FTIR studies of high-pressure formic acid reactions: Extreme chemistry decomposition kinetics

GEOC 181

Joseph M. Zaug1, Wren B. Montgomery2, Alexander F. Goncharov1, Jonathan C. Crowhurst1, W. Michael Howard1, Laurence E. Fried1, and Carl F. Meliuss1. (1) Chemistry and Material Science, University of CA at LLNL, 7000 E. Ave, L-282, Livermore, CA 94550, (2) Earth and Planetary Sciences, University of California at Berkeley, 307 McCone Hall, Berkeley, CA 94720
Using near-simultaneous FTIR and Raman spectroscopy including high-resolution optical video, we have investigated the structure and decomposition of formic acid (HCOOH) confined at high pressures and temperatures. We present a phase diagram, including melting curve and solid-state phase transitions, over a temperature range from 300-550 K and a pressure range from 0.1 to 50 GPa. We propose a detailed kinetic model to follow the decomposition of formic acid at modestly high pressures (1-10 GPa) and temperature (500-1000K) and further include our refinement of a fluid exponential-6 equation of state for formic acid and corresponding reaction species. We discuss, in detail, the implications our experimental observations provide in relation to computed reaction timescales and dominant species generated in our model.

*This work was performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.