Unraveling the cooperative effects of acid sites and kinetics for pyrolysis of CHF₃ to C₂F₄ and C₃F₆ on SO₄²⁻/ZrO₂‐SiO₂

Abstract

The treatment or upgrading of waste trifluoromethane (CHF3, R23), which has a significant greenhouse effect, is of great importance in industry. Herein, series of SO42−/ZrO2‐SiO2 catalysts with different Brønsted and Lewis acid site densities and ratios were prepared for pyrolysis of R23 to tetrafluoroethylene (C2F4, TFE) and hexafluoropropylene (C3F6, HFP). The effects of impregnation concentration of (NH4)2SO4 on specific surface area, crystal phase, and Brønsted and Lewis acid site densities and ratios were respectively demonstrated. The Brønsted and Lewis acid sites were observed to have cooperative effects on R23 transformation and up to 94.6% selectivity of (TFE + HFP) could be achieved at 750°C. The kinetic studies revealed the decomposition of R23 into CF2 carbene and HF was the rate‐determining step, and a deactivation behavior was found due to the site coverage and pore blockage by the oligomers of TFE and HFP.