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Separation and purification of gas mixtures using selective adsorbents is widely used in different industries such as gas drying, air separation, and H2 purification. Equilibrium analysis involving adsorption of binary gas mixtures provides important information related to the adsorbent performance in the separation of gases. In this study, a novel technique termed “differential column technique” was developed for binary isotherm measurement employing streams containing carbon dioxide, carbon monoxide, and ethylene at different compositions. This technique is based on measuring the gas desorption by changing equilibrium pressure conditions. The isotherm curve was generated by summing desorption amounts desorbed at each pressure step. Through the application of this technique, the single-component isotherms of CO2, CO, and ethylene on zeolite NaY were measured, and the isotherms were compared to the results obtained by a standard gravimetric technique. (The average relative deviation is less than 6%.) The main advantage of the technique is the significant time savings, e.g., one experimental run is required to generate an isotherm compared to multirun experiments using a standard breakthrough technique, in addition to using a simpler experimental setup and generally smaller amount of sample (agglomerated or in a powder form). Another important feature of this technique is the relatively simple extension that allows measurements of gas mixture equilibria. As such, the proposed technique has the potential to be used as a fast screening technique for adsorbent selection based on single-component or mixture analysis. To investigate the consistency of the proposed technique, the binary isotherms of competitive, CO2–C2H4, and noncompetitive, CO2–CO, mixtures were investigated at different gas compositions. In addition, the effects of sorbate concentrations in the gas phase and interactions with the NaY zeolite active surface were investigated in relation to the adsorption selectivity and capacity, i.e., strong interaction of both CO2 and ethylene with NaY site resulted in close adsorption selectivity 0.8 ≤ S CO2/C2H4 ≤ 1.7, while CO2 adsorbed more selectively compared to CO, 14 ≤ S CO2/CO ≤ 30, as a result of weak CO interaction with the adsorbent sites. Finally, the binary adsorption isotherms and selectivity were predicted by the multisite Langmuir model using the single component’s isotherm parameters. Modest agreements (error ≤ 28%) were obtained between the predicted and experimental results.

A solid acid derivative of β-cyclodextrin was synthesized as an adsorbent for CO 2 capture. The adsorption characteristics, such as adsorption capacity, selectivity, and uptake rate, under different temperatures and gas pressures were analyzed. The results from scanning electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer−Emmett−Teller (BET) sorption, Fourier transform infrared spectroscopy, andthermogravimetric analysis indicated that the dehydration and grafting of sulfonic groups changed the structure of β-cyclodextrin aggregates into a relatively homogeneous porous structure with a concave−convex surface. Meanwhile, the specific BET surface area and pore volume of the solid acid derivative were increased by 40 and 37 times compared to β-cyclodextrin aggregates. Thereby, the performance of the solid acid derivative of βcyclodextrin toward CO 2 sorption was significantly enhanced, in which CO 2 adsorption capacity at 3.5 bar was increased to 1.78 mmol/g and the selectivity of CO 2 over N 2 , O 2 , and CH 4 at 298 K reached 7. Interestingly, there was no adsorption of nitrogen on the as-prepared solid acid derivative at 77 K based on BET sorption. Lowering the temperature is disadvantageous for N 2 adsorption but helpful to promote CO 2 capture, so that the high selectivity of CO 2 to N 2 sorption can be achieved.

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