Investigation of CO2 Capture from a CO2 + CH4 Gas Mixture by Gas Hydrate Formation in the Fixed Bed of a Molecular Sieve

In this work, we reported an investigation of using a fixed bed of zeolite 13X (FBR) for hydrate-based CO2 capture from a CO2/CH4 gas mixture (40 mol % CO2 and 60 mol % CH4). The experiments were carried out at a fixed temperature of 277.15 K and in the pressure range of (5.2 to 6.7) MPa. The effects of the driving force (overpressure), surfactant sodium dodecyl sulfate (SDS), and the fixed bed saturations on hydrate formation and CO2 selectivity were elucidated. The results indicated that hydrate growth in the fixed zeolite 13X was enhanced as the driving force was increased from 2.5 to 4.0 MPa, but the final gas uptake, CO2 recovery, and CO2 separation factor were reduced. Hydrate formation in the fixed zeolite 13X was promoted in the presence of SDS as compared to that in the absence of SDS. When the initial driving force was fixed at 2.5 MPa, the final gas uptake, CO2 recovery, and separation factor obtained at 75% saturation of the fixed bed were higher than those obtained at 100% and 50% saturations. The comparison between the fixed bed of zeolite 13X and the stirred tank reactors shows that CO2 selectivity obtained in the fixed bed of zeolite 13X was lower than those obtained in the stirred tank reactors. Therefore, zeolite 13X can be used to enhance hydrate formation but may not be a proper candidate for CO2 capture from the CO2/CH4 gas mixture.