Adsorption Of Xylene Isomers Research Articles

Efficient adsorption separation of xylene isomers on Cu-BTC@Fe3O4 by appropriate activation methods

Metal-organic frameworks (MOFs) are a class of nanoporous materials. The development of efficient and environmentally friendly methods for activating MOFs is of great significance for its industrial application. In this work, nanoscale magnetic core-shell Cu-BTC@Fe3O4 was prepared through a secondary growth strategy. The effects of different activation solvents (dichloromethane and ethanol, respectively) and temperatures on the surface area, pore structures and the adsorption of xylene isomers on Cu-BTC@Fe3O4 were investigated. Ethanol as an activation solvent could more easily displace the precursors remaining in the channels of Cu-BTC@Fe3O4 than dichloromethane, while the temperature change has no significant influence on the pore structure. The adsorption separation of xylene isomers on Cu-BTC@Fe3O4 composite materials was studied using the batch vapor-phase adsorption, and liquid-phase breakthrough experiments. The activated Cu-BTC@Fe3O4 (CH2Cl2-200 ​°C ​− ​C2H5OH) material has the highest adsorption capacity of 210.26 ​mg ​g−1 for p-xylene (pX). Cu-BTC@Fe3O4 (C2H5OH) and Cu-BTC@Fe3O4 materials have excellent adsorption capacity for m-xylene (mX), with the values of 200.19 ​mg ​g−1 and 219.63 ​mg ​g−1, respectively, which is about 4 times higher than that of Cu-BTC@Fe3O4 (CH2Cl2). The adsorption capacity sequence of xylene on Cu-BTC@Fe3O4 (C2H5OH) and Cu-BTC@Fe3O4 materials is m-xylene (mX) ​> ​p-xylene (pX) ​> ​o-xylene (oX), and that of other materials is pX ​> ​mX ​> ​oX.

Unusual porous crystals via catenation of 1D ladders: unprecedented mixture effects on the adsorption of xylene isomers in a SCSC mode

The pseudo 2D open-channel crystals formed via catenation of 1D ladders show unusual mixture effects on the adsorption of o-, m-, and p-xylene isomers in a SCSC mode, and are a practical template for structural determination of small hydrocarbons.

Adsorption behavior of water and xylene isomers on AlPO-5 zeolite modified by different transition metals

This work deals with the preparation of MAPO-5 zeolite by a hydrothermal method. In order to study the adsorption properties of this zeolite several transition metals (Fe, Co, Ni, Mn and Zn) were incorporated by a direct route. The obtained zeolites were characterized by various physico-chemical techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, adsorption/desorption of argon, thermogravimetric analysis/differential thermal analysis, scanning electronic microscopy (FEG-ESEM) and Inductively coupled plasma–optical Emission spectrometry (ICP-OES). The prepared zeolites were tested for adsorption of water and xylene isomers (ortho-, para- and meta-xylene). The obtained results showed that the isomorphic substitution of the transition metals in the framework of the zeolite has been achieved with different levels of metals. The isomorphic substitution by zinc showed the best results in terms of the percentage of the incorporated metal, while the substitution by cobalt presented the lowest rate of incorporation in the framework of the zeolite CoAPO-5. The adsorption of water in the vapor state on the zeolite substituted by Ni, Fe and Zn has presented the best adsorption capacity. The adsorption of xylene isomers on MAPO-5 showed different isotherms, confirming that the adsorption behavior differs from one zeolite to another. ZnAPO-5 showed higher adsorption capacity for all xylene isomers with slight selectivity towards meta-xylene.

Adsorption of xylene isomers using Ba-faujasite type zeolite: Equilibrium and kinetics study

In the present study, liquid phase isotherm adsorption of single component of para xylene, meta xylene, ortho xylene, and ethylbenzene onto a commercial molecular sieve adsorbent (SPX3000-fine) at three different temperatures of 25, 50 and 75°C had been investigated. It was found that para xylene was the most adsorbed component followed by ethylbenzene, meta xylene and ortho xylene, showing the strong adsorption of para xylene by the understudy adsorbent. All kinds of used xylene isomers brought out decreased adsorption loading on SPX3000-fine zeolite with increasing the temperature in the range of 25–75°C. Aims to study the description of equilibrium adsorption data, Langmuir, Freundlich, and Tempkin isotherms were applied, which superiority of Langmuir model to describing equilibrium isotherm data with the highest R2 values was obtained. The kinetic study was performed by applying three kinetic models of pseudo-first-order, pseudo-second-order and intraparticle diffusion. According to the obtained results, the pseudo-second-order model is the best representative model to describe the kinetic adsorption data. Also, thermodynamic study revealed that due to the negative values of adsorption heat and Gibbs free energy changes, the adsorption of para xylene in the binary system proceeded an exothermic spontaneous process.

Adsorption of xylene isomers in MOF UiO-66 by molecular simulation

This work presents results of molecular simulations on adsorption of mixtures of the four xylene isomers in the porous zirconium terephthalate UiO-66. The grand-canonical Monte Carlo simulations (GCMC) are compared to multi-component adsorption equilibrium data obtained by breakthrough experiments. Four different force fields for the xylenes were evaluated. The simulations confirm that the experimentally observed ortho-selectivity is preferential in relation to the other isomers. Additionally, it was found that there is a competition between the other three isomers (para-xylene, meta-xylene and ethylbenzene) for adsorption in the UiO-66 structure. Molecular simulation is applied as a powerful research tool in predicting adsorption equilibrium properties of potential adsorbent candidates for xylene isomers mixtures that are essential for the development of adsorption based separation processes.

Adsorption of xylene isomers on Na-BETA zeolite: Equilibrium in batch adsorber

In this article, adsorption of p-xylene, m-xylene, o-xylene, and ethylbenzene on Na-BETA type zeolite in liquid phase at 15, 25, and 35°C has been studied and the single adsorption isotherms have been obtained and reported. The Langmuir isotherm model was used to describe the experimental adsorption isotherm data. It was found that p-xylene is more strongly adsorbed component followed by ethylbenzene, m-xylene and o-xylene. This means that this adsorbent is selective for p-xylene. Using Langmuir isotherm model, the saturation adsorption capacities of the adsorbent were obtained as follows 143mg/g for p-xylene, 105mg/g for ethylbenzene, 83mg/g for m-xylene, and 68mg/g for o-xylene at 25°C. The heat of adsorption was also estimated to be 12.0, 11.4, 9.6, and 8.3kJ/mol−1 for p-xylene, ethylbenzene, m-xylene, and o-xylene, respectively.

Adsorption of xylene isomers on ordered hexagonal mesoporous FDU-15 polymer and carbon materials

The oil industry has been facing the challenges of separation of xylene isomers, o-xylene, m-xylene and p-xylene or removing them from the environment. In our present work, we investigated the adsorption of the three isomers on two mesoporous materials, FDU-15-350 polymer and FDU-15-900 carbon materials. The isomer adsorption capacities are well correlated with their physical pore properties. It is found that the micropores are very crucial for the adsorption of these three isomers. The more micropore volume the adsorbent has, the better the adsorption capacity is. Henry’s constants were also calculated for the three isomers on the two adsorbents. Both on FDU-15-350 polymer and FDU-15-900, the Henry’s constants for the three isomers show the same trend o>m>p xylene which is coincidently in accordance with their polarity trend, indicating more polar adsorbate is preferred for adsorption on the two adsorbents. The isosteric heats of adsorption are correlated with the microporosity and the size of the adsorbate molecule. More microporosity and smaller molecules give higher heats of adsorption. Extracted information on pore properties of adsorbents by using the three isomers has very similar results as that resolved from nitrogen adsorption, indicating the feasibility of using the three isomers as adsorbates to extract pore information.

Studies on adsorption equilibrium of xylenes in AEL framework using biased GCMC and energy minimization

The adsorption of xylene isomers in AlPO 4-11 (AEL network) was investigated using biased grand canonical Monte Carlo (GCMC) simulations. Preferential o-xylene adsorption was predicted by the simulations, in agreement with previously reported experimental data. In AlPO 4-11 the selective adsorption behavior comes from the smaller length of the o-xylene molecule along the crystallographic c-axis compared to p-xylene. This is in contrast to AlPO 4-5 and AlPO 4-8, where the ortho-selectivity is caused by the characteristic face-to-face positioning of o-xylene. Energy minimization studies were also performed in a flexible AlPO 4-11 lattice to study the structural changes upon xylene adsorption. The energy minimization study showed that the AlPO 4-11 crystal distorts upon p- and o-xylene adsorption. The distortion mechanism is related to the strong interaction between xylene methyl groups and the sieve oxygen atoms in the O3 position in the wide region of the pore.