Sorbent enhanced steam reforming (SESR) of methane using dolomite as internal carbon dioxide absorbent: Limitations due to Ca(OH)2 formation

High hydrogen yields can be obtained by sorbent enhanced steam reforming (SESR) of methane at temperatures below 600 °C by using calcined dolomite as internal sorbent together with a Ni/NiAl2O4 catalyst in a fluidized bed reactor. Effluent gas compositions containing >90 mole.% H2 are obtained, indicating that the sorbent acts efficiently after an induction period with low methane conversion. XRD examination of the catalyst/sorbent powder after different times-on-stream shows that during the induction period, CaO of the calcined dolomite reacts with water vapor to form Ca(OH)2. The induction period is directly proportional to the time the catalyst/sorbent mixture is in contact with steam at temperatures below 600 °C where Ca(OH)2 is thermodynamically stable. The catalyst/sorbent mixture can be regenerated at temperatures above 800 °C in H2/N2/H2O atmosphere.