NMR Studies of Emulsions in Porous Media and Applications to Fischer-Tropsch Synthesis
type: CreativeWork
description: As global reserves of conventional fossil fuels are dwindling, Fischer-Tropsch (FT) is a promising and greener method to convert natural gas into liquid fuels. However, it is highly complex and remains thus far poorly understood. The work presented in this thesis employs nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) to gain insight into and elucidate the multiphase behaviour and transport processes of Fischer-Tropsch Synthesis (FTS) reactants and products. In order to achieve this, the world’s first operando NMR compatible reactor was designed, commissioned and built to ultimately optimise the conversion of Gas-to-Liquids (GTL) through the FT process. A particular focus of this work lies on the application of a pulsed-field gradient (PFG) NMR emulsion detection technique to characterise hydrocarbon-in-water emulsions and study their droplet size distribution (DSD) inside porous media under operando conditions ($\geq$180 $\degree$ C and $\geq$36 bar). The initial study into droplet formation was done on $\theta$-Al2O3 pellets by relaxometry and PFG NMR measurements at ambient conditions, where dodecane and water were model compounds for FT products. The relaxation results indicated that water was the surface wetting phase, while dodecane was isolated from the pore surface. Spontaneous dodecane-in-water droplets formed, suggested by the restrictive diffusion behaviour for dodecane in the binary mixture. This trend was confirmed in Q-silica beads as well as in Ru-based FT catalyst pellets. Subsequently, the influence of (i) temperature, (ii) pore size, (iii) surfactant and (iv) surface modification on emulsion formation was investigated. Little impact of temperature and pore size was found for the ranges studied. However, a longer alcohol chain length lead to a small increase in droplet size. Furthermore, if the catalyst surface became hydrophobic with stearic acid, spontaneous emulsion formation did no longer occur. Studying FTS $\textit{in sit…
abstract: As global reserves of conventional fossil fuels are dwindling, Fischer-Tropsch (FT) is a promising and greener method to convert natural gas into liquid fuels. However, it is highly complex and remains thus far poorly understood. The work presented in this thesis employs nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) to gain insight into and elucidate the multiphase behaviour and transport processes of Fischer-Tropsch Synthesis (FTS) reactants and products. In order to achieve this, the world’s first operando NMR compatible reactor was designed, commissioned and built to ultimately optimise the conversion of Gas-to-Liquids (GTL) through the FT process. A particular focus of this work lies on the application of a pulsed-field gradient (PFG) NMR emulsion detection technique to characterise hydrocarbon-in-water emulsions and study their droplet size distribution (DSD) inside porous media under operando conditions ($\geq$180 $\degree$ C and $\geq$36 bar). The initial study into droplet formation was done on $\theta$-Al2O3 pellets by relaxometry and PFG NMR measurements at ambient conditions, where dodecane and water were model compounds for FT products. The relaxation results indicated that water was the surface wetting phase, while dodecane was isolated from the pore surface. Spontaneous dodecane-in-water droplets formed, suggested by the restrictive diffusion behaviour for dodecane in the binary mixture. This trend was confirmed in Q-silica beads as well as in Ru-based FT catalyst pellets. Subsequently, the influence of (i) temperature, (ii) pore size, (iii) surfactant and (iv) surface modification on emulsion formation was investigated. Little impact of temperature and pore size was found for the ranges studied. However, a longer alcohol chain length lead to a small increase in droplet size. Furthermore, if the catalyst surface became hydrophobic with stearic acid, spontaneous emulsion formation did no longer occur. Studying FTS $\textit{in sit…
author: van Thiel, Leonard Rudolf
language: en
keywords: Gas-to-Liquids, Fischer-Tropsch, Emulsions, Porous Media, Nuclear Magnetic Resonance, Magnetic Resonance Imaging, Pulsed-Field Gradient, Diffusion, Oil and Gas
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/05658002-a48b-4298-abbd-efcafca97354/download
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2020-07-17
date modified: 2026-07-22T22:24:14Z
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.51375