Reverting fluoroform back to chlorodifluoromethane and dichlorofluoromethane: Intermolecular Cl/F exchange with chloroform at moderate temperatures
Trifluoromethane is one of the most potent and stable greenhouse gases with global warming potential of 14,800 times higher than CO 2 (100-year time horizon). At present, it is destroyed by incineration or plasma at temperatures above 1200 K. For the first time, this work report that CHF 3 can be reverted to HCFC-22 via the intermolecular Cl/F exchange reaction of CHF 3 with CHCl 3 over AlF 3 catalyst under moderate conditions. As CHF 3 is produced during the manufacture of HCFC-22 via the fluorination of CHCl 3 in liquid phase, no additional feedstock and products are involved for the treatment of CHF 3 in this proposed process. At 593 K and atmospheric pressure, CHF 3 conversion levels of about 18%–20% are achieved and no significant deactivation is observed following time on stream of 100 h. In addition, the catalytic reaction mechanism is proposed. According to the experiments and DFT calculation, the intermolecular Cl/F exchange reaction of CHF 3 with CHCl 3 is mainly initiated by the breakage of C Cl. The present work provides a potential resource utilization route for the treatment of CHF 3 and other hydrofluorocarbons (HFCs).
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