NOVELTY - Separation of impurities from feed gas stream comprises first stage by contacting a feed gas stream with a first sorbent to remove first impurities, where a first effluent stream with lesser impurities relative to the feed gas stream is generated; and second stage by contacting the first effluent with a second sorbent to remove second impurities, where a second effluent stream with lesser impurities relative to the first effluent is generated.    USE - Method for separation of impurities from feed gas stream (claimed) for use as treated gas useful in hydrogen production device, solid oxide fuel cell, proton exchange membrane fuel cell, and for use in refinery and manufacturing plant for production of electricity, value added chemicals, transportation fuels, gases, fertilizers, and liquid hydrocarbons.    ADVANTAGE - The two stage separation process enables selective removal of a specific impurity during each stage.    DETAILED DESCRIPTION - Separation of impurities from feed gas stream comprises:    (A) first stage by contacting a feed gas stream with a first sorbent to remove first impurities, where a first effluent stream with lesser impurities relative to the feed gas stream is generated; and    (B) second stage by contacting the first effluent with a second sorbent to remove second impurities, where a second effluent stream with lesser impurities relative to the first effluent is generated.    The sorbent is kept at 10-130 degrees C while the feed gas stream is at a gaseous hourly space velocity (GHSV) flow rate of 200-200000/hour in the first stage. The sorbent is kept at - 10-80 degrees C while the first effluent is at a GHSV flow rate of 200-200000/hour in the second stage. The impurities include hydrogen sulfide (H2S), carbonyl sulfide, carbon dioxide (CO2), nitrogen dioxide, nitric oxide, nitrous oxide, sulfur dioxide, sulfur trioxide, hydrochloric acid, hydrogen fluoride, hydrogen cyanide, ammonia, water, ethanol, methanol, formaldehyde, chloroform, dichloromethane, methyl chloride, carbon disulfide, thiophen, methyl mercaptan, and/or dimethyl sulfide. The feed gas stream comprises natural gas, coal/biomass gas, biogas, landfill gas, coal mine gas, ammonia syngas, hydrogen gas and oxo-syngas, iron ore reduction gas, reformate gas, refinery gas, indoor air, anode fuel gas, and/or cathode air. An INDEPENDENT CLAIM is included for a sorbent comprising:    (A) first component (for sorbing impurities) including polyethylenimine (PEI), polyethyleneglycolamine, polyethanolamine, polyisopropanolamine, polyalkylene glycol dimethyl ether, polyethylene glycol (PEG), n-methyl pyrrolidinone, n-formylmorpholine, N-acetylmorpholine, propylene carbonate, and/or sulfolane; and    (B) a second component (for supporting first component) comprising porous material including aluminosilicate, activated carbon, carbon sieve, silica gel, fumed silica, and/or silica.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of an apparatus for two stage separation of impurities from feed gas stream.