Location of MTBE and toluene in the channel system of the zeolite mordenite: Adsorption and host–guest interactions

Abstract

a b s t r a c tThis paper reports a study of the location of Methyl Tertiary Butyl Ether (MTBE) and toluene molecules adsorbed in the pores of the organophylic zeolite mordenite from an aqueous solution. The presence of these organic molecules in the zeolite channels was revealed by structure refinement performed by the Rietveld method. About 3 molecules of MTBE and 3.6 molecules of toluene per unit cell were incorporated into the cavities of mordenite, representing 75% and 80% of the total absorption capacity of this zeolite. In both cases a water molecule was localized inside the side pocket of mordenite. The saturation capacity determined by the adsorption isotherms, obtained by batch experiments, and the weight loss given by thermogravimetric (TG) analyses were in very good agreement with these values. The interatomic distances obtained after the structural refinements suggest MTBE could be connected to the framework through a water molecule, while toluene could be bonded to framework oxygen atoms. The rapid and high adsorption of these hydrocarbons into the organophylic mordenite zeolite makes this cheap and environmental friendly material a suitable candidate for the removal of these pollutants from water.

Insights into Adsorption of Chlorobenzene in High Silica MFI and FAU Zeolites Gained from Chromatographic and Diffractometric Techniques

“…Actually, the physical method based on adsorption processes is a recuperative method exploited for in situ water treatments which combines high flexibility of the system, efficiency even at low concentration levels, low energy, cheap operating costs, and possible waste reductions [3]. Different adsorbent materials can be employed, and their efficiency depends on the host-guest interactions between sorbent and sorbate [4][5][6][7][8][9][10][11][12][13]. In general, carbonaceous adsorbents are low cost materials, widely employed in remediation technology.…”

“…The main advantages are related to their high surface area and porous structure, high specific capacity and organic pollutants selectivity. Additionally, fast kinetics, mechanical, biological and chemical stability make them promising and efficient adsorbents [4,[6][7][8][26][27][28]. Furthermore, their high thermal stability guarantees the possibility of regeneration through thermal treatments in order to reintroduce them in new adsorption processes [5,[29][30][31][32][33].…”

“…This work is part of a wider study aimed at systematically evaluating the adsorptive capacity of high silica zeolites (HSZ) (e.g., mordenite, ZSM-5, faujasite, beta, ferrierite [4,7,10,29,30]) for fuel-based compounds differing in chemical properties (e.g., polarity, functional groups, size, host-guest interactions, etc. ), which can provide useful information to accurately predict the behavior of HSZs as well as improve their individual performance.…”

Pressure-induced penetration of guest molecules in high-silica zeolites: the case of mordenite

“…39,40 In its Si-rich form, mordenite has been used for the adsorption of pollutants from aqueous media. [41][42][43][44][45][46] Otherwise, it is worth noting that mordenite has never been exploited up to now to incorporate organic molecules under pressure.…”

“…This material was characterized by different techniques (SEM, surface area, porosimetric analysis, thermogravimetric analysis, and FTIR spectroscopy) and was used in previous work on the adsorption of pollutants from waste water. [41][42][43][44][45][46] FTIR spectroscopy revealed the presence of a large quantity of silanol defects produced by the dealumination process. 44 The high concentration of silanols explains the ability of this sample to adsorb a significant amount of water determined by TG analysis, which should be stabilized in the side pockets where the majority of defects are located.…”