Ethylene Purification Research Articles

Compatible alignment of pore electro-fields for enhanced one-step ethylene purification from ternary gas mixtures

The one-step purification of ethylene (C2H4) from ternary gas mixtures containing acetylene (C2H2), carbon dioxide (CO2), and C2H4 represents an efficient approach. It remains a significant challenge to simultaneously enhance the adsorption capacities of C2H2 and CO2. Herein, we reported a novel adsorbent, BFFOUR-TEPE-Cu, with compatible alignment of pore electro-fields. The one-connected BF4- anions provide more electronegative F atoms to reinforce the alignment of compatible electro-fields, thereby promoting the preferential adsorption of C2H2 and CO2 over C2H4. As a result, BFFOUR-TEPE-Cu exhibits a leading C2H2 capacity of 63.0 cm3 g−1 and C2H2/C2H4 (1/99, v/v) selectivity of 31.1 at 0.1 bar and 298 K. Computational studies reveal the favorable capture of both C2H2 and CO2 due to the compatible electron-fields. Dynamic breakthrough experiments demonstrate the exceptional capability for one-step production of high-purity C2H4 (>99.99 %) from ternary C2H2/CO2/C2H4 (1/9/90) gas mixture with a C2H4 productivity of 3.4 mol kg−1.

Decoding the zeolite cage effect in one-step ethylene purification from CO2/C2H2/C2H4 mixtures

Utilizing physical adsorption for ethylene purification from complex mixtures can significantly reduce the energy cost for production. The purification of multi-component systems through a single adsorption process presents a considerable challenge, largely stemming from the absence of customized strategies and thorough investigations into adsorption behaviours. We aim to understand adsorbents through a unique cage recognition approach and leverage these insights to develop an effective purification adsorbent, with the successful synthesis of SSZ-16 zeolite meeting requirements for multi-component purification. This zeolite, featuring a long aft supercage and a narrow gme cage construct two adsorption cages. The dense π-electron cloud of C2H2 enables a stronger interaction in aft cage, while CO2 is selectively captured within the environmentally compatible gme cage, demonstrating significantly higher C2H2 and CO2 adsorption capacity. The separation experiments reveal that SSZ-16 exhibits exceptional performance, with an unprecedented polymer-grade C2H4 productivity of 2099.16 L/kg from the CO2/C2H2/C2H4 mixture.

One-step purification of ethylene from ternary mixtures in an ultra-microporous interpenetrating MOF with unique constriction channels and F sites

The industrial importance of efficient purification of C2H4 from ternary C2H6/C2H4/C2H2 mixtures using a single adsorbent is significant, yet few adsorbents can achieve this challenging separation because of their very similar physical properties. Herein, we fabricated a robust metal–organic framework (MOF) that possessed unique constriction channels based on wide pockets and narrow windows as well as rich F sites and showed one-step C2H4 purification from C2H6/C2H4/C2H2 mixtures. The constriction channel restricts the adsorption of C2H4 in a degree, leading to high adsorption selectivity for both C2H6/C2H4 (1.9) and C2H2/C2H4 (2.9). Breakthrough experiments demonstrated that the material could efficiently separate C2H4 from C2H6/C2H4/C2H2 mixtures to produce highly pure C2H4 (>99.9%). Theoretical calculations provided a deep insight into the sorption mechanism, which revealed stronger multiple interactions between C2H6 or C2H2 molecules and pore walls compared to C2H4 molecules.

Understanding pore features of pillar-layered MOFs on one-step C2H4 purification from C2H6/C2H4 mixtures

Purification of ethylene from ethane through adsorption separation is a key industrial process in present chemical field, since the similar physical properties of both C2H4 and C2H6 that makes them difficult to separate. Therefore, constructing C2H6-selective adsorbents and clarifying its structure–activity relationship is a very difficult undertaking. In this study, 3D pillar-layered metal organic frameworks (MMOF-kgm (M = Zn, Co, Ni) and NiMOF-sql) with different topologies, kagome and square lattice, were constructed by using the cheap ligands (1,4-benzenedicarboxylic acid and triethylenediamine). The effect of pore features on C2H6/C2H4 separation performance and the separation mechanism were systematically investigated by the above two isomeric MOFs. In particular, NiMOF-kgm with kagome topology provides narrower triangular pore shows notably adsorption of C2H6 over C2H4, which is validated by gas adsorption, IAST selectivity and breakthrough measurements. The selective adsorption mechanisms of MOF with kagome topology were further revealed through DFT calculations. This study provides in-depth insights into optimizing the pore structure of MOFs to enhance C2H6/C2H4 separation performance, offering new design strategies for developing efficient materials for ethane-selective adsorbent for one-step ethylene purification.

Multiscale screening of metal‐organic frameworks for one‐step ethylene purification in pressure‐swing adsorption processes

AbstractPurification of polymer‐grade (99.9%) C2H4 from C2 hydrocarbon mixture is industrially important but challenging. Cryogenic distillation is energy intensive. Recently, pressure/vacuum swing adsorption (P/VSA) processes using metal‐organic frameworks (MOFs) as adsorbents have been attracting increasing attention as an alternative technology. A multiscale hierarchical framework is proposed to select promising MOFs and design suitable P/VSA processes by combining property‐based material screening and model‐based process optimization. Using this framework, we successfully identified seven promising one‐step C2H4 purification MOFs that outperformed the benchmark TJT‐100 in both C2H4 purity and recovery for the 5/90/5 C2H2/C2H4/C2H6 feed mixture. Among them, OFUCAV exhibited the highest C2H4 productivity of 0.158 mol/m3/s while JAVTAC demonstrated the lowest energy consumption of 42.76 kWh/tonne. The latter can potentially save 80% of the energy consumption compared to cryogenic distillation. Moreover, these two P/VSA processes show very high robustness in response to composition fluctuations in the feed stream.

A Propeller-Like Ligand-Directed Construction of a Tetranuclear Cerium-Organic Framework for Single-Step Ethylene Purification from Ternary C2 Mixtures.

The efficient single-step purification of ethylene from ternary C2 mixtures containing ethane and acetylene is challenging and demanding. Herein, we introduce a novel cerium-based metal-organic framework (MOF) of Ce-NTB-rtk synthesized via a ligand-conformer strategy. The Ce-NTB-rtk features a rare tetranuclear cerium cluster and 2D kgd layers pillared by a 3D rtl framework concomitant with an extraordinary (3,3,12)-c network. The compound encompasses microporous cavities replete with a nonpolar microenvironment. Gas sorption and breakthrough experiments demonstrate its superior affinity for C2H6 and C2H2 over C2H4, enabling effective single-step ethylene purification. Computational simulations reveal that preferential adsorptions are facilitated by different interaction strengths of C-H···O hydrogen bonds. The performance of Ce-NTB-rtk in separation selectivity and regeneration capacity makes it a promising candidate for sustainable and cost-effective ethylene purification, showcasing the potential of MOFs in advanced gas separation applications.

Precise Pore Engineering of Zirconium Metal‐Organic Cages for One‐Step Ethylene Purification from Ternary Mixtures

AbstractOne‐step purification of ethylene from ternary mixtures (C2H2, C2H4, and C2H6) can greatly reduce the energy consumption of the separation process, but it is extremely challenging. Herein, we use crystal engineering and reticular chemistry to introduce unsaturated bonds (ethynyl and alkyne) into ligands, and successfully design and synthesized two novel Zr‐MOCs (ZrT‐1‐ethenyl and ZrT‐1‐alkyne). The introduction of carbon‐carbon unsaturated bonds provides abundant adsorption sites within the framework while modulating the pore window size. Comprehensive characterization techniques including single crystal and powder X‐ray diffraction, as well as electrospray ionization time‐of‐flight mass spectrometry (ESI‐TOF‐MS) confirm that ZrT‐1‐ethenyl and ZrT‐1‐alkyne possess an isostructural framework with ZrT‐1 and ZrT‐1‐Me, respectively. Adsorption isotherms and breakthrough experiments combined with theoretical calculations demonstrate that ZrT‐1‐ethenyl can effectively remove trace C2H2 and C2H6 in C2H4 and achieve separation of C2H2 from C2H4 and CO2. ZrT‐1‐ethenyl can also directly purify C2H4 in liquid solutions. This work provides a benchmark for MOCs that one‐step purification of ethylene from ternary mixtures.

Precise Pore Engineering of Zirconium Metal-Organic Cages for One-Step Ethylene Purification from Ternary Mixtures.

One-step purification of ethylene from ternary mixtures (C2H2, C2H4, and C2H6) can greatly reduce the energy consumption of the separation process, but it is extremely challenging. Herein, we use crystal engineering and reticular chemistry to introduce unsaturated bonds (ethynyl and alkyne) into ligands, and successfully design and synthesized two novel Zr-MOCs (ZrT-1-ethenyl and ZrT-1-alkyne). The introduction of carbon-carbon unsaturated bonds provides abundant adsorption sites within the framework while modulating the pore window size. Comprehensive characterization techniques including single crystal and powder X-ray diffraction, as well as electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) confirm that ZrT-1-ethenyl and ZrT-1-alkyne possess an isostructural framework with ZrT-1 and ZrT-1-Me, respectively. Adsorption isotherms and breakthrough experiments combined with theoretical calculations demonstrate that ZrT-1-ethenyl can effectively remove trace C2H2 and C2H6 in C2H4 and achieve separation of C2H2 from C2H4 and CO2. ZrT-1-ethenyl can also directly purify C2H4 in liquid solutions. This work provides a benchmark for MOCs that one-step purification of ethylene from ternary mixtures.

Tailored Postsynthetic Nitration of a Hypercrosslinked Polymer for Single-Step Ethylene Purification from a Ternary C2 Gas Mixture.

Purifying C2H4 from a ternary C2H2/C2H4/C2H6 mixture poses a substantial industrial challenge due to their close physical and chemical properties. In this study, we introduce an innovative design approach to regulate and optimize the nitration degree of a hypercrosslinked polymer to achieve targeted separation performance. We synthesized a porous organic polymer (HCP) using the solvent knitting method and carried out its postsynthetic nitration, resulting in HCP-NO2-1 and HCP-NO2-2 with different nitration degrees. Notably, the adsorption capacity shifted from C2H6 > C2H4 ≈ C2H2 for HCP to C2H2 > C2H6 > C2H4 for HCP-NO2-1 and to C2H2 > C2H4 ≈ C2H6 for HCP-NO2-2, demonstrating the controllable nature of the separation process via the polar nitro group insertion. Remarkably, HCP-NO2-1 exhibited a desirable, selective separation of C2H4 from the C2H6/C2H4/C2H2 mixture thanks to an exquisite combination of the acidic proton-polar nitro group and nonpolar C-H∙∙∙π interactions. Separation capability was further corroborated by computational simulations and breakthrough tests. This work marks a significant advancement as the first successful postsynthetic functionalization strategy for C2H4 purification from a ternary gas mixture among porous organic polymers.

Interpenetrated In(III)-MOF with Multiple Recognition Sites for Single-Step Ethylene Purification.

An interpenetrated indium(III) metal-organic framework (MOF), NTUniv-73, with a rarely reported tetrameric indium cluster is developed for streamlining ethylene purification from C2 gases. At 298 K, the adsorption capacities exhibited a complete reversal sequence of C2H6 > C2H2 > C2H4. Grand canonical Monte Carlo simulation indicated that the corners in a octahedral cage facilitated the C2H2/C2H4 separation, while the pocket-like aperture situated between adjacent octahedral cages allows for full contact of C2H6. Breakthrough experiments illustrated that NTUniv-73 could yield pure C2H4 in a single step with a productivity of 0.42 mmol g-1.

Direct Ethylene Purification from a Four-Component Gas Mixture by a Microporous MOF with Aromatic Pore Surface and Carboxylates.

The single-step purification of ethylene (C2H4) from a mixture of carbon dioxide (CO2), acetylene (C2H2), ethylene (C2H4), and ethane (C2H6) was achieved through MOF Compound-1, where the aromatic pore surface and carboxylates selectively recognized C2H6 and CO2, respectively, resulting in a reversal of the adsorption orders for both gases (C2H6 > C2H4 and CO2 > C2H4). Breakthrough testing verified that the C2H4 purification ability could be enhanced 2.6 times after adding impure CO2. Grand Canonical Monte Carlo (GCMC) simulations demonstrate that there are interactions between CO2 and C2H6 molecules as well as between CO2 molecules themselves. These interactions contribute to the enhancement of the C2H4 purification ability upon the addition of CO2 and the increased adsorption of CO2.

Metal-Organic Framework Featuring Cubic Caged Structures for One-Step Ethylene Purification from Ethylene/Ethane Mixtures.

Separation of C2H6/C2H4 mixtures is of significant importance in the chemical industry but remains a challenge due to the physicochemical similarities of C2H6 and C2H4. Herein, a metal-organic framework (MOF), [Zn4(μ4-O)(PCTF)3]n (Zn-PCTF) (PCTF2-= 5-trifluoromethyl-1H-pyrazole-4-carboxylic), is provided for the removal of C2H6 from C2H6/C2H4 mixtures. Zn-PCTF displays a three-dimensional framework featuring one-dimensional pore channels with periodic bottleneck segments. The well-balanced C2H6 adsorption capacity (79.0 cm3 g-1 at 298 K) and C2H6/C2H4 selectivity (1.8) for Zn-PCTF under ambient conditions boost Zn-PCTF with highly promising potentials for efficient purification of C2H4 from C2H6/C2H4 mixtures, which is verified by the dynamic column breakthrough experiments. The well-matched caged pores and suitable pore chemistry (particularly the presence of abundant Lewis base sites (N, O, and F) on the pore surfaces) for C2H6 account for the high-performance C2H6/C2H4 separation of Zn-PCTF unveiled by computational simulations.

Study on adsorption and purification materials for ethylene in cold storage

In view of the lack of systematic quantitative and comparative studies on the purification effect of ethylene adsorbent in cold storage, starting from the selection of purification materials, this paper analyzed the purification effect of different zeolite materials on ethylene through a small test chamber, and screened out the best zeolite adsorbents used in self-made purification device. Combined with characterization analysis, purification efficiency evaluation and adsorption capacity of zeolite material, the removal performance of ethylene was investigated. The results showed that the zeolite samples with rough and porous surface showed better adsorption performance for ethylene. The larger the specific surface area and total pore volume, the stronger the adsorption capacity to ethylene. In addition, the presence of Na elements and mesoporous increased the exchange capacity and pore volume, which also played a certain role in the ethylene adsorption process. Experimental result demonstrates that clean air volume (CADR) of ethylene is 232 m3/h, the ethylene removal rate at 30 min is 98.19%, and the purification energy efficiency is 1.39. At the same time, the adsorption capacity of the selected zeolite sample is 1380.5 μg/g by dynamic adsorption experiment, and the service life of the filter element of the self-made purification device is estimated to be 166 days. This study can provide a theoretical basis for ethylene purification in cold storage.

One-Step Ethylene Purification from a Seven-Component Cracking Gas Mixture with Sorbent-Sorbate Induced-fit

One-Step Ethylene Purification from a Seven-Component Cracking Gas Mixture with Sorbent-Sorbate Induced-fit

Hydroxyl-functionalized linker endows an ultra-microporous aluminum based metal–organic framework with electronegative site for enhancing ethane/ethylene separation

Efficient purification of ethylene (C2H4) from the cracking gas containing a small amount of ethane (C2H6) by selective adsorption of C2H6 is meaningful but remains challenging. Aluminum-based metal–organic frameworks (Al-MOFs) with ultra-microporous structure show preferential adsorption of C2H6 over C2H4, relying on the existence of multiple hydrogen bonding acceptors (e.g., AlO6 polyhedra) for C2H6 molecule in the confined pores. However, most Al-MOFs exhibit limited C2H6/C2H4 selectivity (<2), which lack other strong preferential binding sites for C2H6. Here we report that a hydroxyl functionalized Al-MOF (i.e., CAU-1-OH) exhibits notably improved C2H6/C2H4 selectivity (2.13) and C2H6 uptake (3.95 mmol g−1) at 298 K and 1 bar compared to its amino-functionalized counterpart, CAU-1-NH2. Prior to experiment, theoretical calculations were performed, revealing that O atom from hydroxyl group in CAU-1-OH acts as a fairly strong hydrogen bond acceptor due to its more negative charge than N atom in CAU-1-NH2. The in-situ infrared experiment further confirmed the formation of multiple hydrogen bonds (C–H⋅⋅⋅O) between CAU-1-OH and C2H6 molecules, which plays vital role for C2H6-selective capture. The actual potential for C2H4 purification was fully demonstrated by dynamic breakthrough experiments, in which CAU-1-OH displayed excellent separative performance from C2H6/C2H4 (1/15, v/v) mixture. Moreover, the structural stability and excellent recyclability suggested and the promise for cost-effective industrial application in C2H6/C2H4 separation.

Metal-cluster-powered ultramicropore alliance in pore-space-partitioned metal-organic frameworks for benchmark one-step ethylene purification

Metal-cluster-powered ultramicropore alliance in pore-space-partitioned metal-organic frameworks for benchmark one-step ethylene purification

Hierarchically porous MOF@COF structures with ultrafast gas diffusion rate for C2H6/C2H4 separation

For ethylene purification, C2H6-selective metal–organic frameworks (MOFs) show great potential to directly produce polymer-grade C2H4 from C2H6/C2H4 mixtures. Most C2H6-traping MOFs are ultra-microporous structures so as to strengthen multiple supramolecular interactions with C2H6. However, the narrowed pore channels of C2H6-traping MOFs cause large guest diffusion barriers, greatly hampering their practical applications. Herein, we present a feasible strategy by precisely constructing hierarchically porous MOF@COF core–shell structures to address this issue. Additional mesoporous diffusion channels were incorporated between MOF crystals through the construction of the COF shell, thereby enhancing the gas adsorption kinetics. Notably, designing a core–shell MOF@COF structure with an optimal coating amount of mesoporous COF shell will further improve the gas diffusion rate. Breakthrough experiments reveal that the tailored MOF@COF composites can effectively achieve C2H6/C2H4 separation and maintain its separation performance over five continuous measurement cycles. This investigation opens up a new avenue to solve the diffusion/transfer issues and provides more opportunities and potentials for MOF@COF composites in practical separation applications.

Experimental study and modeling of the liquid phase hydrogenation of acetylene

Selective hydrogenation of acetylene is an important process for both ethylene purification and ethylene production from acetylene in the industry. Herein, we proposed liquid phase acetylene hydrogenation for high feed concentrations of C2H2 (8 %) and CO (20 %), which is used to produce ethylene as a subsequent process of partial oxidation of natural gas. The experiments were carried out in a stirred tank reactor using N-methylpyrrolidone (NMP) as solvent and PdAg/SiO2 as catalyst. The liquid phase process obtained a much higher selectivity to ethylene (92 %) with only 8 % selectivity to green oil (GO) and C4, compared to 71 % ethylene selectivity in gas phase hydrogenation. Furthermore, in the liquid phase ethylene selectivity increased with increasing acetylene conversion, especially in the conversion range of 80–100 %. We developed a model incorporating reaction kinetics, mass transfer and reactor model to predict the acetylene conversion and ethylene selectivity in liquid phase hydrogenation. The calculation results indicated that hydrogenation in the liquid phase operated at a lower acetylene concentration and a higher H2/C2H2 ratio, especially under high acetylene conversions. This explains why the liquid phase hydrogenation of acetylene has a much higher selectivity to ethylene than the gas phase process.

Fine-tuning the pore environment of ultramicroporous three-dimensional covalent organic frameworks for efficient one-step ethylene purification

The construction of functional three-dimensional covalent organic frameworks (3D COFs) for gas separation, specifically for the efficient removal of ethane (C2H6) from ethylene (C2H4), is significant but challenging due to their similar physicochemical properties. In this study, we demonstrate fine-tuning the pore environment of ultramicroporous 3D COFs to achieve efficient one-step C2H4 purification. By choosing our previously reported 3D-TPB-COF-H as a reference material, we rationally design and synthesize an isostructural 3D COF (3D-TPP-COF) containing pyridine units. Impressively, compared with 3D-TPB-COF-H, 3D-TPP-COF exhibits both high C2H6 adsorption capacity (110.4 cm3 g−1 at 293 K and 1 bar) and good C2H6/C2H4 selectivity (1.8), due to the formation of additional C-H···N interactions between pyridine groups and C2H6. To our knowledge, this performance surpasses all other reported COFs and is even comparable to some benchmark porous materials. In addition, dynamic breakthrough experiments reveal that 3D-TPP-COF can be used as a robust absorbent to produce high-purity C2H4 directly from a C2H6/C2H4 mixture. This study provides important guidance for the rational design of 3D COFs for efficient gas separation.

Flow Channel with Wrinkles and Calcium Sites in a Ca-MOF for Direct One-Step Ethylene Purification from C2 Gases and MTO Products Separation.

The strategy of flow channel with wrinkles and calcium sites for single-step C2H4 purification from C2 gases and methanol-to-olefins (MTO) products separation was realized in FJI-Y9. The adsorption amounts showed a total reversal order of C3H6 > C2H6 > C2H2 > C2H4 at 298 K. Modeling indicated that the wrinkles and Ca2+ facilitated the full contact of C3H6 and C2H6. Breakthrough experiments illustrated that FJI-Y9 could yield pure C2H4 in a single step with a productivity of 0.78 mmol g-1. In a lone adsorption/desorption cycle for MTO product separation, the productivities of C3H6 and C2H4 were 1.96 and 1.29 mol g-1, standing as the highest recorded values.