Chemical Engineering Department, New Mexico State University, Las Cruces, New Mexico 88003, USA.
Environ Sci Technol. 2010 Mar 1;44(5):1820-6. doi: 10.1021/es9032309.
Adsorption equilibrium and kinetics of CO(2), CH(4), N(2)O, and N(2) on two newly discovered adsorbents, metal-organic frameworks MOF-5 and MOF-177 and one traditional adsorbent, zeolite 5A were determined to assess their efficacy for CO(2), CH(4), and N(2)O removal from air and separation of CO(2) from CH(4) in pressure swing adsorption processes. Adsorption equilibrium and kinetics data for CO(2), CH(4), N(2)O, and N(2) on all three adsorbents were measured volumetrically at 298K and gas pressures up to 800 Torr. Adsorption equilibrium capacities of CO(2) and CH(4) on all three adsorbents were determined gravimetrically at 298 K and elevated pressures (14 bar for CO(2) and 100 bar for CH(4)). The Henry's law and Langmuir adsorption equilibrium models were applied to correlate the adsorption isotherms, and a classical micropore diffusion model was used to analyze the adsorption kinetic data. The adsorption equilibrium selectivity was calculated from the ratio of Henry's constants, and the adsorbent selection parameter for pressure swing adsorption processes were determined by combining the equilibrium selectivity and working capacity ratio. Based on the selectivity and adsorbent selection parameter results, zeolite 5A is a better adsorbent for removing CO(2) and N(2)O from air and separation of CO(2) from CH(4), whereas MOF-177 is the adsorbent of choice for removing CH(4) from air. However, both MOF adsorbents have larger adsorption capacities for CO(2) and CH(4) than zeolite 5A at elevated pressures, suggesting MOF-5 and MOF-177 are better adsorbents for CO(2) and CH(4) storage. The CH(4) adsorption capacity of 22 wt.% on MOF-177 at 298K and 100 bar is probably the largest adsorption uptake of CH(4) on any dry adsorbents. The average diffusivity of CO(2), CH(4) and N(2)O in MOF-5 and MOF-177 is in the order of 10(-9) m(2)/s, as compared to 10(-11) m(2)/s for CO(2), CH(4) and N(2)O in zeolite 5A. The effects of gas pressure on diffusivity for different adsorabte-adsorbent systems were also investigated.
为了评估这两种新发现的吸附剂（金属有机骨架 MOF-5 和 MOF-177）和一种传统吸附剂沸石 5A 从空气中去除 CO2、CH4 和 N2O 以及在变压吸附过程中分离 CO2 和 CH4 的效果，测定了它们对 CO2、CH4、N2O 和 N2 的吸附平衡和动力学。在 298K 和高达 800 托的气体压力下，用体积法测量了所有三种吸附剂对 CO2、CH4、N2O 和 N2 的吸附平衡和动力学数据。在 298K 和升高的压力下（CO2 为 14 巴，CH4 为 100 巴），通过重量法测定了所有三种吸附剂对 CO2 和 CH4 的吸附平衡容量。亨利定律和朗缪尔吸附平衡模型被用来关联吸附等温线，经典的微孔扩散模型被用来分析吸附动力学数据。从亨利常数的比值计算吸附平衡选择性，通过结合平衡选择性和工作容量比来确定变压吸附过程中的吸附剂选择参数。基于选择性和吸附剂选择参数的结果，沸石 5A 是从空气中去除 CO2 和 N2O 以及从 CH4 中分离 CO2 的较好的吸附剂，而 MOF-177 是从空气中去除 CH4 的首选吸附剂。然而，在升高的压力下，两种 MOF 吸附剂对 CO2 和 CH4 的吸附容量均大于沸石 5A，这表明 MOF-5 和 MOF-177 是 CO2 和 CH4 储存的较好吸附剂。在 298K 和 100 巴下，MOF-177 对 CH4 的吸附容量为 22wt.%，这可能是任何干燥吸附剂对 CH4 的最大吸附量。在 MOF-5 和 MOF-177 中，CO2、CH4 和 N2O 的平均扩散系数为 10(-9)m(2)/s，而在沸石 5A 中，CO2、CH4 和 N2O 的扩散系数为 10(-11)m(2)/s。还研究了不同吸附-吸附剂体系中气体压力对扩散系数的影响。
