Global emissions of perfluorocyclobutane (PFC-318, c-C4F8) resulting from the use of hydrochlorofluorocarbon-22 (HCFC-22) feedstock to produce polytetrafluoroethylene (PTFE) and related fluorochemicals Atmospheric Chemistry and Physics

Emissions of the potent greenhouse gas perfluorocyclobutane (c-C4F8, PFC-318, octafluorocyclobutane) into the global atmosphere inferred from atmospheric measurements have been increasing sharply since the early 2000s. We find that these inferred emissions are highly correlated with the production of hydrochlorofluorocarbon-22 (HCFC-22, CHClF2) for feedstock (FS) uses, because almost all HCFC-22 FS is pyrolyzed to produce (poly)tetrafluoroethylene ((P)TFE) and hexafluoropropylene (HFP), a process in which c-C4F8 is a known by-product, causing a significant fraction of global c-C4F8 emissions. We find a global emission factor of ∼0.003 kg c-C4F8 per kilogram of HCFC-22 FS pyrolyzed. Mitigation of these c-C4F8 emissions, e.g., through process optimization, abatement, or different manufacturing processes, such as refined methods of electrochemical fluorination and waste recycling, could reduce the climate impact of this industry. While it has been shown that c-C4F8 emissions from developing countries dominate global emissions, more atmospheric measurements and/or detailed process statistics are needed to quantify c-C4F8 emissions at country to facility levels.

自21世纪初以来，基于大气观测数据推断得到的强效温室气体全氟环丁烷（perfluorocyclobutane，c-C4F8，PFC-318，八氟环丁烷）全球大气排放量呈急剧上升趋势。研究发现，此类推断排放量与作为原料（feedstock，FS）使用的氢氯氟烃-22（hydrochlorofluorocarbon-22，HCFC-22，CHClF2）的生产活动高度相关——几乎所有用作原料的HCFC-22都会通过热解工艺生成（聚）四氟乙烯（(poly)tetrafluoroethylene，(P)TFE）与六氟丙烯（hexafluoropropylene，HFP），而全氟环丁烷正是该过程的已知副产物，全球全氟环丁烷排放量中有相当大的比例源自此类生产活动。经测算，每热解1千克用作原料的HCFC-22，对应的全球平均全氟环丁烷排放因子约为0.003千克。通过工艺优化、污染消减，或采用电化学氟化精制工艺、废弃物回收等替代制造流程等方式减排此类全氟环丁烷排放，可降低该行业的气候影响。尽管已有研究表明，发展中国家的全氟环丁烷排放量占全球总量的主导份额，但仍需更多大气观测数据与/或精细化的工艺统计数据，才能实现从国家到设施层面的全氟环丁烷排放量化。