Raman Spectra of C1-C3 Primary Alcohol Gasification Products in Supercritical Water
Description
Methanol, ethanol, and isopropyl alcohol are gasified in a continuous supercritical water reactor at temperatures from 500 to 560 °C, residence times between 3 and 8 s, a constant pressure of 25 MPa, and a constant initial concentration of 10 vol%. Raman spectra of the reaction products in the reactor effluent stream are collected for each experimental condition and for each alcohol. Product spectra include hydrogen, carbon monoxide, carbon dioxide, formaldehyde, methane, ethylene, ethane, acetaldehyde, acetone, acetic acid, propene, and propane. All spectra are collected at 25 MPa and 20 °C. Spectra are collected using a Raman flowcell from MarqMetrix (Seattle, WA), containing a high-resolution fiber-optic Raman laser, and an optical cell with a sapphire ball lens, which focuses the Raman laser into the effluent stream and collects Raman spectra along the same axis in the backscatter configuration. The Raman laser has an excitation wavelength of 785 nm, and is operated at 300 mW. For each experimental condition, five replicate spectra are collected and averaged, each with a 20 s integration time. This was to minimize measurement noise. The "dark" signal was subtracted automatically with the MarqMetrix data collection software, and the fluorescent background signal was subtracted using a semi-manual MATLAB routine. Spectra were normalized to the height of the prominent sapphire peak.