On-Line Hydrocarbon Speciation Using FTIR and CI-MS

Seven hydrocarbons were determined continuously in gasoline engine exhaust over the US FTP cycle using Fourier Transform Infra Red Spectroscopy (FTIR). Three of the hydrocarbons were also determined using Chemical Ionisation-Mass Spectrometry (CI-MS).

Tests with and without a three way catalyst illustrated the strong dependence of catalyst performance on the composition of the hydrocarbons emitted. For example, the FTIR indicated that over a cold start FTP cycle, the catalyst took 98 seconds to achieve a 50% conversion rate for ethyne, 183 seconds for ethene and 229 seconds for ethane.

The work indicates that FTIR in particular is an appropriate technique for the monitoring of exhaust catalyst performance.