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Lab Methods

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Aromatics, Olefins, and Saturates by FIA

  • Method ASTM D1319
  • Repeatability variable, see method
  • Reproducibility variable, see method
  • Blending linear
  • Additive Correction No

The purpose of this test is to determine types of hydrocarbon over the concentration ranges from 5 to 99 volume % aromatics, 0.3 to 55 volume % olefins, and 1 to 95 volume % saturates in petroleum fractions that distill below 315°C.

The three components identified in this method are very important to classify the type of product that is being analyzed. This will help gasoline blenders, distillate blenders, and refiners make educated decisions about the materials they will be working with.

When blending gasoline, Aromatics are highly desirable. They possess high octane values, low rvps, and usually contain little sulfur unless contaminated. On the negative side they can damage rubber seals and you are limited by the amount of aromatics you can blend into domestic gasoline. Diesel, Jet Fuel, and Kerosene also contain aromatics but are not favorable due to the combustion qualities in these uses.

Olefins as compounds still have room for chemical bonds which cause them to react and become Saturates. This leaves opportunities for products to oxidize or degrade causing issues with gum content and thermal stability testing. This is the main reason Olefins are not desirable in gasoline.

Saturates are compounds that are very stable. They are used as the majority of a gasoline blend due to these properties. They can vary in octane and rvp values but will not usually cause issues with stability.

The method works by using a glass column packed with Silica gel and a small layer of red dye indicator. 0.75mL is injected into the column before adding Alcohol or Iso Amyl. The tube is then sealed and pressure is applied to the column. This in turn pushes the alcohol and sample mixture through the red dye. Once this happens the mixture then separates as it moves through the column. After enough time has passed the red dye line will appear and move down the tube. At this point the tube is marked with a permanent marker under ultra violet light. The ultra violet like will cause the Aromatics to Fluoresce blue, Olefins yellow, and the saturates will not emit any light. The markings are then measured using a meter stick. These lengths are calculated as part of the whole giving a result in volume percent.