Ethylene Purification Research Articles

Kilogram-Scale Fabrication of a Robust Olefin-Linked Covalent Organic Framework for Separating Ethylene from a Ternary C2 Hydrocarbon Mixture.

One-step adsorptive purification of ethylene (C2H4) from a ternary mixture of acetylene (C2H2), C2H4, and ethane (C2H6) by a single material is of great importance but challenging in the petrochemical industry. Herein, a chemically robust olefin-linked covalent organic framework (COF), NKCOF-62, is designed and synthesized by a melt polymerization method employing tetramethylpyrazine and terephthalaldehyde as cheap monomers. This method avoids most of the disadvantages of classical solvothermal methods, which enable the cost-effective kilogram fabrication of olefin-linked COFs in one pot. Furthermore, NKCOF-62 shows remarkably selective adsorption of C2H2 and C2H6 over C2H4 thanks to its unique pore environments and suitable pore size. Breakthrough experiments demonstrate that polymer-grade C2H4 can be directly obtained from C2H2/C2H6/C2H4 (1/1/1) ternary mixtures through a single separation process. Notably, NKCOF-62 is the first demonstration of the potential to use COFs for C2H2/C2H6/C2H4 separation, which provides a blueprint for the design and construction of robust COFs for industrial gas separations.

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.

Efficient C2H6/C2H4 adsorption separation by a microporous heterometal-organic framework

Purification of ethylene (C2H4) is an essential and energy-intensive process in the petrochemical industry. Adsorption separation using ethane (C2H6)-selective porous adsorbents is a highly efficient and straightforward method for obtaining polymer-grade C2H4 from a binary C2H6/C2H4 mixture. However, the design and construction of C2H6-selective adsorbents are very challenging tasks. Herein, we demonstrate a microporous heterometal-organic framework, CuIn(ina)4, can preferentially enrich C2H6 than C2H4. Experimental results revealed that CuIn(ina)4 exhibited remarkable separation performance for the C2H6/C2H4 mixture with a high C2H6 loading capacity (3.3 mmol/g), high IAST selectivity (2.3) and separation potential (1578 mmol/L for equimolar C2H6/C2H4 mixture) under ambient conditions. The effectiveness of CuIn(ina)4 for C2H6/C2H4 adsorption separation was confirmed by theoretical calculations and breakthrough experiments.

The effect of pore structure in ethane-selective metal-organic frameworks for ethylene purification

Separation of ethylene from ethane is of great importance in petrochemical industry. Adsorptive separation making use of porous materials such as metal-organic frameworks (MOFs) is an energy efficient technology compared to the conventional cryogenic distillation. However, preferential adsorption of ethylene over ethane represents the major current challenge. Here we demonstrate how pore structure can significantly alter the adsorption selectivity in two isoreticular Zr-MOFs. A simple ligand functionalization in UiO-66 yields smaller/better matching pore for ethane, and weaker interaction with ethylene, greatly enhancing ethane/ethylene selectivity in MOF-801. Ab initio calculations combined with in situ infrared spectroscopic analysis unveil the nature of host-guest interactions and differences in the overall binding energies. Polymer-grade ethylene (99.9%) can be produced directly from ethane/ethylene mixture in a single step. Having well-balanced adsorption capacity and selectivity, low-cost synthesis and easy scalability MOF-801 stands out as a promising ethane-selective adsorbent for one-step ethylene purification under ambient conditions.

In situ studies of molecular copper compounds for highly selective purification of ethylene

<i>In situ</i> studies of molecular copper compounds for highly selective purification of ethylene

One ethane-selective metal–organic framework with customized pore size and specific binding sites for efficient purification of ethylene

Removing small amount of ethane (C2H6) from ethylene (C2H4) to obtain high-purity C2H4 is of great significance in the industries. However, the construction of C2H6-selective metal–organic frameworks (MOFs) remains challenging, mainly because that C2H4 has smaller kinetic diameter and larger quadrupole moment. Herein, an ultra-microporous MOF (PCP-bdc) with customized pore size and specific binding sites is reported to efficiently purify C2H4 from C2H6/C2H4 mixture. The channel size of PCP-bdc is comparable to the size of C2H6 molecule, which can provide more accessible channel surfaces for C2H6. The channel surface of PCP-bdc is rich of low-polar aromatic groups and the uncoordinated O atoms can interact with C2H6 molecules strongly. Thus, PCP-bdc exhibits a remarkable C2H6/C2H4 (50/50) selectivity (2.82) and C2H6 uptake (53.8 cm3 g−1) at 298 K and 1 bar, which outperform those of many C2H6-selective adsorbents. Density functional theory calculations further reveal the formation of multiple synergies between this MOF and C2H6 enables the efficient separation for C2H6/C2H4 mixture. Breakthrough experiments demonstrate that PCP-bdc can purify C2H4 from C2H6/C2H4 mixture through one-step operation. These results indicate PCP-bdc is a promising adsorbent for C2H6/C2H4 separation.

Customized hourglass-shaped channels in a copper(II)-organic framework for one-step ethylene purification from ethylene/ethane/acetylene ternary mixtures with high adsorption capacity

One-step purification of C2H4 from C2H2/C2H4/C2H6 ternary mixtures represents an important yet challenging task in chemical industry. Favored adsorption of C2H2 and C2H6 over C2H4 has stringent requirements on pore size and surface chemistry of the adsorbents. We report a Cu-MOF (Cu–L), [Cu0.5(L)0.5]·2DMF (H2L = 4′-(1H-1,2,4-triazol-1-yl)-[1,1ꞌ-biphenyl]-3,5-dicarboxyl)) with one-dimensional hourglass-shaped channels decorated by phenyl rings and triazole units. Suitable pore structure and customized pore surface have endowed Cu–L with high adsorption capacities toward C2 hydrocarbons, and preferential adsorption of C2H2 and C2H6 over C2H4. Separation capability of Cu–L has been confirmed by multicomponent breakthrough experiments and polymer-grade C2H4 can be directly obtained from C2H2/C2H6/C2H4 (1/1/1 and 1/9/90, v/v/v) mixtures. The underlying mechanism of preferential adsorption was revealed by Grand Canonical Monte Carlo simulations and DFT calculations.

Single-step ethylene purification from ternary C2 hydrocarbon mixtures in a scalable metal–organic framework

Single-step purification of the ternary C2 hydrocarbon mixture to produce ethylene (C2H4) directly using adsorption-based technologies is desirable for reducing large energy consumption. However, it is challenging to develop an appropriate adsorbent, having preferential adsorption characteristics toward ethane (C2H6) and acetylene (C2H2) rather than C2H4 coupled with high adsorption capacity owing to their similar physicochemical properties. Herein, we present a highly stable, cheap, and scalable CAU-23 adsorbent, which enables single-step production of high-purity C2H4 (>99.9%) from the ternary C2 hydrocarbon mixture. CAU-23 exhibited higher uptake capacity of C2H6 (4.0 mmol g−1) and C2H2 (4.7 mmol g−1) compared to that of C2H4 (3.8 mmol g−1). Further, it showed the reasonable selectivity for both C2H6/C2H4 (1.54) and C2H2/C2H4 (1.5) with an equimolar binary mixture, indicating that the separation performance of CAU-23 is comparable to the benchmark porous materials for separating C2 ternary gas mixture. The breakthrough experiments demonstrated its capability to produce high-purity C2H4 (>99.9%) with various C2H6/C2H4/C2H2 compositions at 298 K and 1 bar with high recyclability. The origin of the separation performance was further explored by using computational simulations of the grand canonical Monte Carlo (GCMC) and density functional theory (DFT).

Fine-Tuning MOFs with Amino Group for One-Step Ethylene Purification from the C2 Hydrocarbon Mixture.

Due to the similar kinetic diameters of C2H2, C2H4, and C2H6, one-step purification of C2H4 from a ternary C2H2/C2H4/C2H6 mixture by adsorption separation is still a challenge. Based on a C2H6-trapping platform and crystal engineering strategy, the N atom and amino group were introduced into NTUniv-58 and NTUniv-59, respectively. Gas adsorption testing of NTUniv-58 showed that both the C2H2 and C2H4 uptake capacities and the C2H2/C2H4 separation ability were boosted compared with the original platform. However, the C2H4 uptake value exceeds the C2H6 adsorption data. For NTUniv-59, the C2H2 uptake at low pressure increased and the C2H4 uptake decreased; thus, the C2H2/C2H4 selectivity was enhanced and the one-step purification of C2H4 from a ternary C2H2/C2H4/C2H6 mixture was realized, which was supported by the enthalpy of adsorption (Qst) and breakthrough testing. Grand canonical monte carlo (GCMC) simulation indicated that the preference for C2H2 over C2H4 originates from multiple hydrogen-bonding interactions between amino groups and C2H2 molecules.

Feasible ethylene separation from a ternary mixture using zeolite-like metal-organic framework@divinylbenzene composite monolith

Ethylene is a vital intermediate in the petrochemical industry, and its purification from a C2 ternary mixture of up to 99.9% is essential to obtain a polymer-grade gas in an energy-demanding process. Adsorption-based separation offers an alternative approach for ethylene purification in a one-step process. Here, we report the fabrication of a monolithic composite from a zeolite-like metal-organic framework with a sodalite topology (sod-ZMOF) incorporated into a divinylbenzene polymer (ZMOF@DVB), to purify ethylene from binary and ternary mixtures of C2 hydrocarbons. The monolithic structure provides the composite with mechanical stability and high permeability, while only 2.31 wt% loading of sod-ZMOF nanoparticles has increased the BET surface area by 2.5 times, focused the pore size at 10.1 Å, and allowed for specific interactions. Gas chromatography was used to investigate the separation performance of the composite, reviling a quite satisfying selectivity of ethane/ethylene (1.89) and acetylene/ethylene (1.28), with comparable values to those of benchmark adsorbents used for similar applications and calculated via the ideal adsorbed solution theory (IAST). It is proposed that the anionic framework boosted the high polarizable ethane molecules' adsorption over ethylene; on the other hand, the Lewis basic nature of the extra-framework imidazolium cations neutralizes the anionic ZMOF structure drives acetylene's preferential adsorption over ethylene. As a proof of concept, imidazolium cations were exchanged in-situ by Na+ cations, and selectivities decreased to 1.37 for ethane/ethylene and 1.15 for acetylene/ethylene. An inverse gas chromatography approach was utilized to evaluate the thermodynamic parameters and showed an enthalpic-entropic motivated separation before cation exchange. However, after removing bulky imidazolium cations, separation became more entropic-driven.

Electrosynthesis of polymer-grade ethylene via acetylene semihydrogenation over undercoordinated Cu nanodots

The removal of acetylene impurities remains important yet challenging to the ethylene downstream industry. Current thermocatalytic semihydrogenation processes require high temperature and excess hydrogen to guarantee complete acetylene conversion. For this reason, renewable electricity-based electrocatalytic semihydrogenation of acetylene over Cu-based catalysts is an attractive route compared to the energy-intensive thermocatalytic processes. However, active Cu electrocatalysts still face competition from side reactions and often require high overpotentials. Here, we present an undercoordinated Cu nanodots catalyst with an onset potential of −0.15 V versus reversible hydrogen electrode that can exclusively convert C2H2 to C2H4 with a maximum Faradaic efficiency of ~95.9% and high intrinsic activity in excess of −450 mA cm−2 under pure C2H2 flow. Subsequently, we successfully demonstrate simulated crude ethylene purification, continuously producing polymer-grade C2H4 with <1 ppm C2H2 for 130 h at a space velocity of 1.35 × 105 ml gcat−1 h−1. Theoretical calculations and in situ spectroscopies reveal a lower energy barrier for acetylene semihydrogenation over undercoordinated Cu sites than nondefective Cu surface, resulting in the excellent C2H2-to-C2H4 catalytic activity of Cu nanodots.

Dynamic Spacer Installation of Multifunctionalities into Metal–Organic Frameworks for Spontaneous One-Step Ethylene Purification from a Ternary C 2 -Hydrocarbons Mixture

Dynamic Spacer Installation of Multifunctionalities into Metal–Organic Frameworks for Spontaneous One-Step Ethylene Purification from a Ternary C ₂ -Hydrocarbons Mixture

Dynamic Spacer Installation of Multifunctionalities into Metal-Organic Frameworks for Spontaneous One-Step Ethylene Purification from a Ternary C 2 -Hydrocarbons Mixture

Dynamic Spacer Installation of Multifunctionalities into Metal-Organic Frameworks for Spontaneous One-Step Ethylene Purification from a Ternary C ₂ -Hydrocarbons Mixture

A Robust Metal-Organic Framework with Scalable Synthesis and Optimal Adsorption and Desorption for Energy-Efficient Ethylene Purification.

Adsorptive separation is an energy-efficient alternative, but its advancement has been hindered by the challenge of industrially potential adsorbents development. Herein, a novel ultra-microporous metal-organic framework ZU-901 is designed that satisfies the basic criteria raised by ethylene/ethane (C2 H4 /C2 H6 ) pressure swing adsorption (PSA). ZU-901 exhibits an "S" shaped C2 H4 curve with high sorbent selection parameter (65) and could be mildly regenerated. Through green aqueous-phase synthesis, ZU-901 is easily scalable with 99 % yield, and it is stable in water, acid, basic solutions and cycling breakthrough experiments. Polymer-grade C2 H4 (99.51 %) could be obtained via a simulating two-bed PSA process, and the corresponding energy consumption is only 1/10 of that of simulating cryogenic distillation. Our work has demonstrated the great potential of pore engineering in designing porous materials with desired adsorption and desorption behavior to implement an efficient PSA process.

A Robust Metal‐Organic Framework with Scalable Synthesis and Optimal Adsorption and Desorption for Energy‐Efficient Ethylene Purification

AbstractAdsorptive separation is an energy‐efficient alternative, but its advancement has been hindered by the challenge of industrially potential adsorbents development. Herein, a novel ultra‐microporous metal‐organic framework ZU‐901 is designed that satisfies the basic criteria raised by ethylene/ethane (C2H4/C2H6) pressure swing adsorption (PSA). ZU‐901 exhibits an “S” shaped C2H4 curve with high sorbent selection parameter (65) and could be mildly regenerated. Through green aqueous‐phase synthesis, ZU‐901 is easily scalable with 99 % yield, and it is stable in water, acid, basic solutions and cycling breakthrough experiments. Polymer‐grade C2H4 (99.51 %) could be obtained via a simulating two‐bed PSA process, and the corresponding energy consumption is only 1/10 of that of simulating cryogenic distillation. Our work has demonstrated the great potential of pore engineering in designing porous materials with desired adsorption and desorption behavior to implement an efficient PSA process.

Functionalization of MOF by polyfluorinated anions toward one-step ethylene purification

Functionalization of MOF by polyfluorinated anions toward one-step ethylene purification

Customizing Metal-Organic Frameworks by Lego-Brick Strategy for One-Step Purification of Ethylene from a Quaternary Gas Mixture.

One-step purification of ethylene (C2 H4 ) from a quaternary gas mixture of C2 H6 /C2 H4 /C2 H2 /CO2 by adsorption is a promising separation process, yet developing adsorbents that synergistically capture various gas impurities remains challenging. Herein, a Lego-brick strategy is proposed to customize pore chemistry in a unified framework material. The ethane-selective MOF platform is further modified with customized binding sites to specifically adsorb acetylene and carbon dioxide, thus one-step purification of C2 H4 with high productivity of polymer-grade product (134mol kg-1 ) is achieved on the assembly of porous coordination polymer-2,5-furandicarboxylic acid (PCP-FDCA) and PCP-5-aminoisophthalic acid (IPA-NH2 ). Computational studies verify that the low-polarity surface of this MOFs-based platform provides a delicate environment for C2 H6 recognition, and the specific binding sites (FDCA and IPA-NH2 ) exhibit favorable trapping of C2 H2 and CO2 via CHδ+ ···Oδ- and Cδ+ ···Nδ- electrostatic interactions, respectively. The proposed Lego-brick strategy to customize binding sites within the MOFs structure provides new ideas for the design of adsorbents for compounded separation tasks.

Efficient separation of ethylene/ethane by incorporation of silver salts into protic imidazole ionic liquids

Efficient purification of ethylene (C2H4) from ethane (C2H6) is one of the seven chemical separations which can change the world. Chemical absorption is considered as the most promising method for C2H4/C2H6 separation. However, the two critical separation properties of absorbent, the solubility and selectivity, are always trade-offs, which are still needed to both promote and balance in the viewpoint of industrial application. Herein, a series of novel silver-containing protic imidazolium ionic liquids (SPILs), with high chemical activity for efficient C2H4 absorption, have been designed and synthesized. The physical properties of the prepared silver-containing ionic liquids (SILs) were first characterized. Then the separation performances of C2H4/C2H6 by SPILs and silver-containing aprotic ionic liquids (SAILs) were carefully compared. The C2H4/C2H6 selectivity of SPILs (16.73) was eight times higher than the value of the latter. Then, the C2H4 absorption mechanism was confirmed by density functional theory (DFT) calculations. The charge density of Ag+ was greater and the Gibbs free energy (ΔG) of C2H4 absorption was more negative in [Bim]n[Ag(NTf2)n+1]. The proposed SPILs, [Bim]1.5[Ag(NTf2)2.5], had a high C2H4/C2H6 selectivity of 41.2 and C2H4 solubility of 1.86 mol C2H4/mol Ag+, which were the highest value of ionic liquids (ILs) absorption reported so far. The [Bim]1.5[Ag(NTf2)2.5] exhibited excellent reversibility after five absorption–desorption cycles. An absorbent designed strategy of SPILs was proposed with enhanced solubility and selectivity for C2H4/C2H6 separation.

Adenine-mediated amide-containing metal-organic framework toward one-step ethylene purification from a ternary mixture

Simultaneous removal of acetylene (C2H2) and ethane (C2H6) from a ternary gas mixture of acetylene/ethylene/ethane via a one-step process to achieve high purity of ethylene (C2H4) is challenging but highly desirable. Herein, an amide-containing adenine-mediated rod metal-organic framework (MOF) of 1 was solvothermally constructed by means of mixed-linker approach. Structural analysis illustrates that 1 displays 1D microporous channels and features open metal site-free concomitant with uncoordinated carboxylate oxygen atoms and amide functional groups decorated interior pore walls. Interestingly, both single-component gas adsorption and ideal adsorbed solution theory (IAST) prediction reveal that 1 is C2H2 and C2H6 selective, which were eventually confirmed by dynamic column breakthrough experiments through not only binary gas mixtures of C2H2/C2H4 and C2H6/C2H4, but also a ternary mixture of C2H2/C2H4/C2H6 to validate one-step ethylene purification.

Benchmark single-step ethylene purification from ternary mixtures by a customized fluorinated anion-embedded MOF

Ethylene (C2H4) purification from multi-component mixtures by physical adsorption is a great challenge in the chemical industry. Herein, we report a GeF62- anion embedded MOF (ZNU-6) with customized pore structure and pore chemistry for benchmark one-step C2H4 recovery from C2H2 and CO2. ZNU-6 exhibits significantly high C2H2 (1.53 mmol/g) and CO2 (1.46 mmol/g) capacity at 0.01 bar. Record high C2H4 productivity is achieved from C2H2/CO2/C2H4 mixtures in a single adsorption process under various conditions. The separation performance is retained over multiple cycles and under humid conditions. The potential gas binding sites are investigated by density functional theory (DFT) calculations, which suggest that C2H2 and CO2 are preferably adsorbed in the interlaced narrow channel with high aff0inity. In-situ single crystal structures with the dose of C2H2, CO2 or C2H4 further reveal the realistic host-guest interactions. Notably, rare C2H2 clusters are formed in the narrow channel while two distinct CO2 adsorption locations are observed in the narrow channel and the large cavity with a ratio of 1:2, which accurately account for the distinct adsorption heat curves.