Fluoroform (CHF<sub>3</sub>) Production from CF<sub>3</sub>CHO Photolysis and Implications for the Decomposition of Hydrofluoroolefins and Hydrochlorofluoroolefins in the Atmosphere
Joshua D. Thomson, Jyoti S. Campbell, Ethan B. Edwards, Christopher Medcraft, Klaas Nauta, María Paula Pérez-Peña, Jenny A. Fisher, David L. Osborn, Scott H. Kable, Christopher S. Hansen
Abstract
Hydrofluoroolefins (HFOs) and hydrochlorofluoroolefins (HCFOs) are the leading synthetic replacements for compounds successively banned by the Montreal Protocol and amendments. HFOs and HCFOs readily decompose in the atmosphere to form fluorinated carbonyls, including CF 3 CHO in yields of up to 100%, which are then photolyzed. A long-standing issue, critical for the transition to safe industrial gases, is whether atmospheric decomposition of CF 3 CHO yields any quantity of CHF 3 (HFC-23), which is one of the most environmentally hazardous greenhouse gases. This comprehensive experimental investigation employs purpose-built photoionization mass spectrometry, Fourier-transform infrared, and microwave spectroscopy techniques and confirms production of CHF 3 following excitation at a tropospherically relevant wavelength (λ = 308 nm) and under atmospheric pressure conditions. Pressure-dependent CHF 3 quantum (Φ) and molar ( Y ) yields are reported from Φ = Y = 0.16 ± 0.03 under collision-free conditions to Φ = (2.3 ± 0.3) × 10 –4, Y = (1.17 ± 0.27) × 10 –3 at 1 bar N 2 .