Page 318 - Adsorbents fundamentals and applications
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HYDROGEN PURIFICATION  303

                        100
                                                  Co(fluomine)
                         90                       Co(fluomine)-X (p)
                       O 2 -binding capacity (% of original)  60  Co(fluomine)-MCM-41
                         80
                                                  Co(fluomine)-X (np)
                         70



                         50
                         40
                         30
                         20
                         10
                          0
                            0     100   200    300   400    500    600
                                          Number of cycles
            Figure 10.20. Stability curves for various O 2 -binding materials after oxygenation and deoxy-
            genation cycling. The materials were each cycled for 15 min in 1 atmosphere O 2 and in Ar at
              ◦
            60 C (to accelerate the decay). The materials are Co(fluomine), Co(fluomine)-LSX synthesized
            with the use of piperidine (p), Co(fluomine)-LSX synthesized without the use of piperidine (np),
            and Co(fluomine)-MCM-41 (Hutson and Yang, 2000b, with permission).

            5A zeolite and YBa 2 Cu 3 O 7-x ,O 2 desorbed when the magnetic field was turned
            on, and adsorbed when it was turned off.


            10.2. HYDROGEN PURIFICATION

            Hydrogen purification is a necessary step in the production of hydrogen, which at
            present is done by catalytic steam reforming of natural gas, naphtha, or refinery
            gases. When hydrogen is the only desired product, the effluent from the steam
            reformer is processed further through a water–gas shift reactor to maximize the
            hydrogen content. Hydrogen purification is also performed to recover hydrogen
            from diverse petroleum-refinery and petrochemical streams, from coke ovens, and
            chemical plants such as ethylene plant effluent gas and ammonia plant purge gas.
            The typical hydrogen concentrations in these mixtures range from 50 to 99%. The
            remainder contains: N 2 ,CO, CH 4 ,CO 2 , water, Ar, C 2 and higher hydrocarbons,
            sulfur containing compounds, and ammonia. The available pressures are 10 to
            60 atm, which are well-suited for PSA processing. The required product purity
            is generally in the range of 99.99%–99.9999+%.
              Hydrogen purification was the first large-scale application of PSA technology.
            The first commercial PSA hydrogen purification unit was installed in conjunction
            with a steam reformer, in Toronto around 1966. The standard five-step PSA
            cycle (with a co-current depressurization step) is used. Three or more pressure
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