Diesel Fuel

Diesel is produced from petroleum, and is sometimes called petrodiesel when there is a need to distinguish it from biodiesel obtained from biomass.   It is a hydrocarbon mixture obtained in the fractional distillation of petroleum between 200 °C and 350 °C at atmospheric pressure.   The density of diesel is about 850 grams per liter whereas gasoline has a density of about 720 g/L, about 15% less.   When burnt, diesel typically releases about 40.9 megajoules (MJ) per liter, whereas gasoline releases 34.8 MJ/L, about 15% less.   Diesel is generally simpler to refine than gasoline and often costs less.   Also, due to its high level of pollutants, diesel fuel must undergo additional filtration which contributes to a sometimes higher cost.   Diesel-powered cars generally have a better fuel economy than equivalent gasoline engines and produce only about 69% as much greenhouse gas pollution.   This greater fuel economy is due to the higher energy per-liter content of diesel fuel and also to the intrinsic efficiency of the diesel engine. While diesel's 15% higher volumetric energy density results in 15% higher greenhouse gas emissions per liter compared to gasoline, the 20–40% better fuel economy achieved by modern diesel-engined automobiles offsets the higher-per-liter emissions of greenhouse gases, resulting in significantly lower carbon dioxide emissions per kilometer. ^{Wiki n.p.}

Diesel fuel often contains higher quantities of sulfur.   European emission standards and preferential taxation have forced oil refineries to dramatically reduce the level of sulfur in diesel fuels.   In contrast the United States has long had "dirtier" diesel, although more stringent emission standards have been adopted with the transition to ultra-low sulfur diesel (ULSD) starting in 2006 and becoming mandatory on June 1, 2010.   U.S. diesel fuel typically also has a lower cetane number (a measure of ignition quality) than European diesel, resulting in worse cold weather performance and some increase in emissions.   High levels of sulfur in diesel are harmful for the environment because they prevent the use of catalytic diesel particulate filters to control diesel particulate emissions.   However, the process for lowering sulfur also reduces the lubricity of the fuel, meaning that additives must be put into the fuel to help lubricate engines.   Biodiesel is an effective lubricant, so adding it to petrodiesel is helpful. ^{Wiki n.p.}

Petroleum-derived diesel is composed of about 75% saturated hydrocarbons, including cycloalkanes, and 25% aromatic hydrocarbons.   The average chemical formula for common diesel fuel is C₁₂H₂₆26, ranging from about C₁₀H₂₂ to C₁₅H₃₂. ^{Wiki n.p.}

Cetane number or CN is a measure of the combustion quality of diesel fuel via the compression ignition process.   Cetane number is a significant expression of diesel fuel quality among a number of other measurements that determine overall diesel fuel quality.   Cetane number is actually a measure of a fuel's ignition delay, the time period between the start of injection and start of combustion (ignition) of the fuel.   In a particular diesel engine, higher cetane fuels will have shorter ignition delay periods than lower cetane fuels.   Cetane numbers are only used for the relatively light distillate diesel oils.   For heavy (residual) fuel oil two other scales are used CCAI and CII.   Generally, diesel engines run well with a CN from 40 to 55.   Fuels with higher cetane number which have shorter ignition delays provide more time for the fuel combustion process to be completed.   Hence, higher speed diesels operate more effectively with higher cetane number fuels.   There is no performance or emission advantage when the CN is raised past approximately 55; after this point, the fuel's performance hits a plateau.   In North America, diesel at the pump can be found in two CN ranges: 40-46 for regular diesel, and 45-50 for premium.   Premium diesel may have additives to improve CN and lubricity, detergents to clean the fuel injectors and minimize carbon deposits, water dispersants, and other additives depending on geographical and seasonal needs. ^{Wiki n.p.}

Cetane (hexadecane), C₁₆H₃₄, is an alkane molecule that ignites very easily under compression, so it was assigned a cetane number of 100.   All other hydrocarbons in diesel fuel are indexed to cetane as to how well they ignite under compression.   The cetane number therefore measures how quickly the fuel starts to burn (auto-ignites) under diesel engine conditions.   Since there are hundreds of components in diesel fuel, with each having a different cetane quality, the overall cetane number of the diesel is the average cetane quality of all the components.   There is very little actual cetane in diesel fuel. ^{Wiki n.p.}

To 1859

1859-1869

1870-1879

1880-1889

1890-1899

1900-1909

1910-1919

1920-1929

1930-1939

1940-1949

1950-1959

1960-1969

1970-1979

1980-1989

1990-1999