Competitive Adsorption of Xylenes at Chemical Equilibrium in Zeolites

Abstract

The separation of xylenes is one of the most important processes in the petrochemical industry. In this article, the competitive adsorption from a fluid-phase mixture of xylenes in zeolites is studied. Adsorption from both vapor and liquid phases is considered. Computations of adsorption of pure xylenes and a mixture of xylenes at chemical equilibrium in several zeolite types at 250 °C are performed by Monte Carlo simulations. It is observed that shape and size selectivity entropic effects are predominant for small one-dimensional systems. Entropic effects due to the efficient arrangement of xylenes become relevant for large one-dimensional systems. For zeolites with two intersecting channels, the selectivity is determined by a competition between enthalpic and entropic effects. Such effects are related to the orientation of the methyl groups of the xylenes. m -Xylene is preferentially adsorbed if xylenes fit tightly in the intersection of the channels. If the intersection is much larger than the adsorbed molecules, p -xylene is preferentially adsorbed. This study provides insight into how the zeolite topology can influence the competitive adsorption and selectivity of xylenes at reaction conditions. Different selectivities are observed when a vapor phase is adsorbed compared to the adsorption from a liquid phase. These insight have a direct impact on the design criteria for future applications of zeolites in the industry. MRE-type and AFI-type zeolites exclusively adsorb p -xylene and o -xylene from the mixture of xylenes in the liquid phase, respectively. These zeolite types show potential to be used as high-performing molecular sieves for xylene separation and catalysis.

Epitaxial Growth of Two-Dimensional MWW Zeolite

“…Compared with MCM-56, the D / L 2 of BN-MWW is 64 times higher for PX, and is 6 times lower for OX. The MCM-56 exposes a significant amount of external 12 MR channels where OX is preferentially adsorbed . Delaminated MWW and exfoliated MWW were further included in comparison , (Figures S42 and S43).…”

“…where q t /q ∞ the normalized loading, D is the diffusivity, and L is the characteristic diffusion length. 45 46 Delaminated MWW and exfoliated MWW were further included in comparison 47,48 (Figures S42 and S43). Among different types of MWW zeolites (Figure S44), BN-MWW exhibits the highest PX diffusion time constant and the largest PX/OX selectivity, which can be attributed to its unique 2D architecture and crystallographic orientation, surface openness and more intact 10 MR interior channels.…”

Clearing Properties Between Coconut Oil and Xylene in Histological Tissue Processing

“…24 Approximately 95% of xylene is produced primarily through the catalytic reformation of petroleum. 25 It is used as a solvent in the manufacturing of chemicals, an ingredient in aviation fuel and gasoline, 26 and a feedstock in manufacturing various polymers, phthalic anhydride, isophthalic acid, terephthalic acid, and dimethyl terephthalate. 27 Xylene is the most recommended clearant due to properties such as its melting range (−47.87C to 13.26C).…”

A full visible LED enabled by a broadband yellow emission nepheline phosphor derived from a europium doped SOD zeolite

“…Zeolites are microporous aluminosilicates constructed by connecting the corner sharing TO 4 tetrahedra (T = Si, Al), [1][2][3] the commercial relevance of which is being demonstrated by a wide range of practical applications such as catalysis, adsorption, ion-exchange, selective separation, etc., [4][5][6][7] owing to their overwhelming advantages including the abundant micropores of molecular dimensions, ion-exchanging ability, tunable morphology and size, and high stability, to name a few. 8,9 Recent advances made in materials community highlight that zeolites can be promising host materials or starting materials for developing luminescent materials through the insertion of luminescent centers within the micropores of zeolites.…”