Thermodynamic screening of solid-gas CO₂ mineral carbonation: a provenance-traceable Gibbs-energy framework across 23...

Screening solid sorbents for CO₂ capture by the standard reaction Gibbs energy, ΔG°, or its turnover temperature does not show how far carbonation proceeds in a dilute gas charge. Established Gibbs-energy minimization is applied explicitly along the reaction extent ξ for 23 solid-gas carbonation reactions from six sorbent families. Gas-phase stoichiometry separates the reactions into three classes, whose profile shapes also depend on the initial charge. In Class I, where CO₂ is the only gaseous participant (18 reactions), an undiluted feed fixes the gas mole fraction, makes G linear in ξ and gives binary equilibrium except at the transition; an inert diluent instead depletes CO₂ along the reaction coordinate and permits partial conversion. Moving from pure CO₂ to 4% CO₂ at 1 bar lowers the boundary to the dilute-feed 50% conversion point by a median 93.8 K across 16 reactions with located inputs. R6 and R7 remain provisional and are excluded from that aggregate. Selected-source sensitivities give 93.8-94.3 K; the wider JANAF magnesite enthalpy interval gives 92.4-95.2 K, with other inputs fixed. These conditional ranges are not comprehensive confidence intervals. At 15% CO₂ and 1 bar, the CaO 90% boundary is 941.6 K. Four Class II reactions release H₂O(g) and are curved without inert; the Class III reaction consumes H₂O(g), and has a linear profile only for an undiluted stoichiometric CO₂/H₂O charge. The database records 104 thermochemical entries for 32 species. Literature comparisons and numerical verification are reported separately. The screen assumes pure phases and single reactions; the Na₂CO₃/NaHCO₃ route and Li₈SiO₆ are excluded because sufficiently complete, traceable inputs were not assembled.