Effect of H2O on Mg(OH)2 carbonation pathways for combined CO2 capture and storage

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Abstract Mg-bearing sorbents, derived from silicate minerals and industrial wastes, can act as combined carbon capture and storage media in various energy conversion systems. Mg(OH) 2 carbonation in the slurry phase occurs spontaneously and recent results show improved gas-solid carbonation with comparable materials in the presence of H 2 O vapor; however, the reaction mechanism is still poorly understood at high temperature and pressure conditions. This study investigated the pathways of H 2 O enhanced Mg(OH) 2 carbonation at elevated temperatures and CO 2 pressures (up to 673 K and 1.52 MPa) in the presence of steam and in the slurry phase. For a given reaction temperature, carbonation conversion showed dramatic increase with increasing H 2 O loading. 2 Comprehensive solid analyses via thermogravimetric analysis, X-ray diffraction, and UV-Raman allowed for qualitative and quantitative compositional characterization of reacted solids. The results suggest thata hydrated environment facilitates the formation of intermediate hydrated magnesium carbonate species. The hydrated carbonates form relatively quickly and can transform into anhydrous carbonates while subjected to greater H 2 O loading, higher temperature, and/or longer reaction time.