Resource utilization of waste HFC-134a refrigerant by supercritical gasification method: A reactive molecular dynamic study

Effective treatment of HFCs (hydrofluorocarbons) waste refrigerants is of great significance for reducing greenhouse gas emissions. In this study, the supercritical water gasification method was applied to the treatment of waste HFCs refrigerants in order to realize the harmless treatment and resource utilization at the same time. Taking widely used HFC-134a (1,1,1,2-Tetrafluoroethane, CF3CFH2) refrigerant as the research object, the gasification mechanism of HFC-134a in supercritical water was studied by the ReaxFF-MD, and the effect of temperature, reactant concentration and pressure on gasification was studied. The results show that the main products of HFC-134a gasification in supercritical water are HF, H-2, CO and CO2. HF is mainly generated by the hydrogen extraction reaction between F radicals and H2O molecules, and the energy barrier is only 31.3 kJ.mol(-1). H-2 is mainly generated by the hydrogen extraction reaction between H radicals and H2O molecules and H atom-containing molecules or radicals. When the F, H radicals and H2O undergo hydrogen extraction reaction, a large number of OH radicals are generated, and the carbon-containing radicals combine with OH radicals to undergo a reforming reaction. After further removal of H and F atoms, CO and CO2 are ultimately generated. Parametric analyses show that higher reaction temperature can speed up the reaction rate and improve the yields of CO and H-2; Lower reactant concentrations help to increase the yields of CO2 and H-2 and have little effect on the yields of HF and CO; Higher pressure boosts the reaction rate to increase CO2 and CH4 yields but decrease the yields of HF, CO and H-2.

Automated summary

The supercritical water gasification method was used to treat waste HFCs refrigerants, and the main products were found to be HF, H2, CO, and CO2. Higher reaction temperature accelerated the reaction rate, lower reactant concentrations increased the yields of CO2 and H2, and higher pressure had various effects on the yields of different products.