Exploring steam stability of mesoporous alumina species for improved carbon dioxide sorbent design

Many different metrics exist to assess the efficacy of a carbon capture sorbent, though one of the pivotal characteristics is stability on regeneration, most notably steam stability, which applies to steam stripping regeneration, a technique proposed for capture of CO₂ from humid flue gas. In this study, the steam stability of two different mesoporous alumina species is compared, with an aim to tune the synthesis methodology and the local structure and crystallinity of the samples to create a stable regenerable sorbent. The roles of calcination temperature and aminopolymer impregnation on sorbent stability and structure are also investigated using a wide range of characterization techniques to specifically probe the influence of the alumina support. We show through this study that support choice, and support stability, can play an important role in sorbent design for carbon capture. We highlight that regular crystallinity (such as in γ-alumina) hinders the formation of pseudo-boehmite, allowing a material to retain its CO₂ uptake. Further, we show that the addition of aminopolymers (PEI) can facilitate phase changes, however aminopolymers help maintain the mesoporosity of the sample, a key metric for CO₂ uptake.