Raman spectroscopic study of cracking and hydrolysis of propane in fused silica capillary capsules between 300 and 400 °C

Isothermal experiments on C 3 H 8 , with or without water, in fused silica capillary capsules were conducted at temperatures (Ts) between 300 and 400 °C for durations up to 322 hours. Reaction progresses were evaluated with Raman spectroscopy at room T before and after heating. After an initial experiment, some samples were reheated to the same T for total durations up to 821 hours. Consumption of water was monitored by calculating the changes in relative volumes of the vapor, aqueous, and C 3 H 8 liquid phases from the lengths of the phases in the capillary. Reactions of C 3 H 8 without water produced a small amount of CH 4 , reaching a steady state after about 100 hours of heating at T < 360 °C. Reactions with water appear to be largely hydrolysis, generating a CH 4 ‐rich vapor phase and methanol and ethanol in the aqueous phase. At fixed T, Raman spectra showed that concentrations of alcohols increased steadily with time as water was consumed. Our observations show that, without iron‐bearing mineral buffers, the reactions between propane and water are relatively limited, forming alcohols without further oxidation to propanoic or ethanoic acid and/or CO 2 . This observation suggests that during deep burial, hydrocarbon gases may be more stable in iron‐poor reservoirs like quartz arenites or carbonate grainstones than in mudstones or arkoses that are rich in redox‐reactive iron‐bearing siliciclastic and diagenetic minerals. Copyright © 2017 John Wiley & Sons, Ltd.