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Kinetics of Formic Acid Decomposition.pdf (1.2 MB)
Kinetics of Formic Acid Decomposition in Subcritical and Supercritical Water - A Raman Spectroscopic Study
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submitted on 05.02.2019 and posted on 06.02.2019by Brian Pinkard, David Gorman, Elizabeth Rasmussen, John Kramlich, Per G. Reinhall, Igor V. Novosselov
The decomposition of formic acid is studied in a
continuous sub- or supercritical water reactor at temperatures between 300 and
430°C, a pressure of 25 MPa, residence times between 4 and 65 s, and a
feedstock concentration of 3.6 wt%. In-situ
Raman spectroscopy is used to produce real-time data and accurately
quantify decomposition product yields of H2, CO2, and CO.
Collected spectra are used to determine global decomposition rates and kinetic
rates for individual reaction pathways. First-order global Arrhenius parameters
are determined as log A (s-1)
= 1.6 ± 0.20 and EA = 9.5
± 0.55 kcal/mol for subcritical decomposition, and log A (s-1) = 12.56 ± 1.96 and EA = 41.90 ± 6.08 kcal/mol for supercritical
decomposition. Subcritical and supercritical Arrhenius parameters for
individual pathways are proposed. The variance in rate parameters is likely due
to changing thermophysical properties of water across the critical point. There
is strong evidence for a surface catalyzed free-radical mechanism responsible
for rapid decomposition above the critical point, facilitated by low density at