Molecule based modeling of the cloud point and the cetane number of green diesel

Abstract

Green diesel has the potential to become a more environmentally friendly alternative for petroleum diesel. It is mainly composed of paraffins in the C16-C20 range. Inherently it has a very good ignition quality, denoted by the cetane number, but a high cloud point. Both cloud point and cetane number are dependent on the molecular composition of the fuel; the degree of branching is especially important. This thesis covers the modelling of the cloud point and cetane number based on the molecular composition of the fuel. A model to predict the cetane number was developed by Ghosh and Jaffe but the parameters of the model were not made public. Utilizing data found in literature, estimates of these parameters are obtained. For the cloud point, a simplified model based on thermodynamics is developed. Both models are used to study the effect of different reaction conditions on cloud point and cetane number . This study found that in order to produce green diesels with very low cloud points (<-15°C) but still high cetane numbers (75-80), very high conversions of normal paraffins to isoparaffins are necessary (>$80). Cracking reactions should be avoided as much as possible since this will lower the cetane number significantly. Hence, developing a catalyst favoring isomerization reactions and inhibiting cracking reactions can be the next key step in the development of green diesel.