Directed Formation of Hydrated and Anhydrous Magnesium Carbonates and Enhanced Water Gas Shift Reaction

The integration of carbon capture and storage (CCS) technologies with energy conversion processes will increase the sustainability of using carboneous fuels. Combined CCS via carbon mineralization, where CO₂ reacts to form solid, stable mineral carbonates represents an attractive solution that avoids the energy costs of sorbent regeneration and public and scientific inquiries surrounding the safety of long-term geological storage of CO₂ in subsurface reservoirs. Magnesite is the most desirable phase within the magnesium carbonate family for carbon storage for a number of reasons: magnesium efficiency, omission of additional crystal waters and thermodynamic stability. Unfortunately, the formation of metastable hydrated magnesium carbonate phases (e.g. MgCO₃•3H₂O and Mg₅(CO₃)₄(OH)₂•4H₂O) interferes with the production of anhydrous magnesite under a variety of reaction conditions because magnesite crystals are slower to both nucleate and grow compared to the hydrated carbonate phases. Furthermore, the reaction conditions required for the formation of each magnesium carbonate phases have not been well understood with conflicting literature data. In this study, the effects of both magnesite (MgCO₃) and inert (Al₂O₃) seed particles on the precipitation of magnesium carbonates from a Mg(OH)₂ slurry were explored as well as the implication of the findings in terms of enhanced water gas shift reaction.