System and method for pre-purification of a feed gas stream

A pre-purification unit configured for use with an air-separation unit, the pre-purification unit comprising:

• a pre-purification vessel having an inlet configured to receive a stream of feed air and an outlet configured to release a purified stream;
• one or more initial adsorbent layers configured to receive the stream of feed air and produce a dry feed air stream;
• a first hopcalite catalyst layer disposed downstream of the one or more initial adsorbent layers configured to remove carbon monoxide from the dry air stream and produce a first intermediate effluent that has a carbon monoxide concentration that is less than or equal to 10% of the carbon monoxide concentration in the stream of feed air, and wherein the first hopcalite catalyst layer includes a first hopcalite material that comprises a mixture of copper oxide and manganese oxide;
• an intermediate adsorbent layer disposed downstream of the first hopcalite catalyst layer, the adsorbent layer configured to remove at least carbon dioxide from the first intermediate effluent and produce a second intermediate effluent that has a carbon dioxide concentration less than or equal to 10 ppm;
• a second hopcalite catalyst layer disposed downstream of the intermediate adsorbent layer, the second hopcalite catalyst layer configured to remove hydrogen from the second intermediate effluent and yield an intermediate purified stream that has a hydrogen concentration that is less than or equal to 500 ppb or less than 20% of the hydrogen concentration in the stream of feed air, whichever concentration is lower, and a carbon monoxide concentration that is less than or equal to 50 ppb or less than 10% of the carbon monoxide concentration in the stream of feed air, whichever concentration is lower, and wherein the second hopcalite catalyst layer includes a second hopcalite material that comprises a mixture of copper oxide and manganese oxide;
• a final adsorbent layer disposed downstream of the second hopcalite catalyst layer configured to remove at least carbon dioxide from the intermediate purified stream and produce a purified stream that has less than or equal to 10 ppm of water and less than or equal to 10 ppm of carbon dioxide;
• and
• wherein a volume of the first hopcalite material in the first hopcalite catalyst layer is different than a volume of the second hopcalite material in the second hopcalite catalyst layer.