Carbon dioxide adsorption on nitrogen enriched carbon adsorbents: Experimental, kinetics, isothermal and thermodynamic studies

Abstract

Nitrogen enriched porous carbons were prepared by nanocasting method using hexamethoxymethylmelamine (HMMM) as precursor and MCM-41 silica as template. Carbonization temperature was varied from 500°C to 800°C and was followed by physical activation with CO2 at the same temperature. These materials were evaluated as adsorbents for CO2 capture. Textural and morphological properties of these carbons show that they have mesoporosity derived from template removal. Carbonization and activation at 700°C produced carbon with highest surface area of 463m2/g and total pore volume of 0.48cm3/g with nitrogen content of 9.2wt%. Both of these properties account for the highest CO2 uptake of 0.80mmol/g at 30°C using pure CO2. CO2 uptake decreased with increase in temperature suggesting occurrence of physiosorption process. Additionally, these prepared carbons exhibited stable cyclic adsorption capacity. CO2 adsorption kinetics on these adsorbents follow pseudo-first order model with maximum error of ca. 5.4%. The adsorbent surface was found to be energetically heterogeneous as suggested by Temkin isotherm model. Thermodynamics suggested exothermic, random and spontaneous nature of the process.