Highly Adsorptive Separation of Ethane/Ethylene by An Ethane-Selective MOF MIL-142A

Abstract

In the petrochemical industry, ethane/ethylene (C2H6/C2H4) separation is one of the most important processes. Herein, we reported an iron-based metal–organic framework MIL-142A for efficiently trapping C2H6 from C2H6/C2H4 mixture, exhibiting preferential adsorption of C2H6 over C2H4. After various characterization techniques to confirm the successful preparation of MIL-142A, the C2H6 and C2H4 adsorptive separation performance was systematically investigated. Results showed that MIL-142A had remarkably higher C2H6 adsorption capacities than that of C2H4 at 298, 288, and 278 K, such as C2H6 and C2H4 adsorption capacities of 3.8 and 2.9 mmol/g at 298 K and 100 kPa, respectively. In addition, the C2H6 and C2H4 adsorption heats were relatively low and in the corresponding ranges 27.3–25.1 and 26.2–23.8 kJ/mol, which is a favorable property for the regeneration of MIL-142A with less energy penalty. Furthermore, it was inferred that the difference between the adsorption heat for C2H6 and C2H4 with the MIL-142A framework governed the selective adsorption of C2H6 over C2H4. The ideal adsorbed solution theory (IAST) selectivity of C2H6/C2H4 was high up to 5.8 in the initial low pressure and then decreased to 1.5 at 298 K and 100 kPa. Besides, breakthrough experiments also corroborated its efficient separation of C2H6/C2H4 mixture. Additionally, MIL-142A had excellent moisture stability, and its framework remained still intact after being exposed to humid conditions (80% RH) for 15 days. These comprehensive properties demonstrated that this unique material MIL-142A, as a high-performance C2H6-selective adsorbent, can be potentially used for highly adsorptive separation of the C2H6/C2H4 mixture.

A Series of Mesoporous Metal‐Organic Frameworks with Tunable Windows Sizes and Exceptionally High Ethane over Ethylene Adsorption Selectivity

“…The corresponding selectivity factors for MOFs reported up to now at ambient conditions are typically quite low (S < 3) with MAF-49 being the only exception with appreciable selectivity S = 9.0. [22,[28][29][30][31][32][33][34][42][43][44][45][46][47][48][49][50][51][52][53][54][55] Theb est C 2 H 6 /C 2 H 4 absorption selectivity obtained for NIIC-20-Bu at similar conditions (S = 15.4) is 1.7 times higher than that for MAF-49 and greatly surpasses the majority of other literature results reported so far (Table S9). Other than the adsorption selectivity,the adsorption uptake is an equally important parameter for an adsorbent for gas separation applications.I nt his regard, am ore accurate evaluation of porous materials should be revealed from the selectivity vs.uptake plot.…”

Designer Metal–Organic Frameworks for Size‐Exclusion‐Based Hydrocarbon Separations: Progress and Challenges

“…Multicomponent column breakthrough experiments mimicking industrial mixtures comprising ethane, ethylene, methane, and carbon dioxide confirmed that ethane was retained in the column for the longest time and polymergrade ethylene (purity >99.95%) could be obtained with relatively high efficiency. Other ethane-selective MOFs include PCN-250, [66] PCN-245, [65] ZIF-7, [71][72] MIL-142, [64] and recently reported Cu(Qc) 2 [67] and MUF-15. [61]…”

Moisture stability of ethane‐selective Ni(II), Fe(III), Zr(IV)‐based metal–organic frameworks

“…The mass loss of 32.1% for H 4 bptc is close to the theoretical value (32.4%) calculated from the formula Zr 6 O 4 (OH) 4 (bptc) 3 . Therefore, Zr‐bptc is thermally stable to 702 K. The thermal decomposition temperature of Zr‐bptc (702 K) outperformed most reported ethane‐selective MOFs, such as IRMOF‐8 (673 K), PCN‐250 (673 K), PCN‐245 (625 K), Ni(bdc)(ted) 0.5 (673 K), ZIF‐69 (643 K), and MIL‐142A (573 K), but slight lower than UiO‐66 (739 K) . The high thermal stability of Zr‐bptc and UiO‐66 probably lies on the strong Zr‐O coordination bonds and the 12‐connected Zr 6 (μ 3 ‐O) 4 (μ 3 ‐OH) 4 (COO) 12 SBU of Zr‐bptc and UiO‐66.…”

“…The adsorption selectivities decrease sharply from 5.5 (ethane/ethylene = 1:1) and 6.6 (ethane/ethylene = 1:15) to 1.4 (ethane/ethylene = 1:1 or 1:15) at <1 kPa region, and the selectivity nearly keeps the constant of 1.4 at 1–100 kPa. The adsorption selectivity of Zr‐bptc (1.4) at 298 K and 100 kPa is moderate (Table S3), and the selectivity is comparable to activated carbon (1.2), C‐PDA‐5 (1.51), ZIF‐4 (1.5), MIL‐142A (1.5), and Cu(ina) 2 (1.25) . But the ethane/ethylene selectivity of Zr‐bptc is slightly lower than PCN‐245 (1.80) and Ni(bdc)(ted) 0.5 (1.85) .…”