Speciation and Quantitation of Hydrocarbons in Gasoline Engine Exhaust

Abstract

A capillary column gas chromatographic (GC) method for the speciation and quantitation of individual hydrocarbons in exhaust from gasoline engines is described, and the method is applied to the analysis of exhaust from an experimental stratified-charge engine. A single-column GC technique is used to characterize C5-C12 hydrocarbon emissions, and a multidimensional GC technique with an alumina—KCI porous-layer-open-tubular (PLOT) column is used for C1-C4 hydrocarbons. The method employs a gas-sample introduction device (G-SID) constructed from a six-port valve and a pressure transducer. Precise measurement and control of sample pressure in the G-SID facilitates sample handling and simplifies detector calibration. The strategy for speciating hydrocarbons in exhaust includes a detailed GC analysis of the liquid fuel followed by the application of commercially available software with a retention index database. Spreadsheet and graphics software are used to extract meaningful information from the large sets of exhaust emission data. In particular, the data suggest that localized regions of fuel-rich combustion in the stratified-charge engine contribute significant amounts of unburned fuel to the exhaust, even under overall conditions of lean combustion. The data also provide information about an experimental emissions-control system that appears to be more active for aromatics, naphthenes, and olefins than for normal- and isoparaffins.