Quantitative structure–property relationship approach to predicting xylene separation with diverse exchanged faujasites

Abstract

Streamlining the xylene separation process on faujasites is a promising way to design innovative adsorbents for this application. For this purpose, we present herein an original quantitative structure-property relationship (QSPR) approach. It deals with the development of a multi-linear predictive model correlating the separation properties with a set of structural descriptors for the adsorbents. The implementation of such an approach makes it necessary to (i) set an appropriate design of experiment (DOE), (ii) prepare an adsorbent database, (iii) test the adsorbent database for xylene separation and (iv) compute a set of relevant descriptors. The selected descriptors essentially characterize the nature of the confinement in the faujasite supercage, i.e., the size of the cations localized in adsorption sites II, as well as the occupancy ratio of both adsorption sites II and III. Two different statistical methods were applied to develop a structure-property relationship model linking experimental selectivity and the set of descriptors. A multiple linear regression model enables the prediction of para/meta-xylene selectivity with a correlation coefficient R2 of 0.78, while a linear discriminant analysis predicts the assignment of the adsorbents to four identified classes with a total prediction percentage of 76%.

Metrics for Evaluation and Screening of Metal–Organic Frameworks for Applications in Mixture Separations

“…The freezing point of p -xylene is significantly higher than that of other C8 aromatics; on cooling, therefore, pure p -xylene crystals are the first to emerge from the solution. Selective adsorption of p -xylene from liquid-phase mixtures of C8 aromatics is achieved with cation-exchange FAU zeolite adsorbent, such as BaX, in a simulated moving bed (SMB) adsorption device. − The hierarchy of adsorption strengths in BaX is dictated by molecular packing, or entropy, effects that prevail under pore saturation conditions in liquid-phase SMB separations. ,− Unlike PSA technologies for gaseous separations, the SMB process operates continuously under steady-state conditions; see the schematic in Figure .…”

Hydrogen Storage, Magnetism and Electrochromism of Silver Doped FAU Zeolite: First-principles Calculations and Molecular Simulations

“…The transition metal (TM) cations introduced by exchanging Si or Al covalent atoms with lower valence state atoms of III or II main group in zeolite framework at specific porous locations can present specific physical-chemistry environment due to the characteristic metal-framework interaction and dominate the adsorption and heterogeneous catalysis performance [1]. Recent studies primarily focus into controlling reactivity and exploring the correlated mechanism especially for the octahedral zeolites (faujasites) [1,2,3]. The octahedral framework structure of faujasites with nanoscale pore is constructed by eight sodalite cages that are connected by oxygen bridges between hexagonal faces, so as to build a large central supercage with a cavity of ~12 Å diameter and 12 faces of atomic ring with 7~8 Å diameter [4,5].…”