Study of Adsorbate Interactions of Alumina Surfaces Using Nuclear Magnetic Resonance Methods
type: CreativeWork
description: Gamma type alumina (gamma-Al2O3) is a fundamental material in heterogeneous catalysis with a growing demand for environmentally benign solid acid catalysts to replace toxic and corrosive liquid solvents for a wide range of applications including renewable energy production, fine chemicals and petrochemicals. Given the complexity and amorphous nature of gamma-Al2O3, the role of water continues to be ambiguous and of significant interest for industry. This thesis has applied a combination of analytical techniques including high throughput experimentation (HTE), advanced NMR techniques, multivariate linear regression (MLR), X-ray diffraction (XRD), nitrogen porosimetry and thermogravimetric analysis (TGA) to address the fundamental research questions; what is the role of water in thermal, hydrothermal pretreatments and operating conditions for dimethyl methyl ether (DME) synthesis and is the hydroxyl coverage related to the catalytic activity? Advanced NMR techniques were performed, including NMR relaxometry and diffusiometry at 43 MHz to determine the absorbate-adsorbent interactions of the reactant (methanol, CH3OH) of DME synthesis and the by-product (water, H2O) following a thermal or a variation of a steam pretreatment step for gamma-Al2O3. Two types of steaming protocols were investigated, the critical difference being that one protocol steamed the alumina catalyst at the set-point only, whereas the alternative protocol also steamed the samples during the ramp and cool down. The two types of steam pretreatments and thermal pretreatments as a function of temperature (200-450 °C) were compared and showed a negligible interaction strength of small, rigid alkanes relative to the strongly interacting polar water and methanol guest molecules within the mesoporous oxide. Functional-specific analysis of methanol was performed via deuterated variants (CD3OH, CH3OD), with the molecular motion of the hydroxyl and aliphatic functional group differentiated. Tortuosity analysi…
abstract: Gamma type alumina (gamma-Al2O3) is a fundamental material in heterogeneous catalysis with a growing demand for environmentally benign solid acid catalysts to replace toxic and corrosive liquid solvents for a wide range of applications including renewable energy production, fine chemicals and petrochemicals. Given the complexity and amorphous nature of gamma-Al2O3, the role of water continues to be ambiguous and of significant interest for industry. This thesis has applied a combination of analytical techniques including high throughput experimentation (HTE), advanced NMR techniques, multivariate linear regression (MLR), X-ray diffraction (XRD), nitrogen porosimetry and thermogravimetric analysis (TGA) to address the fundamental research questions; what is the role of water in thermal, hydrothermal pretreatments and operating conditions for dimethyl methyl ether (DME) synthesis and is the hydroxyl coverage related to the catalytic activity? Advanced NMR techniques were performed, including NMR relaxometry and diffusiometry at 43 MHz to determine the absorbate-adsorbent interactions of the reactant (methanol, CH3OH) of DME synthesis and the by-product (water, H2O) following a thermal or a variation of a steam pretreatment step for gamma-Al2O3. Two types of steaming protocols were investigated, the critical difference being that one protocol steamed the alumina catalyst at the set-point only, whereas the alternative protocol also steamed the samples during the ramp and cool down. The two types of steam pretreatments and thermal pretreatments as a function of temperature (200-450 °C) were compared and showed a negligible interaction strength of small, rigid alkanes relative to the strongly interacting polar water and methanol guest molecules within the mesoporous oxide. Functional-specific analysis of methanol was performed via deuterated variants (CD3OH, CH3OD), with the molecular motion of the hydroxyl and aliphatic functional group differentiated. Tortuosity analysi…
author: Siddall, Gemma
language: eng
keywords: gamma alumina, methanol dehydration, catalyst pretreatment, active sites, NMR
license: https://creativecommons.org/licenses/by/4.0/
date published: 2022-01-17
date modified: 2026-07-22T22:24:11Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.86223