Experimental investigation of CO₂ adsorption and desorption on multi-type amines loaded HZSM-5 zeolites

Solid adsorbents were prepared by fixing amines to HZSM-5 zeolites via wet impregnation method, and the CO₂ adsorption properties were investigated in a fixed-bed adsorption system followed by the structural, thermodynamic and kinetic studies. The HZSM-5 with 25 in Si/Al ratio and ~2.3 μm in average particle size was found to be a favourable CO₂ adsorbent support; whereby CO₂ adsorbents supporting monoethanolamine (MEA) and hydroxyethyl ethylenediamine (AEEA) exhibited good CO₂ adsorption capacities, with maximum values of 4.27 and 4.44 mmol/g being achieved, respectively. Desorption kinetics and thermodynamic studies showed that the CO₂ desorption process of AEEA loaded HZSM-5 exhibited a low activation energy of 54.27 kJ/mol. This low activation energy attributes to two possible reasons: HZSM-5 zeolite provides a large number of free H⁺ ions, which directly participate in carbamate breakdown; HZSM-5 can also provide metal atoms (Al) that attach to the N atom of carbamate, thereby stretching the C-N bond and promoting decomposition. Furthermore, the AEEA loaded HASM-5 adsorbent has high adsorption-desorption stability in the regeneration cycle tests, revealing the energy efficiency of the CO₂ desorption process and low CO₂ capture cost.