Anna Lif

Reduction of soot emissions when combusting water-in-diesel emulsion and microemulsion fuel in a direct injection diesel engine

The emissions from a direct injection diesel engine measured according to the ECE R49 13-mode cycle and as a function of exhaust gas recirculation are compared for diesel fuel without water addition, and for water-in-diesel as emulsion and microemulsion. The effect of water addition on the soot emissions was remarkably strong for both the emulsion and microemulsion fuels. The average weighted soot emission values for the 13-mode cycle were 0.0024 and 0.0023 g/kWh for the two most interesting emulsion and microemulsion fuels tested, respectively; 5-fold lower than the US 2007 emission limit.

Fischer–Tropsch diesel emulsions stabilised by microfibrillated cellulose and nonionic surfactants

Water-in-diesel emulsion fuels have been prepared with a combination of sorbitan monolaurate and glycerol monooleate as emulsifier and with microfibrillated cellulose (MFC) of different hydrophilic/hydrophobic character as stabilizer. The MFC was treated with either octadecylamine or poly(styrene-co-maleic anhydride), resulting in very hydrophobic fibrils. The most stable emulsion was achieved with a combination of hydrophilic (untreated) and hydrophobic MFC and only minute amounts of the stabilizer gave a pronounced effect. Even with the optimized formulation the lifetime of the emulsion was shorter than previously reported when a conventional polymeric stabilizer was used, however. The water drop sizes in the emulsions were determined by three methods: optical images, light scattering, and NMR diffusometry. All three methods gave water drops sizes of ca 2 μm. The NMR diffusometry indicated that besides the micrometer-sized emulsion drops a significant fraction of the water is present in small droplets of micelle size. The chemical exchange of water between these two populations of pools is believed to be the reason for the relatively low stability of the system.

Water-in-Diesel Microemulsions Studied by NMR Diffusometry

Water-in-diesel microemulsion fuels are attractive in that they are thermodynamically stable and visually similar to regular diesel. This is contrary to water-in-diesel emulsion fuels, which are inherently unstable and have a milk-like appearance. Both emulsion- and microemulsion-based fuels give large reductions in soot emissions in combustion. In this work microemulsions have been formulated with nonionic surfactants and with varying amounts of water and the microemulsion regions have been determined in the temperature interval from 17 to 50°C. The extension of the microemulsion regions has been assessed with amount of surfactant, type of surfactant and temperature as parameters. The internal structure of the microemulsions has been investigated by NMR diffusometry by which the diffusion coefficients of diesel hydrocarbons, water and the surfactants are determined. The diffusometry measurements indicate that the water is present as spherical water domains. They also show that as the amount of water increases, the water domains first swell and then increase in number.

Chemical and enzymatic ester hydrolysis in a Winsor I system

Alkaline- and lipase-catalyzed hydrolysis of 4-nitrophenyldecanoate have been performed in a Winsor I type microemulsion. The reaction occurred in the lower-phase oil-in-water microemulsion. After the reaction was complete a Winsor I→III transition was induced by a rise in temperature. The products formed, 4-nitrophenol and decanoic acid, partitioned into the upper oil phase and could easily be obtained by separation of this phase and evaporation of the solvent. The surfactant and the enzyme (in the case of the lipase-catalyzed reaction) resided in the middle-phase microemulsion and could be reused.