Newsletter Issue 28

Research Notes

Ethanol Effect on Gasoline Oxidation Stability when ETBE is Included in the Blend

Delgado, J. and Miras, M., Repsol YPF Technology Center
M??stoles, Madrid, Spain

It has been verified that ETBE forms precursors of oxidation in the presence of ethanol. An adequate dosage of antioxidant is able to stabilize the gasoline in any case. The European Union, in promoting renewable fuels, has imposed a minimum replacement of conventional fuels: 2% in the 2005 and 5.75% in the 2010. Repsol YPF is investing renewable energies, so that for a long time it has been incorporating ETBE in some of its gasoline formulations, and this ether is made from bioethanol.

The effect of the ethanol on the gasoline is a subject broadly studied, especially on volatility and compatibility, although there are aspects that still require to deepen, as it is the ethanol effect on gasoline stability. The oxidation stability of a representative gasoline population of 95 samples from the Spanish market has been evaluated. A total of 21 fuels have been formulated and the ethanol effect over each one has been studied.

A study has been made on the stability to the oxidation of gasoline-bioethanol blends. The effect of conventional gasoline has been compared with gasoline that incorporates 5% of ethanol. In most cases, ethanol improves stability but in some occasions it has been observed that ethanol causes the destabilization of the gasoline. This study explores the causes of this phenomenon.

In this report, the results of the designed experiences are developed to corroborate or to reject each one of the previous hypotheses, with the objective to verify, to isolate and to solve the destabilization observed in some mixtures when the ethanol is added.