Part 1 - spectroscopic studies of coal solvent interaction. Part 2 - solvation studies.
thesisposted on 19.11.2015, 08:47 by Benjamin William. Taylor
An overview of coal from a geological context and a review of the use of ESR in coal research is presented. A series of ESR experiments conducted with a selection of coals are described. These include attempts to identify the environments in which iron (III), manganese (II) and vanadyl ions are bound within coal. It is concluded that the principle vanadyl environment is a porphyrin-like structure and that for iron (III) is clay. No specific environment is proposed for manganese(II) but, a mineral environment is most likely. Extraction by organic solvents yields an extract apparently enriched in iron(III). Possible interpretations of this result are discussed. IR spectroscopy is used to study carbonyl groups carried by a range of organic solvents introduced into coals. It is concluded that the solvents are hydrogen-bonding to trapped water and carboxylic acid functional groups at the coal surface. Weaknesses in the experimental techniques used are discussed and proposals for future experiments in the area are made. The NMR chemical shifts of probe species in binary solvent systems are used in an investigation of the Covington model of preferential solvation. It is concluded that, while a useful treatment, the model is flawed in any system where solvent molecules outside the primary solvation shell exert an influence on solute chemical shift. The IR spectra of the CN stretch of MeCN in methanol shows a transition from discrete bands to a merged band with increasing temperature. The lifetime of the bonded dimer is calculated from curve fitting data. The calculated lifetime, ca. 1 ps, agrees with values reported from molecular dynamics modelling. Data from molecular dynamics simulations of the TIP4P model for water is used to analyse hydrogen bonding using geometric bonding criteria. Populations of free OH groups and lone pairs are presented for various geometric criteria. It is concluded that molecular dynamics simulations of water are not at variance with Symons' model for the structure of water.