Adsorption Equilibria Of Gas Mixtures Research Articles

Multi-Compound H2, CH4, and N2 Adsorption Analysis

In order to study the purification of hydrogen and its separation from gas mixtures by adsorption, different models describing the adsorption equilibrium of gas mixtures have been tested; seven of them have been compared with experimental multi-component data obtained from the literature. The measurements include three-component mixtures of hydrogen, nitrogen, and methane. All the models used in this study are purely predictive; such models are competitive isotherm models which use only the previously obtained coefficients of the single-component isotherms. A mathematical description of each model is developed and discussed. Based on the results of numerical experiments, an analysis of how best to apply the Sips multi-component approach and the Ideal Adsorbed Solution theory is developed. A discussion on the ability and accuracy of the different models to describe the multi-component adsorption equilibria is developed. Based on this research, the Jovanovic model, which best reproduces the experimental results of the adsorption equilibrium in all cases, can be recommended as the most appropriate to use.

Molecular Dynamic Calculations of the Adsorption Equilibrium of Gas Mixtures in Micropores of Active Carbon and on Graphene Surfaces

As an addition to previously obtained data, it has been shown that the adsorption isotherms calculated by the molecular dynamics method for components of light hydrocarbon mixtures in micropores of active carbons and on graphene surfaces are quantitatively described by equations of lattice models with well-coordinated equation parameters.

Olefin/Paraffin Separation in Open Metal Site Cu-BTC Metal–Organic Framework

Adsorption in metal–organic frameworks with coordinatively unsaturated sites (CU’s) offers a cost-effective alternative to cryogenic processes for olefin/paraffin separation. Since experiments on adsorption equilibrium of gas mixtures are challenging, molecular simulation methods can be exploited to characterize the adsorption at CU’s. This work computationally addresses the adsorptive olefin/paraffin separation using Cu-BTC. To this end, we developed a parametrization of specific interactions between hydrocarbon molecules and the CU’s, which is of great interest for the modeling community. We obtain the host–guest interacting parameters for linear hydrocarbons by fitting to experimental single-component adsorption isotherms of ethane, ethene, propane, and propene and examine their transferability to larger hydrocarbons. In addition, we propose force field parameters for branched isobutane and isobutene. We then predict the adsorption selectivity of the binary alkane/alkene mixtures for chains from two to...

Effective Model for Olefin/Paraffin Separation using (Co, Fe, Mn, Ni)‐MOF‐74

AbstractAn increase in demand for energy efficient processes for the separation of saturated and unsaturated light hydrocarbons mixtures drives the need of noncryogenic processes. The adsorptive separation using Metal‐Organic Frameworks with coordinatively unsaturated metal sites may provide a cost‐effective alternative due to the strong binding of the metal cation with the unsaturated hydrocarbons. Since experiments on adsorption equilibrium of gas mixtures are challenging, we propose classical force field based simulations to analyse the ability of MOF‐74 with different metal substitutions for the separation of C2 and C3 olefin/paraffin binary mixtures. We parametrized the force field by fitting to available experimental single‐component adsorption isotherms of ethane, ethene, propane, and propene in M–MOF‐74 (M=Co, Fe, Mn, and Ni). The force field was validated for a variety of temperatures ranged from 273 K to 353 K. We then conducted Monte Carlo simulations in the Grand‐Canonical ensemble to elucidate the adsorption mechanisms of the saturated/unsaturated hydrocarbon mixtures, at 318 K and 353 K. We computed the adsorption isotherms, and from these the adsorption selectivity, and addressed the variations of MOF properties with different metal cations. Fe‐based MOF‐74 appears the best option for both ethane/ethene and propane/propene separation applications. This finding partly agrees with previous work based on the Ideal Adsorbed Solution Theory.

Application of a high-throughput analyzer in evaluating solid adsorbents for post-combustion carbon capture via multicomponent adsorption of CO2, N2, and H2O.

Despite the large number of metal-organic frameworks that have been studied in the context of post-combustion carbon capture, adsorption equilibria of gas mixtures including CO2, N2, and H2O, which are the three biggest components of the flue gas emanating from a coal- or natural gas-fired power plant, have never been reported. Here, we disclose the design and validation of a high-throughput multicomponent adsorption instrument that can measure equilibrium adsorption isotherms for mixtures of gases at conditions that are representative of an actual flue gas from a power plant. This instrument is used to study 15 different metal-organic frameworks, zeolites, mesoporous silicas, and activated carbons representative of the broad range of solid adsorbents that have received attention for CO2 capture. While the multicomponent results presented in this work provide many interesting fundamental insights, only adsorbents functionalized with alkylamines are shown to have any significant CO2 capacity in the presence of N2 and H2O at equilibrium partial pressures similar to those expected in a carbon capture process. Most significantly, the amine-appended metal organic framework mmen-Mg2(dobpdc) (mmen = N,N'-dimethylethylenediamine, dobpdc (4-) = 4,4'-dioxido-3,3'-biphenyldicarboxylate) exhibits a record CO2 capacity of 4.2 ± 0.2 mmol/g (16 wt %) at 0.1 bar and 40 °C in the presence of a high partial pressure of H2O.

Measurement and prediction of adsorption equilibrium for a H2/N2/CH4/CO2 mixture

AbstractAdsorption equilibrium data for the pure gases, H2, N2, CH4, CO2, and a H2/N2/CH4/CO2 mixture on activated carbon JX101 were collected by static and dynamic methods, respectively. The tested range covered temperatures of 283–328 K and pressures up to 30 × 105 Pa. The difference in the adsorption mechanisms between the super‐ and sub‐critical components was considered for both correlation of pure gas adsorption and prediction of multicomponent adsorption equilibrium. The surface heterogeneity, interaction among the adsorbed molecules, and the non‐ideal behavior of the adsorbed phase were also accounted for. As a consequence, the pure gas adsorption data were accurately correlated, and the multicomponent adsorption equilibrium was satisfactorily predicted by a proposed model. Applicability of the new model was verified with the present experimental data and with literature values. In all cases, the new model produced better agreement between the predicted data and the experimentally measured data than previous models. This indicates that the new model is probably applicable to predict the adsorption equilibrium of gas mixtures either partially or totally composed of supercritical gases. © 2007 American Institute of Chemical Engineers AIChE J, 2007

速度論に基づく活性炭における混合ガスの吸着平衡の予測

The multicomponent adsorption rate theory based on Dubinin-Astakhov model (MART-DA), which has been proposed in the previous report, is a practical model for predicting break-through curves of gas mixtures on activated carbon filter. In this paper, the MART-DA has been tested for abilities to predict total and component capacities reported for 13 sets of binary gas adsorption equilibria. Verified by the experimental data, it has been found that the MART-DA is successful in predicting adsorption equilibria of gas mixtures on activated carbon, and this precisions of prediction is comparable to that of the ideal adsorbed solution theory (IAST). From the mathematical study, a multicomponent adsorption isotherm equation (for N⪰2) has been derived from the MART-DA. For pure gas adsorption (for N=1), this isotherm equation is theoretically identical with Dubinin-Astakhov equation. Moreover, it has been clarified that the adsorption/desorption kinetics calculated from MART-DA is equivalent to the linear driving force (LDF) approximated adsorption rate calculation.

Adsorption equilibria of single gas and gas mixture on homogeneous surfaces: a unified approach based on statistical thermodynamics developments. Part II: extension to gas mixture adsorption

Theoretical description of single gas and gas mixture adsorption equilibria can be achieved in many different ways depending on the kind of approach (microscopic or macroscopic). In this paper, we present a statistical thermodynamics approach for the calculation of mixed gas adsorption equilibrium data on uniform surfaces. The non-ideality of both the mixed gas phase and the adsorbed phase is considered by using the Redlich–Kwong EOS associated to the classic Lorentz–Berthelot mixing rules. This is an interesting way to extend the model presented in Part I and to predict multicomponent gas adsorption equilibria for highly non-ideal systems from parameters deduced from pure gas data. We present mixture adsorption isotherms and selectivity curves calculated using our model.

Prediction of multicomponent adsorption equilibrium of gas mixtures including supercritical components

A new model to predict the adsorption equilibrium of mixtures containing supercritical components was presented. The difference in the adsorption mechanism between the supercritical components and the condensable components was accounted for in the new model. Lateral interaction in the adsorbed phase was also considered in the local isotherm. The new model was verified by the experimental data of the mixture CH 4/CO 2/C 2H 6 on activated carbon JX101 collected for 283–313 K and pressures up to 10 × 10 5 Pa . It was also verified with the experimental data published previously in literature. Considerable improvement in the prediction precision was achieved in using the new model to predict the adsorption of mixtures on activated carbon.

Gravimetric Measurement of Adsorption Equilibria of Gas Mixture CO/H2 with a Magnetic Suspension Balance

A new magnetic suspension balance (MSB) and a new experimental procedure have been developed which allow the adsorption equilibria of binary gas or vapor mixtures to be measured purely gravimetrically, i.e., by using only the balance. No additional analytic instrumentation, such as gas chromatograph or mass spectrometer, is required. The principle behind the measurements, the new instrument and the measurement procedure are described in detail. The MSB and the experimental procedure have been tested by performing coadsorption measurements with CO/H2 mixtures on a commercial 5Å zeolite.

Effects of non-ideal adsorption equilibria of gas mixtures on column dynamics

A theoretical study has been made for simulating the dynamic behavior of non-ideal gas mixtures in an isothermal fixed-bed adsorber. A mathematical model was developed which takes into account the non-ideality of adsorbable species on the adsorbed phase under equilibrium. The model is based on both the real adsorbed solution theory (RAST), which incorporates the activity coefficients in the multicomponent isotherm equations to account for the deviations from ideality, and the linear driving force (LDF) model for representing diffusion resistance inside the adsorbent particles. To describe the effect of non-ideal adsorption equilibrium of gas mixtures on the breakthrough curves, we considered several model mixtures of binary and ternary components which exhibit non-ideal behavior with azeotropic crossovers in the composition domains at equilibrium. Sample calculations of a fixed-bed adsorption were done with various inlet gas compositions of binary and ternary mixtures, respectively, at a fixed total concentration. From the calculation results, it was shown that the order of breakthrough curves could be changed at a certain value of inlet gas composition ratio. This result implies that the dynamic behaviors of fixed-bed adsorption are greatly influenced by multicomponent equilibrium models. Furthermore, the reversal phenomenon of breakthrough curves could not be simulated by the ideal adsorbed solution theory (IAST).

Adsorption of gas mixtures on adsorbents with heterogeneous surfaces

A method is presented for estimating the adsorption equilibrium of gas mixtures. This method is based on the hypothesis of energetic heterogeneity of adsorbents and assumes that the ideal adsorbed solution (IAS) theory is valid for describing gas mixture adsorption locally. An empirical procedure based on adsorption data of binary gas mixtures is developed for matching the energetic states of a given adsorbate with those of the other adsorbates. Predictions derived from this method were found to agree closely with the experimental data on systems which are known to be highly nonideal and cannot be dealt with adequately with existing theories.

Computer algorithm and graphical method for calculating adsorption equilibria of gas mixtures.

Adsorption equilibria of gas mixtures are predicted from single-gas isotherms that obey the Toth equation by a graphical procedure. Since the design of gas adsorbers requires repetitive calculations, a fast-converging algorithm has been designed for execution on a computer. Predicted adsorption isotherms agree very well with experimental data at low and moderate surface coverage.