Pressure swing adsorption process for fractionating a multi-component mixture

A pressure swing adsorption process for fractionating a multi-component mixture, said process comprising:

• subjecting first and second adsorbent beds in a paired relationship to a continuous cycle having sequential feed, co-current depressurization, evacuation, and countercurrent repressurization stages;
• said first and second adsorbent beds having opposed entry and discharge sections through which said multi-component mixture passes into and is discharged from said first and second adsorbent beds, said first adsorbent beds containing a first adsorbent selected to preferentially adsorb a primary component of said multi-component mixture and said second adsorbent beds containing said first adsorbent in said entry sections thereof and a second adsorbent, selected to preferentially adsorb a secondary component of said multi-component mixture, said second adsorbent located downstream from said entry sections;
• said feed stage being conducted by feeding said first and second adsorbent beds with said multi-component mixture so that said primary component adsorbs within said first adsorbent and said secondary component adsorbs within said second adsorbent and to a lesser extent adsorbs within said first adsorbent to produce a waste stream discharged from said discharge sections of said second adsorbent beds;
• said co-current depressurization stages being conducted by depressurizing said first adsorbent beds through said second adsorbent beds to drive said secondary component from said first adsorbent contained within said first adsorbent beds to said second adsorbent beds and also, thereby driving part of the primary component adsorbed within said first adsorbent of said first adsorbent bed to said first adsorbent contained within said entry sections of said second adsorbent beds;
• said evacuation stages being conducted by evacuating each of said first and second adsorbent beds to produce a primary product stream enriched in said primary component and a secondary product stream enriched in said secondary component, respectively;
• and
• said countercurrent repressurization stages being conducted by countercurrently repressurizing said first and second adsorbent beds with said waste stream so that said first and second adsorbent beds repressurize, a concentration of primary and secondary components contained within said waste stream adsorb in said second and first adsorbents, and said primary component contained within said first adsorbent of said entry sections of said second adsorbent beds is driven back to said first adsorbent contained within said first adsorbent beds.