Page 17 - Shimadzu Journal vol.8 Issue2

Hydrocarbon Processing Industry

Analytical method for determining

aromatics and olefins in fuel

as an alternative to FIA method

Ryo Kubota, Shimadzu Corporation
Andrew Fornadel PhD, Shimadzu Scientific Instruments, USA

Fuels such as gasoline, diesel, and jet fuels used in automobiles cause excess smoke and particulate emissions and, at high concen-
and aircraft have various quality control parameters to ensure trations, can negatively affect the durability of engine components.
their performance and to comply with environmental regulations. The upper concentration limit for aromatics is specified in ASTM
Fuels consist of hundreds of different hydrocarbon molecules such D1655 for jet fuel and the U.S. Federal Aviation Administration
as paraffins, olefins, and aromatics. Because aromatics and olefins (FAA) requires fuels to conform with this standard. 4
affect combustion characteristics and can cause air pollution, their
concentration in fuels is restricted by fuel quality and environmen- The Fluorescent Indicator Adsorption (FIA) method is the con-
tal regulations. ventional method to measure the volume-percentage of aromatics,
Aromatics and olefins in fuels are known to cause air pollution olefins and paraffins in fuel, with the technique having first been
and generate harmful compounds in exhaust gases. For example, introduced in 1940s. The FIA method is a rudimentary chromatog-
aromatics in diesel fuel can affect combustion and the formation raphy technique and works by adding a fuel sample to a long, glass
of particulate and polycyclic aromatic hydrocarbons (PAH) and column packed with activated silica gel (Fig. 1). A small amount of
NOx emissions. Combustion of olefins in gasoline can lead to the silica gel is mixed with a specially-formulated UV-fluorescent dye
formation of ozone whereas aromatics can cause the formation of and added onto the top of the packing and is then dye is desorbed
carcinogens such as benzene in exhaust gas . Aromatic compounds with the addition of alcohol. Air or another gas is used to pressurize
1
are also known to affect elastomeric seals and o-rings in engines the top of the column, forcing the sample and the dye to elute. The
and need to be maintained at a proper concentration. Therefore, fuel components have different affinities for the silica packing, with
quality standards in each country and Worldwide Fuel Charter saturates eluting furthest on the column and aromatics showing the
(WWFC) show the specification of upper limit concentration of least elution, with olefins in between. The different dye components
2
aromatics and olefins in diesel and gasoline , and the United States adsorb uniquely to the individual fuel components (e.g., aromatics,
Environmental Protection Agency (U.S. EPA) regulates the con- olefins, and saturates). After a length of time, the column is exposed
tent of these components . In jet fuels, aromatic compounds can to UV light and distinct fluorescent bands of color indicate the start
3

Shimadzu Journal vol.8 Issue2 59