A comprehensive comparison of zeolite-5A molecular sieves and amine-grafted SBA-15 silica for cyclic adsorption-desorption of carbon dioxide in enclosed environments

This study investigated the performance of two adsorbent materials, namely commercially available zeolite-5A and an amine-grafted SBA-15 silica ( "aminosilica ") synthesized in lab, for air revitalization in enclosed environments. Adsorbent performance metrics were evaluated, in the presence of 1 vol% CO2 in N-2 at 25 degrees C, in terms of equilibrium CO2 uptake, CO2 adsorption kinetics, activation temperature and duration, regeneration temperature and duration, and cyclic stability. Aminosilica and zeolite-5A achieved similar performance in terms of equilibrium CO2 uptake (5.7 wt%) and cyclic stability (less than 2% CO2 uptake loss over 20 cycles). The main differences were that the aminosilica demonstrated (i) 43% faster CO2 adsorption kinetics in the first five minutes of adsorption cycle, (ii) lower activation temperature (80 versus 180 degrees C), (iii) lower regeneration temperature (90 versus 200 degrees C), (iv) 50% shorter activation duration, and (v) 35% shorter regeneration duration. The aminosilica also showed stable performance when regenerated in the presence of air at elevated temperature (8.6% CO2 uptake loss over 100 cycles). These indicators make the aminosilica material a potentially viable adsorbent for CO2 removal from dilute streams, including air revitalization applications.