Thermal Decomposition and Oxidative Decomposition Mechanism of HFC-134a by Experimental and DFT Method

In response to the Kigali Amendment to the Montreal Protocol and global low-carbon emission environmental requirements,the phase-out and decomposition of numerous HFC refrigerants have become urgent,necessitating efficient and mild decomposition methods.This study investigates the thermal decomposition and oxidative thermal decomposition pathways of the typical hydrofluorocarbon refrigerant HFC-134a,employing a combination of experimental and quantum chemical DFT simulation methods.Quantum chemical simulations reveal that the initial reaction bond cleavage serves as the rate-determining step during the thermal decomposition process,with the most easily detectable closed-shell products including CF_(2)=CHF,HF,CH_(3)F,CHF_(3),CH_(2)F_(2),and CF_(4).Reactive oxygen species can significantly reduce the Gibbs free energy barrier for HFC-134a decomposition.To achieve efficient degradation of HFC-134a,appropriate catalysts should be developed and selected to increase the level of reactive oxygen species in the reaction system.Experimental studies further corroborate that HFC-134a may undergo degradation through distinct reaction pathways under varying temperature(240℃to360℃)and pressure(0.1 MPa to 4.5 MPa)conditions,in agreement with simulation predictions.