The mystery of how 1,3-substituted imidazolium-based ionic liquids (ILs) can provide high stabilization for transition-metal(0) nanoclusters, that is, in the absence of the usual strongly coordinating anions, has been probed. 2H NMR product and kinetic studies of 1,3-substituted imidazolium ILs under D2 reveal that nanocluster-catalyzed H/D exchange occurs at the 2- (as well as at the 4-, 5-, and 8-) C-H positions of the imidazolium cation. The results (i) provide compelling evidence that N-heterocyclic carbene formation and ligation of nanoclusters is occurring in ILs; and (ii) argue that N-heterocyclic carbenes merit further investigation as heretofore unappreciated stabilizers of transition-metal nanoclusters.
Fluid volatility is an important property of liquid fuels that previously has not been adequately addressed in the development of surrogate models for the thermophysical properties of these fluids. Especially important and timely is the development of surrogates for aviation fuels. In the present context, models refer to mathematical descriptions such as equations of state that provide a predictive capability. In this work, we demonstrate how the incorporation of volatility data, in the form of a distillation curve, leads to the development of improved surrogate models for aviation fuels. As an example, we present a seven-component surrogate mixture model for the thermophysical properties of a natural gas derived, synthetic aviation fuel known as S-8. We then compare the properties of the surrogate model with experimental density, sound speed, viscosity, thermal conductivity, and distillation curve data for the real fuel.
We have developed surrogate mixture models to represent the thermophysical properties of two kerosene rocket propellants, RP-1 and RP-2. The surrogates were developed with a procedure that incorporated experimental data for the density, sound speed, viscosity, thermal conductivity, and the advanced distillation curves for samples of the two fuels. The surrogate for RP-1 contains four components (α-methyldecalin, n-dodecane, 5-methylnonane, and heptylcyclohexane), and the surrogate for RP-2 contains five components (α-methyldecalin, n-dodecane, 5-methylnonane, 2,4-dimethylnonane, and heptylcyclohexane). Comparisons with experimental data demonstrate that the models are able to represent the density, sound speed, viscosity, and thermal conductivity of both fuels to within (at a 95% confidence level) 0.4, 2, 2, and 4%, respectively. The volatility behavior, as measured by the advanced distillation curves, is reproduced to within 0.5%.
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