Computational Modeling and Advanced Synthesis Techniques for the Improved Design of Zeolite Catalysts
| dc.contributor.advisor | Grabow, Lars C. | |
| dc.contributor.advisor | Rimer, Jeffrey D. | |
| dc.contributor.committeeMember | Harold, Michael P. | |
| dc.contributor.committeeMember | Epling, William S. | |
| dc.contributor.committeeMember | Brgoch, Jakoah | |
| dc.contributor.committeeMember | Konstantinov, Ivan A. | |
| dc.creator | Ghorbanpour, Arian | |
| dc.date.accessioned | 2019-11-12T03:36:54Z | |
| dc.date.available | 2019-11-12T03:36:54Z | |
| dc.date.created | December 2015 | |
| dc.date.issued | 2015-12 | |
| dc.date.submitted | December 2015 | |
| dc.date.updated | 2019-11-12T03:36:55Z | |
| dc.description.abstract | Zeolites are the most widely used catalysts in industry due to a unique combination of features such as porous structure and high surface area, voids and channels of molecular dimensions, tunable active sites, and environmentally benign properties. To realize their great potential requires a thorough knowledge of structure-function relationships for rational zeolite design. Active sites in zeolites are created by Al substitution of framework Si atoms in crystallographically different positions on the exterior or in the interior of zeolite crystals. This leads to heterogeneous chemical/kinetic behavior of various active sites, which can be employed to tune the activity, selectivity, and lifetime of zeolites in catalytic processes. On the experimental side of this project, we enhance the shape selectivity of ZSM-5, an important zeolite catalyst in the petrochemical industry, by manipulating its active site distribution. Therefore, an advanced synthesis method was designed to passivate the external surface of ZSM-5 particles and suppress the reaction of bulky reactants over the exterior of the catalyst particles. The inert overlayer growth is performed at very low thicknesses and in an epitaxial structure so that the mass transfer limitations due to the added layer is minimized and the activity of internal active sites is not compromised. We continue our investigation of the impact of heterogeneous distribution of active sites through atomic-scale modeling. Our density functional theory (DFT) simulation of H-ZSM-5 internal active sites reveal a large variation in the acidity and adsorption characteristics of 12 distinct active sites. The modeling of a test reaction, the dehydration of methanol to dimethyl ether (DME), indicates that the pore confinement effects that vary among different H-ZSM-5 active site locations result in nonidentical kinetic behavior through different extents of transition state stabilization. This heterogeneous performance not only causes different rates of reaction, but also impacts the dominant reaction mechanism at typical reaction conditions. The distribution of H-ZSM-5 active sites in the form of paired acid sites, more likely to form in Al-rich zeolites, is also studied, which shows evidence for significant adsorption and kinetic variations compared to isolated active sites. | |
| dc.description.department | Chemical and Biomolecular Engineering, Department of | |
| dc.format.digitalOrigin | born digital | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.citation | Portions of this document appear in: Ghorbanpour, Arian, Abhishek Gumidyala, Lars C. Grabow, Steven P. Crossley, and Jeffrey D. Rimer. "Epitaxial growth of ZSM-5@ Silicalite-1: A core–shell zeolite designed with passivated surface acidity." ACS nano 9, no. 4 (2015): 4006-4016. And in: Ghorbanpour, Arian, Jeffrey D. Rimer, and Lars C. Grabow. "Periodic, vdW-corrected density functional theory investigation of the effect of Al siting in H-ZSM-5 on chemisorption properties and site-specific acidity." Catalysis Communications 52 (2014): 98-102. | |
| dc.identifier.uri | https://hdl.handle.net/10657/5379 | |
| dc.language.iso | eng | |
| dc.rights | The author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. UH Libraries has secured permission to reproduce any and all previously published materials contained in the work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s). | |
| dc.subject | Zeolites | |
| dc.subject | H-ZSM-5 | |
| dc.subject | Catalysis | |
| dc.subject | Active sites | |
| dc.subject | Heterogeneity | |
| dc.subject | Core-shell | |
| dc.subject | DFT | |
| dc.title | Computational Modeling and Advanced Synthesis Techniques for the Improved Design of Zeolite Catalysts | |
| dc.type.dcmi | Text | |
| dc.type.genre | Thesis | |
| thesis.degree.college | Cullen College of Engineering | |
| thesis.degree.department | Chemical and Biomolecular Engineering | |
| thesis.degree.discipline | Chemical Engineering | |
| thesis.degree.grantor | University of Houston | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy |