Molecular Simulation of Post-combustion Carbon Capture using Hydrotalcites

Abstract

Hydrotalcites (HT) stand out as solid sorbents for CO2 capture in the search for alternatives to mitigate climate change. HT show high thermal stability, low-cost synthesis and easy regeneration. However, the main challenges to enable their commercial use are their comparatively low adsorption capacity compared to chemical solvents, and the scalability of the process.

Computational methods enable the analysis of materials properties using fewer resources than experimental studies. This work aims to use them to study the changes that HT undergo during calcination and to evaluate their CO2 adsorption capacity. For the first time, a reactive environment is used to analyse the HT potential as adsorbents. The calcination process was studied with
molecular dynamics (MD) simulations and the adsorption capacity with Grand Canonical Monte Carlo (GCMC) simulations, both using the ReaxFF engine in the AMS 2019 software. The surface area of the calcined structure was compared with experimental data.

Insights obtained from MD showed that the presence of water molecules is necessary to transform the interlayer carbonates into CO2 during the calcination process. The structure resulting from the calcination studies showed a surface area of 247.63 𝑚2/𝑔, close to the maximum value reported for experimental data of HT calcined at 400°. Preliminary results of the adsorption studies showed 9.85 mol CO2/kgHT adsorption due to chemisorption, and to physisorption with a mean of 24.92 mol CO2/kgHT. Future work will focus on the refinement of the parameters used to carry out the simulations to improve the accuracy of the results

Keywords: post-combustion carbon capture; adsorption; hydrotalcites; molecular simulation; Molecular dynamics; GCMC