(582cp) Measurement of Raman Spectra during Thermal Oxidation of Hydrocarbon Fuels

Spectral measurements of Raman scattering in fluids at elevated temperatures and pressures can be challenging because of fluorescence and thermal radiation. These limitations severely hinder the ability to track small changes to the chemical composition in reacting environments, such as during the thermal stressing of hydrocarbon fuels. To aid in these measurements, a fiber-coupled, in-line, Raman flow cell was developed that is capable of withstanding 300 °C (572 °F) and 3.5 MPa (510 psi) without active cooling. The flow cell was used to collect high quality spectra of different fuels and model compounds from room temperature up to 300 °C, and the signal-to-noise (S/N) reduction at temperature was quantified. Chemometric multivariate calibration models were created that were able to remove the fluorescence background from the samples. The system was used to examine thermal degradation in multi-component fuel mixtures over a 24 hour period and quantify deposition of degradation products on the vessel walls. Flow cell development, measurement techniques, model development, and application cases will be presented.