Decomposition of 1,1,1-trichloroethane in hot compressed water in anti-corrosive fused silica capillary reactor and Raman spectroscopic measurement of CO2 product

Decomposition of 1,1,1-trichloroethane (TCA) in hot compressed water, with or without an oxidizer, was studied using an optically transparent anti-corrosive fused silica capillary reactor (FSCR), and Raman spectroscopy. The phase behavior of TCA in water during hydrolysis/oxidation was observed continuously under a microscope and recorded with a digital-camera/recording system, A new phase behavior of TCA was found in the presence of excess H2O2; TCA was first gasified during heating, followed by liquefaction under increasing internal pressure as a result of the formation of O2 from the decomposition of H2O2, and subsequently gasified again during further heating up to 400 °C. The gaseous products of TCA oxidation in hot compressed water were monitored quantitatively and qualitatively using Raman spectroscopy. The effects of the operating parameters, namely the stoichiometric amount of oxidizer, temperature, and reaction time, were investigated. In our experiments, it was found that 100% CO2 yield was achieved with a 175% stoichiometric amount of H2O2 at 420 °C after 360 s. Temperature plays a key role in the decomposition of TCA and the formation of CO2 in the supercritical water oxidation (SCWO) process. Based on our results, a reaction mechanism for TCA decomposition in hot compressed water was proposed. The global reaction kinetics showed that the formation of CO2 in the SCWO of TCA was a first-order reaction.

Graphical abstractPhase changes of decomposition of 1,1,1-Trichloroethane in hot compressed water in FSCR, (a) deionized water and (b) excess H2O2 and (c) insufficient H2O2.Figure optionsDownload full-size imageDownload high-quality image (317 K)Download as PowerPoint slideHighlights► Using optical anti-corrosive capillary reactors in combination with microscope. ► Phase changes were observation and recorded. ► FSCR-based method is low in energy and materials consumptions, safe and efficient. ► The decomposition of TCA in hot compressed water in FSCR is uncatalyzed. ► Qualitative and quantitative analyses of the gaseous phase products CO2 by Raman.