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 degrees 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.% H-2 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 degrees C where Ca(OH)(2) is thermodynamically stable. The catalyst/sorbent mixture can be regenerated at temperatures above 800 degrees C in H-2/N-2/H2O atmosphere. (c) 2006 Elsevier B.V. All rights reserved.