X.-T. Mu,Y.-S. Ouyang,L.-M. Pei,Z.-X. Peng,S.-Q. Shao,S.-M. Wang,H. Xiong,Y. Xiao,Q.-Y. Yang
Adsorptive separation of C 2 H 6 from C 2 H 4 by adsorbents is an energy-efficient and promising method to boost the polymer grades C 2 H 4 production. However, that C 2 H 6 and C 2 H 4 display very similar physical properties, making their separation extremely challenging. In this work, by regulating the pore environment in a family of chitosan-based carbon materials (C-CTS-1, C-CTS-2, C-CTS-4, and C-CTS-6)- we target ultrahigh C 2 H 6 uptake and C 2 H 6 /C 2 H 4 separation, which exceeds most benchmark carbon materials. Explicitly, the C 2 H 6 uptake of C-CTS-2 (166 cm 3 /g at 100 kPa and 298 K) has the second-highest adsorption capacity among all the porous materials. In addition, C-CTS-2 gives C 2 H 6 /C 2 H 4 selectivity of 1.75 toward a 1:15 mixture of C 2 H 6 /C 2 H 4 . Notably, the adsorption enthalpies for C 2 H 6 in C-CTS-2 are low (21.3 kJ/mol), which will facilitate regeneration in mild conditions. Furthermore, C 2 H 6 /C 2 H 4 separation performance was confirmed by binary breakthrough experiments. Under different ethane/ethylene ratios, C-CTS-X extracts a low ethane concentration from an ethane/ethylene mixture and produces high-purity C 2 H 4 in one step. Spectroscopic measurement and diffraction analysis provide critical insight into the adsorption/separation mechanism. The nitrogen functional groups on the surface play a vital role in improving C 2 H 6 /C 2 H 4 selectivity, and the adsorption capacities depend on the pore size and micropore volume. Moreover, these robust porous materials exhibit outstanding stability (up to 800 °C) and can be easily prepared on a large scale (kg) at a low cost (∼$26 per kg), which is very significant for potential industrial applications.
Chaohui He,Yong Wang,Yang Chen,Xiaoqing Wang,Jiangfeng Yang,Libo Li,Jinping Li
The development of ethane (C 2 H 6 )-selective adsorbents displaying high uptake and selectivity to purify ethylene (C 2 H 4 ) to obtain polymer-grade raw materials is a meaningful, but challenging process. Tailoring the pore chemistry of a metal-organic framework is an effective strategy used to construct high performance adsorbents. Herein, BUT-10 with a tailored pore environment for tuning the C 2 H 6 adsorption ability has been synthesized via introducing functional sites into UiO-67. The single component gas adsorption capacity, adsorption heat and adsorption selectivity of BUT-10 have been proven to be effectively increased after modifying the pore environment. Computational studies have revealed that the stronger adsorption affinity for C 2 H 6 was achieved via multiple adsorbate-framework interactions in the appropriate pore environment. Breakthrough experiments using BUT-10 as a C 2 H 6 -selective adsorbent have shown that polymer grade C 2 H 4 was directly produced from C 2 H 6 /C 2 H 4 (1/15 v/v) mixtures using a single separation process under ambient conditions.
Tong Li,Xiaoxia Jia,Hui Chen,Zeyu Chang,Libo Li,Yong Wang,Jinping Li
Adsorption separation technology using adsorbents is promising as an alternative to the energy-demanding cryogenic distillation of natural gas (CH4/N2) separation. Although a few adsorbents, such as metal–organic frameworks (MOFs), with high performance for CH4/N2 separation, have been reported, it is still challenging to target the desired adsorbents for the actual CH4/N2 separation under humid conditions because the adsorption capacity and selectivity of the adsorbents might be mainly dampened by water vapor. Except for the high CH4 uptake and CH4/N2 selectivity, the adsorption material should simultaneously have excellent stability against moisture and relatively low-water absorption affinity. Here, we tuned the ligands and metal sites of reticular MOFs, Zn-benzene-1,4-dicarboxylic acid–1,4-diazabicyclo[2.2.2]octane (Zn-BDC–DABCO) (DMOF), affording a series of isostructural MOFs (DMOF-N, DMOF-A1, DMOF-A2, and DMOF-A3). Because of the finely engineered pore size and introduced aromatic rings in the functional DMOF, gas sorption results reveal that the materials show improved performance with a benchmark CH4 uptake of 37 cm3/g and a high CH4/N2 adsorption selectivity of 7.2 for DMOF-A2 at 298 K and 1.0 bar. Moisture stability experiments show that DMOF-A2 is a robust MOF with low water vapor capacity even at ∼40% relative humidity (RH) because of the presence of more hydrophobic aromatic rings. Breakthrough experiments verify the excellent CH4/N2 separation performances of DMOF-A2 under high humidity.
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