Comparison of Diesel Fuel Oxygenate Additives to the Composition-Explicit Distillation Curve Method. Part 1: Linear Compounds with One to Three Oxygens

There is a great deal of interest in formulating oxygenated diesel fuels that produce low particulate emissions. The most common oxygenate additives for diesel fuels include the glycol ethers, glycol esters, alcohols, ethers, and ketones. It is important to characterize the mixture properties of diesel fuel with oxygenate additives, to assess the degree of departure of the oxygenated fuels from the base fuel. One of the most important properties to use for this purpose is the volatility, as expressed by the distillation curve. We have recently introduced several important improvements in the measurement of distillation curves of complex fluids. The modifications to the classical measurement provide (1) a composition-explicit data channel for each distillate fraction (for both qualitative, quantitative, and trace analysis), (2) temperature measurements that are true thermodynamic state points that can be modeled with an equation of state, (3) temperature, volume, and pressure measurements of low uncertainty suitable for equation of state development, (4) consistency with a century of historical data, (5) an assessment of the energy content of each distillate fraction, and (6) a corrosivity assessment of each distillate fraction. In this paper, we present measurements for dimethoxymethane, butyl methyl ether, 1,2-dimethoxyethane, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, and diethylene glycol dimethyl ether. We find that the more volatile additives cause significant early departures from the distillation curves of diesel fuel, while the less volatile additives act more to displace the entire curve. We also note that the additive affects the curve shape and temperature profile even after being totally depleted, an observation made in earlier studies of oxygenate additive mixtures.