Avaliação da influência de algumas características moleculares sobre a octanagem dos hidrocarbonetos presentes na gasolina

Abstract

This work is part of a larger project whose objective is the development of alternative methodologies for the determination of octane number of gasoline, which is the subject of the doctoral work of engineer Dinarte Santos (Petrobras). One of the methodologies proposed in this project seeks to estimate the octane number (ON) of gasoline from the ON of the pure hydrocarbons that constitute it. However, in the course of that project it was found that not all pure hydrocarbons that are present in gasoline have their ON reported in the databases. Thus, the need to estimate the ON of these hydrocarbons arose and this, in turn, served as an opportunity for the present work. From the literature review we have hypothesized that the antiknock characteristics of the pure hydrocarbons could be explained by the geometric characteristics of the molecules. Thus, in order to verify this hypothesis, several features were analyzed, including the number of carbon atoms, molecular mass, polar moment of inertia, molecular length and combinations of these characteristics. Due to the large number of hydrocarbon families with different structural characteristics, analyzes were performed for groups with features common to each other. For the simplest molecules, such as n-alkanes and non-branched alkenes without cis-trans isomerism, octane numbers has been found to be strongly influenced by the number of carbon atoms, the polar moment of inertia and the molecular length. For more complex molecules, the most influential factors were the polar moment of inertia and the molecular length. In the case of branched hydrocarbons, the ratio between the polar moment of inertia and the number of ramifications, as well as the ratio between the molecular length and the number of ramifications of the molecule, were relevant.