Ternary Hydrocarbon Mixtures Research Articles

Synergistic C2H2 Binding Sites in Hydrogen-Bonded Supramolecular Framework for One-Step C2H4 Purification from Ternary C2 Mixture.

Purification of C2H4 from the ternary C2 hydrocarbon mixture in one step is of critical significance but still extremely challenging according to its intermediate physical properties between C2H6 and C2H2. Hydrogen-bonded organic frameworks (HOFs) stabilized by supramolecular interactions are emerging as a new kind of adsorbents that facilitate green separation. However, it remains a problem to efficiently realize the one-step C2H4 purification from C2H6/C2H4/C2H2 mixture because of the low C2H2/C2H4 selectivity. We herein report a robust microporous HOF (termed as HOF-TDCPB) with dense O atoms and aromatic rings distributed on the pore surface which provide C2H6 and C2H2 preferred environment simultaneously. Dynamic breakthrough experiments indicate that HOF-TDCPB can not only obtain high-purity C2H4 from binary C2 mixture, but also firstly realize one-step C2H4 purification from ternary C2H6/C2H4/C2H2 mixture, with the C2H4 productivity of 3.2 L/kg (>99.999 %) for one breakthrough cycle. Furthermore, HOF-TDCPB displays outstanding stability in air, organic solvents and water, which endow it excellent cycle performance even under high-humidity conditions. Theoretical calculations indicate that multiple O sites on pore channels can create synergistic binding sites for C2H2, thus affording overall stronger multipoint interactions.

Synergistic C2H2 Binding Sites in Hydrogen‐Bonded Supramolecular Framework for One‐Step C2H4 Purification from Ternary C2 Mixture

AbstractPurification of C2H4 from the ternary C2 hydrocarbon mixture in one step is of critical significance but still extremely challenging according to its intermediate physical properties between C2H6 and C2H2. Hydrogen‐bonded organic frameworks (HOFs) stabilized by supramolecular interactions are emerging as a new kind of adsorbents that facilitate green separation. However, it remains a problem to efficiently realize the one‐step C2H4 purification from C2H6/C2H4/C2H2 mixture because of the low C2H2/C2H4 selectivity. We herein report a robust microporous HOF (termed as HOF‐TDCPB) with dense O atoms and aromatic rings distributed on the pore surface which provide C2H6 and C2H2 preferred environment simultaneously. Dynamic breakthrough experiments indicate that HOF‐TDCPB can not only obtain high‐purity C2H4 from binary C2 mixture, but also firstly realize one‐step C2H4 purification from ternary C2H6/C2H4/C2H2 mixture, with the C2H4 productivity of 3.2 L/kg (>99.999 %) for one breakthrough cycle. Furthermore, HOF‐TDCPB displays outstanding stability in air, organic solvents and water, which endow it excellent cycle performance even under high‐humidity conditions. Theoretical calculations indicate that multiple O sites on pore channels can create synergistic binding sites for C2H2, thus affording overall stronger multipoint interactions.

Experimental study on Joule-Thomson refrigeration system with R1150/R290/R601a for ultra-low temperature medical freezer

Since the global outbreak of the COVID-19, the requirement for ultra-low temperature medical freezers has increased rapidly. Joule-Thomson refrigeration systems, known for their simple structure and low cost, are an excellent choice for ultra-low temperature medical freezers. To further improve the performance of Joule-Thomson system for large-capacity ultra-low temperature freezer, this study conducted a series of experiments on the performance of a ternary hydrocarbon mixture R1150/R290/R601a. The impacts of refrigerant charge, capillary tube size, compressor speed, and environmental temperature on the steady-state and dynamic performance were investigated in detail. The results showed that under a fixed system configuration and charge, the freezer can achieve an ultra-low temperature of −82.2 °C and a COP of 0.256 at an environmental temperature of 25 °C, while maintaining a low compressor pressure ratio not exceeding 12. Furthermore, the matching relationship between capillary size and charge was emphatically studied, and it was found that the optimal refrigerant charge increased as the inside diameter of the capillary tube decreased or its length increased. The inside diameter had a more significant effect on system performance than the length. The suitable charge was 225–275 g for capillary tubes with an inside diameter of 1.4 mm, and increased to 400–450 g for an inside diameter of 0.7 mm. In addition, the experiments with various compressor speeds indicated that, before the cabinet temperature dropped to −40 °C, the variation of compressor speed had little effect on the pull-down rate. However, the higher the compressor speed, the lower the cabinet temperature that can be achieved. When the speed was 3500 rpm, the system achieved its lowest daily energy consumption, which was 8.42 kW·h/24 h.

Topological isomer effect on one-step C2H4 purification from ternary C2 hydrocarbon mixture

One-step separation of C2H4 from ternary C2H2/C2H4/C2H6 hydrocarbon mixtures is desirable yet challenging in the industry due to their similar sizes and physical properties. Herein, we investigate the topological isomer effect on the relationship of pore environments and one-step separation of C2H4. IAM-8 and NU-912 are topological isomers that are obtained with the identical molecular formula [Zr6(μ3-O)8(H2O)8(PPTBA)2)]·(solvents)x (H4PPTBA = 4,4′,4′',4′''-(pyrrolo[3,2-b]pyrrole-1,2,4,5-tetrayl) tetrabenzoic acid) but with different topologies, (4,8)-connected sqc and scu, respectively. Both IAM-8 and NU-912 exhibit inverse adsorption behaviors. The IAM-8 shows excellent C2H6/C2H4 (v/v = 10/90) selectivity of 2.1 and a large uptake ratio of 120% (78.70/65.78 cm3 g−1) at 298 K and 1 bar. The NU-912 exhibits relatively lower C2H6/C2H4 (v/v = 10/90) selectivity of 1.5 and adsorption capacity (63.00/47.00 cm3 g−1) at 298 K and 1 bar. GCMC and DFT simulations show that the higher adsorption capacity of IAM-8 relative to that of NU-912, as well as the C2H6/C2H4 selectivity of IAM-8 over NU-912, is due to pore size and shape matching. Dynamic breakthrough experiments demonstrate that polymer-grade C2H4 (>99.9%) can be harvested in one step from a ternary mixture of C2H2/C2H6/C2H4 (1/9/90, v/v/v) for both materials, but indeed showing a better performance for IAM-8. This work is the first case to demonstrate the topological isomer effect to fulfill the pore matching requirement in promoting the challenging one-step C2H4 separation.

Viscosities and Densities of Binary and Ternary Mixtures of Aliphatic and Polyaromatic Hydrocarbons: Pyrene +1-Methylnaphthalene + Dodecane at T = (293.15 to 343.15) K. Experiment and Modeling.

This work presents new experimental viscosity and density data for aromatic and polyaromatic compounds in binary and ternary pyrene, 1-methylnaphthalene, and dodecane mixtures. The lack of experimental viscosity data for these mixtures requires the development of a new database, which is vital for understanding the behavior of mixtures in more complex systems, such as asphaltenes and fuels. The mixtures proposed in this work have been measured over a temperature range of (293.15 to 343.15) K at atmospheric pressure. Several mixture compositions have been studied at these conditions: 1.0, 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0% pyrene mass fraction. The concentration of pyrene correlates with an increase in the viscosity and density values. At the lowest temperature in binary mixtures, the corresponding values reach 4.4217 mPa·s for viscosity and 1.0447 × 103 kg·m-3 for density, respectively. In ternary mixtures, the introduction of dodecane leads to the lowest maximum values of 3.5555 mPa·s for viscosity and 1.0112 × 103 kg·m-3 for density at the same temperature. The experimental data have been employed for the specific modification of viscosity models. These modifications could facilitate the prediction of the viscosity of mixtures that are more complex than those presented in this work. Various viscosity models have been employed, such as Linear, Ratcliff and Khan, modified UNIFAC-Visco, and Krieger-Dougherty. The settings in the models used reliably reproduce the experiment reliably. However, the Ratcliff model agrees excellently with the experiment, having a low standard deviation (2.0%) compared to other models. Furthermore, a model based on the equation of state of Guo is proposed to predict the viscosity values by modifying the specific parameters and adjusting them to the mixtures proposed in this work. The results from this study are compared to previous work, where pyrene, toluene, and heptane mixtures were analyzed. In this case, we find that the decrease of aggregation grade in the present systems is predicted by the model fixed in this work.

Direct Ethylene Purification from Cracking Gas via a Metal–Organic Framework Through Pore Geometry Fitting

The direct one-step separation of polymer-grade C2H4 from complex light hydrocarbon mixtures has high industrial significance but is very challenging. Herein, an ethylene-adsorption-weakening strategy is applied for precise regulation of the pore geometry of four tailor-made metal–organic frameworks (MOFs) with pillar-layered structures, dubbed TYUT-10/11/12/13. Based on its pore geometry design and functional group regulation, TYUT-12 exhibits exceptional selective adsorption selectivity toward C3H8, C3H6, C2H6, C2H2, and CO2 over C2H4; its C2H6/C2H4 adsorption selectivity reaches 4.56, surpassing the record value of 4.4 by Fe2(O2)(dobdc) (dobdc4− = 2,5-dioxido-1,4-benzenedicarboxylate). The weak π–π stacking binding affinity toward C2H4 in TYUT-12 is clearly demonstrated through a combination of neutron powder diffraction measurements and theoretical calculations. Breakthrough experiments demonstrate that C2H4 can be directly obtained from binary, ternary, quaternary, and six-component light hydrocarbon mixtures with over 99.95% purity.

Flexible Microporous Framework for One-Step Acquisition of Ethylene from Ternary C2 Hydrocarbons.

One-step purification of ethylene (C2H4) from ternary C2 hydrocarbon mixtures is a crucial task and an enduring challenge because of their similar molecular size and physical properties. Owing to their intriguing structural dynamics, flexible MOFs have attracted more attention for gas adsorption and separation. Herein, we report a flexible MOF FJI-W-66 that exhibits rarely seen "breathing" behaviors for C2 hydrocarbons. Upon activation, the channels of guest-free FJI-W-66a significantly contract to a nearly closed-pore state. FJI-W-66a shows the stepwise adsorption isotherms for C2 hydrocarbons, which suggests the occurrence of structural transformation between less open and more open phases. Breakthrough experiments provide evidence that FJI-W-66a can selectively separate C2H4 from C2H2/C2H4/C2H6 mixtures with different ratios under ambient conditions, realizing the one-step acquisition of C2H4 from ternary C2 hydrocarbons.

Incorporation of multiple supramolecular binding sites into a robust MOF for benchmark one-step ethylene purification

One-step adsorption separation of C2H4 from ternary C2 hydrocarbon mixtures remains an important and challenging goal for petrochemical industry. Current physisorbents either suffer from unsatisfied separation performance, poor stability, or are difficult to scale up. Herein, we report a strategy of constructing multiple supramolecular binding sites in a robust and scalable MOF (Al-PyDC) for highly efficient one-step C2H4 purification from ternary mixtures. Owing to suitable pore confinement with multiple supramolecular binding sites, Al-PyDC exhibits one of the highest C2H2 and C2H6 uptakes and selectivities over C2H4 at ambient conditions. The gas binding sites have been visualized by single-crystal X-ray diffraction studies, unveiling that the low-polarity pore surfaces with abundant electronegative N/O sites provide stronger multiple supramolecular interactions with C2H2 and C2H6 over C2H4. Breakthrough experiments showed that polymer-grade C2H4 can be separated from ternary mixtures with a maximum productivity of 1.61 mmol g−1. This material can be prepared from two simple reagents using a green synthesis method with water as the sole solvent, and its synthesis can be easily scaled to multikilogram batches. Al-PyDC achieves an effective combination of benchmark separation performance, high stability/recyclability, green synthesis and easy scalability to address major challenges for industrial one-step C2H4 purification.

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).

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.

Adsorption in a centrifugal field: A thermodynamic analysis

External fields such as gravitational, centrifugal or electrical fields lead to an uneven spatial distribution of the chemical compounds of a system. In this work, we conceive a scenario where a packing bed is submitted to a centrifugal field, so that centrifugation and adsorption occur simultaneously. Our rotating packed bed is made up by two main regions: one, representing the bulk phase, the other, representing the total pore volume available for adsorption. At constant temperature, total volume, and total amount, the distribution of species of selected binary and ternary mixtures of hydrocarbons, carbon dioxide, and hydrogen sulfide is predicted by minimizing the total Helmholtz energy of the system. Confinement-modified equations of state are employed as thermodynamic model for the adsorbed phase, while the Peng-Robinson equation of state is used in bulk phase calculations. Our purely thermodynamic analysis reveal that coupling both phenomena could be useful to enhance adsorption, or increase the separation obtained when only centrifugation is considered.

Sublethal Effects of Ternary Mixtures of Polycyclic Aromatic Hydrocarbons on Selected Liver Biomarkers of Clarias gariepinus

The effect of ternary mixtures of polycyclic aromatic hydrocarbons in Clarias gariepinus was investigated. Apparently healthy juvenile fish (n = 90) weighing 19.7±1.8 g were exposed to sublethal concentrations of naphthalene, phenathrene and benzo[a]pyrene over a period of 35 days after which liver biomarker analyses were carried out on blood plasma fraction. The observed total plasma protein was 35.1 g/L while the albumin and total bilirubin concentrations were 15.9 g/L and 4.6 μmol/L respectively. The plasma concentrations of the liver enzymes were 25.27 IU/L, 9.37 IU/L, and 28.01 IU/L for alanine transaminase (ALT), aspartate transaminase (AST), and alkaline phosphatase (ALP) respectively. While there were significant declines in plasma total protein and albumin, significant elevation was observed in plasma total bilirubin. Significant increases were also observed in the activities of the liver enzymes, alanine transaminase (ALT), aspartate transaminase (AST) and alkaline phosphatase (ALP). Exposed liver and gill sections showed histopathological alteration. There was steatosis accompanied with moderate dense infiltrates in the liver while the gills showed channel dilatations with hyperplasia. Findings from this study suggest that PAH mixtures cause changes in the activities of liver metabolic enzymes as well as alter the normal architecture of liver and gills in exposed aquatic organisms.

Experimental measurement and theoretical prediction for lower flammability limits of ternary hydrocarbon mixtures

AbstractThe present work experimentally investigated the lower flammability limits of methane‐ethylene‐propane‐air mixtures at ambient temperature and pressure in a 20 L confined chamber. Moreover, a calculated flame temperature (CFT) modeling for predicting the lower flammability limit of multicomponent mixed combustible gas was proposed based on the law of conservation of energy. The results indicated that the relative error of Le Chatelier's law is 2.88% in the prediction of the lower flammability limit of the tested multicomponent mixed combustible medium. Also, the relative error of CFT modeling is only 1.47%, which is reduced by 48.96% and can significantly improve the prediction accuracy of the lower flammability limit of multicomponent mixtures. Furthermore, using the premixed laminar flame speed reactor, the USC 2.0 mechanism was employed to obtain the behavior of ternary hydrocarbon mixtures near the flammability limits. The sensitivity analysis showed that competition between the chain branching reaction R1 (H + O2 ⟺ O + OH) and the chain termination reaction R12 (H + CH3(+M) ⟺ CH4(+M)) was crucial in determining the lower flammable limit.

Synergistic binding sites in a hybrid ultramicroporous material for one-step ethylene purification from ternary C2 hydrocarbon mixtures.

One-step separation of C2H4 from ternary C2H2/C2H4/C2H6 hydrocarbon mixtures is of great significance in the industry but is challenging due to the similar sizes and physical properties of C2H2, C2H4, and C2H6. Here, we report an anion-pillared hybrid ultramicroporous material, CuTiF6-TPPY, that has the ability of selective recognition of C2H4 over C2H2 and C2H6. The 4,6-connected fsc framework of CuTiF6-TPPY exhibits semi–cage-like one-dimensional channels sustained by porphyrin rings and TiF62− pillars, which demonstrates the noticeably enhanced adsorption of C2H2 and C2H6 over C2H4. Dynamic breakthrough experiments confirm the direct and facile high-purity C2H4 (>99.9%) production from a ternary gas mixture of C2H2/C2H6/C2H4 (1/9/90, v/v/v) under ambient conditions. Computational studies and in situ infrared reveal that the porphyrin moieties with large π-surfaces form multiple van der Waals interactions with C2H6; meanwhile, the polar TiF62− pillars form C–H•••F hydrogen bonding with C2H2. In contrast, the recognition sites for C2H4 in the framework are less marked.

Zeolitic Octahedral Metal Oxides with Ultra‐Small Micropores for C2 Hydrocarbon Separation

AbstractSeparation of C2 hydrocarbons, C2H6, C2H4, and C2H2, remains significant challenges in chemical industry. However, there are only few adsorbents that can effectively isolate C2 hydrocarbons from their mixtures particularly at a high temperature. Herein, we design a zeolitic octahedral metal oxide based on ϵ‐Keggin polyoxometalates with metal ion linkers. Single gas adsorption of the material shows the different adsorption performances for the C2 hydrocarbons and the strong interaction of the material with the C2 hydrocarbons. Dynamic competitive adsorption experiments show that the material efficiently separates each of the binary C2 hydrocarbon mixtures and even the ternary C2 hydrocarbon mixtures with high selectivity. The material keeps high separation performance even the temperature was increased to 85 °C. The material is stable and is able to be reused without loss of the separation performance.

Zeolitic Octahedral Metal Oxides with Ultra-Small Micropores for C2 Hydrocarbon Separation.

Separation of C2 hydrocarbons, C2 H6 , C2 H4 , and C2 H2 , remains significant challenges in chemical industry. However, there are only few adsorbents that can effectively isolate C2 hydrocarbons from their mixtures particularly at a high temperature. Herein, we design a zeolitic octahedral metal oxide based on ϵ-Keggin polyoxometalates with metal ion linkers. Single gas adsorption of the material shows the different adsorption performances for the C2 hydrocarbons and the strong interaction of the material with the C2 hydrocarbons. Dynamic competitive adsorption experiments show that the material efficiently separates each of the binary C2 hydrocarbon mixtures and even the ternary C2 hydrocarbon mixtures with high selectivity. The material keeps high separation performance even the temperature was increased to 85 °C. The material is stable and is able to be reused without loss of the separation performance.

Behaviour of a Ternary Mixture with the Net Separation Ratio Close to Zero

The behaviour of the ternary hydrocarbon mixture of toluene-methanol-cyclohexane in mass proportion 0.62/0.31/0.07 is studied. The direct numerical simulation is carried out for the two-dimensional closed cavity heated from above. The mixture is supposed to be in the gravity field. The behavior of the mixture is predominantly caused by the Soret effect (thermal diffusion). An important parameter, responsible for the Soret effect, is the net separation ratio, Ψ. For the mixture under consideration, the two sets of values of Ψ are known. In both cases, the values of Ψ turn out to be close to zero, but in one case Ψ is slightly positive, and it is slightly negative in the second one. This results in qualitative difference in the evolution of the mixture under consideration. If Ψ > 0, the mixture comes to the mechanical equilibrium. If Ψ < 0, we observe the system to be at the border of stability, under small perturbation there is no instability, but for the perturbation amplitude higher than a threshold value of the convective single-vortex flow arises.

Optimized critical parameters for n-alkanes up to C100 for reliable multiphase behavior of hydrocarbon mixture using SRK EOS

The Soave-Redlich-Kwong equation of state (SRK EOS) is widely used for phase behavior simulation of hydrocarbon mixtures. However, its applicability and reliability are limited for heavier hydrocarbon mixtures and reservoir fluids. This research presents optimized critical temperatures (TC), critical pressures (PC), and acentric factors (ω) parameters for n-alkanes up to C100 for improved volumetric and compositional multiphase behavior predictions.Parameters TC, PC, and ω for C7 to C100 are optimized using Particle Swarm Optimization (PSO) to match the density as well as vapor pressure data. Average absolute relative deviations (AARDs) achieved are 1.9% and 2.4% respectively for density and vapor pressure matches, corresponding values for the unoptimized case are 53.23%, and 3.90% respectively. The case of optimization of ω only to match vapor pressure has AARD of 2.0% in comparison to 3.90% from unoptimized values.Binary interaction parameters (BIPs) are optimized by matching upper critical end point (UCEP) for CO2, CH4, C2, and C3 binaries with n-alkanes with their optimized TC PC ω, optimized ω (and unoptimized TC and PC) only, and unoptimized TC PC ω values cases. It is found that optimized TC PC ω is correctly able to show the presence of three-phases for all 23 ternary hydrocarbon mixtures.

Theoretical and numerical analysis of Soret-driven convection in a horizontal porous layer saturated by an n-component mixture: Application to ternary hydrocarbon mixture tetralin, isobutyl benzene, n-dodecane with mass fractions 0.8-0.1-0.1

The purpose of this paper is to present an analytical model for the thermogravitational separation process in a porous rectangular cavity, saturated by a multi-component mixture. In the first part, an analytical and a numerical study of the onset of the Soret driven convection of an n-component mixture saturating a homogeneous porous horizontal layer are presented. This study is based on the classical Darcy-Boussinesq equations which admit a mechanical equilibrium solution associated with the pure double diffusive regime. This solution is linearly stable up to a critical value of the stability parameters. The dispersion relation is obtained for an n-component mixture and the associated critical parameters are calculated analytically and numerically using the Galerkin spectral method for the stationary transition. Concerning the oscillatory transition, only the Galerkin spectral method is used. The second part of the study presents an analytical model based on the parallel flow approximation. The analytical solution for the unicellular flow is obtained and the separation is expressed in terms of the Lewis numbers (Le), the separation ratio (ψ), the cross diffusion coefficients (Cr) and the thermal Rayleigh number (Ra). The analytical results are validated using direct numerical simulations. The numerical and the analytical results obtained are in good agreement.

Use of a New Size-Weighted Combining Rule to Predict Adsorption in Siliceous Zeolites

The results of extensive grand canonical Monte Carlo simulations of adsorption in siliceous zeolites are reported and used to assess the accuracy of a size-weighted (SW) combining rule for Lennard-Jones cross-parameters. Adsorption isotherms, Henry’s Law constants, and isosteric heats were computed for 45 different systems consisting of unary, binary, ternary, and quaternary mixtures of light hydrocarbons in silicalite, pure methanol, and carbon dioxide in silicalite and light hydrocarbons in siliceous forms of the zeolites TON, LTA, and CHA. A comparison is made with the conventional Lorentz–Berthelot (LB) combining rule as well as other force fields and experimental data. In addition, the influence of intramolecular scaling methods and long-range tail corrections on computed properties was evaluated. Overall, the SW combining rule gives similar, and sometimes superior, results when compared to the LB combining rule as well as force fields tuned to experimental data.