Improvements in the Measurement of Distillation Curves. 3. Application to Gasoline and Gasoline + Methanol Mixtures

Abstract

In previous work, several significant improvements in the measurement of distillation curves for complex fluids were introduced. The modifications to the classical measurement provide for (1) temperature and volume measurements of low uncertainty, (2) temperature control based upon fluid behavior, and, most important, (3) a composition-explicit data channel in addition to the usual temperature-volume relationship. This latter modification is achieved with a new sampling approach that allows precise qualitative as well as quantitative analyses of each fraction, on the fly. Moreover, as part of the improved approach, the distillation temperature is measured in two locations. The temperature is measured in the usual location, at the bottom of the takeoff in the distillation head, but it is also measured directly in the fluid. The measurement in the fluid is a valid equilibrium thermodynamic state point that can be theoretically explained and modeled. The usual temperature measurement location (in the head) provides a temperature that is not a thermodynamic state point for a variety of reasons but which is comparable to historical measurements made for many decades. We also use a modification of the Sidney Young equation (to correct the temperatures to standard atmospheric pressure) in which explicit account is taken of the average length of the carbon chains of the fluid. In this paper, we have applied the advanced approach to samples of 91 AI gasoline and to mixtures of this gasoline with methanol (10 and 15%, vol/vol) as examples of oxygenates. On the individual fractions, we have done chemical analysis by gas chromatography (using flame ionization detection and mass spectrometry). For the methanol blends, the approach allows characterization of the azeotropic inflections in terms of fraction composition and energy content.

Properties of a 5050 mixture of jet-A + S-8

“…The absence of such a convergence in Figure 2 can be interpreted as further evidence of the absence of azeotropic behavior. This is in contrast to what was observed for the gasoline oxygenates, in which the convergence of T k and T h (due to azeotrope formation) was observed [12]. While the gross examination of the distillation curves is instructive and valuable for many design purposes, the composition channel of the advanced approach can provide even greater understanding and information content.…”

“…Simply stated, the distillation curve is a plot of the distillation temperature of the fluid plotted against the volume fraction distilled [6]. We have recently introduced an advanced approach to the measurement of the distillation curve that takes the information content to a much higher level [7][8][9][10][11][12][13][14]. The new metrology provides: C c = C(760 -P a )(273 + T c ), Representative distillation curve data for the three mixtures of Jet-A with S-8, along with data for the starting materials, are presented in Table 5.…”

Composition-Explicit Distillation Curves of Waste Lubricant Oils and Resourced Crude Oil: A Diagnostic for Re-Refining and Evaluation

“…The results of this analysis show that the first drop of the used automotive oil does not contain a Gaussianlike "envelope" of peaks characteristic of a heavy hydrocarbon mixture, but instead contains several common components of gasoline (Smith and Bruno, 2007a), including shorter hydrocarbons, cyclic paraffins such as naphthalenes and indanes and some aromatics (primarily alkyl-substituted benzenes). While these data indicate that further treatment of this specific sample of used oil will be required before it is suitable for re-use, it also shows that for this particular sample of used oil, the residual fuel will only affect the very earliest distillate fractions.…”

“…Although the method is specified only for application to low olefinic gasolines and it has significant limitations, it is of practical relevance to many complex fluid analyses and is often applied to gas turbine fuels, diesel fuels, rocket propellants and missile fuels. The uncertainty and the potential pitfalls of this method were treated earlier (Smith and Bruno, 2007a). Additionally, it is possible that not all of the components of the higher boiling fractions of distillate are sufficiently volatile to permit analysis by GC.…”

Relating Complex Fluid Composition and Thermophysical Properties with the Advanced Distillation Curve Approach

“…We have demonstrated how this can be applied to the distillate fractions corresponding to the data grid of the distillation curve [23]. It is not necessary to identify all the components of the fraction; a substantial subset of the major constituents is adequate, and the uncertainty caused by the use of a subset is negligible [37][38][39].…”