A Classroom Demonstration of Water-Induced Phase Separation of Alcohol-Gasoline Biofuel Blends

摘要

Fuel ethanol use is increasing in the United States because of concerns about domestic energy security, climate change, and air quality. In 2007, the United States produced nearly 6.5 billion gallons of fuel ethanol, an increase of nearly 35% over 2006 production, and production is expected to increase as more ethanol biorefineries are built (1). Ethanol can be readily produced locally from biomass feedstocks such as corn, sugar cane, or other starch or sugar-containing plant material, thereby reducing dependence on foreign petroleum supplies. In the future, it is anticipated that ethanol will also be made from lignocellulosic biomass, such as wood and grass. In fact, the Energy Independence and Security Act of 2007 mandates the use of 36 billion gallons of renewable fuels by 2022, including 21 billion gallons of advanced biofuels such as cellulosic ethanol. Climate change, largely driven by increasing atmospheric CO_2 concentration from the burning of fossil-based fuels, and defor?estation to a lesser degree, can be partially addressed by biofuels such as ethanol, despite the use of fossil fuels during production. Owing to the recycling of atmospheric CO2 in the biomass feedstock, biofuels can offer significant reductions in greenhouse gas (mostly CO_2) emissions, as evaluated on a full life-cycle or "well-to-wheels" basis (2). The Clean Air Act requires the use of oxygenated gasoline additives in some areas of the United States to reduce unwanted vehicle emissions. Since the late 1970s when the phase-out of leaded gasoline began, methyl tert-butyl ether (MTBE) and ethanol have been added to gasoline to improve the octane rating and to reduce emissions. However, ethanol has recently become the most attractive oxygenate owing to environmental and health concerns with MTBE. Butanol, another alcohol that can be produced biologically, is also being proposed as a biofuel (3).