Low-Temperature Miscibility of Ethanol-Gasoline-Water Blends in Flex Fuel Applications

Abstract

The miscibility of blends of gasoline and hydrous ethanol was investigated experimentally at −25°C and −2°C. Furthermore, the maximum water content was found for ethanol in flex fuel blends. The results strongly indicate that blends containing ethanol with a water content above that of the ethanol/water azeotrope (4.4% water by mass) can be used as Flex Fuel blends together with gasoline at ambient temperatures of −25°C and −2°C, without phase separation occurring. Additionally, it was shown that the ethanol purity requirement of ethanol-rich flex fuel blends falls with increasing ethanol content in the gasoline-rich flex fuel blend.

Keywords:

• bioethanol
• biofuel
• ethanol
• flex fuel
• flex fuel vehicle
• gasohol
• gasoline
• hydrous ethanol
• miscibility
• phase separation
• ternary phase diagram

Acknowledgments

The authors wish to thank the Danish Technological Institute (Aarhus), where the experimental work was conducted.

Notes

¹More recently, some miscibility tests of ethanol-gasoline-water have been reported, but only for low-level ethanol blends (< 15%) (Peng et al., 1996; French and Malone, 2005; Gramajo de Doz. et al., 2004).

² http://www.shell.com/home/page/dk-da/produkt_og_sikkerhedsdatablade/app_products_0310_1510.html.

³The experimental data can be found in Appendix II: Experimental Data.

⁵Meaning of subscripts: FFBE is mass percentage relates to the ethanol-rich FFB; FFBG is mass percentage relates to the gasoline-rich FFB; PSP is mass percentage relates to the blend at the phase separation point.