(610a) A Review of the Alcohols-to-Gasoline Conversion Processes

Even though ethanol is the major product of the biofuels industry, its use as a fuel still presents critical issues. The properties of ethanol (an oxygenated single molecule) are largely different than those of gasoline (a mixture of hydrocarbons), leading to fungibility problems with the use of ethanol in blends with gasoline. For instance, ethanol can cause corrosion problems in transport pipelines that were designed to work only with gasoline. In addition, large energy inputs are required for distillation. For these reasons, it is important not to limit ethanol use to gasoline blending. The direct conversion of ethanol into gasoline has been studied as an alternative: it presents an opportunity to turn bioethanol into a feedstock for directly building hydrocarbon mixtures. These hydrocarbons can be used as transportation fuels with the current infrastructure. In addition, this application does not require fuel grade ethanol, reducing distillation energy inputs. Ethanol, methanol and larger alcohols can be converted into gasoline at 300-400°C in the presence of a zeolite catalyst (HZSM-5). Initially, the alcohol is dehydrated to ethylene, followed by its transformation into higher hydrocarbons. This review will present the current status of the technologies for the conversion of alcohols into gasoline-like molecules, with emphasis on ethanol (ETG) and methanol (MTG). Reaction mechanisms for zeolite catalysis and technical issues like catalyst deactivation by coke deposition will be discussed.