Modeling of the evolution of the porous structure during a physical activation process for the production of activated biocarbon: A novel low conversion approach

Many experimental studies have shown the feasibility of using biomass precursors to produce activated carbon, often improving the properties obtained from traditional materials. However, hardly any models focus on the development of porosity during the process. Among the so-called pore models, the random pore model (RPM) is the most popular and accurately predicts the evolution of the porous structure due to pore growth and coalescence. However, in activation processes with a low degree of conversion, in which pore formation is the dominant mechanism, the RPM does not correctly predict the evolution of the specific surface area since it does not consider the appearance and creation of new porosity. In this work, a new model is proposed that predicts the specific surface area created due to the formation of new pores. Subsequently, it is combined with the determination of the variation of the specific surface area predicted by the RPM due to the growth and coalescence of existing pores. The validation of the new pore evolution model with activated carbon samples obtained at different conversions shows that the model proposed adequately predicts the specific surface area and pore distribution evolution throughout the activation process.