Production of alcohol blend usable in flexible fuel vehicles via fischer-tropsch synthesis field of the invention

Abstract

Alternative fuel compositions, blends of the alternative fuel compositions and gasoline, and methods for their preparation and use are disclosed. The alternative fuel compositions ideally include ethanol, isopropyl alcohol, and one or more of sec-butanol and t-butanol, and ideally include no more than 3% methanol, and no more than 15% C 5 or higher alcohols. The fuel compositions can be prepared using Fischer-Tropsch synthesis to convert syngas to a product stream comprising C 2-4 olefins, and hydrolyzing these olefins. The process facilitates isolation of C 2-4 alkanes, because the boiling point difference of these alkanes is significantly lower than that of the C 2-4 alcohols. Ideally, the compositions provide more energy per unit volume than E85, even without the addition of gasoline, although the compositions can be blended with gasoline in any desired ratio. The resulting alternative fuel can be derived, at least in part, from renewable resources, in that the syngas can be derived from renewable resources, and a significant portion of the molecule is derived from the water used to hydrolyze the olefins. The alternative fuel compositions, and blends thereof with gasoline, can help reduce U.S. dependence on foreign crude oil.

1 . An alternative fuel composition, comprising a mixture of: a) ethanol, b) isopropanol, and c) one or more alcohols selected from the group consisting of sec-butanol and t-butanol. 
     
     
         2 . The composition of  claim 1 , wherein the composition further comprises gasoline. 
     
     
         3 . The composition of  claim 1 , wherein the composition comprises less than 10% of alcohols with a molecular weight greater than butanol. 
     
     
         4 . The composition of  claim 1 , wherein the composition comprises at least 15% sec-butanol and/or t-butanol by volume. 
     
     
         5 . The composition of  claim 1 , wherein the energy content of the fuel composition meets or exceeds that of ASTM D5798-99 (Standard Specification for Fuel Ethanol for Automotive Spark-ignition Engines). 
     
     
         6 . The composition of  claim 1 , wherein the composition is comprises less than 3% of each of n-butanol and methanol. 
     
     
         7 . The composition of  claim 1 , wherein the alcohols are produced by converting syngas to a C2-4 olefin-containing product stream using Fisher-Tropsch synthesis, and subjecting all or a portion of the C 2-4  olefins to olefin hydration. 
     
     
         8 . A method for forming an alternative fuel composition comprising a mixture of: a) ethanol, b) isopropanol, and c) one or more alcohols selected from the group consisting of sec-butanol, and t-butanol, comprising the steps of:
 i) converting syngas to a C 2 - 4  olefin-containing product stream via Fisher-Tropsch synthesis, and/or   ii) subjecting all or a portion of the C 2 - 4  olefins to olefin hydration   
     
     
         9 . The method of  claim 8 , wherein a C 2 - 4  olefin-rich stream is isolated before being converted to alcohols. 
     
     
         10 . The method of  claim 8 , wherein the composition comprises less than 10% of alcohols with a molecular weight greater than butanol. 
     
     
         11 . The method of  claim 8 , wherein the composition comprises at least 15% sec-butanol and/or t-butanol by volume. 
     
     
         12 . The method of  claim 8 , wherein the energy content of the alcohol fuel composition meets or exceeds that of ASTM (D5798-99 Standard Specification for Fuel Ethanol for Automotive Spark-ignition Engines). 
     
     
         13 . The method of  claim 8 , wherein the olefin hydration is performed on a composition comprising C 2-4  alkanes and C 2-4  olefins. 
     
     
         14 . The method of  claim 8 , wherein all or part of the C 2-4  alkanes are isolated following the olefin hydration. 
     
     
         15 . The method of  claim 8 , wherein all or part of the C 2-4  alkanes are dehydrogenated to form hydrogen and additional C 2-4  olefins. 
     
     
         16 . The method of  claim 15 , wherein the composition comprises less than 3% of each of n-butanol and methanol. 
     
     
         17 . The method of  claim 8 , wherein the syngas is derived from cellulosic biomass. 
     
     
         18 . The fuel composition of  claim 1 , further comprising gasoline. 
     
     
         19 . The composition of  claim 18 , wherein the composition comprises between about 75 and about 95 percent by volume of gasoline and between about 5 and about 25 percent by volume of the composition of  claim 1 . 
     
     
         20 . An alternative fuel composition, consisting essentially of a mixture of:
 a) ethanol, b) isopropanol, and c) one or more alcohols selected from the group consisting of sec-butanol and t-butanol.