In-situ hydrogenation of dual function material for integrated CO2 capture and methanation with the presence of steam

• The impacts of external and internal steams on DFM hydrogenation were investigated. • CH 4 selectivity and carbonate conversion decreased with the presence of external steam. • b -CO 3 2- and m -CO 3 2- species can be hydrogenated into CH 4 or desorbed into CO 2 by steam. • Conversion of carbonate species is a competing process between hydrogenation and desorption. • Steam products impose strong moisture-driven desorption effects with large bed height. The impacts of steam on hydrogenation of dual function materials (DFM) for Integrated CO 2 Capture and in-situ methanation (ICCM) is a new area requiring detailed investigations prior to industrialization. This work investigated impacts from steams on hydrogenation of Ru-Na 2 CO 3 /γ-Al 2 O 3 DFM for ICCM that containing Na 2 O adsorbent, Ru sites, and γ-Al 2 O 3 support. DFM performance was examined in cyclic reactions as introducing external steam during hydrogenation, and the behaviors of adsorbed CO 2 species during hydrogenation were characterized by in-situ DRIFTS and H 2 -TPSR. CH₄ selectivity decreased sharply from 84.3 % to 1.2 % as increasing external steam concentrations to 20 vol.%, and the conversion of adsorbent component decreased from 298.5 μmol g -1 to 167.1 μmol g -1 . b -CO 3 2- and m -CO 3 2- formed at Na 2 CO 3 /γ-Al 2 O 3 interface were the carbonate species that could be hydrogenated into CH 4 , some of which were desorbed into CO 2 due to moisture-driven desorption effects. With the presence of external steam in H 2 reactants, the conversion of carbonate species is a competing process between hydrogenation and moisture-driven desorption. In ICCM reaction with external steam present, b -CO 3 2- was preferred to be desorbed into CO 2 ; while for m -CO 3 2- , desorption into CO 2 by steam and hydrogenation into CH 4 proceeded in parallel. Strong moisture-driven desorption effects from steam product were demonstrated in a fixed-bed reactor, which also led to rapid decrease of localized selectivity of CH 4 along bed height. This work investigated into the impacts from external and internal steams on the in-situ hydrogenation of Ru-Na 2 CO 3 /γ-Al 2 O 3 dual function materials, which containing Na 2 CO 3 adsorbent, Ru active sites, and γ-Al 2 O 3 supports for the Integrated CO 2 Capture and in-situ methanation.