Separation Of Hydrocarbons Research Articles

Estimation of mixed-gas selectivity of membranes using the linear friction-based model

The development of analytical models for predicting the transport properties of membranes in the separation of multicomponent mixtures is highly relevant because (1) measurements of permeability and sorption of gas mixtures in membrane materials are laborious and time-consuming, and (2) estimation of transport properties based on pure gas measurements is desirable, however, rather unreliable and can lead to serious errors. In this paper, within the framework of the well-known frictional-coefficient formalism, we present nonlinear equations for the fluxes of gas mixture components through the membrane, which take into account the diffusional coupling of the fluxes compared to independent gas transport. As a result, an analytical equation for the mixed-gas selectivity was obtained. This equation has an implicit form, which is not quite convenient for practical application, since it has to be solved numerically. A simple explicit expression for mixed gas selectivity was derived using the so-called linear transport model, which is a linearized version of the original nonlinear flux equations. It is important to emphasize that a comparison of the linear model with the formally more rigorous nonlinear model showed only minor quantitative differences. The input parameters for the model are the single gas transport parameters. Testing the linear model using experimental data for the separation of hydrocarbons (n-butane/methane, n-butane/i-butane, propylene/propane) revealed an acceptable fit. A comparison of the model with recent experimental data on the separation of CO2-containing mixtures using microporous polymers is also presented. It is found that the calculated CO2/N2 mixed gas selectivity is in good agreement with the experimental data, while only a semi-quantitative agreement is observed for the CO2/CH4 separation. Besides, it is shown that the model developed for binary gas separation can be extended to ternary gas mixtures.

A Copper-Based Metal-Organic Framework for Selective Separation of C2 Hydrocarbons from Methane at Ambient Conditions: Experiment and Simulation.

C2 hydrocarbon separation from methane represents a technological challenge for natural gas upgrading. Herein, we report a new metal-organic framework, [Cu2L(DEF)2]·2DEF (UNT-14; H4L = 4,4',4″,4‴-((1E,1'E,1″E,1‴E)-benzene-1,2,4,5-tetrayltetrakis(ethene-2,1-diyl))tetrabenzoic acid; DEF = N,N-diethylformamide; UNT = University of North Texas). The linker design will potentially increase the surface area and adsorption energy owing to π(hydrocarbon)-π(linker)/M interactions, hence increasing C2 hydrocarbon/CH4 separation. Crystallographic data unravel an sql topology for UNT-14, whereby [Cu2(COO)4]···[L]4- paddle-wheel units afford two-dimensional porous sheets. Activated UNT-14a exhibits moderate porosity with an experimental Brunauer-Emmett-Teller (BET) surface area of 480 m2 g-1 (vs 1868 m2 g-1 from the crystallographic data). UNT-14a exhibits considerable C2 uptake capacity under ambient conditions vs CH4. GCMC simulations reveal higher isosteric heats of adsorption (Qst) and Henry's coefficients (KH) for UNT-14a vs related literature MOFs. Ideal adsorbed solution theory yields favorable adsorption selectivity of UNT-14a for equimolar C2Hn/CH4 gas mixtures, attaining 31.1, 11.9, and 14.8 for equimolar mixtures of C2H6/CH4, C2H4/CH4, and C2H2/CH4, respectively, manifesting efficient C2 hydrocarbon/CH4 separation. The highest C2 uptake and Qst being for ethane are also desirable technologically; it is attributed to the greatest number of "agostic" or other dispersion C-H bond interactions (6) vs 4/2/4 for ethylene/acetylene/methane.

Comparison of carrier gases for the separation and quantification of mineral oil hydrocarbon (MOH) fractions using online coupled high performance liquid chromatography-gas chromatography-flame ionisation detection

On-line coupled high performance liquid chromatography-gas chromatography-flame ionisation detection (HPLC-GC-FID) was used to compare the effect of hydrogen, helium and nitrogen as carrier gases on the chromatographic characteristics for the quantification of mineral oil hydrocarbon (MOH) traces in food related matrices. After optimisation of chromatographic parameters nitrogen carrier gas exhibited characteristics equivalent to hydrogen and helium regarding requirements set by current guidelines and standardisation such as linear range, quantification limit and carry over. Though nitrogen expectedly led to greater peak widths, all required separations of standard compounds were sufficient and humps of saturated mineral oil hydrocarbons (MOSH) and aromatic mineral oil hydrocarbons (MOAH) were appropriate to enable quantitation similar to situations where hydrogen or helium had been used. Slightly increased peak widths of individual hump components did not affect shapes and widths of the MOSH and MOAH humps were not significantly affected by the use of nitrogen as carrier gas. Notably, nitrogen carrier gas led to less solvent peak tailing and smaller baseline offset. Overall, nitrogen may be regarded as viable alternative to hydrogen or helium and may even extend the range of quantifiable compounds to highly volatile hydrocarbon eluting directly after the solvent peak.

Janus polytricyclononenes with trialkoxysilyl groups containing long alkyl tails for membrane separation of hydrocarbons

Janus vinyl-addition polytricyclononenes bearing tri(n-alkoxy)silyl groups with long n-alkyl tails (C6, C8, C10) were designed and synthesized as potential membrane materials for separation of C2+ gaseous hydrocarbons. The conditions of vinyl-addition polymerization of corresponding substituted tricyclononenes with C6 and C8n-alkyl tails were optimized for obtaining high-molecular-weight (Mw up to 106) polymers in high yields (up to 74%). The synthesized polymers were non-crystalline and rubbery. The permeability of a wide range of individual gases was studied for the synthesized polytricyclononenes. The permeability of the CH4/n-C4H10 mixture was studied for the synthesized polymers as well as for the previously described analogous polymers with shorter n-alkyl tails (C3, C4). The analysis of the results obtained led to some interesting conclusions. First, among polymers with C6-8n-alkyl tails, permanent gas permeability almost does not depend on their length, whereas hydrocarbon permeability increases. Second, the solubility-controlled hydrocarbon separation selectivity (C2/C1, C3/C1 and C4/C1) increases with the length of alkyl tails, and this tendency remains in mixed gas experiments. Third, Janus polytricyclononenes with tri(n-alkoxy)silyl groups are strongly plasticized by pure n-butane, but, in the case of the separation of a gas mixture with a low amount of n-butane, the contribution of plasticization is significantly less even at high feed stream pressure.

Spatially Confined π-Complexation within Pore-Space-Partitioned Metal-Organic Frameworks for Enhanced Light Hydrocarbon Separation and Purification.

Ultramicroporous metal-organic frameworks (MOFs) are demonstrated to be advantageous for the separation and purification of light hydrocarbons such as C2H2, C2H4, and CH4. The introduction of transition metal sites with strong π-complexation affinity into MOFs is more effective than other adsorption sites for the selective adsorption of π-electron-rich unsaturated hydrocarbon gases from their mixtures. However, lower coordination numbers make it challenging to produce robust MOFs directly utilizing metal ions with π-coordination activity, such as Cu+, Ag+, and Pd2+. Herein, a series of novel π-complexing MOFs (SNNU-33s) with a pore size of 4.6Å are precisely constructed by cleverly introducing symmetrically matched C3-type [Cu(pyz)3] (pyz = pyrazine) coordinated fragments into 1D hexagonal channels of MIL-88 prototype frameworks. Benifit from the spatial confinement combined with π-complex-active Cu+ of [Cu(pyz)3], pore-space-partitioned SNNU-33 MOFs all present excellent C2H2/CH4, C2H4/CH4, and CO2/CH4 separation ability. Notably, the optimized SNNU-33b adsorbent demonstrates top-level IAST selectivity values for C2H2/CH4 (597.4) and C2H4/CH4 (69.8), as well as excellent breakthrough performance. Theoretical calculations further reveal that such benchmark light hydrocarbon separation and purification ability is mainly ascribed to the extra-strong binding affinity between Cu+ and π-electron donor molecules via a spatially confined π-complexation process.

A Highly Stable Microporous Calcium-Based MOF for C2H2/CO2 Separation with Low Regenerative Energy.

Most of the porous materials used for acetylene/carbon dioxide separation have the problems of poor stability and high energy requirements for regeneration, which significantly hinder their practical application in industries. Here, we report a novel calcium-based metal-organic framework (NKM-123) with excellent chemical stability against water, acids, and bases. Additionally, it has exceptional thermal stability, retaining its structural integrity at temperatures up to 300 °C. This material exhibits promising potential for separating C2H2 and CO2 gases. Furthermore, it demonstrates an adsorption heat of 29.3 kJ mol-1 for C2H2, which is lower than that observed in the majority of MOFs used for C2H2/CO2 separations. The preferential adsorption of C2H2 over that of CO2 is confirmed by dispersion-corrected density functional theory (DFT-D) calculations. In addition, the potential of industrial feasibility of NKM-123 for C2H2/CO2 separation is confirmed by transient breakthrough tests. The robust cycle performance and structural stability of NKM-123 during multiple breakthrough tests show great potential in the industrial separation of light hydrocarbons.

Polynorbornenes with carbocyclic substituents: A perspective approach to highly permeable gas separation membranes

Gas transport properties of two sets of polynorbornenes bearing carbocyclic substituents of different nature (cyclohexyl, norbornyl, phenyl groups, and framed oligocyclic moieties) were systematically studied. The influence of side chain carbocyclic substituents on gas permeability and separation selectivity for CO2-containing gas pairs and gaseous hydrocarbons was evaluated. It was found that the presence of carbocyclic moieties in side chains of polynorbornenes promotes the increase in gas permeability similarly to that of SiMe3 groups, with this effect being enhanced by the increase in the number of cycles in the substituents. As a result, P(CO2) of the metathesis polymer with pentacene-based substituents is equal to 1200 Barrer. Studied polynorbornenes with carbocyclic substituents displayed promising gas separation selectivities: CO2/N2 separation selectivity up to 41 (above the 2008 upper bound in the Robeson diagram) and solubility-controlled hydrocarbon separation selectivity up to 16 for the n-butane/methane gas pair. For the polymer with pentacene-based substituents, the separation of the mixture of hydrocarbons and aging were studied. The studies revealed that the mixed gas C4/C1 separation selectivity of this polymer reaches 4, and a two-time reduction of permeability occurs in 8.5 months. Therefore, the incorporation of carbocyclic groups in the side chains of polynorbornenes can be considered as an efficient strategy for the design of polymeric gas separation membrane materials.

Effective C4 Separation by Zeolite Metal-Organic Framework Composite Membranes.

Inorganic zeolites have excellent molecular sieving properties, but they are difficult to process into macroscopic structures. In this work, we use metal-organic framework (MOF) glass as substrates to engineer the interface with inorganic zeolites, and then assemble the discrete crystalline zeolite powders into monolithic structures. The zeolites are well dispersed and stabilized within the MOF glass matrix, and the monolith has satisfactory mechanical stabilities for membrane applications. We demonstrate the effective separation performance of the membrane for 1,3-butadiene (C4H6) from other C4 hydrocarbons, which is a crucial and challenging separation in the chemical industry. The membrane achieves a high permeance of C4H6 (693.00±21.83 GPU) and a high selectivity over n-butene, n-butane, isobutene, and isobutane (9.72, 9.94, 10.31, and 11.94, respectively). This strategy opens up new possibilities for developing advanced membrane materials for difficult hydrocarbon separations.

Effective C4 Separation by Zeolite Metal–Organic Framework Composite Membranes

AbstractInorganic zeolites have excellent molecular sieving properties, but they are difficult to process into macroscopic structures. In this work, we use metal–organic framework (MOF) glass as substrates to engineer the interface with inorganic zeolites, and then assemble the discrete crystalline zeolite powders into monolithic structures. The zeolites are well dispersed and stabilized within the MOF glass matrix, and the monolith has satisfactory mechanical stabilities for membrane applications. We demonstrate the effective separation performance of the membrane for 1,3‐butadiene (C4H6) from other C4 hydrocarbons, which is a crucial and challenging separation in the chemical industry. The membrane achieves a high permeance of C4H6 (693.00±21.83 GPU) and a high selectivity over n‐butene, n‐butane, isobutene, and isobutane (9.72, 9.94, 10.31, and 11.94, respectively). This strategy opens up new possibilities for developing advanced membrane materials for difficult hydrocarbon separations.

Exploring ionic liquids for the extraction separation of aromatic hydrocarbons from diesel via multiple interaction analyses coupled with experimental evaluation

The separation of aromatic hydrocarbons from petroleum fractions is of great significance for both the quality upgrading of products and value-added utilization of aromatic compounds. However, the separation of polycyclic aromatic hydrocarbons (PAHs) and their derivatives from diesel remains challenging because of their lower solubility and selectivity as compared to the monocyclic aromatic compounds. In this work, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TF2N]) was screened from 320 ionic liquid (IL) candidates through solvent capacity predication using COSMO-RS method. Liquid-liquid equilibrium experiments were carried out using a series of tetralin/n-decane mixtures with different tetralin concentrations to evaluate the extraction performance of several solvents. The results indicate that [EMIM][TF2N] has high selectivity up to 95.73 for tetralin over n-decane, which is 4.5 and 3.9 times higher than that of dimethyl sulfoxide and sulfolane. During five regeneration cycles, the [EMIM][TF2N] exhibits consistent extraction performance and nearly complete recovery. Molecular polarity index (MPI) analysis indicates that tetralin has larger dissolving affinity to solvents as compared to n-decane. Combined analyses of interaction energy, energy decomposition, and visualization of weak interaction reveal that the crucial role of weak hydrogen bond in dominating the complex solvent–solute interactions. Compared to n-decane, tetralin shows a stronger interaction with the solvents due to the existence of C-H···π and hydrogen bond interactions. The great difference in interaction energy between {[EMIM]+ + tetralin} and {[EMIM]+ + n-decane}, therefore, endows [EMIM][TF2N] with high selectivity for tetralin. Given the dominant role of cation, a IL, [CN1 = C2SCCS2(CC = C)C1][TF2N] having both high selectivity and high solvent capacity was subsequently explored using the cation generation method based on the SeqVAE model. Furthermore, present study proposes a strategy for the design of ILs for separation and other specific application circumstances.

Investigating Hydrocarbon Gases Permeability Through Hollow Fiber Hybrid Carbon Membrane

Hydrocarbon separation from natural gases is a critical procedure in the chemical and petrochemical industries. This study used hollow fiber carbon membranes (HFCMs) made from a commercially available co-polyimide, P84, with zeolite-carbon composite (ZCC) as a filler to separate light hydrocarbons like CH4/C3H8 and CH4/C2H6. The Arrhenius technique was used to evaluate the effects of temperature fluctuations (298, 323, and 373 K) on the membrane. X-ray diffraction exhibited a characteristic graphite peak at 2θ ~ 44°, indicating the creation of an effective carbon membrane. SEM investigation revealed the compactness of both pristine and hybrid carbon membrane structures. The operating temperature has a significant influence on the gas penetration through the membrane when evaluating gas permeation. The hybrid carbon membrane has the highest permeability for CH4, C2H6, and C3H8 at 373 K. (81.86, 61.82, and 58.28 Barrer, respectively). The carbon membrane also showed greatest selectivity for CH4/C3H8 and CH4/C2H6 at 323 K (2.24 and 2.04, respectively). Adsorption and surface diffusion were the membrane's transport mechanisms. By adding filler to the membrane, the gas permeability was temperature dependent.

Two-Dimensional Nanoporous Cross-linked Polymer Networks as Emerging Candidates for Gas Adsorption.

This paper illustrates the gas adsorption properties of newly synthesized nanoporous cross-linked polymer networks (CPNs). All synthesized CPNs possess N-rich functional groups and are used for the utilization of carbon dioxide and methane. Good gas adsorption and selectivities are obtained for all of the samples. Among the materials, HEREON2 outperforms better selectivity for methane separation from nitrogen rather than zeolites, activated carbons, molecular sieves, covalent organic frameworks, and metal-organic frameworks (MOFs). The accessibility of the N-rich functionalities makes these materials potential candidates for the separation of hydrocarbons via increased polarizabilities. High-pressure adsorption experiments showed that the synthesized two-dimensional nanoporous materials also have a high affinity toward carbon dioxide. HEREON2 powders showed an increased experimental CO2/N2 selectivity of ∼25,000 at 50 bar due to the presence of nitrogen groups in the structure. Fourier-transform infrared spectroscopy (FTIR), solid-state NMR, X-ray diffraction, thermogravimetric analysis, energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were applied for the characterization of the synthesized nanoporous CPNs. The results show a potential new pathway for future CPN membrane development.

Complete separation of benzene-cyclohexene-cyclohexane mixtures via temperature-dependent molecular sieving by a flexible chain-like coordination polymer

The separation and purification of C6 cyclic hydrocarbons (benzene, cyclohexene, cyclohexane) represent a critically important but energy intensive process. Developing adsorptive separation technique to replace thermally driven distillation processes holds great promise to significantly reduce energy consumption. Here we report a flexible one-dimensional coordination polymer as an efficient adsorbent to discriminate ternary C6 cyclic hydrocarbons via an ideal molecular sieving mechanism. The compound undergoes fully reversible structural transformation associated with removal/re-coordination of water molecules and between activated and hydrocarbon-loaded forms. It exhibits distinct temperature- and adsorbate-dependent adsorption behavior which facilitates the complete separation of benzene, cyclohexene and cyclohexane from their binary and ternary mixtures, with the record-high uptake ratios for C6H6/C6H12 and C6H10/C6H12 in vapor phase and highest binary and ternary selectivities in liquid phase. In situ infrared spectroscopic analysis and ab initio calculations provide insight into the host-guest interactions and their effect on the preferential adsorption and structural transformation.

A molecular T-pentomino for separating BTEX hydrocarbons

Methods to separate molecules (e.g., petrochemicals) are exceedingly important industrially. A common approach for separations is to crystallize a host molecule that either provides an enforced covalent cavity (intrinsic cavity) or packs inefficiently (extrinsic cavity). Here we report a self-assembled molecule with a shape highly biased to completely enclose space and, thereby, pack efficiently yet hosts and allows for the separation of BTEX hydrocarbons (i.e., benzene, toluene, ethylbenzene, xylenes). The host is held together by N → B bonds and forms a diboron assembly with a shape that conforms to a T-shaped pentomino. A T-pentomino is a polyomino, which is a plane figure that tiles a plane without cavities and holes, and we show the molecule to crystallize into one of six polymorphic structures for T-pentomino tiling. The separations occur at mild conditions while rejecting similarly shaped aromatics such as xylene isomers, thiophene, and styrene. Our observation on the structure and tiling of the molecular T-pentomino allows us to develop a theory on how novel synthetic molecules that mimic the structures and packing of polyominoes can be synthesized and—quite counterintuitively—developed into a system of hosts with cavities used for selective and useful separations.

Hydrocarbon Extraction with Ionic Liquids.

Separation and reaction processes are key components employed in the modern chemical industry, and the former accounts for the majority of the energy consumption therein. In particular, hydrocarbon separation and purification processes, such as aromatics extraction, desulfurization, and denitrification, are challenging in petroleum refinement, an industrial cornerstone that provides raw materials for products used in human activities. The major technical shortcomings in solvent extraction are volatile solvent loss, product entrainment leading to secondary pollution, low separation efficiency, and high regeneration energy consumption due to the use of traditional organic solvents with high boiling points as extraction agents. Ionic liquids (ILs), a class of designable functional solvents or materials, have been widely used in chemical separation processes to replace conventional organic solvents after nearly 30 years of rapid development. Herein, we provide a systematic and comprehensive review of the state-of-the-art progress in ILs in the field of extractive hydrocarbon separation (i.e., aromatics extraction, desulfurization, and denitrification) including (i) molecular thermodynamic models of IL systems that enable rapid large-scale screening of IL candidates and phase equilibrium prediction of extraction processes; (ii) structure-property relationships between anionic and cationic structures of ILs and their separation performance (i.e., selectivity and distribution coefficients); (iii) IL-related extractive separation mechanisms (e.g., the magnitude, strength, and sites of intermolecular interactions depending on the separation system and IL structure); and (iv) process simulation and design of IL-related extraction at the industrial scale based on validated thermodynamic models. In short, this Review provides an easy-to-read exhaustive reference on IL-related extractive separation of hydrocarbon mixtures from the multiscale perspective of molecules, thermodynamics, and processes. It also extends to progress in IL analogs, deep eutectic solvents (DESs) in this research area, and discusses the current challenges faced by ILs in related separation fields as well as future directions and opportunities.

Separation of benzene and toluene associated with vapochromic behaviors by hybrid[4]arene-based co-crystals

The combination of macrocyclic chemistry with co-crystal engineering has promoted the development of materials with vapochromic behaviors in supramolecular science. Herein, we develop a macrocycle co-crystal based on hybrid[4]arene and 1,2,4,5-tetracyanobenzene that is able to construct vapochromic materials. After the capture of benzene and toluene vapors, activated hybrid[4]arene-based co-crystal forms new structures, accompanied by color changes from brown to yellow. However, when hybrid[4]arene-based co-crystal captures cyclohexane and pyridine, neither structures nor colors change. Interestingly, hybrid[4]arene-based co-crystal can separate benzene from a benzene/cyclohexane equal-volume mixture and allow toluene to be removed from a toluene/ pyridine equal-volume mixture with purities reaching 100%. In addition, the process of adsorptive separation can be visually monitored. The selectivity of benzene from a benzene/cyclohexane equal-volume mixture and toluene from a toluene/ pyridine equal-volume mixture is attributed to the different changes in the charge-transfer interaction between hybrid[4]arene and 1,2,4,5-tetracyanobenzene when hybrid[4]arene-based co-crystal captures different vapors. Moreover, hybrid[4]arene-based co-crystal can be reused without losing selectivity and performance. This work constructs a vapochromic material for hydrocarbon separation.

Recent Progress and Challenges in the Field of Metal–Organic Framework-Based Membranes for Gas Separation

Metal–organic frameworks (MOFs) represent the largest class of materials among crystalline porous materials ever developed, and have attracted attention as core materials for separation technology. Their extremely uniform pore aperture and nearly unlimited structural and chemical characteristics have attracted great interest and promise for applying MOFs to adsorptive and membrane-based separations. This paper reviews the recent research into and development of MOF membranes for gas separation. Strategies for polycrystalline membranes and mixed-matrix membranes are discussed, with a focus on separation systems involving hydrocarbon separation, CO2 capture, and H2 purification. Challenges to and opportunities for the industrial deployment of MOF membranes are also discussed, providing guidance for the design and fabrication of future high-performance membranes. The contributions of the underlying mechanism to separation performance and adopted strategies and membrane-processing technologies for breaking the selectivity/permeability trade-off are discussed.

Separation of Aromatic Hydrocarbons from Straight-Run Naphtha by Bimetallic Halides

Separation of Aromatic Hydrocarbons from Straight-Run Naphtha by Bimetallic Halides

Advanced separation of mineral oil aromatic hydrocarbons by number of aromatic rings using donor-acceptor-complex chromatography to extend on-line coupled liquid chromatography-gas chromatography

An automated implementation for a subfractionation of mineral oil aromatic hydrocarbons (MOAH) into a mono-/di-aromatic fraction (MDAF) and a tri-/poly-aromatic fraction (TPAF) is presented, which is highly demanded by the European Food Safety Authority (EFSA) respecting the genotoxic and carcinogenic potential of MOAH. For this, donor-acceptor-complex chromatography (DACC) was used as a selective stationary phase to extend the conventional instrumental setup for the analysis of mineral oil hydrocarbons via on-line coupled liquid chromatography-gas chromatography-flame ionization detection (LC-GC-FID). A set of six new internal standards was introduced for the verification of the MOAH fractionation and a quantification of MDAF and TPAF, respectively. The automated DACC approach was applied to representative petrochemical references as well as to food samples, such as rice and infant formula, generally showing well conformity with results obtained by state-of-the-art analysis using two-dimensional GC (GCxGC). Relative deviations of DACC/LC-GC-FID compared to GCxGC-FID methods regarding the ≥ 3 ring MOAH content ranged between -50 and +6 % (median: -2 %, all samples, only values above limit of quantification). However, crucial deviations mainly result from “border-crossing” substances, e.g., dibenzothiophenes or partially hydrogenated MOAH. These substances can cause overestimations of ≥ 3 ring MOAH fraction during GCxGC analysis due to co-elution, which is mostly avoided using the DACC approach. Furthermore, the DACC approach can help to minimize underestimations of toxicologically relevant ≥ 3 ring MOAH caused by an unavoidable loss of MOAH during epoxidation, since natural olefins, such as terpenes, predominantly elute in MDAF, which was exemplarily shown for an olive oil and a terpene reference. The presented approach can be implemented easily in existing LC-GC-FID setup for an automated and advanced screening of MOAH to lower the need for elaborate GCxGC analysis also in routine environments.

Fine-regulation of gradient gate-opening in nanoporous crystals for sieving separation of ternary C3 hydrocarbons.

The adsorptive separation of ternary propyne (C3H4)/propylene (C3H6)/propane (C3H8) mixtures is of significant importance due to its energy efficiency. However, achieving this process using an adsorbent has not yet been accomplished. To tackle such a challenge, herein, we present a novel approach of fine-regulation of the gradient of gate-opening in soft nanoporous crystals. Through node substitution, an exclusive gate-opening to C3H4 (17.1 kPa) in NTU-65-FeZr has been tailored into a sequential response of C3H4 (1.6 kPa), C3H6 (19.4 kPa), and finally C3H8 (57.2 kPa) in NTU-65-CoTi, of which the gradient framework changes have been validated by in situ powder X-ray diffractions and modeling calculations. Such a significant breakthrough enables NTU-65-CoTi to sieve the ternary mixtures of C3H4/C3H6/C3H8 under ambient conditions, particularly, highly pure C3H8 (99.9%) and C3H6 (99.5%) can be obtained from the vacuum PSA scheme. In addition, the fully reversible structural change ensures no loss in performance during the cycling dynamic separations. Moving forward, regulating gradient gate-opening can be conveniently extended to other families of soft nanoporous crystals, making it a powerful tool to optimize these materials for more complex applications.