Diesel fuel boiling point

The hydrotreated shale oil is fractionated by distillation methods into gasoline, jet, diesel, and 650°F bottoms (residua). The jet and diesel fuel boiling ranges were determined experimentally to meet flash point and freeze or pour point requirements. Some of the residua was recycled back to the hydrotreater to increase jet and diesel fuel yields. 

The winter period corresponds, of course, to the moment in the year where the diesel fuel and home-heating oil characteristics are noticeably different. Table 5.18 gives a typical example of tbe recorded differences heating oil appears more dense and viscous than diesel fuel, while its initial and final boiling points are higher. 

It should be noted finally that adding gasoline to diesel fuel which was sometimes recommended in the past to improve cold behavior conflicts with the flash point specifications and presents a serious safety problem owing to the presence of a flammable mixture in the fuel tank airspace. Adding a kerosene that begins to boil at 150°C does not have the Scune disadvantage from this point of view. 

Naphthenic acids occur ia a wide boiling range of cmde oil fractions, with acid content increa sing with boiling point to a maximum ia the gas oil fraction (ca 325°C). Jet fuel, kerosene, and diesel fractions are the source of most commercial naphthenic acid. The acid number of the naphthenic acids decreases as heavier petroleum fractions are isolated, ranging from 255 mg KOH/g for acids recovered from kerosene and 170 from diesel, to 108 from heavy fuel oil (19). The amount of unsaturation as indicated by iodine number also increases in the high molecular weight acids recovered from heavier distillation cuts. 

The temperature at which the fuel is boiled off or vaporized at the refinei y is known as the end point temperature listed m ASTM test D86, while ASTM spec D975 uses a 90 percent boiling point or distillation temperature to determine its suitability to vaporize. However, a number of major heavy-duty, highspeed diesel engine manufacturers specify that prior to selecting a diesel fuel you should ensure that a 95 percent distillation temperature is considered to ensure better combustion. 

Lower cloud point in the diesel fuel. Isoparaffins in the light cycle oil boiling range improve the cloud point. 

Petroleum refining begins by fractional distillation of crude oil into three principal cuts according to boiling point (bp) straight-run gasoline (bp 30-200 °C), kerosene (bp 175-300 °C), and heating oil, or diesel fuel (bp 275-400 °C). Further distillation under reduced pressure then yields... 

Crude oil and high-boiling-point, high-viscosity petroleum fractions such as 6 fuel oil, atmospheric tower bottoms, and vacuum gas oil can contain wax which crystallizes at temperatures often above room temperature. It is not unusual for these oils to have base pour points of 100°F (37.8°C) or greater. In order to utilize these heavy oils, the pour point and viscosity of these oils must be reduced. One method which is used to accomplish this is to dilute the heavy oil with lower-viscosity components such as diesel fuel or kerosene. The oil then becomes pumpable at lower temperatures. 

This situation can sometimes be manifested in the fuel distillation profile. More responsive fuels may have lower IBP and EP temperatures than poorly responsive fuels. Also, in poorly responsive fuels, a larger volume of fuel may distill within mid-boiling-point temperature fractions of the fuel distillation profile. The wax crystals which may form from these narrow boiling fractions tend to crystallize rapidly and at about the same temperature. Diesel fuel pumpability problems can be due to this narrow-boiling-point range wax fraction. 

ASTM D-86 look for high EP or residual material. The diesel fuel could be contaminated with high-boiling-point, high-viscosity material. 

Fuel refiners will sometimes blend low levels of coker gas oil or vacuum gas oil into diesel fuel. These high-boiling-point fractions may contain high-molecular-weight polycyclic aromatic compounds which can eventually precipitate to form fuel-insoluble sludge and deposits. 

Diesel fuel with a high T-50, for example >575°F (>302°C), will tend to bum with more smoke, soot, and hydrocarbon odor than fuel with a lower T-50. This is basically due to the incomplete combustion and oxidation of a great number of high-boiling-point, high-carbon-content fuel components in a limited-oxygen-content environment. 

Most alkanes are obtained from the separation of crude oil into various fractions, depending on their boiling points. The first four alkanes are gases. Methane is the main component of natural gas. Propane and butane are also used as fuels. Propane is used for home heating, stoves, and clothes dryers and as a fuel in specially adapted vehicles. The next four alkanes—pentane through octane—are liquids. Various forms of these alkanes are the main constituents of gasoline. Alkanes from nonane (9 carbons) to the 16-carbon hexadecane are used in kerosene and in diesel and jet fuel. 

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