Sorption-enhanced steam methane reforming by in situ CO2 capture on a CaO–Ca9Al6O18 sorbent

Sorption-enhanced steam methane reforming (SESMR) that combines steam methane reforming (SMR) with simultaneous CO2 capture is a promising route for hydrogen production. In this paper, a Ni0.50/Mg2.50Al catalyst and a CaO–Ca9Al6O18 sorbent were prepared by a co-precipitation technique and by a wet mixing method, respectively, and applied to the SESMR process. The experiments conducted in both a thermogravimetric analyzer and a fixed bed reactor demonstrated excellent CO2 capture capacity and long-term stability of CaO–Ca9Al6O18, about 83% of its initial sorption capacity being retained after 50 consecutive carbonation/calcination cycles at 650 °C. The effects of operation conditions on the SESMR process were investigated, and the results showed that low temperature, high H2O/CH4 ratio and low space velocity were favorable for high purity H2, but the sorbent/catalyst ratio has almost no effect on the H2 purity. The impacts of the usage patterns of catalyst and sorbent were also studied. Large catalyst/sorbent particles exhibited lower conversion of CH4 than small particles for the whole time period, but the integration of catalyst and sorbent into one particle (combined catalyst) can offset the loss of conversion of CH4 during the prebreakthrough period. In view of the excellent reactivity and stability as well as the improved mass transfer, the combined catalyst composed of Ni0.50/Mg2.50Al and CaO–Ca9Al6O18 is expected to be a potential candidate for the SESMR process.

• A CaO–Ca9Al6O18 sorbent exhibited excellent CO2 capture capacity and stability.
• Its CO2 capture capacity varied from 0.58 to 0.48 g/g after 50 consecutive cycles.
• The sorbent was applied to the sorption-enhanced steam methane reforming (SESMR).
• Effects of reaction conditions and usage patterns of catalyst/sorbent were studied.
• Integration of catalyst and sorbent into one particle was beneficial for the SESMR.