Experimental and Theoretical Study on the Thermal Decomposition of HFO-1234yf/HFO-1216 Mixtures

As potential alternatives to HFC-134a, the hydrofluoroolefin (HFO) mixture, HFO-1234yf/HFO-1216, offers a low global warming potential (GWP) and reduced or nonflammability. This makes it suitable for use in heat pumps and organic Rankine cycle (ORC) systems. Thermal stability is a critical criterion for screening working fluids in heat pumps and ORC systems. This study investigates the thermal stability of HFO-1234yf/HFO-1216 through a combination of experimental and theoretical approaches. Experimental results indicate that HFO-1234yf/HFO-1216 undergoes decomposition within the temperature range of 170 to 210 °C. The amount of these pyrolysis products was found to increase with rising temperature. At 210 °C, the primary pyrolysis products identified were HF, CHF₃, C₂F₄, C₃HF₅, and C₆F₁₂. Furthermore, the formation mechanisms and pathways of these pyrolysis products have been investigated by using density functional theory (DFT) and ReaxFF reactive molecular dynamics simulations. Among the reactive intermediates, the CF₃ radical was identified as the predominant species readily generated upon thermal activation of both HFO-1234yf and HFO-1216.