U. S. Clean Air Act expands role for oxygenates

The passage of the amended Clean Air Act (CAA) on Nov. 15, 1990, established a permanent role for oxygenates in U.S. gasoline for the foreseeable future. This status for oxygenates was confirmed approximately a month later by analytical results from the first phase of the Auto/Oil Air Quality Improvement Research Program. In view of these events, an evaluation of the potential of the currently acceptable fuel oxygenates is in order. Further, the acute demand for oxygen in gasoline in the 1992-1995 period may reawaken studies of more obscure oxygen compounds and cosolvents for methanol. A broader perspective indicates the mandated presence of oxygen and the exclusion of aromatics from reformulated gasolines will impact all gasoline blend design and composition. While aromatics as a class (including benzene) are the primary targets to be replaced by oxygenates, high-boiling compounds may cause higher vehicle hydrocarbon (HC) emissions. Individual hydrocarbons that boil above 300{sup {degrees}}F have therefore been placed in perspective as potential contributors to HC emissions. Also, the light hydrocarbons that are related to evaporative emissions, and may be replaced by oxygenates, are characterized in this article.