ABSTRACT
In earlier days, ethanol was produced by fermentation of carbohydrates such as starch and molasses. As the petrochemical industry developed, the major source of ethanol became a synthetic process, initially based on a homogeneous process in which ethylene is esterified with H
SO
and then hydrated to ethanol
(indirect hydration)
. This process is still in use, but direct hydration with a heterogeneous catalyst is more common worldwide. In recent decades, fermentation processes have made a comeback for use as an additive (10%) to gasoline in the U.S.A. in areas of high corn production. Actually, the product does not compete on an economic basis, but it has been subsidized by U.S. federal and state programs as an aid to farmers and corn and grain processors.
