Pentane is an organic compound with the formula C5H12—that is, an alkane with five carbon atoms. The term may refer to any of three structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, pentane means exclusively the n-pentane isomer; the other two are called isopentane (methylbutane) and neopentane (dimethylpropane). Cyclopentane is not an isomer of pentane because it has only 10 hydrogen atoms where pentane has 12.
n-Pentane and iso-Pentane occur naturally in crude oil and as a by-product of natural gas production. Cyclopentane, a ring-shaped molecule much sought after by the industry, is found more in naphtha (crude petrol), which is obtained in refineries from so-called cracking processes.
Pentanes are components of some fuels and are employed as specialty solvents in the laboratory. Their properties are very similar to those of butanes and hexanes.
Pentanes are some of the primary blowing agents used in the production of polystyrene foam and other foams. Usually, a mixture of n-, i-, and increasingly cyclopentane is used for this purpose.
Acid-catalyzed isomerization gives isopentane, which is used in producing high-octane fuels.
Because of their low boiling points, low cost, and relative safety, pentanes are used as a working medium in geothermal power stations and organic Rankine cycles. It is also used in some blended refrigerants.
Pentanes are solvents in many ordinary products, e.g. in some pesticides.
| Items | Unit | Actual | Spec. | Test Method |
|---|---|---|---|---|
| Density at 15.6 °C | g/cm³ | 0.62- 0.65 | ASTM D287 | |
| Total Content of i-C5 and n-C5 | % by wt | >98 | G.C. | |
| Color Say bolt | say bolt | Min +27 | < 30 | ASTM D-156 |
| Non-Volatile Matter | mg/100 ml | Max 0.5 | ASTM D-1353 | |
| Total Sulphur | ppm by wt. | Max 10 | ASTM D-5453 | |
| Butane at Lighter | % by wt. | Max 0.5 | G.C. | |
| i-C5 | % by wt. | 20 ± 2 | 30 ± 2 | G.C. |
| n-C5 | % by wt. | 80 ± 2 | 70 ± 2 | G.C. |
| Hexane and Heavier | ppm by wt. | Max 2000 | G.C. | |
| Cyclopentane | ppm by wt. | < 100 | G.C. | |
| Water | ppm by wt. | Max 100 | ASTM D-1364 | |
| Total Olefins | ppm by wt. | Max 100 | G.C. | |
| Appearance | Clear | Clear | Visual | |
| Benzene | ppm by wt. | < 50 | < 100 | G.C. |