Excess Properties of Binary Mixtures Composed of a Polar Component and an Alkane

Characterization of four potential laser-induced fluorescence tracers for diesel engine applications

Four potential laser-induced fluorescence (LIF) tracers, 1-phenyloctane, 1-phenyldecane, 1-methylnaphthalene, and 2-methylnaphthalene, are characterized for diesel engine applications. These tracers, embedded in the diesel primary reference fuels n-C₁₆H₃₄ and iso-C₁₆H₃₄, match the relevant physical properties of commercial diesel fuel much better than the commonly used toluene/iso-octane/n-heptane tracer-fuel system does. The temperature and pressure dependencies of the fluorescence intensities and spectra were measured in a flow cell in nitrogen for each candidate tracer molecule. The results show that the signal intensities of the methylnaphthalenes are about two orders of magnitude higher than for 1-phenyloctane and 1-phenyldecane and show a strong temperature but no pressure, dependence. An analysis of the fluorescence spectrum of 1-methylnaphthalene shows that it also can be used for two-color detection LIF thermometry by choosing appropriate optical filters.

Thermodynamics of binary mixtures containing a very strongly polar compound — Part 3: DISQUAC characterization of NMP + organic solvent mixtures

Binary mixtures of 1-methyl pyrrolidin-2-one (NMP) with alkanes, benzene, toluene, 1-alkanol, or 1-alkyne have been investigated in the framework of the DISQUAC model. The reported interaction parameters change regularly with the molecular structure of the mixture components. The model consistently describes a set of thermodynamic properties, including liquid–liquid equilibria, vapor–liquid equilibria, solid–liquid equilibria, and molar excess enthalpies. A brief comparison of the DISQUAC results and those obtained from the UNIFAC and ERAS models is presented. The experimental excess enthalpies are better represented by DISQUAC than by UNIFAC because this quantity strongly depends on molecular structure. For NMP + alkane mixtures, the liquid–liquid equilibria data are also better represented by DISQUAC, while UNIFAC more accurately describes the vapor–liquid equilibria measurements at temperatures close to the critical point. This result suggests that a mean field theory is not able to represent simultaneously, with the same set of interaction parameters, liquid–liquid and vapor–liquid equilibria at the mentioned temperatures. ERAS fails when treating mixtures with 1-alkanols. This has been attributed to the strong dipole–dipole interactions between NMP molecules, characteristic of the investigated systems. Mixture structure is briefly studied in terms of the concentration–concentration structure factor.Key words: thermodynamics, NMP, organic solvent, self-association, dipole–dipole interactions.