PRODUCTION OF HIGH-PURITY NITROGEN TRIFLUORIDE GAS

PROBLEM TO BE SOLVED: To obtain a high-purity NF3 gas by using acidic ammonium fluoride prepared by reacting a HF gas having a specific purity with an NH3 gas as an electrolyte and carrying out molten electrolysis by using a high-purity Ni electrolyte. SOLUTION: A HF gas having >=99.8wt.% purity is reacted with an NH3 gas having >=99.5wt.% purity in the molar ratio of about 1.5-2.0 to prepare high-purity acidic ammonium fluoride. Then, the acidic ammonium as an electrolyte is poured to an electrolytic bath and is adjusted to about 110-140 deg.C liquid temperature. Then, as a carrier gas such as a N2 gas, etc., is introduced into an anode chamber partitioned by a diaphragm, an electric current having 5-10V voltage and about 1-15A/dm current density is sent from an anode of a Ni electrode having >=98.5wt.% purity to a cathode and molten salt electrolysis is carried out to generate a NF3 gas from the anode and a H2 gas from the cathode. Each gas is taken out by a conduit, the NF3 gas is washed with a chemical solution, passed through a zeolite adsorption column, cooled and liquefied and sent through a rectifying column to give the objective NF3 gas having >=4N purity.