Petroleum Oils

mixtures of macromolecular hydrocarbons obtained from petroleum and used mainly as lubricants. They are also used as hydraulic fluids, cooling lubricants, electrical insulation media, surface-active agents, softeners, components of plastic lubricants, and medicinal preparations. There are two main systems for classification of petroleum oils: according to method of production and fields of application. In terms of method of production, petroleum oils are divided into distillate oils, which are obtained by vacuum distillation of mazuts; residual oils, produced from deasphalted oil tars; and compounded oils, which are mixtures of distillate and residual oils selected according to viscosity and other characteristics.

Modern production processes (including vacuum distillation, deasphalting, selective refining, deparaffination, and contact or hydraulic treatment) provide sufficiently complete extraction of the oil fractions from the petroleum, the necessary purification, and the required physical and chemical properties; in this case, the quality of the oils depends on the chemical composition and properties of the crude petroleum. Promising catalytic oil production processes (such as hydrocracking, hydroisomerization, alkylation, and polymerization) make possible the production of oils of specific chemical composition and properties with a higher yield from the refined raw material. In the USSR, petroleum oils are produced mainly from the sulfurous petroleum of the Volga-Ural region (Romashkino, Mukhanovo, and Tuimazy) and the petroleum of Western Siberia (Ust’-Balyk and Samotlor). These petroleums, by their chemical composition and properties, provide for the production of oils with high performance characteristics. Mangyshlak petroleum is also promising for the production of oils.

Petroleum oils are classified according to fields of application as motor oils, jet aircraft oils, transmission oils, industrial oils, cylinder oils (for steam engines), electrical insulation oils, process oils, and the white oils used in medicine and perfumery. The first five groups are lubricating oils, and the rest are nonlubricating oils.

A list of physical and chemical properties, which depends on the conditions of use, has been developed for each type of oil and is strictly regulated by standards. However, there are a number of characteristics that pertain to almost all petroleum oils. They include, above all, viscosity (or internal friction), which is usually measured at temperatures of 50°C and 100°C. The viscosity range of commercial oils is very great—from 2.0-2.5 centistokes (1 centistoke = 10^-6 m²) at 100°C for light industrial oils up to 60-70 centistokes for heavy cylinder oils. For oils used under arctic conditions (“northern” oils), the viscosity is also specified for negative temperatures, — 40°C and lower; the viscosity index, which characterizes the temperature-viscosity relationship, is an important indicator for these oils. The pour point may range from 17°C for heavy cylinder oils to minus 45°-60°C for some industrial and motor oils. This characteristic must be taken into consideration in selecting conditions for shipment, storage, and use of lubricating products. The permissible high-temperature range for the use of petroleum oils is indirectly characterized by the flash point. Fractional composition is also an important index for petroleum oils, although for the overwhelming majority of petroleum oils, including motor oils, it is not standardized in technical specifications. High dielectric properties, which are characterized primarily by the tangent of the dielectric phase angle, are the principal index for electrical insulation oils.

Most petroleum oils must also have a low ash content and high oxidation resistance. These characteristics are associated with the antiabrasion, antiscale, and corrosion properties of the oils.

To be used in modern engines and machinery with high speeds, loads, and temperatures, petroleum oils must contain various additives, which improve the performance characteristics of the oils (by lowering the pour point, increasing antiabrasion and dispersing properties, and so on). Virtually all commercial oils contain additives or their compositions in amounts ranging from 0.5-1.0 percent to 25 percent or more.

In some cases, synthetic oils having higher specifications are used instead of petroleum oils.