PNNL

Abstract

Increasing standards for emissions and fuel economy have driven the need for downsizing of the internal combustion engines. To accommodate this change and prevent the possibility of knocking, fuels with higher octane numbers are needed. However, octane requirements are not uniform across the whole vehicle drive cycle, which leads to inefficient use of the high-octane fuel components. In approach that has been shown to substantially increase fuel economy, a dual-fuel solution, also called octane-on-demand, can be used and supply fuel with the required octane rating by metering in the appropriate ratio of high and low octane fuels, as dictated by the driving conditions. Barriers associated with introducing two fuels in the marketplace for an octane-on-demand approach can be mitigated by the use of an onboard separation system, which separates a single fuel, such as market E10 gasoline, into the high-octane oxygenate, like ethanol, and the a lower-octane base fuel. Currently investigated onboard separation systems rely on pervaporation membranes, which lose efficiency as the oxygenate is removed, and do not separate the entirety of it, leading to loses of this valuable component. Here, we present chemical separation strategies, such as liquid-solid and liquid-liquid extraction that provide advantages over membrane separation. This paper introduces applications of tailored chemical reactions, solid sorbent materials, and ionic liquids that are shown to have a high oxygenate recovery, and utility extended beyond ethanol to potential future oxygenate additives, such as isomers of butanol.