Most of the US supply of gasoline currently contains 10% ethanol (E10). Meeting the renewable fuel standards (RFS) set forth by Congress requires the addition of ethanol to gasoline at levels higher than the 10% maximum established by the Clean Air Act. Higher ethanol concentrations, such as the new E15 standard approved by EPA, introduce technical problems due to material compatibility in existing engines and a lack of retail infrastructure to handle multiple blend levels. New drop-in biofuels that are chemically indistinguishable from conventional gasoline would alleviate all of these problems and allow the unfettered growth of renewable transportation fuels.
Exelus has developed a new process technology to convert low-cost, bio-derived, hydrous ethanol (“crude ethanol”) and butanes into “Bio-Alkylate”, a hydrocarbon fuel chemically identical to a conventional refinery blendstock called alkylate. The Exelus approach for producing bio-alkylate from bio-ethanol starts with the dehydration of crude ethanol to ethylene in a fixed-bed reactor. This reaction is practiced commercially using gamma-alumina as the catalyst and produces ethylene at high selectivity. Ethylene is then separated from water and fed to a second reactor where it reacts with iso-butane over the ExSact to make alkylate. Catalyst and process innovations are employed to minimize energy consumption and to allow this renewable fuel to be produced profitably. This technology bridges the gap between the production of petroleum-derived fuels and biofuels, effectively incorporating the energy and carbon content of biofuels and butanes into conventional gasoline blendstock
The high octane bio-alkylate fuel produced can be blended with gasoline in any proportion without hitting a "blend wall" or altering the physical or combustion characteristics of the gasoline. All of the carbon and chemical energy contained in the renewable feedstock is incorporated into the final fuel product. This technology removes many of the technical barriers to the increased use of renewable fuels in the gasoline poolr, which can be recycled.
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