Renewable oxygenated additives in biofuels : high pressure densities of mixtures dibutyl-ether + heptane at high temperature and pressure

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.

The increasing worldwide use of bio-fuels constitutes one of the measures considered to reduce greenhouse gas emissions. Bio-fuels also have an important part to play in promoting the security of energy supply, and promoting technological development and innovation. Di-butyl ether (DBE) is used as blending agent in reformulated gasoline and has been included in recent international regulations on the promotion of the use of energy from renewable sources for transport. The DBE is a non-polluting, high octane number blending agent. DBE could be also used as cetane enhancer in bio-diesel fuel, and can be obtained as an added valued additive to second generation bio-fuels. Second generation bio-fuels could be obtained from ligno-cellulosic biomass and waste materials. Ether + alkane mixtures are of interest as model mixtures for gasoline in which the ether act as renewable, high octane number blending agent. From this point of view the study of the binary mixtures dibutyl ether + heptane, are very interesting. Heptane has been chosen as a representative of the linear alkanes that contain real gasoline. Density of the binary mixtures DBE + heptane and its pure compounds have been measured under pressure and reported in this work using a vibrating tube densitometer. Accurate PVT properties of pure ethers and its mixtures are required to develop and test equations of state, because equations of state are critical to design storage and transport systems in the fuel industry. Moreover, high temperature and pressure data serve to validate equations of state which are reliable for the increasingly use of industrial and engine processes under hard conditions. Experimental densities (826 points) for the compressed liquid phase of the binary systems DBE + heptane have been measured at 298.15, 313.15, 333.15, 353.15, 373.15 and 393.15 K and at pressures up to 140 MPa, with an absolute uncertainty of 0.7 kg·m-3. For each composition, the experimental values were correlated using a Tait-type equation. Results show non-linear behaviour of the mixture.