Measuring NMHC and NMOG emissions from motor vehicles via FTIR spectroscopy

• Published in: Atmospheric environment (1994) 2017-02, Vol.150, p.425-433
• Main Authors: Gierczak, Christine A., Kralik, Lora L., Mauti, Adolfo, Harwell, Amy L., Maricq, M. Matti
• Format: Article
• Language: English
• Subjects: Engine exhaust; FTIR; NMHC; NMOG; Vehicle emissions
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2016.11.038

The determination of non-methane organic gases (NMOG) emissions according to United States Environmental Protection Agency (EPA) regulations is currently a multi-step process requiring separate measurement of various emissions components by a number of independent on-line and off-line techniques. The Fourier transform infrared spectroscopy (FTIR) method described in this paper records all required components using a single instrument. It gives data consistent with the regulatory method, greatly simplifies the process, and provides second by second time resolution. Non-methane hydrocarbons (NMHCs) are measured by identifying a group of hydrocarbons, including oxygenated species, that serve as a surrogate for this class, the members of which are dynamically included if they are present in the exhaust above predetermined threshold levels. This yields an FTIR equivalent measure of NMHC that correlates within 5% to the regulatory flame ionization detection (FID) method. NMOG is then determined per regulatory calculation solely from FTIR recorded emissions of NMHC, ethanol, acetaldehyde, and formaldehyde, yielding emission rates that also correlate within 5% with the reference method. Examples are presented to show how the resulting time resolved data benefit aftertreatment development for light duty vehicles. [Display omitted] •Non-methane hydrocarbon and organic gas emissions measured by a single instrument.•Surrogate group of compounds identified for FTIR equivalent to FID NMHC.•Oxygenated compounds included for FTIR measurement of real time NMOG emissions.•Thresholds for including surrogates in spectral analysis developed to maximize S/N.•Reduces noise in NMHC when methane is high and allows real time NMOG measurement.