Converting CO 2 Into Natural Gas Within the Autoclave: A Kinetic Study on Hydrogenation of Carbonates in Aqueous Solution.

Catalytic conversion of carbon dioxide (CO 2 ) into value-added chemicals is of pivotal importance, well the cost of capturing CO 2 from dilute atmosphere is super challenge. One promising strategy is combining the adsorption and transformation at one step, such as applying alkali solution that could selectively reduce carbonate (CO 3 2- ) as consequences of CO 2 adsorption. Due to complexity of this system, the mechanistic details on controlling the hydrogenation have not been investigated in depth. Herein, Ru/TiO 2 catalyst was applied as a probe to elucidate the mechanism of CO 3 2- activation, in which with thermodynamic and kinetic investigations, a compact Langmuir-Hinshelwood reaction model was established which suggests that the overall rate of CO 3 2- hydrogenation was controlled by a specific C-O bond rupture elementary step within HCOO - and the Ru surface was mainly covered by CO 3 2- or HCOO - at independent conditions. This assumption was further supported by negligible kinetic isotope effects (k H /k D ≈1), similarity on reaction barriers of CO 3 2- and HCOO - hydrogenation (ΔH ≠ hydr,Na2CO3 and ΔH ≠ hydr,HCOONa ) and a non-variation of entropy (ΔS ≠ hydr ≈0). More interestingly, the alkalinity of the solution is certainly like a two sides in a sword and could facilitate the adsorption of CO 2 while hold back catalysis during CO 3 2- hydrogenation.