CO2 adsorption on zeolite 13X modified with hydrophobic octadecyltrimethoxysilane for indoor application

Hydrophobic-coated zeolite 13X (HZ) with octadecyltrimethoxysilane (ODTMS) exhibits a higher humidity resistance and CO 2 -adsorption capacity than pristine zeolite 13X in indoor-simulating low–CO 2 –concentration conditions. The hydrophobic coating modifies the surface characteristics and adsorption tendency of CO 2 and H 2 O, and these changes affect the gas selectivity for adsorption. Characteristic analysis (BET, TGA, and DVS) confirmed the rationality behind the use of zeolite@20 wt%ODTMS (HZ-2) for optimal loading of the hydrophobic coating under other experimental conditions. CO 2 and moisture adsorption capacities of HZ-2 decreased by 15% (from 4.0 mmolCO 2 /g to 3.4 mmolCO 2 /g) to 44.1% (from 5.5 mmolH 2 O/g to 3.3 mmolH 2 O/g) under pure-gas conditions, respectively. The moisture resistance developed by the hydrophobic coating improves the CO 2 selectivity in ambient-air conditions; this was tested in an indoor-condition-simulating chamber. The CO 2 -capture performance of HZ-2 increased by 33.3% (from 0.3 mmolCO 2 /g to 0.4 mmolCO 2 /g) and the moisture-adsorption capacity decreased by 41.6% (from 3.3 mmolH 2 O/g to 1.9 mmolH 2 O/g). Furthermore, the CO 2 gas selectivity of hydrophobic coated zeolite increased by 4.1 times. This modified synthesis provides a broader perspective on adsorbents for the utilization of CO 2 -capture in indoor conditions. Hydrophobic functionalized adsorbent (HZ-2) is manufactured with microporous zeolite 13X and hydrophobic octadecyltrimethoxysilane (ODTMS) in simplified process. HZ-2 has high stability in regeneration temperature and cyclic adsorption/desorption process. Furthermore, adsorption capacity and selectivity of CO 2 is enhanced in low concentration of CO 2 indoor condition environment compared to the pristine material.