Thermodynamics of translational and rotational dynamics of C9 hydrocarbons in the pores of zeolite-beta

• Published in: Journal of molecular graphics & modelling Vol. 114; p. 108188
• Main Authors: Al-Bahri, Osama H.S., Borah, Bhaskarjyoti, Elzain, Mohammed, Varanasi, Srinivasa Rao
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2022
• Subjects: Aromatic hydrocarbons; Diffusion; Molecular dynamics; Porous materials; Rotational dynamics; Zeolites; Molecular dynamics; Aromatic hydrocarbons; Rotational dynamics; Diffusion; Zeolites; Porous materials
• ISSN: 1093-3263; 1873-4243
• DOI: 10.1016/j.jmgm.2022.108188

There has been a growing interest in the separation of aromatic hydrocarbon molecules from the petroleum stream using zeolite-based technologies. This led to numerous experimental and molecular simulation studies of the structural and dynamical properties of aromatic hydrocarbons under the confinement of microporous materials like zeolites. The understanding of the behavior of the isomers of the trimethylbenzene under confinement is crucial for their separation and purification from industrial streams. Here, we investigate the translational and rotational dynamics and associated thermodynamics of three isomers of trimethyl benzene, namely, 1,2,3-trimethyl benzene (1,2,3-TMB), 1,2,4-trimethyl benzene (1,2,4-TMB), and 1,3,5-trimethylbenzene (1,3,5-TMB) under the confinement of zeolite-beta (BEA) using molecular dynamics (MD) simulations. The trends in the diffusion coefficients of the TMB isomers calculated from our MD simulation data are in good agreement with the data already available in the literature. Analysis of dynamics and associated thermodynamic properties indicate that 1,2,4-TMB is translationally more facile than the other two isomers. The rotational motion of TMB isomers is largely anisotropic and it is relatively more significant for both 1,2,4-TMB and 1,3,5-TMB. The thermodynamic properties reveal that the distinguishability in the dynamic properties among these three isomers is essentially caused by entropy. These results are not only critical to engineer the separation process of TMB isomers across the zeolite beds but also to understand the different catalytic processes such as trans-alkylation, conversion, cracking etc. [Display omitted] •Our results suggest that trimethyl benzene(TMB) isomers exhibit distinguishable translation and rotational dynamics under the confinement zeolite-β.•Among the three isomers, 1,2,4-TMB exhibits higher translational diffusion due to low activation energy barriers and its rotational motion is largely anisotropic.•The isomer, 1,2,3-TMB exhibits relatively facile reorientation dynamics as compared to other two isomers about any axis on its plane.•Both translational and reorientation dynamics of 1,3,5-TMB are largely hindered due to its larger size.