Chemical and Biological Engineering Department, Zhejiang University, Hangzhou 310027, China.
J Colloid Interface Sci. 2011 May 15;357(2):504-9. doi: 10.1016/j.jcis.2011.01.103. Epub 2011 Feb 17.
Separation of carbon dioxide and methane is an important issue in upgrading low-quality natural gas. Adsorption equilibria and kinetics of CO(2) and CH(4) on a copper metal-organic framework (MOF), Cu(hfipbb)(H(2)hfipbb)(0.5) [H(2)hfipbb=4,4'-(hexafluoroisopropylidene) bis(benzoic acid)], were investigated to evaluate the feasibility of removing CO(2) from CH(4) in a pressure swing adsorption process using this new MOF adsorbent. The heat of adsorption of CO(2) on the Cu-MOF at zero-coverage (29.7 kJ/mol) is much lower than those on a carbon molecular sieve and a zeolite 5A adsorbent; and the heat of adsorption of CH(4) on the Cu-MOF (21.4 kJ/mol) is similar to that on the zeolite 5A adsorbent and smaller than that on a carbon molecular sieve. The Cu-MOF being investigated has apertures of (~3.5 × 3.5 Å), which favors the kinetically controlled separation of CO(2) and CH(4). The kinetic selectivity is found to be 26 at 298 K, and the overall selectivity (combining the equilibrium and kinetic effects) is about 25 for an adsorption separation process. These results suggest that the Cu-MOF adsorbent is an attractive alternative adsorbent for the CO(2)/CH(4) separation.
二氧化碳和甲烷的分离是提高低品质天然气质量的一个重要问题。本研究采用铜基金属有机框架（MOF）Cu(hfipbb)(H(2)hfipbb)(0.5) [H(2)hfipbb=4,4'-(六氟异丙叉)双(苯甲酸)]作为新型吸附剂，考察了 CO(2)和 CH(4)在压力循环吸附过程中在该 MOF 上的吸附平衡和动力学，以评估其从 CH(4)中脱除 CO(2)的可行性。在零覆盖度下，CO(2)在 Cu-MOF 上的吸附热（29.7 kJ/mol）远低于碳分子筛和沸石 5A 吸附剂；而 CH(4)在 Cu-MOF 上的吸附热（21.4 kJ/mol）与沸石 5A 吸附剂相似，小于碳分子筛。研究中的 Cu-MOF 的孔径为（~3.5 × 3.5 Å），有利于 CO(2)和 CH(4)的动力学控制分离。在 298 K 时，动力学选择性为 26，对于吸附分离过程，总选择性（结合平衡和动力学效应）约为 25。这些结果表明，Cu-MOF 吸附剂是 CO(2)/CH(4)分离的一种有吸引力的替代吸附剂。
