Separation Of C2H4 Research Articles

Electro‐field alignment in a novel metal–organic framework for benchmark separation of ethylene from a ternary gas mixture

AbstractOne‐step separation of C2H4 from ternary gas mixtures containing acetylene (C2H2), ethylene (C2H4), and carbon dioxide (CO2) represents a great challenge in chemical industry. Herein, we report the electro‐field alignment in a novel anion‐pillared MOF (SIFSIX‐TEPE‐Cu) for benchmark C2H4 separation from C2H2/CO2/C2H4 gas mixtures. The semi‐cage cavities featuring capped facets generated negative potentials along anion pillars and compensatory positive‐charged electro‐fields along organic ligands (TEPE) that facilitate specific recognitions of C2H2 and CO2 over C2H4. As a result, SIFSIX‐TEPE‐Cu exhibits high adsorption capacities for C2H2 (123 cm3 g−1) and CO2 (65 cm3 g−1) at 1.0 bar and 298 K. Notably, the record‐high C2H2 uptake (78 cm3 g−1) at 0.01 bar and remarkable C2H2/C2H4 selectivity (615.2) renders benchmark trace C2H2 removal ability. Dynamic breakthrough experiments demonstrate the benchmark productivity for high‐purity C2H4 (>99.995%) of 194.7 mol kg−1 and 5.96 mol kg−1 from binary C2H2/C2H4 (1/99, v/v) and ternary C2H2/CO2/C2H4 (1/9/90, v/v/v) gas mixtures.

Construction of Negative Electrostatic Pore Environments in a Scalable, Stable and Low‐Cost Metal‐organic Framework for One‐Step Ethylene Purification from Ternary Mixtures

AbstractOne‐step separation of C2H4 from ternary C2 mixtures by physisorbents remains a challenge to combine excellent separation performance with high stability, low cost, and easy scalability for industrial applications. Herein, we report a strategy of constructing negative electrostatic pore environments in a stable, low‐cost, and easily scaled‐up aluminum MOF (MOF‐303) for efficient one‐step C2H2/C2H6/C2H4 separation. This material exhibits not only record high C2H2 and C2H6 uptakes, but also top‐tier C2H2/C2H4 and C2H6/C2H4 selectivities at ambient conditions. Theoretical calculations combined with in situ infrared spectroscopy indicate that multiple N/O sites on pore channels can build a negative electro‐environment to provide stronger interactions with C2H2 and C2H6 over C2H4. Breakthrough experiments confirm its exceptional separation performance for ternary mixtures, affording one of the highest C2H4 productivity of 1.35 mmol g−1. This material is highly stable and can be easily synthesized at kilogram‐scale from cheap raw materials using a water‐based green synthesis. The benchmark combination of excellent separation properties with high stability and low cost in scalable MOF‐303 has unlocked its great potential in this challenging industrial separation.

Construction of Negative Electrostatic Pore Environments in a Scalable, Stable and Low-Cost Metal-organic Framework for One-Step Ethylene Purification from Ternary Mixtures.

One-step separation of C2 H4 from ternary C2 mixtures by physisorbents remains a challenge to combine excellent separation performance with high stability, low cost, and easy scalability for industrial applications. Herein, we report a strategy of constructing negative electrostatic pore environments in a stable, low-cost, and easily scaled-up aluminum MOF (MOF-303) for efficient one-step C2 H2 /C2 H6 /C2 H4 separation. This material exhibits not only record high C2 H2 and C2 H6 uptakes, but also top-tier C2 H2 /C2 H4 and C2 H6 /C2 H4 selectivities at ambient conditions. Theoretical calculations combined with in situ infrared spectroscopy indicate that multiple N/O sites on pore channels can build a negative electro-environment to provide stronger interactions with C2 H2 and C2 H6 over C2 H4 . Breakthrough experiments confirm its exceptional separation performance for ternary mixtures, affording one of the highest C2 H4 productivity of 1.35 mmol g-1 . This material is highly stable and can be easily synthesized at kilogram-scale from cheap raw materials using a water-based green synthesis. The benchmark combination of excellent separation properties with high stability and low cost in scalable MOF-303 has unlocked its great potential in this challenging industrial separation.

Aminal-Linked Covalent Organic Frameworks with hxl-a and Quasi-hcb Topologies for Efficient C2 H6 /C2 H4 Separation.

In reticular chemistry, topology is a powerful concept for defining the structures of covalent organic frameworks (COFs). However, due to the lack of diversity in the symmetry and reaction stoichiometry of the monomers, only 5% of the two-dimensional topologies have been reported to be COFs. To overcome the limitations of COF connectivity and pursue novel topologies in COF structures, two aminal-linked COFs, KUF-2 and KUF-3,are prepared, with dumbbell-shaped secondary building units. Linear dialdehydes and piperazine are condensed at a ratio of 1:2 to construct an aminal linkage, leading to unreported hxl-a (KUF-2) and quasi-hcb (KUF-3) structures. Notably, KUF-3 displays top-tier C2 H6 /C2 H4 selectivity and C2 H6 uptake at 298 K, outperforming most porous organic materials. The intrinsic aromatic ring-rich and Lewis basic pore environments, and appropriate pore widths enable the selective adsorption of C2 H6 , as confirmed by Grand Canonical Monte Carlo simulations. Dynamic breakthrough curves revealed that C2 H6 can be selectively separated from a gas mixture of C2 H6 and C2 H4 . This study suggests that topology-based design of aminal-COFs is an effective strategy for expanding the field of reticular chemistry and provides the facile integration of strong Lewis basic sites for selective C2 H6 /C2 H4 separation.

The Adsorptive Separation of Ethylene from C2 Hydrocarbons by Metal-Organic Frameworks.

Separating ethylene (C2 H4 ) from the C2 hydrocarbons is of prime industrial importance for the process of high-purity C2 H4 as an essential raw material in the petrochemical industry. Due to their similar physicochemical properties, the separation of C2 H4 from the C2 hydrocarbons typically entails high-energy separation technologies such as cryogenic distillation and extraction. Alternatively, adsorption separation using metal-organic frameworks (MOFs) are low-energy separation technologies that manufacture high-purity gas under mild conditions. In this review, we summarized the recent advances in MOFs for the separation and purification of C2 H4 from the C2 hydrocarbons. The mechanisms underlying separating C2 H4 from the C2 hydrocarbons using MOFs are also highlighted. This review also discussed the major challenges and developments of MOFs to separate C2 H4 from the C2 hydrocarbons.

A Microporous Metal-Organic Framework with Unique Aromatic Pore Surfaces for High Performance C2 H6 /C2 H4 Separation.

Developing adsorptive separation processes based on C2 H6 -selective sorbents to replace energy-intensive cryogenic distillation is a promising alternative for C2 H4 purification from C2 H4 /C2 H6 mixtures, which however remains challenging. During our studies on two isostructural metal-organic frameworks (Ni-MOF 1 and Ni-MOF 2), we found that Ni-MOF 2 exhibited significantly higher performance for C2 H6 /C2 H4 separation than Ni-MOF-1, as clearly established by gas sorption isotherms and breakthrough experiments. Density-Functional Theory (DFT) studies showed that the unblocked unique aromatic pore surfaces within Ni-MOF 2 induce more and stronger C-H⋅⋅⋅π with C2 H6 over C2 H4 while the suitable pore spaces enforce its high C2 H6 uptake capacity, featuring Ni-MOF 2 as one of the best porous materials for this very important gas separation. It generates 12 L kg-1 of polymer-grade C2 H4 product from equimolar C2 H6 /C2 H4 mixtures at ambient conditions.

Ethylene purification in a metal–organic framework over a wide temperature range via pore confinement

The separation of C2H4 from C2H6/C2H4 mixture is of great importance but difficult and energy intensive. Adsorptive separation provides an alternative approach to ameliorate this situation. Here, we report a microporous metal–organic framework (MOF) BUT-315-a as a C2H6-selective adsorbent for the separation of C2H6/C2H4 gas mixture. BUT-315-a combines good IAST selectivity of 2.35 with high C2H6 uptake of 97.5 cm3 g−1, giving superior high separation potential ΔQ (2226 mmol L−1) for equimolar C2H6/C2H4 at 298 K. Impressively, such excellent performance can be preserved at higher temperatures of 313 and 323 K to accommodate industrial conditions. Efficient dynamic separation performance of BUT-315-a has been demonstrated by column breakthrough experiments under varied temperatures and gas ratios. Theoretical calculations further reveal multiple synergistic interactions between C2H6 and the framework. This work highlights a new benchmark material for C2H6/C2H4 separation and provides guidance for designing adsorbent for separation applications.

Molecular Sieving of Acetylene from Ethylene in a Rigid Ultra-microporous Metal Organic Framework.

Rigid molecular sieving materials are the ideal candidates for gas separation (e. g., C2 H2 /C2 H4 ) due to their ultrahigh adsorption selectivity and the absence of gas co-adsorption. However, the absolute molecular sieving effect for C2 H2 /C2 H4 separation has rarely been realized because of their similar physicochemical properties. Herein, we demonstrate the absolute molecular sieving of C2 H2 from C2 H4 by a rigid ultra-microporous metal-organic framework (F-PYMO-Cu) with 1D regular channels (pore size of ca. 3.4 Å). F-PYMO-Cu exhibited moderate acetylene uptake (35.5 cm3 /cm3 ), but very low ethylene uptake (0.55 cm3 /cm3 ) at 298 K and 1 bar, yielding the second highest C2 H2 /C2 H4 uptake ratio of 63.6 up to now. One-step C2 H4 production from a binary mixture of C2 H2 /C2 H4 and a ternary mixture of C2 H2 /CO2 /C2 H4 at 298 K was achieved and verified by dynamic breakthrough experiments. Coupled with excellent thermal and water stability, F-PYMO-Cu could be a promising candidate for industrial C2 separation tasks.

Efficient Trapping of Trace Acetylene from Ethylene in an Ultramicroporous Metal-Organic Framework: Synergistic Effect of High-Density Open Metal and Electronegative Sites.

Acetylene (C2 H2 ) removal from ethylene (C2 H4 ) is a crucial step in the production of polymer-grade C2 H4 but remains a daunting challenge because of the similar physicochemical properties of C2 H2 and C2 H4 . Currently energy-intensive cryogenic distillation processes are used to separate the two gases industrially. A robust ultramicroporous metal-organic framework (MOF), Ni3 (pzdc)2 (7 Hade)2 , is reported for efficient C2 H2 /C2 H4 separation. The MOF comprises hydrogen-bonded linked one-dimensional (1D) chains, and features high-density open metal sites (2.7 nm-3 ) and electronegative oxygen and nitrogen sites arranged on the pore surface as cooperative binding sites. Theoretical calculations, in situ powder X-ray diffraction and Fourier-transform infrared spectroscopy revealed a synergistic adsorption mechanism. The MOF possesses S-shaped 1D pore channels that efficiently trap trace C2 H2 at 0.01 bar with a high C2 H2 uptake of 60.6 cm3 cm-3 and C2 H2 /C2 H4 selectivity.

Fine-Tuning the Pore Environment of the Microporous Cu-MOF for High Propylene Storage and Efficient Separation of Light Hydrocarbons.

Ethylene (C2H4) and propylene (C3H6) are important energy sources and raw materials in the chemical industry. Storage and separation of C2H4 and C3H6 are vital to their practical application. Metal–organic frameworks (MOFs) having adjustable structures and pore environments are promising candidates for C3H6/C2H4 separation. Herein, we obtained a Cu-based MOF synthesized by H3TTCA and pyrazine ligands. By adding different functional groups on the ligands within the MOFs, their pore environments are adjusted, and thus, the C3H6 storage capacity and C3H6/C2H4 separation efficiency are improved. Eventually, the fluoro- and methyl-functionalized iso-MOF-4 exhibits a better gas storage and C3H6/C2H4 separation performance compared with iso-MOF-1 (nonfunctionalized), iso-MOF-2 (fluoro-functionalized), and iso-MOF-3 (methyl-functionalized). A record-high C3H6 uptake of 293.6 ± 2.3 cm3 g–1 (273 K, 1 atm) is achieved using iso-MOF-4. Moreover, iso-MOF-4 shows excellent repeatability, and only 3.5% of C3H6 storage capacities decrease after nine cycles. Employing Grand Canonical Monte Carlo (GCMC) simulations, it is indicated that iso-MOF-4 preferentially adsorbs C3H6 rather than C2H4 at low pressure. Single-crystal X-ray diffraction on C3H6-adsorbed iso-MOF-4 crystals precisely demonstrates the adsorption positions and arrangement of C3H6 molecules in the framework, which is consistent with the theoretical simulations. Remarkably, gas sorption isotherms, molecular simulations, and breakthrough experiments comprehensively demonstrate that this unique MOF material exhibits highly efficient C3H6/C2H4 separation. Additionally, iso-MOF-4 also possesses efficient separation of C3H8/CH4 and C2H6/CH4, indicating its promising potential in storage/separation of light hydrocarbons in industry.

Construction of a Stable Crystalline Polyimide Porous Organic Framework for C2 H2 /C2 H4 and CO2 /N2 Separation.

Utilization of porous materials for gas capture and separation is a hot research topic. Removal of acetylene (C2 H2 ) from ethylene (C2 H4 ) is important in the oil refining and petrochemical industries, since C2 H2 impurities deactivate the catalysts and terminate the polymerization of C2 H4 . Carbon dioxide (CO2 ) emission from power plants contributes to global climate change and threatens the survival of life on this planet. Herein, 2D crystalline polyimide porous organic framework PAF-120, which was constructed by imidization of linear naphthalene-1,4,5,8-tetracarboxylic dianhydride and triangular 1,3,5-tris(4-aminophenyl)benzene, showed significant thermal and chemical stability. Low-pressure gas adsorption isotherms revealed that PAF-120 exhibits good selective adsorption of C2 H2 over C2 H4 and CO2 over N2 . At 298 K and 1 bar, its C2 H2 and CO2 selectivities were predicted to be 4.1 and 68.7, respectively. More importantly, PAF-120 exhibits the highest selectivity for C2 H2 /C2 H4 separation among porous organic frameworks. Thus PAF-120 could be a suitable candidate for selective separation of C2 H2 over C2 H4 and CO2 over N2 .

Ethylene Separation via Hydrate Formation in W/O Emulsions

An hybrid absorption-hydration method was adopted to recover C2H4 from C2H4/CH4 binary gas mixtures and the hydrate formation conditions of C2H4/CH4 mixtures was studied experimentally in diesel in water (w/o) emulsions. Span 20 at a concentration of 1.0 wt% in the aqueous phase was added to form water in diesel emulsions before hydrate formation and then hydrate in diesel slurry was separated after hydrate formation. The influences of initial gas-liquid volume ratio (53–142), pressure (3.4–5.4 MPa), temperature (274.15–278.15 K), water cuts (10–30 vol%), and the mole fraction of C2H4 in feed gas (13.19–80.44 mol%) upon the C2H4 separation efficiency were systematically investigated. The experimental results show that ethylene can be enriched in hydrate slurry phase with high separation factor (S) and recovery ratio (R). Most hydrate formation finished in 20 min, after that, the hydrate formation rate became very slow. The conclusion is useful for determining the suitable operation conditions when adopting an absorption-hydration method to separate C2H4/CH4.

Molecular Dynamics Simulation Study on the Absorption of Ethylene and Acetylene in Ionic Liquids

As environmentally friendly and designable solvents, ionic liquids (ILs) have great potential in the separation of C2H4 and C2H2, which is quite important in chemical industry. The microscopic insight into the intermolecular interaction and the diffusion dynamics at a molecular level is crucial for designing more efficient ILs. In this work, the interaction mechanism and diffusion dynamics for C2H4/C2H2 absorption and separation with five ILs, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), 1-butyl-3-methylimidazolium acetate ([bmim][OAc]), 1-butyl-3-methylimidazolium trifluoroacetate ([bmim][TFA]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]), and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([bmpyrr][Tf2N]), were investigated by molecular dynamics (MD) simulation. The result suggests that the van der Waals interaction between C2H4 and cation plays an important role in C2H4 dissolution in ILs, but the hydrogen bonding interaction between C2H...