidal components, the most important of which is the alkaloid ryanodine [15662-33-9] C25H250 N (8) (mp 219—220°C). This compound is effective as both a contact and a stomach poison. Ryanodine is soluble ia water, methyl alcohol, and most organic solvents but not ia petroleum oils. It is more stable to the action of air and light than pyrethmm or rotenone and has considerable residual action. Ryania has an oral LD q to the rat of 750 mg/kg. The material has shown considerable promise ia the control of the European com borer and codling moth and is used as a wettable powder of ground stems or as a methanohc extract. Ryanodine uncouples the ATP—ADP actomyosia cycle of striated muscle. 

Petroleum Oils. When satisfactorily stable kerosene—soap—water emulsions were produced in 1874, dormant (winter) oil sprays became widely used to control scale insects and mites (1). The first commercial emulsion or miscible oil was marketed in 1904 and by 1930 highly refined neutral or white oils, free from unsaturated hydrocarbons, acids, and highly volatile elements, were found to be safe when appHed to plant foHage, thus gready enlarging the area of usefulness of oil sprays (see Petroleum). 

Low temperature filtration (qv) is a common final refining step to remove paraffin wax in order to lower the pour point of the oil (14). As an alternative to traditional filtration aided by a propane or methyl ethyl ketone solvent, catalytic hydrodewaxing cracks the wax molecules which are then removed as lower boiling products. Finished lubricating oils are then made by blending these refined stocks to the desired viscosity, followed by introducing additives needed to provide the required performance. Table 3 Usts properties of typical commercial petroleum oils. Methods for measuring these properties are available from the ASTM (10). 

Wide range of viscosity ia commercial petroleum oils is illustrated by the representative types listed ia Table 3. Despite this range, the largest proportion of oils are ia the 25-75 mm /s at 40°C viscosity range. Oils ia this range combine generally adequate hydrodynamic load capacity with low power loss, low volatiUty, and satisfactory low temperature properties. 

Fig. 8. Variation of viscosity with temperature for selected petroleum oils.

Although the viscosity index is useful for characterizing petroleum oils, other viscosity—temperature parameters are employed periodically. Viscosity temperature coefficients (VTCs) give the fractional drop in viscosity as temperature increases from 40 to 100°C and is useful in characterizing behavior of siHcones and some other synthetics. With petroleum base stocks, VTC tends to remain constant as increasing amounts of VI improvers are added. Constant B in equation 9, the slope of the line on the ASTM viscosity—temperature chart, also describes viscosity variation with temperature. 

Fig. 10. Viscosity—pressure curve for typical petroleum oils (—) paraffinic (-) aUcycHc and ( ) soHd. To convert MPa to atm, divide by 0.101.

Pour-Point Depressants. The pour point of alow viscosity paraffinic oil may be lowered by as much as 30—40°C by adding 1.0% or less of polymethacrylates, polymers formed by Eriedel-Crafts condensation of wax with alkylnaphthalene or phenols, or styrene esters (22). As wax crystallizes out of solution from the Hquid oil as it cools below its normal pour point, the additive molecules appear to adsorb on crystal faces so as to prevent growth of an interlocking wax network which would otherwise immobilize the oil. Pour-point depressants become less effective with nonparaffinic and higher viscosity petroleum oils where high viscosity plays a dominant role in immobilizing the oil in a pour-point test. 

In 1929, polymerized olefins were the first synthetic oils to be produced commercially in an effort to improve on the properties of petroleum oils. Interest in esters as lubricants appears to date back to 1937 in Germany, and their production and use expanded rapidly during and following World War II to meet the needs of the military and the newly developed jet engines (2). 

Ester fluids are modified with additives in much the same manner as petroleum oils. They are stabili2ed with an oxidation inhibitor, eg, 0.5 wt % phenothia2ine. Improved load capacity for gears and rolling bearings in aircraft engines is provided by 1—5% tricresyl phosphate. Zinc... 

Oils in Greases. Essentially the same type of oil is used in compounding a grease as would normally be selected for oil lubrication. Petroleum oils are used in about 99% of the grease produced and commonly are in the SAE 20—30 viscosity range with about 100 130 mm /s viscosity at 40°C. Such oils provide low volatiHty for long life at elevated temperatures (50) together with low torque down to subzero temperatures. 

The trend for increasing viscosity with increased dose is shown in Eigure 18 for several petroleum oils (72). Eor many lubricant appHcations, a dose that gives a 25% increase in 40°C viscosity can be taken as a tolerance limit. Lower radiation absorption seldom changes the lubricant sufficiently to... 

Fig. 18. Viscosity change of industrial petroleum oils with irradiation (72). To convert Gy to rad, multiply by 100.

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