Journal of the Taiwan Institute of Chemical Engineers ( IF 5.7 ) Pub Date : 2021-12-30 , DOI: 10.1016/j.jtice.2021.104178 Alexander Cholach 1 , Dmitri Yakovin 2
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 (TCry), 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 TCry 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 TCry = 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.
中文翻译:
在相界面从 NF3 中去除 CF4
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。