Applying NMR Relaxation Methods to the Study of Liquids in Porous Media

The work presented within this thesis focusses on the development of NMR relaxation techniques to unambiguously characterise the adsorption behaviour of liquids imbibed within catalytic materials. Principally, this study is centred on γ-alumina, which is used industrially as both a catalyst and a catalyst support. Ratios of fixed field T1 and T2 values were compared with fast field cycling (FFC-) NMR measurements. For each technique the relative advantages and disadvantages were explored, and methodologies allowing a robust implementation of these techniques to study the adsorption were presented. Fixed field measurements of T1,B/T1,pore and e_surf=-T2/T1 were used to compare the relative interaction strength for a range of liquids imbibed within γ-alumina. A strong correlation between the adsorbate polarity and the T1,B/T1,pore ratio of rigid molecules showed the sensitivity of high field NMR to surface adsorption processes. However when flexible molecules were studied the presence of internal motions distorted the trends in the relaxation behaviour, making both the T1,B/T1,pore and e_surf measurements unsuitable. FFC-NMR was explored as an alternative to fixed field NMR. This allowed the measurement of relaxation behaviour over a range of low field strengths. The FFC-NMR data showed a clear ordering of the solid-liquid interaction strengths, which was more consistent with the predicted physical chemistry of the system than the order given by a fixed field analysis. For methanol and acetone imbibed within γ-alumina multicomponent relaxation behaviour was observed. The origin of this was shown to be functionality specific adsorption behaviour, and the presence of a stable reaction intermediate respectively. These observations led to a more granular understanding of the adsorption. A formal modelling approach was then applied to the FFC-NMR data in order to extract quantitative correlation times that described the dynamics of each adsorbate at the catalyst surface. The sensitivity of FFC-NMR to coadsorption was further studied through the use of binary liquid mixtures. A model for the interpretation of the relaxation behaviour of each component in the binary mixture was proposed and used to demonstrate the liquid structuring and micro-phase separation that occurred during adsorption.

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2020

Author dc:creator

• Ward-Williams, Jordan

Advisor dc:contributor.advisor

• Gladden, Lynn

• NMR
• NMR relaxation
• Fast Field Cycling
• Porous Materials
• Alumina
• Microphase Separations

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/7b597db2-082f-46d4-b530-7551f326a1b5/download
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

eng

Author Identifier

0000-0001-9519-0406

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/309110