Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 61

Various alcohols (C_nH_2n+1OH) are used as fuel for internal combustion engines. The first four aliphatic alcohols (methanol, ethanol, propanol, and butanol) are of interest as fuels because they can be synthesized chemically or biologically, and they have characteristics which allow them to be used in internal combustion engines. When obtained from biological materials and/or biological processes, the alcohols are often referred to as bioalcohols (for example, bioethanol). However, there is no chemical difference between biologically produced and chemically produced alcohols.

Most methanol is produced from natural gas, although it can be produced from biomass using similar chemical processes. Ethanol is commonly produced from biological material through fermentation processes. Butanol has the advantage in combustion engines in that its energy density is closer to gasoline than the simpler alcohols (while still retaining over 25% higher octane rating). However, biobutanol is currently more difficult to produce than ethanol or methanol.

One advantage shared by the four major alcohol fuels is the high octane rating which tends to increase the fuel efficiency and largely offsets the lower energy density of vehicular alcohol fuels (as compared to gasoline and diesel fuels), thus resulting in comparable fuel economy in terms of distance per volume metrics, such as kilometers per liter, or miles per gallon.

See also: Alcohol-Blended Fuel.