Native asphalt

Asphalt, prepared from petroleum, often resembles native asphalt. When asphalt is produced by distillation, the product is called residual, or straight-mn, asphalt. However, if the asphalt is prepared by solvent extraction of residua or by light hydrocarbon (propane) precipitation, or if it is blown or otherwise treated, the name should be modified accordingly to qualify the product, eg, propane asphalt. 

Tar sand, also variously called oil sand (in Canada) or bituminous sand, is the term commonly used to describe a sandstone reservoir that is impregnated with a heavy, viscous black extra heavy cmde oil, referred to as bitumen (or, incorrectly, as native asphalt). Tar sand is a mixture of sand, water, and bitumen, but many of the tar sand deposits in the United States lack the water layer that is beHeved to cover the Athabasca sand in Alberta, Canada, thereby faciHtating the hot-water recovery process from the latter deposit. The heavy asphaltic organic material has a high viscosity under reservoir conditions and caimot be retrieved through a weU by conventional production techniques. 

Petroleum asphalts, compared to native asphalts, are organic with only trace amounts of inorganic materials. They derive their characteristics from the nature of their cmde origins with some variation possible by choice of manufacturing process. Although there are a number of refineries or refinery units whose prime function is to produce asphalt, petroleum asphalt is primarily a product of integrated refineries (Fig. 1). Cmdes may be selected for these refineries for a variety of other product requirements and the asphalt (or residuum) produced may vary somewhat in characteristics from one refinery-cmde system to another and even by cut-point (Table 2) and asphalt content (Fig. 2) (5,6). The approximate asphalt yields (%) from various cmde oils are as follows ... 

Asphaltgestein, n. native asphalt, aspbalthaltig, a. containing asphalt, asphaltic,... 

Erd-asphalt, m. earthy asphalt native asphalt, ball, m. terrestrial globe, -balsam, m. petroleum (old name), -beben, n. earthquake. -bebenkunde, /. seismology, -beere, /, strawberry. 

Yen, T. F. Long-Chain Alkyl Substituents in Native Asphaltic Molecules, Nature, Phy. Sci., 1971, 233, 36. 

Marcusson (10) was one of the first in this century to observe similarities between the behavior of asphaltenes of crude oils and native asphalts and coal. 

The term bitumen (also, on occasion, referred to as native asphalt and extra heavy oil) includes a wide variety of reddish-brown to black materials of semisoUd, viscous to brittle character that can exist in nature with no mineral impurity or with mineral matter contents that exceed 50% by weight. Bitumen is frequently found filling pores and crevices of sandstone, limestone, or argillaceous sediments, in which case the organic and associated mineral matrix is known as rock asphalt. 

Bitumen (native asphalt) Bituminous rock Bituminous sand ... 

Finally, in American specifications, the term native asphalt is used instead of the term natural asphalt used in European standards. The term native asphalt is defined as the asphalt occurring as such in nature . 

The term bituminous asphalts is intended to include both native asphalts and asphaltites such as Gilsonite, Glance pitch, and Grahanite. A full description of bituminous asphalts can be found in Abraham s Asphalts and Allied Substances, 6th Edition, Volume 1, Chapter 2, Van Nostrand Co., Inc., particularly Table III on page 60. 

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