Bioderived ether design for low emission and high reactivity transport fuels

Abstract

Bioderived ethers have recently drawn attention as a response to increasing demands on clean alternative fuels. A theory-experiment combined approach was introduced for the five ether molecules representing linear, branched, and cyclic ethers to derive rational design principles for low-emission and high-reactivity ethers. Flow reactor experiments and quantum-mechanical calculations were performed at high (750–1100K) and low temperature (400–700K) regimes to investigate the structural effects on their sooting tendency and reactivity, respectively. At a high-temperature regime, ethers’ high sooting tendency is related to increased C3 and C4 hydrocarbon formation compared to C1 and C2 products from oxidation reactions. On the other hand, the reactivity at the low-temperature regime is determined by the activation energies of reaction steps until ketohydroperoxide formation. These studies found that ethers’ sooting tendency and reactivity are relevant to two structural factors: the carbon type (primary to quaternary) and the relative position of ether oxygen atoms to carbon atoms. These factors were utilized to build a multivariate model to predict the cetane number (CN) and yield sooting index (YSI) of 50 different ethers. The model suggests building blocks with specific carbon types that maximize CN and minimize YSI, leading to the design principles of ethers toward low emissions and high reactivity fuels for transport applications. Ethers with a high CN and low YSI were then proposed using the developed model, and through experimental measurements, it was proved that they are promising biodiesel candidates.