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Are there any chemical absorbants for selective N2 removal from a gaseous mixture ?

I am thinking of something similar to say Pyrogalkol for O2 removal or KOH for CO2 etc.

Of course, N2 being relatively inert I can imagine this would be rather hard but still.

The particular application requires removal of small amounts of N2 ( say less than 1% ) from a gas stream that is mostly Helium.

Alternatively an adsorbent bed is also an option. But do we have adsorbants that would selectively trap N2 but not He?

Otherwise a cryogenic condensor seems the only option? Any other ideas?

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    $\begingroup$ There is probably possible to have a molecular sieve, based on molecule geometry, similarly as is used for oxygen (as alternative to cryoseparation). (Big molecules do not fit, small ones do not stay). $\endgroup$
    – Poutnik
    Jan 13 at 9:34
  • $\begingroup$ @Poutnik Anyone know if such a Molecular sieve or zeolite is commercially available? I could not find any. $\endgroup$ Jan 13 at 9:47
  • $\begingroup$ Why do you want to remove 1% $\ce{N2}$ from helium? $\endgroup$
    – Maurice
    Jan 13 at 9:50
  • $\begingroup$ My Google is not better than yours, sorry. $\endgroup$
    – Poutnik
    Jan 13 at 9:50
  • $\begingroup$ Why not to use helium of guaranteed sufficient purity? // I assume using metallic lithium to form Li3N is not applicable. $\endgroup$
    – Poutnik
    Jan 13 at 9:57

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There are various techniques to trap $\ce{N2}$ by adsorption in a molecular sieve, or behind a semi-permeable membrane, rather than chemically combining it.

Though one could do as Cavendish, Rayleigh and Ramsay did, reacting the nitrogen with added oxygen in an electrical arc and absorbing the reaction products, or use a metal getter, as used in radio tubes (valves, if you prefer), those would be inefficient and costly.

look at this ACS article that discusses the economics of helium purification.

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