Method of refining nitrogen trifluoride gas
AssigneeCentral Glass Company, Limited
InventorsTakashi Suenaga, Tukasa Fujii, Kobayashi, Yoshiyuki
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Abstract
The invention provides a selective adsorption method for refining NF.sub.3 gas containing CF.sub.4 as impurity. At a temperature not higher than 10.degree. C. the NF.sub.3 gas is brought into contact with a crystalline and porous synthetic zeolite, which is substantially uniform in pore size and about 4.9 .ANG. in effective pore size and is commerciallized under the name of molecular sieve 5A, on condition that the content of water of crystallinity in the synthetic zeolite is 1-10 wt. %, and preferably 6-10 wt. %. The synthetic zeolite efficiently adsorbs NF.sub.3 with little adsorption of CF.sub.4.
Claims7
A method of refining a nitrogen trifluoride gas containing CF.sub.4 as impurity, the method comprising the steps of:
- (a) bringing said nitrogen trifluoride gas into contact with a crystalline and porous synthetic zeolite, which is substantially uniform in pore size and about 4.9 .ANG. in effective pore size, on condition that the content of water of crystallinity in said synthetic zeolite is in the range from 4 to 10 wt% and that said synthetic zeolite is maintained at a temperature not higher than 10.degree. C. to thereby allow said synthetic zeolite to selectively adsorb NF.sub.3 gas;
- (b) after step (a) shielding said synthetic zeolite from any gas which contains CF.sub.4 ;
- and
- (c) after step (b) causing said synthetic zeolite to desorb refined NF.sub.3 gas and collecting the desorbed refined NF.sub.3 gas.
Dependencies are inferred from the claim text.