Jiawei Zhou,Ming Liu,Xue Chen,Shiyang Bai,Jihong Sun
The purification and separation of CO 2 , CH 4 , and N 2 from biogas, flue gas, and coalbed gas for carbon capture and storage are main technology in mitigating the greenhouse effect. The Mg-MOF-74@clinoptilolite (Mg-MOF-74@CP) composites are successfully synthesized through an interfacial growth of Mg-MOF-74 onto the surfaces of the synthesized CP for adsorption and separation of CO 2 , CH 4 , and N 2 . The structural characteristics of the resultant composites are systematically characterized by various characterizations. In particular, small-angle X-ray scattering (SAXS) patterns are used to elucidate the fractal structural evolutions of the parent CP, Mg-MOF-74, and Mg-MOF-74@CP. Meanwhile, the single-component adsorption isotherms for CO 2 , CH 4 , and N 2 are demonstrated. The breakthrough measurements on CO 2 /CH 4 and cycling tests on CO 2 are conducted. The results elucidate that the CO 2 equilibrium capacity of Mg-MOF-74@CP is higher than that of parent CP, displaying a high affinity toward CO 2 , the longer breakthrough time and enhancement of CO 2 uptake exhibit a better separation performance. The cycling tests on CO 2 reveal that the Mg-MOF-74@CP could be used repetitively, promoting its practical application in an energy-saving and economical way. Additionally, the adsorption isotherms and adsorption sites of the prepared Mg-MOF-74@CP are simulated using the Grand Canonical Monte Carlo (GCMC) method, elucidating the mechanism of the gas separation performance of Mg-MOF-74@CP.
Chao Lv,Ruiyang Wang,Jia Gao,Ning Ding,Shunni Dong,Jingjing Nie,Junting Xu,Binyang Du
Enhanced phase separation and inverse order-to-order phase transition with increasing temperature was observed for a series of poly (acrylic acid)- b -poly (propylene oxide)- b -poly (acrylic acid) triblock copolymers with various block lengths by temperature-variable synchrotron small-angle X-ray scattering (SAXS). This abnormal phase behavior was attributed to the change of hydrogen (H)-bonding interaction in block copolymers upon increasing temperature and theoretically explained from thermodynamic viewpoint. The temperature-dependent FTIR analysis revealed that increasing temperature led to the weakening of overall H-bonding interactions and the increase of free C O and C–O–C groups. The Flory-Huggins interaction parameter χ of PAA and PPO blocks was positive and increased with increasing temperature as determined from the SAXS profiles of disordered block copolymer. The thermodynamic calculation indicated that the increase of Δ H was larger than the decrease of – T Δ S with increasing temperature because of the relatively large value of χ , leading to the increase of overall Δ G mix and hence the enhanced phase separation at higher temperature.
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