HFO-1123, disproportionation reaction, suppression materials
In the field of refrigeration and air conditioning, the transition from using chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) refrigerants to using hydrofluorocarbon (HFC) refrigerants is in progress, driven by the need to prevent the depletion of the stratospheric ozone layer. Although HFC refrigerants are useful from the viewpoint of ozone layer protection, their high global warming potential (GWP) is a serious concern. Following the passing of the Kigali Amendment to the Montreal Protocol, UN member nations are now required to switch to low-GWP refrigerants, such as hydrofluoro-olefins (HFO), and natural refrigerants. HFO-1123 is a substance with a very low GWP and it is expected to become a new refrigerant in refrigeration and air-conditioning equipment. However, it is known that HFO-1123 may undergo a disproportionation reaction under high-temperature and high-pressure conditions. This reaction is a self-decomposition reaction accompanied by severe pressure and temperature rises. Therefore, in order to put HFO-1123 into practical use, it is first necessary to develop technology to suppress the disproportionation reaction. The conditions that lead to a disproportionation reaction of HFO-1123 are influenced by the temperature and pressure of the reaction gas as well as by the initiating energy. It is also known that the disproportionation reaction of HFO-1123 can be suppressed by mixing other substances into the refrigerant. In this study, we investigate the effects of mixed substances of varying constituents and concentrations on the suppression of disproportionation reactions at various temperatures and pressures. Using a metallic pressure vessel having a volume of 0.65 L, energy is inputted into pure HFO-1123 by melting molybdenum thin wire with electricity as well as into a mixture containing HFO-1123 and other substances under various temperature and pressure conditions. The changes in pressure and temperature are then measured. Based on the obtained experimental data, the effects of the mixed substances on the reaction are evaluated. Then, a model to estimate the chance of disproportionation reactions of HFO-1123 is proposed. The validity of the model is examined using the experimental results.