High-purity hydrogen via the sorption-enhanced steam methane reforming reaction over a synthetic CaO-based sorbent and a Ni catalyst

Sorbent-enhanced steam methane reforming (SE-SMR) is an emerging technology for the production of high-purity hydrogen from hydrocarbons with in situ CO₂ capture. Here, SE-SMR was studied using a mixture containing a Ni-hydrotalcite-derived catalyst and a synthetic, Ca-based, calcium aluminate supported CO₂ sorbent. The fresh and cycled materials were characterized using N₂ physisorption, X-ray diffraction, and scanning and transmission electron microscopy. The combination of a Ni-hydrotalcite catalyst and the synthetic CO₂ sorbent produced a stream of high-purity hydrogen, that is, 99 vol % (H₂O- and N₂-free basis). The CaO conversion of the synthetic CO₂ sorbent was 0.58 mol CO₂/mol CaO after 10 cycles, which was more than double the value achieved by limestone. The favorable CO₂ capture characteristics of the synthetic CO₂ sorbent were attributed to the uniform dispersion of CaO on a stable nanosized mayenite framework, thus retarding thermal sintering of the material. On the other hand, the cycled limestone lost its nanostructured morphology completely over 10 SE-SMR cycles due to its intrinsic lack of a support component.