PNNL

Abstract

Catalytic thermochemical processes can convert biomass-derived liquids into hydrocarbon mixtures that are potential liquid transportation blendstocks. However, few measurements of the autoignition behavior of these mixtures are reported in the open literature. Pacific Northwest National Laboratory reports on the autoignition behavior of 36 mixtures of catalytically upgraded liquids—including distillation fractions—from biomass liquefaction technologies. The technologies whose output was subsequently upgraded include direct routes (fast pyrolysis and hydrothermal liquefaction) and indirect routes (syngas to ethanol). The propensity of the biomass-derived hydrocarbons to autoignite was measured using an ignition quality tester (IQT) according to ASTM D6890, which measures the time it takes a fuel-air mixture to autoignite under conditions relevant to cetane number measurements to yield a derived cetane number (DCN). This measurement was converted to a derived research octane number (dRON) using three empirical correlations reported in the literature (Kalghatgi, et al., 2005; Naser, et al., 2017; and, McCormick, et al., 2017). The simulated distillation curve of each sample was measured using ASTM D2887, and the relationship between the boiling range fraction and dRON was evaluated. Gas chromatography/mass spectrometry (GC/MS), 13C nuclear magnetic resonance (NMR), and 1H NMR were used to determine the chemical composition of the liquids, and the impact on research octane number (RON) of various functional groups present in the mixture was assessed. In general, aromatics and olefins enhanced octane number, in agreement with existing literature. The presence of esters was also found to increase dRON. The derived RON (dRON) method requires smaller samples and gave an acceptable approximation of the RON measured using a certified fuel rating engine.