Experimental and modeling kinetic study of the CO2 absorption by Li4SiO4

• Global rate for CO2 absorption by Li4SiO4 was first order in CO2.
• Chemical reaction and product layer diffusion fit the conversion-time model.
• Intrinsic activation energy of 28.6 kcal/mol mainly governs the reaction.

Nowadays, research aims to produce H2 efficiently through modifying conventional processes by removing CO2 at high temperature (T ≥ 500 °C). The sorption enhanced reforming (SER) is an example of such a process where CO2 capture offers significant energy savings (≈23%). Besides, feedstock to this process may include different sources of biofuels. An essential part of this new reaction system is the use of a solid CO2 absorbent. Among absorbents stands lithium orthosilicate (Li4SiO4) for its high absorption capacity and thermal stability. Therefore, the present research aims to study and model the kinetics of CO2 absorption by Li4SiO4 in a temperature range of 550–650 °C. Results were consistent with a first order reaction dependence with respect to CO2 concentration. Apparent activation energy of the gas–solid reaction (22.5 kcal/mol) is approximately equal the intrinsic activation energy (28.6 kcal/mol), suggesting that the surface reaction resistance determines the overall reaction rate.