Optimization and quantum chemical predictions for the dehydrogenation kinetics of Ammonia Borane–Ionic Liquid mixtures

• Logistic growth model for solid Ammonia Borane (AB) decomposition.
• Avrami Erofeyev model for AB + Ionic Liquid (IL) mixtures.
• Predictions of Infinite Dilution Activity Coefficient (IDAC) of AB in IL.
• Confirmation by quantum chemical calculations on AB–IL complex.

This work attempts to predict the reaction kinetics of two different hydrogen storage pathways namely Ammonia Borane (AB) and Ionic Liquid (IL) assisted AB. The reaction kinetics has been predicted for six reported ILs at 85 °C with AB using the Multiobjective GA toolbox. In addition, solid state AB thermal decomposition at 85 °C has been also studied. It was found that the Avrami Erofeyev model which is known to be useful for AB + IL mixtures, however fails when applied to predict reaction kinetics for solid state AB decomposition. To overcome this challenge we have used logistic growth model for solid state decomposition. Thus we propose a logistic growth model for solid AB decomposition while an Avrami Erofeyev model for AB–IL mixtures. The logistic growth model was characterized by a single step reaction for the solid state decomposition of AB, while the Avrami Erofeyev model for AB + IL mixtures successfully predicted two single step reactions. Both the models were able to reproduce the experimental trends with an overall deviation of less than 2%.We have also attempted to correlate the Infinite Dilution Activity Coefficient (IDAC) value of AB in IL with the activation energies of the mixture using the quantum chemical based COSMO-RS theory. All the IDAC values being close to unity indicated a high solubility with IL. A general trend of increase in hydrogen release with decreasing IDAC values was observed for the AB–IL mixtures.