Background The close boiling points of carbon tetrafluoride (CF₄) and nitrogen trifluoride (NF₃) and the chemical inertness of CF₄ make it difficult to remove it from NF₃.

Methods A method for cleaning NF₃ from CF₄ at the gas-liquid interface is proposed. The purification is carried out by a sequence of cycles: (1) fractional condensation of NF₃ at a cryostat temperature (T_Cry)_, at which the equilibrium pressure of CF₄ exceeds its partial pressure in the feed mixture; and (2) pumping out the gas phase enriched with CF₄ and high-boiling impurities. The cycles are repeated at a next T_Cry corresponding to the new CF₄ content, and are completed by cryogenic distillation of the condensate with the removal of low-boiling impurities.

Findings The CF₄ content of 5000 ppm in a 25 g NF₃ sample was reduced to less than 100 ppm in three cycles at T_Cry = 120 K; a CF₄ separation coefficient above 40 was achieved. The method can be used for the industrial production of high-purity NF₃, with the cryostat refrigerant being the only consumable material, as well as for the separation of other substances with close boiling points, such as isomers or isotopes.

背景的沸点接近四氟化碳的点（CF ₄）和三氟化氮（NF ₃）和CF的化学惰性₄使得难以将其从NF删除₃。

方法提出了一种在气液界面从CF ₄中清洗NF _{3 的}方法。纯化是通过循环的序列进行：（1）NF的分级冷凝₃在低温恒温器温度（Ť_惊魂）_，在该CF的平衡压力₄超过了在进料混合物中的分压; (2)抽出富含CF ₄和高沸点杂质的气相。在对应于新的 CF ₄含量的下一个T _Cry重复循环，并通过冷凝物的低温蒸馏并去除低沸点杂质来完成。

结果在T _Cry  = 120 K 的三个循环中，25 g NF ₃样品中 5000 ppm的 CF ₄含量降低到低于 100 ppm ；实现了高于 40的 CF ₄分离系数。该方法可用于高纯NF ₃的工业生产，低温制冷剂是唯一的消耗材料，也可用于分离其他沸点相近的物质，如异构体或同位素。