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Experimental and Computational Studies of Overbased Detergents.

Bearchell, Christopher Alan. (1999) Experimental and Computational Studies of Overbased Detergents. Doctoral thesis, University of Surrey (United Kingdom)..

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Abstract

This thesis describes an experimental and computational study of overbased detergent oil additives, used to neutralise acidic by-products of engine combustion. Aspects of interest in this study include the experimental synthesis, physical and structural characterisation of a range of overbased detergents, the application of ab initio calculations and Molecular Dynamics simulations to overbased detergent particles and the investigation of the self-assembly of model overbased detergent particles by mesoscale simulation techniques. Langmuir trough experiments and the first successful deposition of overbased detergents as multilayer Langmuir-Blodgett films have provided further evidence for overbased phenate particles being oblate spheroids. The combination of Magic Angle Spinning NMR and ab initio quantum mechanical calculations gave improved peak assignments and possible evidence for deprotonated hydroxy groups on the phenolic units of the surfactant molecules. This study and Molecular Dynamics simulations suggest that the core structures simultaneously have features consistent with both the calcite and aragonite phases of calcium carbonate. Furthermore, the ion arrangements in the core are sensitive to surfactant type with the core surface and surfactant positions being highly inter-dependent. The first simulations of model calixarate particles suggest these particles can adopt both a prolate or oblate spheroidal shape, and the possibility of an intrinsic shape polydispersity. This could account for the poorly defined Langmuir IT vs. A curves obtained for this class of overbased detergent. Molecular Dynamics simulations of phenates and calixarates incorporating a stearate co-surfactant suggest that these particles are more spherical and uniformly covered by the organic species. Parallels are drawn between the overbased detergent systems and microemulsions. Mesoscale simulations of three phase systems demonstrate the importance of surfactant geometry on micelle formation and self-assembly of the species. The microemulsion packing/structure rules have been reformulated to take into account the finite headgroup volume and verified by these simulations.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors : Bearchell, Christopher Alan.
Date : 1999
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 1999.
Depositing User : EPrints Services
Date Deposited : 30 Apr 2019 08:08
Last Modified : 20 Aug 2019 15:33
URI: http://epubs.surrey.ac.uk/id/eprint/851526

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