Development of Al-stabilized CaO–nickel hybrid sorbent–catalyst for sorption-enhanced steam methane reforming

• Al–stabilized CaO–nickel hybrid sorbent–catalyst prepared by limestone acidification.
• The hybrid sorbent–catalyst with 25 wt% NiO provided the best results.
• CH4 conversion of 99.1% in cyclic SESMR operation (10 cycles).
• H2 production efficiency of 96.1% (10 cycles) and 97.3% (30 cycles).

In this work, Al-stabilized CaO–Ni hybrid sorbent–catalysts integrated in a single particle with various nickel loadings (12, 18 and 25 wt% NiO) were developed and tested in cyclic hydrogen production by sorption-enhanced steam methane reforming (SESMR) process. A simple wet-mixing technique based on limestone acidification and two-step calcination was employed to produce hybrid materials with different nickel loadings. All developed materials were characterized by BET, XRD, SEM and TEM and studied during 25 CO2 sorption/regeneration cycles as well as for 10 SESMR cycles. Based on both CO2 sorption and SESMR results, it was concluded that the proposed hybrid sorbent–catalyst with NiO loading of 25 wt% led to the best performances: (i) CaO molar conversion is 41.2% at the end of the 25th sorption cycle and (ii) average CH4 conversion and H2 production efficiency during 10 SESMR cycles are remarkable (99.1% and 96.1%, respectively). For the most efficient hybrid sorbent–catalyst (25 wt% NiO), the influence of CH4 flow rate and steam to carbon ratio (S/C) was also investigated, as well as its behavior during long-term cyclic operation of SESMR (30 cycles), where the H2 production time was just limited to pre-breakthrough period. The very efficient performance (average of H2 yield 97.3%) of the proposed hybrid sorbent–catalyst material in long-term operation confirmed its high potential for use in SESMR process.