Methodology for the Development of Empirical Models Relating ~(13)C NMR Spectral Features to Fuel Properties

摘要

Effective formulation of new gasoline or diesel fuels for internal combustion engines would benefit from the development of reliable models for predicting key fuel properties based on a set of molecular descriptors obtained from a single measurement. This is particularly relevant in the case of renewable fuels, where the available fuel sample quantity may be limited. In this work, we present a statistically based methodology for building empirical models to predict multiple properties from one-dimensional C-13 nuclear magnetic resonance (NMR) spectra measured on around 200 mu L of a liquid fuel. NMR spectra contain information about the molecular composition of a sample and the carbon types and molecular substructures therein. Our approach uses this information to build sparse, interpretable models, where the predicted properties are linked to specific molecular features. The approach takes into consideration the constrained nature of the features making up the one-dimensional NMR spectrum, which, after standardization, represents a relative fuel composition. We point to the limitations in interpretability that arise when building this type of empirical predictive model and suggest how these limitations may be diminished. Among the many properties important for maximizing engine performance and minimizing emissions, we build models that predict derived cetane number and distillation temperatures, as these are of particular interest because of their links to fuel economy, drivability, and engine-out emissions. The results suggest that the properties of interest may be impacted by only a few of the 27 C-13 NMR regions represented in the data, pointing to new directions for further testing in the development of improved fuels.