title: Unraveling the adsorption mechanism of mono- and diaromatics in faujasite zeolite.
abstract: Monte Carlo simulations are performed to study the adsorption of aromatic molecules (toluene, styrene, o-xylene, m-xylene, p-xylene, 1,3,5-trimethylbenzene, and naphthalene) in all-silica faujasite (FAU) zeolite. For monoaromatics, a two-stage "ideal adsorption" and "insertion adsorption" mechanism is found by careful inspection of locations and distributions of the adsorbed toluene molecules. The validity of this mechanism is confirmed for all monoaromatics considered in the current study. Remarkably, the number of C atoms per unit cell corresponding to the inflection point of adsorbate loading (CI-P) is defined as a valid and convenient characterizing factor in the packing efficiency of monoaromatics in the FAU zeolite. For the case of naphthalene, a type of diaromatic, the three-stage mechanism is proposed, which consists of the first two stages and a third stage of "overideal adsorption". The so-called overideal adsorption is labeled because the naphthalene molecules start to occupy the S site nonideally at loadings that approach saturation, leading to a more localized feature of the adsorbates. The explicit adsorption mechanism can be used to understand the loading dependence of isosteric adsorption heat for the aromatics concerned.
authors.affiliation: †State Key Laboratory of Heavy Oil Processing, China University of Petroleum (Beijing), 18 Fuxue Road, Beijing 102249, China.
authors.forename: Huimin
authors.initials: H
authors.lastname: Zheng
authors.affiliation: †State Key Laboratory of Heavy Oil Processing, China University of Petroleum (Beijing), 18 Fuxue Road, Beijing 102249, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhao
authors.affiliation: †State Key Laboratory of Heavy Oil Processing, China University of Petroleum (Beijing), 18 Fuxue Road, Beijing 102249, China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Ji
authors.affiliation: †State Key Laboratory of Heavy Oil Processing, China University of Petroleum (Beijing), 18 Fuxue Road, Beijing 102249, China.
authors.forename: Jinsen
authors.initials: J
authors.lastname: Gao
authors.affiliation: †State Key Laboratory of Heavy Oil Processing, China University of Petroleum (Beijing), 18 Fuxue Road, Beijing 102249, China.
authors.forename: Chunming
authors.initials: C
authors.lastname: Xu
authors.affiliation: ‡Scientific Development Division, TOTAL S.A., 24 Cours Michelet, 92069 Cedex Paris La Defense, France.
authors.forename: Francis
authors.initials: F
authors.lastname: Luck
keywords: FAU zeolite; Monte Carlo simulation; adsorption; aromatics