Diesel fuel contains long chain n-alkanes which can phase separate at low temperatures and result in formation of large flat wax crystals. Such wax crystals can block fuel filters which results in fuels starvation and vehicle failure. These problems have become exacerbated by the introduction of biofuel, with thousands of vehicles failing in winter conditions. To-date, these issues have been addressed by developing chemistries to nucleate wax (and hence produce more smaller crystals) and also by introducing polymers which incorporate in a plane of crystallization and hence produce needle-like crystals. Both approaches reduce filter blockages, through modification of crystal structure. However, wax crystals do still form and the possibility of filter blockage and deposit formation throughout the fuel system (including in fuel injectors) does still exist.
If wax nucleation could be effectively understood and controlled, then tailored cold weather properties could be designed. Recent research has highlighted the presence of ordering prior to nucleation of crystals. If the factors affecting such pre-nucleation ordering were understood, it may be possible to prevent (or control) nucleation and hence wax crystal formation. Nucleation of wax then occurs via two possible mechanisms: instantaneous and progressive, which are influenced by the composition of the fuel (Paraffinic, Olefinics, Napthenics, Aromatics etc).The aim of the project will be to develop an understanding of the fundamental principles involved in pre-nucleation ordering of n-alkanes and biofuel components and to link instantaneous and progressive nucleation to the chemical composition of the fuel. This work will be used as a way of automating additive selection on 'Fuel tiles'
This project is mostly experimental with some complementary molecular, solid-state and morphological modelling required. The majority of experimental facilities are available at the University of Leeds in the School of Chemical and Process Engineering. Various techniques will be used throughout the project including polythermal (metastable zone widths and KHBR analysis) and isothermal (induction time) crystallisation studies, x-ray diffraction, crystal 16, thermochemical methods, optical microscopy and small angle x-ray (SAXS) both in Leeds and at Diamond Light Source.