Selective Separation of BTEX Mixtures Using Metal–Organic Frameworks

Abstract

We use molecular simulation to study the selective adsorption of BTEX mixtures (benzene, toluene, ethylbenzene, xylenes) in metal–organic frameworks. The adsorption of these compounds is a basic step in reutilizing petrochemical industry derivatives. BTEX mixture components are precursors to polymers such as poly(ethylene terephthalate). It is also important to store these molecules due to their high toxicity to humans. We study the storage, adsorption selectivity, distribution, and overall behavior of the adsorbed molecules inside the structures. We use MOF-1, MIL-47, and IRMOF-1 to test the effect of the size of the cavities and the topology of the structure in the adsorption of the components of the mixture. We found that these structures are useful to separate ethylbenzene and o-xylene from the BTEX mixtures.

Metal organic frameworks as sorption media for volatile and semi-volatile organic compounds at ambient conditions

“…If expressed as Henry’s constants (mol kg −1 Pa −1 ) (Table S7), the MOF-199 values for benzene, toluene, and p-xylene in the present work (at 298 K) are comparable to those of MOF-1, MIL-47, and IRMOF-1 extrapolated to 298 from 448 K using the van’t Hoff equation and reported isosteric ΔH ab 56. For instance, in the case of toluene, the Henry’s constant of MOF-199 (>5.3), in this work is comparable to that of MOF-1 (14.2)56. However, for the benzene/MOF-199 system at 298 K, our Henry’s constant (>2.1) at a benzene pressure of 0.0081 Pa is significantly larger than the 5.08 × 10 −2 (at a benzene pressure of 44 Pa) calculated from the data given by Yang et al 57…”

“…However, MOF-199 demonstrated maximum equilibrium adsorption capacities for phenols (27.9 mg g −1 ) and indoles (12.2 mg g −1 ) ( Table 3 ). If expressed as Henry’s constants (mol kg −1 Pa −1 ) ( Table S7 ), the MOF-199 values for benzene, toluene, and p-xylene in the present work (at 298 K) are comparable to those of MOF-1, MIL-47, and IRMOF-1 extrapolated to 298 from 448 K using the van’t Hoff equation and reported isosteric ΔH ab 56 . For instance, in the case of toluene, the Henry’s constant of MOF-199 (>5.3), in this work is comparable to that of MOF-1 (14.2) 56 .…”

Structural, energetic and dynamic insights into the abnormal xylene separation behavior of hierarchical porous crystal

“…Based on the Einstein’s equation, the self-diffusion coefficients of oX, mX, and pX can be fitted as 9.53(5) × 10 −10 , 5.25(2) × 10 −10 , and 3.81(2) × 10 −10 m 2 /s, respectively, which are similar with other PCPs with channel diameters of ca. 10 Å 42 44 . The importance of the small and flexible apertures of 1 for the abnormal xylene separation behavior can be also demonstrated by MD simulations for two hypothetical materials derived from 1 , in which pX molecules were fixed into the small apertures as observed by the crystal structure ( 1a ) or the host framework was treated as a rigid body ( 1b ).…”

“…On the other hand, as a method for long-range averaged structural information at the thermodynamic equilibrium state, crystallography may qualitatively judges the relative strengths of host-guest interactions (i.e., cannot quantitatively determine the host-guest interaction energies) and can hardly reveal the dynamic or kinetic information of the guest molecules. In this regard, computational simulation can serve as an important supplementary for studying the energetic and kinetic aspects of the host-guest system 41 42 43 44 45 46 47 .…”

Exploiting Large‐Pore Metal–Organic Frameworks for Separations through Entropic Molecular Mechanisms

“…Currently,o ne of the best performing MOFs is the strongly ortho-selective MIL-47 structure. [139,140,147] To designa nd find structures that could perform better,w e should look for structures that:1 )are highly para-xylene selective, 2) have al arge capacity,a nd 3) make use of that large pore volumeb yo perating at, or near, saturation conditions. To rres-Knoop et al screened for commensurate stacking and focusedo ns tructures with pore dimensions around 10 .…”