New process converts crude ethanol into bio-alkylate
Exelus, Inc. (www.exelusinc.com) has developed a process that converts low-cost, bio-derived, hydrous ethanol into “bio-alkylate”, a hydrocarbon fuel chemically identical to a conventional refinery blendstock called alkylate. This technology would bridge the production of petroleum-derived fuels and biofuels, effectively incorporating the energy and carbon content of bio-ethanol into conventional gasoline.
The Environmental Protection Agency has recently agreed to let refiners add as much as 15% ethanol to a new blend, up from the current 10%. Conventional vehicles cannot safely use fuels with significantly higher concentrations of ethanol without retrofits to replace gaskets and metal components susceptible to chemical attack by ethanol. Few gas pumps are certified as safe to use E15.
Bio-alkylation offers a simple way around this problem while also addressing the concerns of Congress that higher ethanol blends could damage engines. The bifurcation of the gasoline supply into E15+, only used by newer vehicles, and E10, used by all other vehicles and motorized equipment, is also avoided. This process allows the renewable content of gasoline to reach 50% without any changes to the nation’s engine and fuel infrastructure
Most of the energy consumed in a conventional bio-ethanol plant is used to distill ethanol from water. The Exelus process uses wet ethanol as the feed, providing a 32% energy savings compared to anhydrous ethanol production. The fuel produced can be blended with gasoline in any proportion without altering the physical or combustion characteristics of the gasoline. This technology removes many of the technical barriers to the increased use of renewable fuels in the gasoline pool.
The bio-alkylation process utilizes research funded partly by a $1 million grant from the US Department of Energy’s ARPA-E program. Mitrajit Mukherjee, president of Exelus points out, “The price of bio-alkylate is estimated at $2/gallon – a figure which does not include any price credits for ethanol. In addition, since bio-alkylate has the same energy density as conventional gasoline, adding higher amounts (of bio-alkylate) will not affect automobile mpg characteristics.”
Dr. Mark Hartney, who leads ARPA-E’s Innovative Materials & Processes for Advanced Carbon Capture Technologies program and oversees Exelus’ alkylation research project, says, “In one short year Exelus has made great strides in developing engineered solid-acid catalysts that can take low value feedstocks, such as refinery flare gas, and convert them into high-octane gasoline blendstock – and they have been able to do it in an economically attractive way.”
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