Insight into thermal dissociation of tri-n-octylamine hydrochloride: The key to realizing CO2 mineralization with waste calcium/magnesium chloride liquids

A thermal dissociation process (ideally, 100% atom utilization) to regenerate the amine extractant and to produce gaseous HCl which is the key to realizing the CO 2 mineralization with metal chloride waste liquids was investigated. Solvent effects on the thermal dissociation of tri-n-octylamine hydrochloride (TOAHCl) were predicted to be prominent via analyzing structure parameters, charge distribution, solvation free energy, apparent basicity, and N-H frequency with the help of molecular simulation and experiments. Inert solvents with low polarity such as decalin, dodecane were favorable in thermal dissociation experiments. In particular, decalin enhanced the dissociation most effectively which is in agreement with the prediction. In dilute solutions, the thermal dissociation kinetics was shown to be first order. The apparent reaction rate (3.0 × 10 −4 −1.5 × 10 −2 min −1 ) and activation energy (58.219-121.827 kJ/mol) differ a lot at 180-190°C in various solvents, confirming a strong solvent effect. A two-stage reaction scheme in dilute solutions has been proposed from the experimental study. The overall process is entropically driven, with the removal of HCl into gas phase from the solvated state. The work could offer a fundamental direction for the further actual process.