Residuum, decomposition petroleum

A residuum, often shortened to resid, is the residue obtained from petroleum after nondestmctive distillation has removed all the volatile materials. The temperature of the distillation is usually below 345°C because the rate of thermal decomposition of petroleum constituents is substantial above 350°C. Temperatures as high as 425°C can be employed in vacuum distillation. When such temperatures are employed and thermal decomposition occurs, the residuum is usually referred to as pitch. By inference, the name is used in the same manner as when it refers to the nonvolatile residue from the thermal decomposition of coal tar (3). 

When a residuum is obtained from a crude oil and thermal decomposition has commenced, it is more usual to refer to this product as pitch. The differences between parent petroleum and the residua are due to the relative amounts of... 

In the preliminary assay of petroleum the method of distillation is often used to give a rough indication of the boiling range of the crude (ASTM D-2892, IP 123). The test is carried out at atmospheric pressure and is stopped at 300°C (572°F) to avoid thermal decomposition. The distillate and the residuum can be further examined by tests such as specific gravity (ASTM D-1298, IP 160), sulfur content (ASTM D-129, IP 61), and viscos-... 

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