Decomposition Mechanism of Environmentally Friendly HFO-1234ze (E)/CO2 Mixed Gas at Different Temperatures

Due to the greenhouse effect of SF6 gas, new environmentally friendly substitute gases represented by C4F7N, C5F10O, C6F12O, and HFO-1234ze(E) have received widespread attention. However, there is still a lack of research on the decomposition mechanism of these gas molecules when the internal temperature of the equipment increases due to local overheating or discharge conditions. To further investigate the feasibility of using new environmentally friendly gases to replace SF6 gas, more researches are needed. This article takes HFO-1234ze(E) molecules as an example and uses the ReaxFF reactive molecular dynamics method and density functional theory to simulate and study the decomposition of HFO-1234ze(E) molecules and 20%HFO-1234ze(E)/80%CO2 mixture gases at different temperatures from a microscopic perspective. The results show that HFO-1234ze(E) molecules have seven different decomposition pathways, and the C= O bond in CO2 decomposes first. The C—F and C= C bonds in HFO-1234ze(E) have higher enthalpy values, making them difficult to break. As the temperature increases, the time of decomposi- tion occurs earlier. When the temperature is below 2 000 K, HFO-1234ze(E)/CO2 mixture gas will hardly decompose. However, when the temperature reaches 2 000 K, HFO-1234ze(E) molecule remains stable, while CO2 molecule rapidly decomposes. At temperatures above 2 600 K, for every 2 000 K increase in temperature, about 5 more HFO-1234ze(E) molecules decompose, and about 35 more CO2 molecules decompose, until complete decomposition is reached. The mixture gas mainly decomposes into various free radicals such as CO, O2, C2O2, HF, CF4, C2F6, C3F6, and C3H3F3, among which CO is a toxic gas and HF molecules are strongly corrosive. Measures should be taken to monitor their content. The chemical properties of other decomposition products are relatively stable and environmentally friendly, and still have a certain insulating capacity. This indicates that the mixture of 20%HFO-1234ze(E) and 80%CO2 can completely replace SF6 gas to a certain extent, providing a theoretical basis and engineering guidance for further research on other new environmentally friendly mixed gases. © 2023 Editorial Department of Journal of Sichuan University. All rights reserved.