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Title: Magnetic resonance as a probe of solvent effects in heterogeneous catalysis
Author: Clayton, C.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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The first experimental work discussed in this thesis is a series of reaction studies to look at the effect of four solvents - methanol, propan-1-ol, propan-2-ol and octanol - on the hydrogenation of 4-tertiary butyl phenol (TBP). Experiments are first done in a stirred pot-type reactor with two different sized catalyst particles and the rate and selectivity were compared. The same reaction was also performed in a small trickle bed reactor so that the effect of the reactor could be considered along with the effect of particle size and solvent. The next three areas of experimental work, use NMR to examine the effect of the four solvents on mass transport issues. Firstly the diffusion of solvents within alumina pellets is investigated using a technique known as pulsed-field gradient (PFG) NMR. A two component model is fitted to the data and is explained on the basis that the larger diffusion coefficient gives the pore (or ordinary) diffusion rate, while the smaller diffusion coefficient gives a rate of diffusion which is reduced due to the effect of interaction with the pore wall. The same technique is then exploited to study the effect of the solvent on diffusion of TBP in liquid mixtures. In particular, the effect of concentration is considered, and models for diffusion at infinite dilution are compared with data extrapolated from experimental data. Strong association is seen between the TBP and the smaller polar solvents which weakens with increasing alcohol solvent size. The effect of temperature on the diffusion of solvents is effectively modelled by an Arrhenius equation. Magnetic Resonance Imaging (MRI) is used to look at the effect of the solvent on the hydrodynamics during trickle flow. 2D cross-sectional images were taken through the trickle bed were taken and algorithms were developed and applied to calculate the hold-up and wetting efficiency for each solvent over at least five different liquid flowrates. The solvents were then ranked based on these characteristics and trends seen between solvents were found mainly to depend on the viscosity of the solvent.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available