Application PetroOxy: Save on Expensive Antioxidant Additives for Spark-Ignition Fuels

Additives improve the stability and performance of fuel. The correlation of oxidation stability to antioxidant concentration can be determined with the PetroOxy to prevent the excessive use of valuable antioxidant materials and operate cost effective.

Background Information

The rapid small scale tester, PetroOxy, is a fast, safe and user friendly alternative to the traditional bomb method (ASTM D525 / EN ISO 7536). The instrument measures the induction period of spark-ignition fuels in compliance to ASTM D7525, which can be used as an indication of the oxidation and storage stability. Compared to other oxidation and storage stability test methods, this approach uses a small sample and gives test results in a short time period.

Measuring the Influence of Antioxidant Additives

Oxidation stability is an integral part of the standard specification for spark-ignition fuels (ASTM D4814 / EN 228). "Raw" gasoline with high olefin content are hydrated and treated with antioxidant additives to fulfill these standard specifications. The "raw" gasoline LCC top with an olefin content of approx. 40 % was used and the influence of the antioxidant additive concentration was investigated with the PetroOxy and ASTM D525. The results showed that the correlation between the PetroOxy and bomb method is excellent (Fig. 2) and that test results are obtained much faster with the PetroOxy method (approx. 20 times faster). Moreover, the correlation of induction period with antioxidant concentration showed that for ASTM D4814 approx. 6 ppm and for EN 228 approx. 30 ppm of antioxidant is needed to fulfill the specification (Fig. 1). The use of much larger concentrations of antioxidant is excessive and not cost effective.

Fig. 1: Correlation of PetroOxy induction period with antioxidant concentration for the “raw” gasoline LCC top (approx. 40 % olefin content).
Colors indicate the compliance of the gasoline oxidation stability with ASTM D4814.
Green: in compliance. Red: no compliance

PetroOxy Standard Methods

ASTM D7525, ASTM D7545, EN 16091, IP 595

Test Procedure

5 mL of sample is loaded in the test cell and the pressure lid/cover is closed. The test cell is automatically charged with oxygen pressure and heated to the standardized temperature. The pressure is monitored until a pressure drop of 10 % from pmax is detected, which is defined as induction period according to ASTM D7525.

PetroOxy vs. ASTM D525 / EN ISO 7536

Fig. 2: The PetroOxy has an excellent correlation to ASTM D525 and is approximately 20 times faster.

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