Selective removal of nitrogen from natural gas by pressure swing adsorption

A process for the separation of nitrogen and hydrocarbons from a natural gas stream, which comprises:

• passing said natural gas stream to a first pressure swing adsorption unit containing a hydrocarbon-selective sorbent so as to preferentially adsorb at least C4+ hydrocarbons to produce a first product stream comprising methane, nitrogen and a reduced level of said hydrocarbons relative to said natural gas stream;
• and
• passing said first product stream to a second pressure swing absorption unit containing a nitrogen-selective sorbent so as to preferentially adsorb nitrogen and produce a second product stream enriched with methane and a low pressure purge stream having a higher molar concentration of nitrogen than said first product stream.

A pressure swing absorption (PSA) process for the separation of nitrogen from a mixture of the same with methane which comprises:

• (a) passing a feed stream comprising said mixture in contact with a nitrogen-selective sorbent in a PSA unit so as to preferentially adsorb nitrogen and produce a methane-rich product stream containing at least 70 mol. % methane and a low pressure purge stream having a higher molar concentration of nitrogen than said mixture;
• and
• (b) co-currently depressurizing said PSA unit to form a recycle stream rich in methane, said recycle stream having a pressure less than said methane-rich product stream, but greater than said purge stream, recycling said recycle stream to said feed stream.