Comparison of Gasoline Particulate Indices Using U.S. Market Gasoline Samples

Simulated distillation (SimDis) uses wide bore capillary gas chromatography (GC) to provide a detailed volatility profile of blended gasoline. The boiling point distribution from SimDis analysis is correlated to the hydrocarbon contents of spark ignition fuels and provide the resolution necessary to characterize the compositions of the fuel. Recent publications on simulated distillation applied to spark ignition fuel reveal the merits of indexing a gasoline fuel so that it can be correlated to the tendency of particulate emissions from vehicles. With this in mind, SimDis can be a useful and quick tool in assessing the PM-formation potential of market gasolines. Heavy aromatic compounds that are present in spark ignition fuels are major contributors to vehicle particulate emissions. These compounds are present in the higher boiling portion (T70+) of the distillation profiles. As demonstrated in recent studies, the particulate indices of gasoline samples are indicative of the relative amount of particulate that a fuel forms during combustion. [1,2] These indices include Particulate Matter Index (PMI), Particulate Evaluation Index (PEI), and most recent PEISimDis calculation. [3,4,5] PMI and PEI require a detailed and lengthy GC separation process to yield the data needed for calculation. PEISimDis is reliant upon the much quicker method of SimDis and is primarily focused on the contributions from heavy aromatics. This paper will present a continued study of PEISimDis and its efficacy for PM prediction using a collection of the latest market gasoline fuel samples from the United States. How industry standard particulate indices are affected by PMI distribution, application of SimDis profiles, and the correlations of evaporative temperatures, especially above T90, will all be examined. Additionally, an analysis of SimDis cut-points (%-off values) of this collection of market samples will be performed to demonstrate the opportunity and effect of cutting heavy molecules for fuel quality improvement.